1.
Near-Earth object
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A near-Earth object is any small Solar System body whose orbit brings it into proximity with Earth. By definition, a solar system body is a NEO if its closest approach to the Sun is less than 1.3 astronomical unit and it is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the Earth. NEOs have become of increased interest since the 1980s because of increased awareness of the potential danger some of the asteroids or comets pose, and mitigations are being researched. In January 2016, NASA announced the Planetary Defense Coordination Office to track NEOs larger than 30 to 50 meters in diameter and coordinate an effective threat response, NEAs have orbits that lie partly between 0.983 and 1.3 AU away from the Sun. When a NEA is detected it is submitted to the IAUs Minor Planet Center for cataloging, some NEAs orbits intersect that of Earths so they pose a collision danger. The United States, European Union, and other nations are currently scanning for NEOs in an effort called Spaceguard. In the United States and since 1998, NASA has a mandate to catalogue all NEOs that are at least 1 kilometer wide. In 2006, it was estimated that 20% of the objects had not yet been found. In 2011, largely as a result of NEOWISE, it was estimated that 93% of the NEAs larger than 1 km had been found, as of 5 February 2017, there have been 875 NEAs larger than 1 km discovered, of which 157 are potentially hazardous. The inventory is much less complete for smaller objects, which still have potential for scale, though not global. Potentially hazardous objects are defined based on parameters that measure the objects potential to make threatening close approaches to the Earth. Mostly objects with an Earth minimum orbit intersection distance of 0.05 AU or less, objects that cannot approach closer to the Earth than 0.05 AU, or are smaller than about 150 m in diameter, are not considered PHOs. This makes them a target for exploration. As of 2016, three near-Earth objects have been visited by spacecraft, more recently, a typical frame of reference for looking at NEOs has been through the scientific concept of risk. In this frame, the risk that any near-Earth object poses is typically seen through a lens that is a function of both the culture and the technology of human society, NEOs have been understood differently throughout history. Each time an NEO is observed, a different risk was posed and it is not just a matter of scientific knowledge. Such perception of risk is thus a product of religious belief, philosophic principles, scientific understanding, technological capabilities, and even economical resourcefulness.03 E −0.4 megatonnes. For instance, it gives the rate for bolides of 10 megatonnes or more as 1 per thousand years, however, the authors give a rather large uncertainty, due in part to uncertainties in determining the energies of the atmospheric impacts that they used in their determination
2.
National Emergency Alarm Repeater
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The National Emergency Alarm Repeater was a civilian emergency warning device in the United States. It was a 2–3 square box designed to plug into a power outlet to receive a special signal sent over the electric power transmission lines. Research and testing for the NEAR program was developed in 1956 during the Cold War to supplement the existing siren warning systems, despite this advantage, upon the introduction of the Emergency Broadcast system, the stockpiled NEAR repeaters were destroyed by their respective manufacturers. A similar program was proposed in the United Kingdom during the 1960s, the device is a buzzer installed into ordinary electrical outlets. The devices would be set off in an emergency by altering the regular AC signal being generated and transmitted by the power companies. The indoor buzzers would be supplemented with outdoor warning sirens, EMP effects of a high-altitude nuclear could have disabled the system. After a decade of support for testing and development, the program was terminated. Status of NEAR program still cloudy to utilities, III, Warning Systems, Federal Warning Systems, page 9. Gilbert, Wayne The Cold War Artifact that NEAR-ly Changed My Life Denverpost. com Nuclear Survival Manual,1963, www. archive. org Original Patent document, US3,284,791, of one type of NEAR receiver
3.
433 Eros
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433 Eros is an S-type near-Earth asteroid approximately 34. 4×11. 2×11.2 kilometres in size, the second-largest near-Earth asteroid after 1036 Ganymed. It was discovered in 1898 and was the first near-Earth asteroid discovered and it was the first asteroid orbited by an Earth probe. It belongs to the Amor group, Eros is a Mars-crosser asteroid, the first known to come within the orbit of Mars. Objects in such an orbit can remain there for only a few hundred years before the orbit is perturbed by gravitational interactions. It is a potential Earth impactor, about five times larger than the impactor that created Chicxulub crater, the NEAR Shoemaker probe visited Eros twice, first with a 1998 flyby, and then by orbiting it in 2000 when it extensively photographed its surface. On February 12,2001, at the end of its mission, Eros was discovered on 13 August 1898 by Gustav Witt in Berlin and Auguste Charlois at Nice. Witt was taking a 2-hour exposure of Beta Aquarii to secure astrometric positions of asteroid 185 Eunike, a similar program was then carried out, during a closer approach, in 1930–1931 by Harold Spencer Jones. The value obtained by this program was considered definitive until 1968, Eros was the first asteroid detected by the Arecibo Observatorys radar system. Eros was one of the first asteroids visited by a spacecraft, the first one orbited, NASA spacecraft NEAR Shoemaker entered orbit around Eros in 2000, and landed in 2001. Eros is named after the Greek god of love, Erōs and it is pronounced /ˈɪərɒs/ EER-os or sometimes /ˈɛrɒs/ ERR-os. The rarely used form of the name is Erotian /ᵻˈroʊʃən/. Surface gravity depends on the distance from a spot on the surface to the center of a bodys mass, eross surface gravity varies greatly because Eros is not a sphere but an elongated peanut-shaped object. The daytime temperature on Eros can reach about 100 °C at perihelion, nighttime measurements fall near −150 °C. Eross density is 2.67 g/cm3, about the same as the density of Earths crust and it rotates once every 5.27 hours. NEAR scientists have found that most of the larger rocks strewn across Eros were ejected from a crater in an impact approximately 1 billion years ago. This event may also be responsible for the 40 percent of the Erotian surface that is devoid of craters smaller than 0.5 kilometers across and it was originally thought that the debris thrown up by the collision filled in the smaller craters. An analysis of crater densities over the surface indicates that the areas with lower density are within 9 kilometers of the impact point. Some of the lower density areas were found on the side of the asteroid
4.
NASA
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President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is also responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1. In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were also transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history. Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, however, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
5.
Applied Physics Laboratory
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The, located in Howard County, Maryland, near Laurel and Columbia, is a not-for-profit, university-affiliated research center employing 6,000 people. APL is primarily a defense contractor and it serves as a technical resource for the Department of Defense, NASA, and other government agencies. The Lab is a research and development organization rather than an academic division of Johns Hopkins University. Hopkins Whiting School of Engineering offers part-time graduate programs through its Engineering for Professionals program, courses are taught at seven locations in the Baltimore-Washington Metropolitan Area, including the APL Education Center. Its founding director was Merle Anthony Tuve, the Laboratory succeeded in developing the variable-time proximity fuze that played a significant role in the Allied victory. In response to the success, the APL created the MK57 gun director in 1944. Pleased with the APLs work, the Navy then tasked it with the mission to find a way to negate guided missile threats, from there on, the APL became very involved in wartime research. Expected to disband at the end of the war, APL instead became involved in the development of guided missile technology for the Navy. At governmental request, the University continued to maintain the Laboratory as a public service, APL was originally located in Silver Spring, Maryland in a used-car garage at the former Wolf Motor Company building at 8621 Georgia Avenue. APL moved to Laurel beginning in 1954, with the construction of a two million dollar building and a $700,000 wing expansion in 1956, the final staff transitioned to the new facility in 1975. Before moving to Laurel, APL also maintained the Forest Grove Station, north of Silver Spring on Georgia Avenue near todays Forest Glen Metro, the Forest Grove Station was vacated and torn down in 1963 and flight simulations were moved to Laurel. The Laboratorys name comes from its origins in World War II, about half of the technical staff are engineers, and 25% have computer science and math degrees. APL conducts programs in fundamental and applied research, exploratory and advanced development, test and evaluation, in 1965, the US Army contracted with APL to develop and implement a test and evaluation program for the Pershing missile systems. In 1990, APL became involved with Operation Desert Storm and was involved in the Gulf Crisis Room among other efforts, in the same decade, APL, along with Johns Hopkins University, developed an algorithm that allowed for automatic mammogram analysis. In 2014, the APL made history with the use of Modular Prosthetic Limbs by a bilateral shoulder-level amputee. APL used pattern recognition algorithms to track which muscles were contracting, the Lab is currently developing the Solar Probe Plus mission to probe the outer corona of the Sun. Located on a 399-acre campus, APL is also home to a Johns Hopkins graduate program in engineering and applied sciences, the U. S. Navy continues to be APLs primary long-term sponsor. The Laboratory performs work for the Missile Defense Agency, the Department of Homeland Security, intelligence agencies, the Defense Advanced Research Projects Agency, the Laboratory supports NASA through space science, spacecraft design and fabrication, and mission operations
6.
Coordinated Universal Time
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Coordinated Universal Time, abbreviated to UTC, is the primary time standard by which the world regulates clocks and time. It is within about 1 second of mean time at 0° longitude. It is one of closely related successors to Greenwich Mean Time. For most purposes, UTC is considered interchangeable with GMT, the first Coordinated Universal Time was informally adopted on 1 January 1960. This change also adopted leap seconds to simplify future adjustments, a number of proposals have been made to replace UTC with a new system that would eliminate leap seconds, but no consensus has yet been reached. Leap seconds are inserted as necessary to keep UTC within 0.9 seconds of universal time, see the Current number of leap seconds section for the number of leap seconds inserted to date. The official abbreviation for Coordinated Universal Time is UTC and this abbreviation arose from a desire by the International Telecommunication Union and the International Astronomical Union to use the same abbreviation in all languages. English speakers originally proposed CUT, while French speakers proposed TUC, the compromise that emerged was UTC, which conforms to the pattern for the abbreviations of the variants of Universal Time. Time zones around the world are expressed using positive or negative offsets from UTC, the westernmost time zone uses UTC−12, being twelve hours behind UTC, the easternmost time zone, theoretically, uses UTC+12, being twelve hours ahead of UTC. In 1995, the nation of Kiribati moved those of its atolls in the Line Islands from UTC-10 to UTC+14 so that the country would all be on the same day. UTC is used in internet and World Wide Web standards. The Network Time Protocol, designed to synchronise the clocks of computers over the internet, computer servers, online services and other entities that rely on having a universally accepted time use UTC as it is more specific than GMT. If only limited precision is needed, clients can obtain the current UTC from a number of official internet UTC servers, for sub-microsecond precision, clients can obtain the time from satellite signals. UTC is also the standard used in aviation, e. g. for flight plans. Weather forecasts and maps all use UTC to avoid confusion about time zones, the International Space Station also uses UTC as a time standard. Amateur radio operators often schedule their radio contacts in UTC, because transmissions on some frequencies can be picked up by many time zones, UTC is also used in digital tachographs used on large goods vehicles under EU and AETR rules. UTC divides time into days, hours, minutes and seconds, days are conventionally identified using the Gregorian calendar, but Julian day numbers can also be used. Each day contains 24 hours and each hour contains 60 minutes, the number of seconds in a minute is usually 60, but with an occasional leap second, it may be 61 or 59 instead
7.
Delta II
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Delta II is an American expendable launch system, originally designed and built by McDonnell Douglas. Delta II is part of the Delta rocket family and entered service in 1989, Delta II vehicles included the Delta 6000, and two Delta 7000 variants. In the early 1980s, all United States expendable launch vehicles were planned to be phased out in favor of the Space Shuttle, production of Delta, Atlas-Centaur, and Titan 34D had ended. McDonnell Douglas, at time the manufacturer of the Delta family. These were intended to launch a series of GPS Block II satellites, the Air Force exercised additional contract options in 1988, expanding this order to 20 vehicles, and NASA purchased its first Delta IIs in 1990 for the launch of three Earth-observing satellites. The first Delta II launch occurred in 1989, with a Delta 6925 boosting the first GPS Block II satellite into a 20,000 km high orbit, the first Delta II 7000-series flew in 1990, replacing the RS-27 engine of the 6000-series with the more powerful RS-27A. Additionally, the steel-cased Castor 4A solid boosters of the 6000 series were replaced with the composite-cased GEM40, all further Delta II launches except three were of this upgraded configuration, and the 6000-series was retired in 1992. McDonnell Douglas began Delta III development in the mid-90s as increasing satellite mass required more powerful launch vehicles, the upgraded boosters would still find use on the Delta II, leading to the Delta II Heavy. In total, the Delta II family has launched 153 times, no one was injured, and the launch pad itself was not seriously impacted, though several cars were destroyed and a few buildings were damaged. In 2007, Delta II completed its 75th consecutive successful launch, with the launch of SMAP in 2015, the Delta II has enjoyed 98 consecutive successful launches, with two more scheduled in 2017 and 2018. Should these launches be successful, the Delta II would achieve an unprecedented 100 consecutive launch successes, the first stage of the Delta II is propelled by a Rocketdyne RS-27 main engine burning RP-1 and liquid oxygen. This stage is referred to as the Extra-Extended Long Tank Thor. The RS-27 used on the 6000-series Delta II produced 915 kN, the stage is 26 meters long and 2.4 meters wide, weighs over 100 t when fueled, and burns for 260 seconds. In addition, two LR101-NA-11 vernier engines provide guidance for the first stage, for additional thrust during launch, the Delta II uses solid boosters. For the 6000-series, Delta II used Castor 4A boosters, while the 7000-series uses Graphite-Epoxy Motors manufactured by ATK, the vehicle can be flown with three, four, or, most commonly, nine boosters. The second stage of Delta II is the Delta-K, powered by a restartable Aerojet AJ10-118K engine burning hypergolic Aerozine-50 and these propellants are highly toxic and corrosive, and once loaded the launch must occur within approximately 37 days or the stage will have to be refurbished or replaced. This stage also contains a combined platform and guidance system that controls all flight events. The Delta-K stage is 6 meters long and 2.4 meters wide, contains up to 6 t of propellant, for low Earth orbit, Delta II is not equipped with a third stage
8.
Cape Canaveral Air Force Station
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Cape Canaveral Air Force Station is an installation of the United States Air Force Space Commands 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in Brevard County, Florida, CCAFS is the primary head of Americas Eastern Range with three launch pads currently active. The Cape Canaveral Air Force Station Skid Strip provides a 10, 000-foot runway close to the launch complexes for military airlift aircraft delivering heavy, a number of American space exploration firsts were launched from CCAFS, including the first U. S. Earth satellite, first U. S. astronaut, first U. S. astronaut in orbit, first two-man U. S. spacecraft, first U. S. unmanned lunar landing, and first three-man U. S. spacecraft. The CCAFS area had used by the United States government to test missiles since 1949. On June 1,1948, the U. S. Navy transferred the former Banana River Naval Air Station to the U. S. Air Force, with USAF renaming the facility the Joint Long Range Proving Ground Base on June 10,1949. On October 1,1949, the Joint Long Range Proving Ground Base was transferred from the Air Materiel Command to the Air Force Division of the Joint Long Range Proving Ground. On May 17,1950, the base was renamed the Long Range Proving Ground Base, in 1951, the Air Force established the Air Force Missile Test Center. Early American sub-orbital rocket flights were achieved at Cape Canaveral in 1956 and these flights occurred shortly after sub-orbital flights launched from White Sands Missile Range, such as the Viking 12 sounding rocket on February 4,1955. Following the Soviet Unions successful Sputnik 1, the US attempted its first launch of a satellite from Cape Canaveral on December 6,1957. However, the rocket carrying Vanguard TV3 blew up on the launch pad, NASA was founded in 1958, and Air Force crews launched missiles for NASA from the Cape, known then as Cape Canaveral Missile Annex. The row of Titan and Atlas launch pads along the coast came to be known as Missile Row in the 1960s, nASAs first manned spaceflight program was prepared for launch from Canaveral by U. S. Air Force crews. Mercurys objectives were to place a spacecraft in Earth orbit, investigate human performance and ability to function in space. Suborbital flights were launched by derivatives of the Armys Redstone missile from LC-5, Orbital flights were launched by derivatives of the Air Forces larger Atlas D missile from LC-14. The first American in orbit was John Glenn on February 20,1962, three more orbital flights followed through May 1963. Flight control for all Mercury missions was provided at the Mercury Control Center located at Canaveral near LC-14 and he had also convinced Gov. C. Farris Bryant to change the name of Cape Canaveral to Cape Kennedy and this resulted in some confusion in public perception, which conflated the two. This name was used through the Gemini and early Apollo programs, however, the geographical name change proved to be unpopular, owing to the historical longevity of Cape Canaveral
9.
253 Mathilde
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253 Mathilde /məˈtɪldə/ is a main-belt asteroid about 50 km in diameter that was discovered by Johann Palisa in 1885. It has an elliptical orbit that requires more than four years to circle the Sun. This asteroid has a slow rate of rotation, requiring 17.4 days to complete a 360° revolution about its axis. It is a primitive C-type asteroid, which means the surface has a proportion of carbon. This asteroid was visited by the NEAR Shoemaker spacecraft during June 1997, during the flyby, the spacecraft imaged a hemisphere of the asteroid, revealing many large craters that have gouged out depressions in the surface. It was the first C-type asteroid to be explored and, until 21 Lutetia was visited in 2010, in 1880, Johann Palisa, the director of the Austrian Naval Observatory, was offered a position as an assistant at the newly completed Vienna Observatory. Although the job represented a demotion for Johann, it gave him access to the new 27-inch refractor, by this point Johann had already discovered 27 asteroids, and he would employ the Vienna 27-inch and 12-inch instruments to find an additional 94 asteroids before he retired. Among his discoveries was the asteroid 253 Mathilde, found on November 12,1885, the initial orbital elements of the asteroid were then computed by V. A. Lebeuf, another Austrian astronomer working at the observatory. The name of the asteroid was suggested by Lebeuf, after Mathilde, in 1995, ground-based observations determined that 253 Mathilde is a C-type asteroid. It was also found to have a long period of rotation. On June 27,1997, the NEAR Shoemaker spacecraft passed within 1,212 km of 253 Mathilde while moving at a velocity of 9.93 km/s. This close approach allowed the spacecraft to capture over 500 images of the surface, however, only one hemisphere of 253 Mathilde was imaged during the fly-by. This was only the third asteroid to be imaged from a nearby distance, the asteroid has a number of extremely large craters, with the individual craters being named for coal fields and basins around the world. The two largest craters, Ishikari and Karoo, are as wide as the average radius. The impacts appear to have spalled large volumes off the asteroid, no differences in brightness or colour were visible in the craters and there was no appearance of layering, so the asteroids interior must be very homogeneous. There are indications of material movement along the downslope direction, the density measured by NEAR Shoemaker,1,300 kg/m³, is less than half that of a typical carbonaceous chondrite, this may indicate that the asteroid is very loosely packed rubble pile. The same is true of several C-type asteroids studied by ground-based telescopes equipped with adaptive optics systems, up to 50% of the interior volume of 253 Mathilde consists of open space. However, the existence of a 20-km-long scarp may indicate that the asteroid does have some structural strength, the low interior density is an inefficient transmitter of impact shock through the asteroid, which also helps to preserve the surface features to a high degree
10.
Discovery Program
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NASAs Discovery Program is a series of lower-cost, highly focused American scientific space missions that are exploring the Solar System. It was founded in 1992 to implement then-NASA Administrator Daniel S. Goldins vision of faster, better, cheaper planetary missions, Discovery missions differ from traditional NASA missions where targets and objectives are pre-specified. Instead, these missions are proposed and led by a scientist called the Principal Investigator. Proposing teams may include people from industry, small businesses, government laboratories, proposals are selected through a competitive peer review process. All of the completed Discovery missions are accomplishing ground-breaking science and adding significantly to the body of knowledge about the Solar System, NASA also accepts proposals for competitively selected Discovery Program Missions of Opportunity. These opportunities are offered through NASAs Stand Alone Mission of Opportunity program. In 1989, the Solar System Exploration Division at NASA Headquarters initiated a series of workshops to define a new strategy for exploration through the year 2000, a fast-paced study for a potential mission was requested and funding arrangements were made in 1990. On February 17,1996, NEAR became the first mission to launch in the Discovery Program, also, Phoenix and MAVEN were in the Mars Scout Program not Discovery program. NEAR Shoemaker, a mission to study asteroid 433 Eros, launched on February 17,1996, the spacecraft entered orbit around Eros in 2000 and successfully touched down on its surface one year later. It has succeeded its primary and extended mission and is now complete, the Project Scientist was Andrew Chang of The Johns Hopkins University Applied Physics Laboratory. Mars Pathfinder, a Mars lander to deploy Sojourner rover on the surface, launched in 1996, it landed on Mars on July 4,1997. It has completed its primary and extended mission, the Principal Investigator was Matthew Golombek of NASA’s Jet Propulsion Laboratory. Lunar Prospector, a Moon orbiter to characterize the lunar mineralogy, launched in 1998, it spent 1½ years in lunar orbit. It has completed its primary and extended mission and deliberately impacted onto the Moons surface, the Principal Investigator was Alan Binder of the Lunar Research Institute. Stardust, a mission to collect interstellar dust and dust particles from the nucleus of comet 81P/Wild for study on Earth, launched in 1999, it successfully collected samples between 2000–2004, then the sample return capsule returned to Earth on January 15,2006. The capsule is on display at the National Air and Space Museum in Washington D. C, scientists worldwide are studying the comet dust samples while citizen scientists are finding interstellar dust bits through the Stardust@home project. The spacecraft was assigned a new task, called Stardust-NExT to revisit Tempel 1, having completed its primary and extend missions, Stardust did a final burn to deplete its remaining fuel on March 24,2011. The Principal Investigator was Donald Brownlee of the University of Washington, Genesis, a mission to collect solar wind charged particles for analysis on Earth
11.
Mars Pathfinder
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Mars Pathfinder is an American robotic spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight wheeled robotic Mars rover named Sojourner, the lander then opened, exposing the rover which conducted many experiments on the Martian surface. The mission carried a series of instruments to analyze the Martian atmosphere, climate, geology. The mission was directed by the Jet Propulsion Laboratory, a division of the California Institute of Technology, the project manager was JPLs Tony Spear. This mission was the first of a series of missions to Mars that included rovers, although the Soviet Union successfully sent rovers to the Moon as part of the Lunokhod program in the 1970s, its attempts to use rovers in its Mars program failed. The Mars Pathfinder was also remarkable for its low cost relative to other unmanned space missions to Mars. Originally, the mission was conceived as the first of the Mars Environmental Survey program, to prove that the development of faster, better and cheaper spacecraft was possible. To show that it was possible to send a load of scientific instruments to another planet with a simple system, to demonstrate NASAs commitment to low-cost planetary exploration by finishing the mission with a total expenditure of $280 million, including the launch vehicle and mission operations. The Mars Pathfinder conducted different investigations on the Martian soil using three scientific instruments, the MET structure included three windsocks mounted at three heights on a pole, the topmost at about one meter and generally registered winds from the West. The Sojourner rover had an Alpha Proton X-ray Spectrometer, which was used to analyze the components of the rocks, the rover also had two black-and-white cameras and a color one. A third camera with the resolution but taking color images was located on the back, near the APXS. It provided images of the APXSs target area and the tracks on the ground. All three cameras were CCDs manufactured by Eastman Kodak Company, and were controlled by the rovers CPU and they all had auto-exposure and capabilities for handling bad pixels, and the image parameters were included in the transmitted images as part of the image header. The rover could compress the front cameras images using the block truncation coding algorithm, the cameras optical resolution was sufficient to resolve 0.6 cm details across a 0.65 m range. Scientists chose it because they found it to be a relatively safe surface to land on and one that contained a wide variety of rocks deposited during a catastrophic flood. After the landing, at 19. 13°N33. 22°W /19.13, -33.22, succeeded, the landers on-board computer used redundant on-board accelerometers to determine the timing of the parachute inflation. Twenty seconds later the heatshield was pyrotechnically released, another twenty seconds later the lander was separated and lowered from the backshell on a 20 m bridle. When the lander reached 1.6 km above the surface and this information was used by the computer to determine the precise timing of the landing events that followed
12.
Eugene Merle Shoemaker
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Eugene Merle Shoemaker, also known as Gene Shoemaker, was an American geologist and one of the founders of the field of planetary science. He is best known for co-discovering the Comet Shoemaker–Levy 9 with his wife Carolyn S. Shoemaker and David H. Levy. Shoemaker was born in Los Angeles, California, the son of Muriel May, a teacher, and George Estel Shoemaker, who worked in farming, business, teaching, and motion pictures. For his Ph. D. degree at Princeton, Shoemaker studied the dynamics of Barringer Meteor Crater, located near Winslow. To understand the dynamics, Shoemaker inspected craters that remained after underground atomic bomb tests at the Nevada Test Site at Yucca Flat and he found a ring of ejected material that included shocked quartz, a form of quartz that has a microscopically unique structure caused by intense pressure. Shoemaker helped pioneer the field of astrogeology by founding the Astrogeology Research Program of the United States Geological Survey in 1961 at Flagstaff, Arizona and he was its first director. He was prominently involved in the Lunar Ranger missions to the Moon, Shoemaker was also involved in the training of the American astronauts. Shoemaker would train astronauts during field trips to Meteor Crater and Sunset Crater near Flagstaff and he was a CBS News television commentator on the early Apollo missions, especially the Apollo 8 and Apollo 11 missions, appearing with Walter Cronkite during live coverage of those flights. He was awarded the John Price Wetherill Medal from the Franklin Institute in 1965, coming to Caltech in 1969, he started a systematic search for Earth orbit-crossing asteroids, which resulted in the discovery of several families of such asteroids, including the Apollo asteroids. Shoemaker advanced the idea that sudden geologic changes can arise from asteroid strikes, previously, astroblemes were thought to be remnants of extinct volcanoes — even on the Moon. Shoemaker received the Barringer Medal in 1984 and a National Medal of Science in 1992, in 1993, he co-discovered Comet Shoemaker–Levy 9 using the 18 Schmidt camera at Palomar Observatory. This comet was unique in that it provided the first opportunity for scientists to observe the impact of a comet. Shoemaker–Levy 9 collided with Jupiter in 1994, the resulting impact caused a massive scar on the face of Jupiter. Most scientists at the time were dubious of whether there would even be any evident markings on the planet, Shoemaker spent much of his later years searching for and finding several previously unnoticed or undiscovered impact craters around the world. Shoemaker died on July 18,1997 during one such expedition in a head on car accident while on the Tanami Road northwest of Alice Springs and his vehicle and another were thought to be using the center, relatively smooth part of a heavily rutted, unimproved road. On seeing Shoemaker approaching, the driver of the vehicle pulled hard to his left, and had Shoemaker done the same. But Shoemaker, as an American accustomed to driving on the side of the road, reflexively pulled hard to his right. A head-on collision in which Shoemakers vehicle was traveling at 80 km/h, the occupants of the other vehicle were rendered unconscious, but not seriously injured
13.
Robotic spacecraft
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A robotic spacecraft is an uncrewed spacecraft, usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost, in addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, many artificial satellites are robotic spacecraft, as are many landers and rovers. The first robotic spacecraft was launched by the Soviet Union on 22 July 1951, four other such flights were made through the fall of 1951. The first artificial satellite, Sputnik 1, was put into a 215-by-939-kilometer Earth orbit by the USSR) on 4 October 1957, on 3 November 1957, the USSR orbited Sputnik 2. Weighing 113 kilograms, Sputnik 2 carried the first living animal into orbit, since the satellite was not designed to detach from its launch vehicles upper stage, the total mass in orbit was 508.3 kilograms. In a close race with the Soviets, the United States launched its first artificial satellite, Explorer 1, into a 193-by-1, 373-nautical-mile orbit on 31 January 1958. Explorer I was a 80. 75-inch long by 6. 00-inch diameter cyllynder weighing 30.8 pounds, compared to Sputnik 1, a 58-centimeter sphere which weighed 83.6 kilograms. Explorer 1 carried sensors which confirmed the existence of the Van Allen belts, on 17 March 1958, the US orbited its second satellite, Vanguard 1, which was about the size of a grapefruit, and remains in a 360-by-2, 080-nautical-mile orbit as of 2016. Nine other countries have successfully launched satellites using their own vehicles, France, Australia, Japan and China, the United Kingdom, India, Israel, Iran. In spacecraft design, the United States Air Force considers a vehicle to consist of the mission payload, the bus provides physical structure, thermal control, electrical power, attitude control and telemetry, tracking and commanding. JPL divides the system of a spacecraft into subsystems. These include, This is the backbone structure. It, provides overall mechanical integrity of the spacecraft ensures spacecraft components are supported and can withstand launch loads This is sometimes referred to as the command, components in the telecommunications subsystem include radio antennas, transmitters and receivers. These may be used to communicate with stations on Earth. The supply of power on spacecraft generally come from photovoltaic cells or from a radioisotope thermoelectric generator. Other components of the subsystem include batteries for storing power and distribution circuitry that connects components to the power sources, spacecraft are often protected from temperature fluctuations with insulation
14.
Space probe
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A space probe is a robotic spacecraft that does not orbit the Earth, but, instead, explores further into outer space. A space probe may approach the Moon, travel through space, flyby, orbit, or land on other planetary bodies. Approximately fifteen missions are currently operational, once a probe has left the vicinity of Earth, its trajectory will likely take it along an orbit around the Sun similar to the Earths orbit. To reach another planet, the simplest practical method is a Hohmann transfer orbit, more complex techniques, such as gravitational slingshots, can be more fuel-efficient, though they may require the probe to spend more time in transit. Some high Delta-V missions can only be performed, within the limits of modern propulsion, a technique using very little propulsion, but requiring a considerable amount of time, is to follow a trajectory on the Interplanetary Transport Network. First man-made object to land on the Moon, or any other extra terrestrial surface. First mission to photograph the far side of the Moon, launched in 1959, first robotic sample return probe from the Moon. It was sent to the Moon on November 10,1970, first successful in-place analysis of another planet. It may have also been the first space probe to impact the surface of another planet, the Venera 7 probe was the first spacecraft to successfully soft land on another planet and to transmit data from there back to Earth. Upon its arrival at Mars on November 13,1971, Mariner 9 became the first space probe to orbit around another planet. Although, the spacecraft failed shortly after landing, the Mars Exploration Rovers, Spirit and Opportunity surface and geology, and searched for clues to past water activity on Mars. They were each launched in 2003 and landed in 2004, communication with Spirit stopped on sol 2210. JPL continued to attempt to regain contact until May 24,2011, Opportunity arrived at Endeavour crater on 9 August 2011, at a landmark called Spirit Point named after its rover twin, after traversing 13 miles from Victoria crater, over a three-year period. As of January 26,2016, Opportunity has lasted for more than twelve years on Mars — although the rovers were intended to last only three months. The first dedicated missions to a comet, in this case and they dropped landers and balloons at Venus before their rendezvous with Halleys Comet. This Japanese probe was the first non-US, non-Soviet interplanetary probe, a second Japanese probe, it made ultraviolet wavelength observations of the comet. The first space probe to penetrate a comets coma and take images of its nucleus. First solar wind sample return probe from sun-earth L1, first sample return probe from a comet tail
15.
Johns Hopkins University
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The Johns Hopkins University is an American private research university in Baltimore, Maryland. Founded in 1876, the university was named for its first benefactor, the American entrepreneur, abolitionist and his $7 million bequest—of which half financed the establishment of The Johns Hopkins Hospital—was the largest philanthropic gift in the history of the United States at that time. Daniel Coit Gilman, who was inaugurated as the institutions first president on February 22,1876, led the university to revolutionize higher education in the U. S. by integrating teaching and research. Adopting the concept of a school from Germanys ancient Heidelberg University. Johns Hopkins is organized into 10 divisions on campuses in Maryland and Washington, D. C. with international centers in Italy, China, and Singapore. The two undergraduate divisions, the Krieger School of Arts and Sciences and the Whiting School of Engineering, are located on the Homewood campus in Baltimores Charles Village neighborhood. The medical school, the school, and the Bloomberg School of Public Health are located on the Medical Institutions campus in East Baltimore. Johns Hopkins was a member of the American Association of Universities. Over the course of almost 140 years, thirty-six Nobel laureates have been affiliated with Johns Hopkins, founded in 1883, the Blue Jays men’s lacrosse team has captured 44 national titles and joined the Big Ten Conference as an affiliate member in 2014. On his death in 1873, Johns Hopkins, a Quaker entrepreneur and childless bachelor, bequeathed $7 million to fund a hospital and university in Baltimore, Maryland. At that time this fortune, generated primarily from the Baltimore, the first name of philanthropist Johns Hopkins is the surname of his great-grandmother, Margaret Johns, who married Gerard Hopkins. They named their son Johns Hopkins, who named his own son Samuel Hopkins, Samuel named one of his sons for his father and that son would become the universitys benefactor. Milton Eisenhower, a university president, once spoke at a convention in Pittsburgh where the Master of Ceremonies introduced him as President of John Hopkins. Eisenhower retorted that he was glad to be here in Pittburgh, the original board opted for an entirely novel university model dedicated to the discovery of knowledge at an advanced level, extending that of contemporary Germany. Building on the German education model of Wilhelm von Humboldt, it dedicated to research. Johns Hopkins thereby became the model of the research university in the United States. Its success eventually shifted higher education in the United States from a focus on teaching revealed and/or applied knowledge to the discovery of new knowledge. The trustees worked alongside four notable university presidents – Charles W. Eliot of Harvard, Andrew D. White of Cornell, Noah Porter of Yale College and they each vouched for Daniel Coit Gilman to lead the new University and he became the universitys first president
16.
Mineral
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A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids, the study of minerals is called mineralogy. There are over 5,300 known mineral species, over 5,070 of these have been approved by the International Mineralogical Association, the silicate minerals compose over 90% of the Earths crust. The diversity and abundance of species is controlled by the Earths chemistry. Silicon and oxygen constitute approximately 75% of the Earths crust, which translates directly into the predominance of silicate minerals, minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Minerals can be described by their various properties, which are related to their chemical structure. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, more specific tests for describing minerals include magnetism, taste or smell, radioactivity and reaction to acid. Minerals are classified by key chemical constituents, the two dominant systems are the Dana classification and the Strunz classification, the silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a unit of a 4− silica tetrahedron—that is, a silicon cation coordinated by four oxygen anions. These tetrahedra can be polymerized to give the subclasses, orthosilicates, disilicates, cyclosilicates, inosilicates, phyllosilicates, other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates. The first criterion means that a mineral has to form by a natural process, stability at room temperature, in the simplest sense, is synonymous to the mineral being solid. More specifically, a compound has to be stable or metastable at 25 °C, modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula, many mineral groups and species are composed of a solid solution, pure substances are not usually found because of contamination or chemical substitution. Finally, the requirement of an ordered atomic arrangement is usually synonymous with crystallinity, however, crystals are also periodic, an ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form, hardness, and cleavage. There have been recent proposals to amend the definition to consider biogenic or amorphous substances as minerals. The formal definition of an approved by the IMA in 1995, A mineral is an element or chemical compound that is normally crystalline. However, if geological processes were involved in the genesis of the compound, Mineral classification schemes and their definitions are evolving to match recent advances in mineral science
17.
Mass
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In physics, mass is a property of a physical body. It is the measure of a resistance to acceleration when a net force is applied. It also determines the strength of its gravitational attraction to other bodies. The basic SI unit of mass is the kilogram, Mass is not the same as weight, even though mass is often determined by measuring the objects weight using a spring scale, rather than comparing it directly with known masses. An object on the Moon would weigh less than it does on Earth because of the lower gravity and this is because weight is a force, while mass is the property that determines the strength of this force. In Newtonian physics, mass can be generalized as the amount of matter in an object, however, at very high speeds, special relativity postulates that energy is an additional source of mass. Thus, any body having mass has an equivalent amount of energy. In addition, matter is a defined term in science. There are several distinct phenomena which can be used to measure mass, active gravitational mass measures the gravitational force exerted by an object. Passive gravitational mass measures the force exerted on an object in a known gravitational field. The mass of an object determines its acceleration in the presence of an applied force, according to Newtons second law of motion, if a body of fixed mass m is subjected to a single force F, its acceleration a is given by F/m. A bodys mass also determines the degree to which it generates or is affected by a gravitational field and this is sometimes referred to as gravitational mass. The standard International System of Units unit of mass is the kilogram, the kilogram is 1000 grams, first defined in 1795 as one cubic decimeter of water at the melting point of ice. Then in 1889, the kilogram was redefined as the mass of the prototype kilogram. As of January 2013, there are proposals for redefining the kilogram yet again. In this context, the mass has units of eV/c2, the electronvolt and its multiples, such as the MeV, are commonly used in particle physics. The atomic mass unit is 1/12 of the mass of a carbon-12 atom, the atomic mass unit is convenient for expressing the masses of atoms and molecules. Outside the SI system, other units of mass include, the slug is an Imperial unit of mass, the pound is a unit of both mass and force, used mainly in the United States
18.
Magnetic field
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A magnetic field is the magnetic effect of electric currents and magnetic materials. The magnetic field at any point is specified by both a direction and a magnitude, as such it is represented by a vector field. The term is used for two distinct but closely related fields denoted by the symbols B and H, where H is measured in units of amperes per meter in the SI, B is measured in teslas and newtons per meter per ampere in the SI. B is most commonly defined in terms of the Lorentz force it exerts on moving electric charges, Magnetic fields can be produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. In quantum physics, the field is quantized and electromagnetic interactions result from the exchange of photons. Magnetic fields are used throughout modern technology, particularly in electrical engineering. The Earth produces its own field, which is important in navigation. Rotating magnetic fields are used in electric motors and generators. Magnetic forces give information about the carriers in a material through the Hall effect. The interaction of magnetic fields in electric devices such as transformers is studied in the discipline of magnetic circuits, noting that the resulting field lines crossed at two points he named those points poles in analogy to Earths poles. He also clearly articulated the principle that magnets always have both a north and south pole, no matter how finely one slices them, almost three centuries later, William Gilbert of Colchester replicated Petrus Peregrinus work and was the first to state explicitly that Earth is a magnet. Published in 1600, Gilberts work, De Magnete, helped to establish magnetism as a science, in 1750, John Michell stated that magnetic poles attract and repel in accordance with an inverse square law. Charles-Augustin de Coulomb experimentally verified this in 1785 and stated explicitly that the north and south poles cannot be separated, building on this force between poles, Siméon Denis Poisson created the first successful model of the magnetic field, which he presented in 1824. In this model, a magnetic H-field is produced by magnetic poles, three discoveries challenged this foundation of magnetism, though. First, in 1819, Hans Christian Ørsted discovered that an electric current generates a magnetic field encircling it, then in 1820, André-Marie Ampère showed that parallel wires having currents in the same direction attract one another. Finally, Jean-Baptiste Biot and Félix Savart discovered the Biot–Savart law in 1820, extending these experiments, Ampère published his own successful model of magnetism in 1825. This has the benefit of explaining why magnetic charge can not be isolated. Also in this work, Ampère introduced the term electrodynamics to describe the relationship between electricity and magnetism, in 1831, Michael Faraday discovered electromagnetic induction when he found that a changing magnetic field generates an encircling electric field
19.
Regolith
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Regolith is a layer of loose, heterogeneous superficial material covering solid rock. It includes dust, soil, broken rock, and other related materials and is present on Earth, the Moon, Mars, some asteroids, the term regolith combines two Greek words, rhegos, blanket, and lithos, rock. Merrill first defined the term in 1897, writing, In places this covering is made up of material originating through rock-weathering or plant growth in situ, in other instances it is of fragmental and more or less decomposed matter drifted by wind, water or ice from other sources. This entire mantle of unconsolidated material, whatever its nature or origin, biota and organic components derived from it. Regolith can vary from being essentially absent to hundreds of metres in thickness and its age can vary from instantaneous to hundreds of millions of years old. Regolith on Earth originates from weathering and biological processes, if it contains a significant proportion of biological compounds it is conventionally referred to as soil. People also call various types of earthly regolith by such names as dirt, dust, gravel, sand, Regolith is also important to engineers constructing buildings, roads and other civil works. The mechanical properties of regolith vary considerably and need to be documented if the construction is to withstand the rigors of use, Regolith may host many mineral deposits, for example mineral sands, calcrete uranium, and lateritic nickel deposits, among others. Elsewhere, understanding regolith properties, especially geochemical composition, is critical to geochemical and geophysical exploration for mineral deposits beneath it, the regolith is also an important source of construction material, including sand, gravel, crushed stone, lime, and gypsum. The regolith is the zone through which aquifers are recharged and through which aquifer discharge occurs, many aquifers, such as alluvial aquifers, occur entirely within regolith. The composition of the regolith can also strongly influence water composition through the presence of salts, Regolith covers almost the entire lunar surface, bedrock protruding only on very steep-sided crater walls and the occasional lava channel. The impact of micrometeoroids, sometimes travelling faster than 96,000 km/h and this melting and refreezing welds particles together into glassy, jagged-edged agglutinates, reminiscent of tektites found on Earth. The regolith is generally from 4 to 5 m thick in mare areas, below this true regolith is a region of blocky and fractured bedrock created by larger impacts, which is often referred to as the megaregolith. The density of regolith at the Apollo 15 landing site averages approximately 1.35 g/cm3 for the top 30 cm, and it is approximately 1. 85g/cm3 at a depth of 60 cm. The term lunar soil is used interchangeably with lunar regolith but typically refers to the finer fraction of regolith. Some have argued that the soil is not correct in reference to the Moon because soil is defined as having organic content. However, standard usage among lunar scientists is to ignore that distinction, lunar dust generally connotes even finer materials than lunar soil, the fraction which is less than 30 micrometers in diameter. The average chemical composition of regolith might be estimated from the concentration of elements in lunar soil
20.
Solar wind
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The solar wind is a stream of charged particles released from the upper atmosphere of the Sun. This plasma consists of electrons, protons and alpha particles with thermal energies between 1.5 and 10 keV. Embedded within the plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and its particles can escape the Suns gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. At a distance of more than a few radii from the sun. The flow of the wind is no longer supersonic at the termination shock. The Voyager 2 spacecraft crossed the shock more than five times between 30 August and 10 December 2007, Voyager 2 crossed the shock about a billion kilometers closer to the Sun than the 13.5 billion kilometer distance where Voyager 1 came upon the termination shock. The spacecraft moved outward through the shock into the heliosheath. Other related phenomena include the aurora, the tails of comets that always point away from the Sun. The existence of flowing outward from the Sun to the Earth was first suggested by British astronomer Richard C. In 1859, Carrington and Richard Hodgson independently made the first observation of what would later be called a solar flare, george FitzGerald later suggested that matter was being regularly accelerated away from the Sun and was reaching the Earth after several days. In 1910 British astrophysicist Arthur Eddington essentially suggested the existence of the wind, without naming it. The idea never caught on even though Eddington had also made a similar suggestion at a Royal Institution address the previous year. In the latter case, he postulated that the material consisted of electrons while in his study of Comet Morehouse he supposed them to be ions. The first person to suggest that the material consisted of both ions and electrons was Kristian Birkeland. His geomagnetic surveys showed that activity was nearly uninterrupted. In 1916, Birkeland proposed that, From a physical point of view it is most probable that solar rays are neither exclusively negative nor positive rays, in other words, the solar wind consists of both negative electrons and positive ions. Three years later in 1919, Frederick Lindemann also suggested that particles of both polarities, protons as well as electrons, come from the Sun
21.
Asteroid
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Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids and these terms have historically been applied to any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. As minor planets in the outer Solar System were discovered and found to have volatile-based surfaces that resemble those of comets, in this article, the term asteroid refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the remnants of planetesimals. The large majority of known asteroids orbit in the belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects, individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups, C-type, M-type, and S-type. These were named after and are identified with carbon-rich, metallic. The size of asteroids varies greatly, some reaching as much as 1000 km across, asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition, while asteroids are composed of mineral and rock, comets are composed of dust. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice, the difference between asteroids and meteoroids is mainly one of size, meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials, only one asteroid,4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be visible to the eye for a short time. As of March 2016, the Minor Planet Center had data on more than 1.3 million objects in the inner and outer Solar System, the United Nations declared June 30 as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, the first asteroid to be discovered, Ceres, was found in 1801 by Giuseppe Piazzi, and was originally considered to be a new planet. In the early half of the nineteenth century, the terms asteroid. Asteroid discovery methods have improved over the past two centuries. This task required that hand-drawn sky charts be prepared for all stars in the band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, the expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers
22.
Meteoroid
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A meteoroid is a small rocky or metallic body in outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects, objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars and this phenomenon is called a meteor or shooting star. A series of many meteors appearing seconds or minutes apart and appearing to originate from the fixed point in the sky is called a meteor shower. If that object withstands ablation from its passage through the atmosphere as a meteor and impacts with the ground, an estimated 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earths atmosphere each year. In 1995, Beech and Steel, writing in the Quarterly Journal of the Royal Astronomical Society, according to Rubin and Grossman, the minimum size of an asteroid is given by what can be discovered from Earth-bound telescopes, so the distinction between meteoroid and asteroid is fuzzy. Some of the smallest asteroids discovered are 2008 TS26 with H =33.2 and 2011 CQ1 with H =32.1 both with a size of 1 meter. Objects smaller than meteoroids are classified as micrometeoroids and cosmic dust, the Minor Planet Center does not use the term meteoroid. Almost all meteoroids contain extraterrestrial nickel and iron and they have three main classifications, iron, stone, and stony-iron. Some stone meteoroids contain grain-like inclusions known as chondrules and are called chondrites, stoney meteoroids without these features are called achondrites, which are typically formed from extraterrestrial igneous activity, they contain little or no extraterrestrial iron. The composition of meteoroids can be inferred as they pass through Earths atmosphere from their trajectories and their effects on radio signals also give information, especially useful for daytime meteors, which are otherwise very difficult to observe. From these trajectory measurements, meteoroids have been found to have many different orbits, some clustering in streams associated with a parent comet. Debris from meteoroid streams may eventually be scattered into other orbits, the study of meteorites also gives insights into the composition of non-ephemeral meteoroids. Most meteoroids come from the belt, having been perturbed by the gravitational influences of planets. Some meteoroids are pieces of planets or moons, such as Mars or our moon, meteoroids travel around the Sun in a variety of orbits and at various velocities. The fastest ones move at about 42 kilometers per second through space in the vicinity of Earths orbit, Earth travels at about 29.6 kilometers per second. Thus, when meteoroids meet Earths atmosphere head-on, the speed may reach about 71 kilometers per second. Meteoroids moving through Earths orbital space average about 20 km/s, on January 17,2013 at 05,21 PST, a 1 meter-sized comet from the Oort cloud entered Earth atmosphere over a wide area in California and Nevada
23.
Comet
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A comet is an icy small Solar System body that, when passing close to the Sun, warms and begins to evolve gasses, a process called outgassing. This produces an atmosphere or coma, and sometimes also a tail. These phenomena are due to the effects of radiation and the solar wind acting upon the nucleus of the comet. Comet nuclei range from a few hundred metres to tens of kilometres across and are composed of collections of ice, dust. The coma may be up to 15 times the Earths diameter, if sufficiently bright, a comet may be seen from the Earth without the aid of a telescope and may subtend an arc of 30° across the sky. Comets have been observed and recorded since ancient times by many cultures, Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun from the Oort cloud by gravitational perturbations caused by passing stars, hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition, Comets are distinguished from asteroids by the presence of an extended, gravitationally unbound atmosphere surrounding their central nucleus. This atmosphere has parts termed the coma and the tail, however, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System, the discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. As of November 2014 there are 5,253 known comets, however, this represents only a tiny fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System is estimated to be one trillion. Roughly one comet per year is visible to the eye, though many of those are faint. Particularly bright examples are called Great Comets, the word comet derives from the Old English cometa from the Latin comēta or comētēs. That, in turn, is a latinisation of the Greek κομήτης, Κομήτης was derived from κομᾶν, which was itself derived from κόμη and was used to mean the tail of a comet. The astronomical symbol for comets is ☄, consisting of a disc with three hairlike extensions. The solid, core structure of a comet is known as the nucleus, cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen gases such as carbon dioxide, carbon monoxide, methane, and ammonia. As such, they are described as dirty snowballs after Fred Whipples model
24.
X-ray spectroscopy
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X-ray spectroscopy is a gathering name for several spectroscopic techniques for characterization of materials by using x-ray excitation. When an electron from the shell of an atom is excited by the energy of a photon. When it returns to the low level, the energy which it previously gained by the excitation is emitted as a photon which has a wavelength that is characteristic for the element. Analysis of the X-ray emission spectrum produces qualitative results about the composition of the specimen. Comparison of the spectrum with the spectra of samples of known composition produces quantitative results. Atoms can be excited by a beam of charged particles such as electrons, protons or a beam of X-rays. These methods enable elements from the periodic table to be analysed, with the exception of H, He. In an energy-dispersive X-ray spectrometer, a detector measures energy of incoming photons. To maintain detector integrity and resolution it should be cooled with liquid nitrogen or by Peltier cooling, EDS is widely employed in electron microscopes and in cheaper and/or portable XRF units. In a wavelength dispersive X-ray spectrometer the single crystal diffracts the photons which are collected by a detector, without any motion there will be just one wavelength detected. By moving crystal and detector, a region of spectrum is observed. In contrast to EDS, WDS method is a method of sequential spectrum acquisition, while WDS is slower than EDS and more sensitive to positioning specimen in the spectrometer, it has superior spectral resolution and sensitivity. William Lawrence Bragg and William Henry Bragg, son and father, jointly they measured the X-ray wavelengths of many elements to high precision, using high-energy electrons as excitation source. The cathode ray tube or a tube was the method used to pass electrons through a crystal of numerous elements. They also painstakingly produced numerous diamond-ruled glass diffraction gratings for their spectrometers, the law of diffraction of a crystal is called Braggs law in their honor. Intense and wavelength-tunable X-rays are now typically generated with synchrotrons, in a material, the X-rays may suffer an energy loss compared to the incoming beam. This energy loss of the beam reflects an internal excitation of the atomic system. In the X-ray region there is sufficient energy to probe changes in the electronic state, for instance, in the ultra soft X-ray region, crystal field excitations give rise to the energy loss
25.
Gamma-ray spectrometer
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A gamma-ray spectrometer is an instrument for measuring the distribution of the intensity of gamma radiation versus the energy of each photon. The study and analysis of spectra for scientific and technical use is called gamma spectroscopy. Because the energy of each photon of EM radiation is proportional to its frequency, semi-conductor detectors, based on cooled germanium or silicon detecting elements, have been invaluable for such applications. A number of investigations have been performed to observe the spectra of the Sun and other astronomical sources. Gamma-ray spectrometers have been used for the elemental and isotopic analysis of airless bodies in the Solar System, especially the Moon. These surfaces are subjected to a bombardment of high-energy cosmic rays. Thus an orbiting instrument can in principle map the distribution of the elements for an entire planet. Examples include the mapping of 20 elements observed in the exploration of Mars, the Eros asteroid and they are usually associated with neutron detectors that can look for water and ice in the soil by measuring neutrons. Knowing what elements are at or near the surface will give detailed information about how planetary bodies have changed over time, to determine the elemental makeup of the Martian surface, the Mars experiment used a gamma-ray spectrometer and two neutron detectors. GRS instruments supply data on the distribution and abundance of chemical elements, in this case, the chemical element thorium was mapped, with higher concentrations shown in yellow/orange/red in the left-hand side image shown on the right. Some constructions of scintillation counters can be used as gamma-ray spectrometers, the gamma photon energy is discerned from the intensity of the flash of the scintillator, a number of low-energy photons produced by the single high-energy one. Spectrometers for space missions conversely tend to be of the germanium kind, when exposed to cosmic rays, chemical elements in soils and rocks emit uniquely identifiable signatures of energy in the form of gamma rays. The gamma-ray spectrometer looks at these signatures, or energies, coming from the present in the target soil. By measuring gamma rays coming from the body, it is possible to calculate the abundance of various elements. Gamma rays, emitted from the nuclei of atoms, show up as emission lines on the instruments spectrum output. While the energy represented in these emissions determines which elements are present, Spectrometers are expected to add significantly to the growing understanding of the origin and evolution of planets like Mars and the processes shaping them today and in the past. How are gamma rays and neutrons produced by cosmic rays, incoming cosmic rays—some of the highest-energy particles—collide with the nucleus of atoms in the soil. When nuclei are hit with energy, neutrons are released
26.
Charge-coupled device
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A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by shifting the signals between stages within the one at a time. CCDs move charge between capacitive bins in the device, with the shift allowing for the transfer of charge between bins, in recent years CCD has become a major technology for digital imaging. In a CCD image sensor, pixels are represented by p-doped metal-oxide-semiconductors capacitors, the charge-coupled device was invented in 1969 at AT&T Bell Labs by Willard Boyle and George E. Smith. The lab was working on bubble memory when Boyle and Smith conceived of the design of what they termed, in their notebook. The device could be used as a shift register, the essence of the design was the ability to transfer charge along the surface of a semiconductor from one storage capacitor to the next. The concept was similar in principle to the device, which was developed at Philips Research Labs during the late 1960s. The first patent on the application of CCDs to imaging was assigned to Michael Tompsett, the initial paper describing the concept listed possible uses as a memory, a delay line, and an imaging device. The first experimental device demonstrating the principle was a row of closely spaced metal squares on a silicon surface electrically accessed by wire bonds. The first working CCD made with integrated circuit technology was a simple 8-bit shift register and this device had input and output circuits and was used to demonstrate its use as a shift register and as a crude eight pixel linear imaging device. Development of the device progressed at a rapid rate, by 1971, Bell researchers led by Michael Tompsett were able to capture images with simple linear devices. Several companies, including Fairchild Semiconductor, RCA and Texas Instruments, picked up on the invention, fairchilds effort, led by ex-Bell researcher Gil Amelio, was the first with commercial devices, and by 1974 had a linear 500-element device and a 2-D100 x 100 pixel device. Steven Sasson, an engineer working for Kodak, invented the first digital still camera using a Fairchild 100 x 100 CCD in 1975. The first KH-11 KENNAN reconnaissance satellite equipped with charge-coupled device array technology for imaging was launched in December 1976, under the leadership of Kazuo Iwama, Sony also started a large development effort on CCDs involving a significant investment. Eventually, Sony managed to mass-produce CCDs for their camcorders, before this happened, Iwama died in August 1982, subsequently, a CCD chip was placed on his tombstone to acknowledge his contribution. He was also awarded the 2012 IEEE Edison Medal For pioneering contributions to imaging devices including CCD Imagers, cameras, in a CCD for capturing images, there is a photoactive region, and a transmission region made out of a shift register. An image is projected through a lens onto the capacitor array, once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbor. The last capacitor in the array dumps its charge into a charge amplifier, by repeating this process, the controlling circuit converts the entire contents of the array in the semiconductor to a sequence of voltages
27.
Laser rangefinder
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A laser rangefinder is a rangefinder which uses a laser beam to determine the distance to an object. Due to the speed of light, this technique is not appropriate for high precision sub-millimeter measurements. The pulse may be coded to reduce the chance that the rangefinder can be jammed and it is possible to use Doppler effect techniques to judge whether the object is moving towards or away from the rangefinder, and if so, how fast. The precision of the instrument is determined by the rise or fall time of the laser pulse, one that uses very sharp laser pulses and has a very fast detector can range an object to within a few millimeters. Some of the light might reflect off leaves or branches which are closer than the object, giving an early return. All these effects have to be taken into account, the distance between point A and B is given by D = c t 2 where c is the speed of light in the atmosphere and t is the amount of time for the round-trip between A and B. T = φ ω where φ is the delay made by the light traveling. Time of flight - this measures the time taken for a pulse to travel to the target. With the speed of light known, and a measurement of the time taken. Many pulses are fired sequentially and the response is most commonly used. This technique requires very accurate sub-nanosecond timing circuitry, multiple frequency phase-shift - this measures the phase shift of multiple frequencies on reflection then solves some simultaneous equations to give a final measure. Interferometry - the most accurate and most useful technique for measuring changes in distance rather than absolute distances, rangefinders provide an exact distance to targets located beyond the distance of point-blank shooting to snipers and artillery. They can also be used for military reconciliation and engineering, handheld military rangefinders operate at ranges of 2 km up to 25 km and are combined with binoculars or monoculars. When the rangefinder is equipped with a magnetic compass and inclinometer it is capable of providing magnetic azimuth, inclination. Some rangefinders can also measure a targets speed in relation to the observer, some rangefinders have cable or wireless interfaces to enable them to transfer their measurement data to other equipment like fire control computers. Some models also offer the possibility to use night vision modules. Most handheld rangefinders use standard or rechargeable batteries, the more powerful models of rangefinders measure distance up to 25 km and are normally installed either on a tripod or directly on a vehicle or gun platform. In the latter case the module is integrated with on-board thermal, night vision
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Magnetometer
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A compass is a simple example of a magnetometer, one that measures the direction of an ambient magnetic field. Magnetometers are widely used for measuring the Earths magnetic field and in geophysical surveys to detect anomalies of various types. They are also used in the military to detect submarines, consequently, some countries, such as the United States, Canada and Australia, classify the more sensitive magnetometers as military technology, and control their distribution. Magnetic fields are vector quantities characterized by strength and direction. The strength of a field is measured in units of tesla in the SI units. 10,000 gauss are equal to one tesla, measurements of the Earths magnetic field are often quoted in units of nanotesla, also called a gamma. Gaussmeters and teslameters are magnetometers that measure in units of gauss or tesla, in some contexts, magnetometer is the term used for an instrument that measures fields of less than 1 millitesla and gaussmeter is used for those measuring greater than 1 mT. There are two types of magnetometer measurement. Vector magnetometers measure the components of a magnetic field. Total field magnetometers or scalar magnetometers measure the magnitude of the magnetic field. Magnetometers used to study the Earths magnetic field may express the components of the field in terms of declination. Absolute magnetometers measure the magnitude or vector magnetic field, using an internal calibration or known physical constants of the magnetic sensor. Relative magnetometers measure magnitude or vector magnetic field relative to a fixed but uncalibrated baseline, also called variometers, relative magnetometers are used to measure variations in magnetic field. Magnetometers may also be classified by their situation or intended use, stationary magnetometers are installed to a fixed position and measurements are taken while the magnetometer is stationary. Portable or mobile magnetometers are meant to be used while in motion, laboratory magnetometers are used to measure the magnetic field of materials placed within them and are typically stationary. The performance and capabilities of magnetometers are described through their technical specifications, major specifications include Sample rate is the amount of readings given per second. The inverse is the time in seconds per reading. Sample rate is important in mobile magnetometers, the sample rate, bandwidth or bandpass characterizes how well a magnetometer tracks rapid changes in magnetic field
29.
Gravity
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Gravity, or gravitation, is a natural phenomenon by which all things with mass are brought toward one another, including planets, stars and galaxies. Since energy and mass are equivalent, all forms of energy, including light, on Earth, gravity gives weight to physical objects and causes the ocean tides. Gravity has a range, although its effects become increasingly weaker on farther objects. The most extreme example of this curvature of spacetime is a hole, from which nothing can escape once past its event horizon. More gravity results in time dilation, where time lapses more slowly at a lower gravitational potential. Gravity is the weakest of the four fundamental interactions of nature, the gravitational attraction is approximately 1038 times weaker than the strong force,1036 times weaker than the electromagnetic force and 1029 times weaker than the weak force. As a consequence, gravity has an influence on the behavior of subatomic particles. On the other hand, gravity is the dominant interaction at the macroscopic scale, for this reason, in part, pursuit of a theory of everything, the merging of the general theory of relativity and quantum mechanics into quantum gravity, has become an area of research. While the modern European thinkers are credited with development of gravitational theory, some of the earliest descriptions came from early mathematician-astronomers, such as Aryabhata, who had identified the force of gravity to explain why objects do not fall out when the Earth rotates. Later, the works of Brahmagupta referred to the presence of force, described it as an attractive force. Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and this was a major departure from Aristotles belief that heavier objects have a higher gravitational acceleration. Galileo postulated air resistance as the reason that objects with less mass may fall slower in an atmosphere, galileos work set the stage for the formulation of Newtons theory of gravity. In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. Newtons theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the position of the planet. A discrepancy in Mercurys orbit pointed out flaws in Newtons theory, the issue was resolved in 1915 by Albert Einsteins new theory of general relativity, which accounted for the small discrepancy in Mercurys orbit. The simplest way to test the equivalence principle is to drop two objects of different masses or compositions in a vacuum and see whether they hit the ground at the same time. Such experiments demonstrate that all objects fall at the rate when other forces are negligible
30.
4660 Nereus
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4660 Nereus is a small asteroid. It was discovered by Eleanor F. Helin on February 28,1982, Nereus is potentially a very important asteroid. It is an Apollo and Mars-crosser, with an orbit that frequently comes very close to Earth, indeed, because of its small size and close orbit, its delta-V for rendezvous of ~5 km/s is smaller than the Moons, which is about 6.3 km/s. Nereus makes seven approaches to Earth of less than 5 million km between 1900 and 2100, the closest will be in February 2060, at 1.2 million km. The next close approach is in December 2021, when it will be 3.9 million km away, Nereus is classified as a potentially hazardous asteroid, due to both its absolute magnitude and its minimum orbit intersection distance. The asteroid is classified as E-type, so it could be associated with aubrite meteorites. Nereus was proposed for visitation by both the private Near Earth Asteroid Prospector probe, and the Japanese sample return mission Hayabusa, however, the NEAP probe was not realized, and the Hayabusas launch was delayed by 10 months and the probe had to be redirected to 25143 Itokawa. 4660 Nereus was considered as a target of the NEAR unmanned robotic spacecraft mission. NEAR eventually launched, but visited 253 Mathilde and 433 Eros, Nereus has been imaged by radar, revealing a slightly elongated shape which would allow for stable orbits around it. Earlier optical measurements had given a diameter of about 330 ±50 meters. More recent work on the analysis of the data gives a much more detailed shape for Nereus as well as a fairly detailed terrain map of the surface. Nereus has an ellipsoidal shape with dimensions of 510 x 330 x 241 m. On the ends of its longest axis, one end appears narrower and rounder than the other, larger end, the larger end also appears to have a flatter region on one side of it. Nereus rotates about an axis perpendicular to its longest axis much like a silver spoon spinning on a table. Although the discoverer is given the opportunity to name the asteroid, Helin donated naming rights to the Planetary Society which organized a naming contest
31.
Comet Encke
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Comet Encke or Enckes Comet is a periodic comet that completes an orbit of the Sun once every 3.3 years. Like most comets, it has a low albedo, reflecting only 4. 6% of the light it receives. The diameter of the nucleus of Enckes Comet is 4.8 km, as its official designation implies, Enckes Comet was the first periodic comet discovered after Halleys Comet. It was independently observed by astronomers, the second being Caroline Herschel in 1795. Its orbit was calculated by Johann Franz Encke, who through laborious calculations was able to link observations of comets in 1786,1795,1805 and 1818 to the same object. In 1819 he published his conclusions in the journal Correspondance astronomique and it was recovered by Carl Ludwig Christian Rümker at Parramatta Observatory on 2 June 1822. Comets are in orbits that evolve over time due to perturbations. Given Enckes low orbital inclination near the ecliptic and brief orbital period of 3 years, Enckes orbit gets as close as 0.17309 AU to Earth. On 4 July 1997, Encke passed 0.19 AU from Earth, on 18 November 2013, it passed 0.02496 AU from Mercury. Close approaches to Earth usually occur every 33 years, the failed CONTOUR mission was launched to study this comet, and also Schwassmann-Wachmann 3. On April 20,2007, STEREO-A observed the tail of Comet Encke to be torn off by magnetic field disturbances caused by a coronal mass ejection. The tail grew back due to the shedding of dust. Comet Encke is believed to be the originator of several related meteor showers known as the Taurids, a shower has similarly been reported affecting Mercury. Near-Earth object 2004 TG10 may be a fragment of Encke, measurements on board the NASA satellite MESSENGER have revealed Encke may contribute to seasonal meteor showers on Mercury. The Mercury Atmospheric and Surface Composition Spectrometer instrument discovered seasonal surges of calcium since the probe began orbiting the planet in March 2011. The spikes in calcium levels are thought to originate from small dust particles hitting the planet, however, the general background of interplanetary dust in the inner Solar System cannot, by itself, account for the periodic spikes in calcium. This suggests a source of additional dust, for example. More than one theory has associated Enckes Comet with impacts of cometary material on Earth, the Tunguska event of 1908, probably caused by the impact of a cometary body, has also been postulated by Czechoslovakian astronomer Ľubor Kresák as a fragment of Comet Encke
32.
4 Vesta
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Vesta, minor-planet designation 4 Vesta, is one of the largest objects in the asteroid belt, with a mean diameter of 525 kilometres. It was discovered by the German astronomer Heinrich Wilhelm Olbers on 29 March 1807 and is named after Vesta, Vesta is the second-most-massive and second-largest body in the asteroid belt after the dwarf planet Ceres, and it contributes an estimated 9% of the mass of the asteroid belt. It is slightly larger than Pallas, though more massive. Vesta is the last remaining rocky protoplanet of the kind that formed the terrestrial planets, numerous fragments of Vesta were ejected by collisions one and two billion years ago that left two enormous craters occupying much of Vestas southern hemisphere. Debris from these events has fallen to Earth as howardite–eucrite–diogenite meteorites, Vesta is the brightest asteroid visible from Earth. Its maximum distance from the Sun is slightly greater than the distance of Ceres from the Sun. NASAs Dawn spacecraft entered orbit around Vesta on 16 July 2011 for an exploration and left orbit on 5 September 2012 en route to its final destination. Researchers continue to examine data collected by Dawn for additional insights into the formation, Heinrich Olbers discovered Pallas in 1802, the year after the discovery of Ceres. He proposed that the two objects were the remnants of a destroyed planet and these orbital intersections were located in the constellations of Cetus and Virgo. Olbers commenced his search in 1802, and on 29 March 1807 he discovered Vesta in the constellation Virgo—a coincidence, because Ceres, Pallas, and Vesta are not fragments of a larger body. Because the asteroid Juno had been discovered in 1804, this made Vesta the fourth object to be identified in the region that is now known as the asteroid belt, the discovery was announced in a letter addressed to German astronomer Johann H. Schröter dated 31 March. Gauss decided on the Roman virgin goddess of home and hearth, Vesta was the fourth asteroid to be discovered, hence the number 4 in its formal designation. The name Vesta, or national variants thereof, is in use with two exceptions, Greece and China. In Greek, the name adopted was the Hellenic equivalent of Vesta, Hestia, in English, in Chinese, Vesta is called the hearth-god star, 灶神星 zàoshénxīng, in contrast to the goddess Vesta, who goes by her Latin name. Upon its discovery, Vesta was, like Ceres, Pallas, the symbol representing the altar of Vesta with its sacred fire and was designed by Gauss. In Gausss conception, this was drawn, in its modern form, after the discovery of Vesta, no further objects were discovered for 38 years, and the Solar System was thought to have eleven planets. However, in 1845, new asteroids started being discovered at a rapid pace and it soon became clear that it would be impractical to continue inventing new planetary symbols indefinitely, and some of the existing ones proved difficult to draw quickly. That year, the problem was addressed by Benjamin Apthorp Gould, who suggested numbering asteroids in their order of discovery, thus, the fourth asteroid, Vesta, acquired the generic symbol ④
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S-type asteroid
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S-type asteroids, or silicaceous asteroids, are of a stony composition, hence the name. Approximately 17% of asteroids are of type, making it the second most common after the C-type. S-types are moderately bright and consist mainly of iron- and magnesium-silicates and they are dominant in the inner asteroid belt within 2.2 AU, common in the central belt within about 3 AU, but become rare farther out. The largest is 15 Eunomia, with the next largest members by diameter being 3 Juno,29 Amphitrite,532 Herculina and 7 Iris. Their spectrum has a steep slope at wavelengths shorter than 0.7 µm. The 1 µm absorption is indicative of the presence of silicates, often there is also a broad but shallow absorption feature centered near 0.63 µm. The composition of asteroids is similar to a variety of stony meteorites which share similar spectral characteristics. This whole S assemblage of asteroids is spectrally quite distinct from the carbonaceous C-group, Asteroid spectral types L-type asteroid K-type asteroid X-type asteroid Bus, S. J. Binzel, R. P. Phase II of the Small Main-belt Asteroid Spectroscopy Survey, A feature-based taxonomy
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Gamma-ray burst
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In gamma-ray astronomy, Gamma-ray bursts are extremely energetic explosions that have been observed in distant galaxies. They are the brightest electromagnetic events known to occur in the universe, Bursts can last from ten milliseconds to several hours. After an initial flash of gamma rays, a longer-lived afterglow is usually emitted at longer wavelengths, a subclass of GRBs appear to originate from a different process, the merger of binary neutron stars. The sources of most GRBs are billions of years away from Earth. All observed GRBs have originated from outside the Milky Way galaxy, although a class of phenomena. It has been hypothesized that a gamma-ray burst in the Milky Way, pointing directly towards the Earth, GRBs were first detected in 1967 by the Vela satellites, which had been designed to detect covert nuclear weapons tests. Following their discovery, hundreds of models were proposed to explain these bursts. These discoveries, and subsequent studies of the galaxies and supernovae associated with the bursts, clarified the distance and luminosity of GRBs, definitively placing them in distant galaxies. Gamma-ray bursts were first observed in the late 1960s by the U. S. Vela satellites, the United States suspected that the USSR might attempt to conduct secret nuclear tests after signing the Nuclear Test Ban Treaty in 1963. On July 2,1967, at 14,19 UTC, uncertain what had happened but not considering the matter particularly urgent, the team at the Los Alamos Scientific Laboratory, led by Ray Klebesadel, filed the data away for investigation. As additional Vela satellites were launched with better instruments, the Los Alamos team continued to find inexplicable gamma-ray bursts in their data, the discovery was declassified and published in 1973. Most early theories of gamma-ray bursts posited nearby sources within the Milky Way Galaxy, if the sources were from within our own galaxy they would be strongly concentrated in or near the galactic plane. The absence of any pattern in the case of GRBs provided strong evidence that gamma-ray bursts must come from beyond the Milky Way. However, some Milky Way models are consistent with an isotropic distribution. For decades after the discovery of GRBs, astronomers searched for a counterpart at other wavelengths, astronomers considered many distinct classes of objects, including white dwarfs, pulsars, supernovae, globular clusters, quasars, Seyfert galaxies, and BL Lac objects. This suggested an origin of either very faint stars or extremely distant galaxies and this fading emission would be called the afterglow. Early searches for this afterglow were unsuccessful, largely because it is difficult to observe a bursts position at longer wavelengths immediately after the initial burst, the William Herschel Telescope identified a fading optical counterpart 20 hours after the burst. Once the GRB faded, deep imaging was able to identify a faint, distant host galaxy at the location of the GRB as pinpointed by the optical afterglow, because of the very faint luminosity of this galaxy, its exact distance was not measured for several years
35.
Perihelion and aphelion
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The perihelion is the point in the orbit of a celestial body where it is nearest to its orbital focus, generally a star. It is the opposite of aphelion, which is the point in the orbit where the body is farthest from its focus. The word perihelion stems from the Ancient Greek words peri, meaning around or surrounding, aphelion derives from the preposition apo, meaning away, off, apart. According to Keplers first law of motion, all planets, comets. Hence, a body has a closest and a farthest point from its parent object, that is, a perihelion. Each extreme is known as an apsis, orbital eccentricity measures the flatness of the orbit. Because of the distance at aphelion, only 93. 55% of the solar radiation from the Sun falls on a given area of land as does at perihelion. However, this fluctuation does not account for the seasons, as it is summer in the northern hemisphere when it is winter in the southern hemisphere and vice versa. Instead, seasons result from the tilt of Earths axis, which is 23.4 degrees away from perpendicular to the plane of Earths orbit around the sun. Winter falls on the hemisphere where sunlight strikes least directly, and summer falls where sunlight strikes most directly, in the northern hemisphere, summer occurs at the same time as aphelion. Despite this, there are larger land masses in the northern hemisphere, consequently, summers are 2.3 °C warmer in the northern hemisphere than in the southern hemisphere under similar conditions. Apsis Ellipse Solstice Dates and times of Earths perihelion and aphelion, 2000–2025 from the United States Naval Observatory
36.
Astronomical unit
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The astronomical unit is a unit of length, roughly the distance from Earth to the Sun. However, that varies as Earth orbits the Sun, from a maximum to a minimum. Originally conceived as the average of Earths aphelion and perihelion, it is now defined as exactly 149597870700 metres, the astronomical unit is used primarily as a convenient yardstick for measuring distances within the Solar System or around other stars. However, it is also a component in the definition of another unit of astronomical length. A variety of symbols and abbreviations have been in use for the astronomical unit. In a 1976 resolution, the International Astronomical Union used the symbol A for the astronomical unit, in 2006, the International Bureau of Weights and Measures recommended ua as the symbol for the unit. In 2012, the IAU, noting that various symbols are presently in use for the astronomical unit, in the 2014 revision of the SI Brochure, the BIPM used the unit symbol au. In ISO 80000-3, the symbol of the unit is ua. Earths orbit around the Sun is an ellipse, the semi-major axis of this ellipse is defined to be half of the straight line segment that joins the aphelion and perihelion. The centre of the sun lies on this line segment. In addition, it mapped out exactly the largest straight-line distance that Earth traverses over the course of a year, knowing Earths shift and a stars shift enabled the stars distance to be calculated. But all measurements are subject to some degree of error or uncertainty, improvements in precision have always been a key to improving astronomical understanding. Improving measurements were continually checked and cross-checked by means of our understanding of the laws of celestial mechanics, the expected positions and distances of objects at an established time are calculated from these laws, and assembled into a collection of data called an ephemeris. NASAs Jet Propulsion Laboratory provides one of several ephemeris computation services, in 1976, in order to establish a yet more precise measure for the astronomical unit, the IAU formally adopted a new definition. Equivalently, by definition, one AU is the radius of an unperturbed circular Newtonian orbit about the sun of a particle having infinitesimal mass. As with all measurements, these rely on measuring the time taken for photons to be reflected from an object. However, for precision the calculations require adjustment for such as the motions of the probe. In addition, the measurement of the time itself must be translated to a scale that accounts for relativistic time dilation
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Gravity assist
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Gravity assistance can be used to accelerate a spacecraft, that is, to increase or decrease its speed or redirect its path. The assist is provided by the motion of the body as it pulls on the spacecraft. It was used by interplanetary probes from Mariner 10 onwards, including the two Voyager probes notable flybys of Jupiter and Saturn, a gravity assist around a planet changes a spacecrafts velocity by entering and leaving the gravitational field of a planet. The spacecrafts speed increases as it approaches the planet and decreases while escaping its gravitational pull, because the planet orbits the sun, the spacecraft is affected by this motion during the maneuver. To increase speed, the flies with the movement of the planet, to decrease speed. The sum of the energies of both bodies remains constant. A slingshot maneuver can therefore be used to change the spaceships trajectory, a close terrestrial analogy is provided by a tennis ball bouncing off the front of a moving train. Imagine standing on a platform, and throwing a ball at 30 km/h toward a train approaching at 50 km/h. The driver of the sees the ball approaching at 80 km/h. Because of the motion, however, that departure is at 130 km/h relative to the train platform. Translating this analogy into space, in the reference frame. After the slingshot occurs and the leaves the planet, it will still have a velocity of v. In the Sun reference frame, the planet has a velocity of v, and by using the Pythagorean Theorem. After the spaceship leaves the planet, it will have a velocity of v + v = 2v and this example is also one of many trajectories and gained speeds the spaceship can have. The linear momentum gained by the spaceship is equal in magnitude to that lost by the planet, so the spacecraft gains velocity, however, the planets enormous mass compared to the spacecraft makes the resulting change in its speed negligibly small. These effects on the planet are so slight that they can be ignored in the calculation, realistic portrayals of encounters in space require the consideration of three dimensions. The same principles apply, only adding the planets velocity to that of the spacecraft requires vector addition, due to the reversibility of orbits, gravitational slingshots can also be used to reduce the speed of a spacecraft. Both Mariner 10 and MESSENGER performed this maneuver to reach Mercury, if even more speed is needed than available from gravity assist alone, the most economical way to utilize a rocket burn is to do it near the periapsis
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Orbital inclination
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Orbital inclination measures the tilt of an objects orbit around a celestial body. It is expressed as the angle between a plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth directly above the equator, the plane of the orbit is the same as the Earths equatorial plane. The general case is that the orbit is tilted, it spends half an orbit over the northern hemisphere. If the orbit swung between 20° north latitude and 20° south latitude, then its orbital inclination would be 20°, the inclination is one of the six orbital elements describing the shape and orientation of a celestial orbit. It is the angle between the plane and the plane of reference, normally stated in degrees. For a satellite orbiting a planet, the plane of reference is usually the plane containing the planets equator, for planets in the Solar System, the plane of reference is usually the ecliptic, the plane in which the Earth orbits the Sun. This reference plane is most practical for Earth-based observers, therefore, Earths inclination is, by definition, zero. Inclination could instead be measured with respect to another plane, such as the Suns equator or the invariable plane, the inclination of orbits of natural or artificial satellites is measured relative to the equatorial plane of the body they orbit, if they orbit sufficiently closely. The equatorial plane is the perpendicular to the axis of rotation of the central body. An inclination of 30° could also be described using an angle of 150°, the convention is that the normal orbit is prograde, an orbit in the same direction as the planet rotates. Inclinations greater than 90° describe retrograde orbits, thus, An inclination of 0° means the orbiting body has a prograde orbit in the planets equatorial plane. An inclination greater than 0° and less than 90° also describe prograde orbits, an inclination of 63. 4° is often called a critical inclination, when describing artificial satellites orbiting the Earth, because they have zero apogee drift. An inclination of exactly 90° is an orbit, in which the spacecraft passes over the north and south poles of the planet. An inclination greater than 90° and less than 180° is a retrograde orbit, an inclination of exactly 180° is a retrograde equatorial orbit. For gas giants, the orbits of moons tend to be aligned with the giant planets equator, the inclination of exoplanets or members of multiple stars is the angle of the plane of the orbit relative to the plane perpendicular to the line-of-sight from Earth to the object. An inclination of 0° is an orbit, meaning the plane of its orbit is parallel to the sky. An inclination of 90° is an orbit, meaning the plane of its orbit is perpendicular to the sky
39.
Rocket engine
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A rocket engine is a type of jet engine that uses only stored rocket propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines, obtaining thrust in accordance with Newtons third law, most rocket engines are internal combustion engines, although non-combusting forms also exist. Vehicles propelled by rocket engines are commonly called rockets, since they need no external material to form their jet, rocket engines can perform in a vacuum and thus can be used to propel spacecraft and ballistic missiles. Compared to other types of jet engines, rocket engines have the highest thrust, are by far the lightest, the ideal exhaust is hydrogen, the lightest of all gases, but chemical rockets produce a mix of heavier species, reducing the exhaust velocity. Rocket engines become more efficient at high velocities, since they do not require an atmosphere, they are well suited for uses at very high altitude and in space. Here, rocket is used as an abbreviation for rocket engine, chemical rockets are powered by exothermic chemical reactions of the propellant. Thermal rockets use a propellant, heated by a power source such as electric or nuclear power. Solid-fuel rockets are chemical rockets which use propellant in a solid state, liquid-propellant rockets use one or more liquid propellants fed from tanks. Hybrid rockets use a propellant in the combustion chamber, to which a second liquid or gas oxidiser or propellant is added to permit combustion. Monopropellant rockets use a single propellant decomposed by a catalyst, the most common monopropellants are hydrazine and hydrogen peroxide. Rocket engines produce thrust by the expulsion of an exhaust fluid which has accelerated to a high speed through a propelling nozzle. The fluid is usually a gas created by high pressure combustion of solid or liquid propellants, consisting of fuel and oxidiser components, within a combustion chamber. The nozzle uses the energy released by expansion of the gas to accelerate the exhaust to very high speed. An alternative to combustion is the rocket, which uses water pressurised by compressed air, carbon dioxide, nitrogen, or manual pumping. Chemical rocket propellants are most commonly used, which undergo exothermic chemical reactions which produce hot gas which is used by a rocket for propulsive purposes. Alternatively, a chemically inert reaction mass can be heated using a power source via a heat exchanger. Solid rocket propellants are prepared as a mixture of fuel and oxidising components called grain, liquid-fuelled rockets force separate fuel and oxidiser components into the combustion chamber, where they mix and burn. Hybrid rocket engines use a combination of solid and liquid or gaseous propellants, both liquid and hybrid rockets use injectors to introduce the propellant into the chamber
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Infrared
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It extends from the nominal red edge of the visible spectrum at 700 nanometers, to 1000000 nm. Most of the radiation emitted by objects near room temperature is infrared. Like all EMR, IR carries radiant energy, and behaves both like a wave and like its quantum particle, the photon, slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has an effect on Earths climate. Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements and it excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines absorption and transmission of photons in the infrared range, Infrared radiation is used in industrial, scientific, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected, Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, and to detect overheating of electrical apparatuses. Thermal-infrared imaging is used extensively for military and civilian purposes, military applications include target acquisition, surveillance, night vision, homing, and tracking. Humans at normal body temperature radiate chiefly at wavelengths around 10 μm, Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 mm. This range of wavelengths corresponds to a range of approximately 430 THz down to 300 GHz. Below infrared is the portion of the electromagnetic spectrum. Sunlight, at a temperature of 5,780 kelvins, is composed of near thermal-spectrum radiation that is slightly more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level, of this energy,527 watts is infrared radiation,445 watts is visible light, and 32 watts is ultraviolet radiation. Nearly all the radiation in sunlight is near infrared, shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, almost all thermal radiation consists of infrared in mid-infrared region, much longer than in sunlight. Of these natural thermal radiation processes only lightning and natural fires are hot enough to produce much visible energy, thermal infrared radiation also has a maximum emission wavelength, which is inversely proportional to the absolute temperature of object, in accordance with Wiens displacement law. Therefore, the band is often subdivided into smaller sections. Due to the nature of the blackbody radiation curves, typical hot objects, such as exhaust pipes, the three regions are used for observation of different temperature ranges, and hence different environments in space
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