1.
Viking (satellite)
–
It was launched on an Ariane 1 rocket as a piggyback payload together with the French satellite SPOT1, on February 22,1986. Operations ended on May 12,1987, Viking was used to explore plasma processes in the magnetosphere and the ionosphere. Space was limited underneath the SPOT1 satellite, and Viking had to be quite sturdy in order to withstand the stress of launch, the basic shape of the Swedish satellite was a flat octagonal disc,0.5 metres thick and 1.9 metres across. The mechanical interface of the payload adapter from the Ariane rocket was duplicated on top of Viking and this enabled it to be added to the launch with a minimum of redesign of the SPOT satellite. After SPOT had been released, Viking fired its own engine and was sent into its proper polar orbit. Once in orbit,4 wire segments of 40 metre length each were spooled out in a direction from the edge of the spinning satellite disc. Also,2 stiff rods of 4 metre length were extended in the axial direction, a sensor pod was stationed at the end of each of these, forming three orthogonal pairs. Together they could measure the field of the earth in all three dimensions. Stiff booms were extended for other types of sensors and antennas. The mission produced an amount of extremely useful scientific data. Since then, many scientific articles have been written using this important data set. After the scientific mission ended, both Viking and the stage of the rocket used to launch the satellite became derelict objects that would continue to orbit Earth for many years. As of September 2013, both remain in orbit. Viking information at NSSDC Master Catalog
2.
Jet Propulsion Laboratory
–
The Jet Propulsion Laboratory is a federally funded research and development center and NASA field center in La Cañada Flintridge, California and Pasadena, California, United States. The JPL is managed by the nearby California Institute of Technology for NASA, the laboratorys primary function is the construction and operation of planetary robotic spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASAs Deep Space Network and they are also responsible for managing the JPL Small-Body Database, and provides physical data and lists of publications for all known small Solar System bodies. The JPLs Space Flight Operations Facility and Twenty-Five-Foot Space Simulator are designated National Historic Landmarks, JPL traces its beginnings to 1936 in the Guggenheim Aeronautical Laboratory at the California Institute of Technology when the first set of rocket experiments were carried out in the Arroyo Seco. Malinas thesis advisor was engineer/aerodynamicist Theodore von Kármán, who arranged for U. S. Army financial support for this GALCIT Rocket Project in 1939. In 1941, Malina, Parsons, Forman, Martin Summerfield, in 1943, von Kármán, Malina, Parsons, and Forman established the Aerojet Corporation to manufacture JATO motors. The project took on the name Jet Propulsion Laboratory in November 1943, during JPLs Army years, the laboratory developed two deployed weapon systems, the MGM-5 Corporal and MGM-29 Sergeant intermediate range ballistic missiles. These missiles were the first US ballistic missiles developed at JPL and it also developed a number of other weapons system prototypes, such as the Loki anti-aircraft missile system, and the forerunner of the Aerobee sounding rocket. At various times, it carried out testing at the White Sands Proving Ground, Edwards Air Force Base. A lunar lander was developed in 1938-39 which influenced design of the Apollo Lunar Module in the 1960s. The team lost that proposal to Project Vanguard, and instead embarked on a project to demonstrate ablative re-entry technology using a Jupiter-C rocket. They carried out three successful flights in 1956 and 1957. Using a spare Juno I, the two organizations then launched the United States first satellite, Explorer 1, on February 1,1958, JPL was transferred to NASA in December 1958, becoming the agencys primary planetary spacecraft center. JPL engineers designed and operated Ranger and Surveyor missions to the Moon that prepared the way for Apollo, JPL also led the way in interplanetary exploration with the Mariner missions to Venus, Mars, and Mercury. In 1998, JPL opened the Near-Earth Object Program Office for NASA, as of 2013, it has found 95% of asteroids that are a kilometer or more in diameter that cross Earths orbit. JPL was early to employ women mathematicians, in the 1940s and 1950s, using mechanical calculators, women in an all-female computations group performed trajectory calculations. In 1961, JPL hired Dana Ulery as their first woman engineer to work alongside male engineers as part of the Ranger and Mariner mission tracking teams, when founded, JPLs site was a rocky flood-plain just outside the city limits of Pasadena. Almost all of the 177 acres of the U. S, the city of La Cañada Flintridge, California was incorporated in 1976, well after JPL attained international recognition with a Pasadena address
3.
Martin Marietta
–
The Martin Marietta Corporation was an American company founded in 1961 through the merger of Glenn L. Martin Company and American Marietta Corporation. The combined company became a leader in chemicals, aerospace, in 1995, it merged with Lockheed Corporation to form Lockheed Martin. Martin Marietta formed in 1961 by the merger of the Glenn L. Martin Company, Martin, based in Baltimore, was primarily an aerospace concern with a recent focus on missiles, namely its Titan program. American-Marietta was headquartered in Chicago and produced paints, dyes, metallurgical products, construction materials, in 1982, Martin Marietta was subject to a hostile takeover bid by the Bendix Corporation, headed by William Agee. Bendix bought the majority of Martin Marietta shares and in effect owned the company, however, Martin Mariettas management used the short time separating ownership and control to sell non-core businesses and launch its own hostile takeover of Bendix. Thomas G. Pownall, CEO of Martin Marietta, was successful,1961, Martin Marietta formed by merger of the Glenn L. Martin Marietta Corp. g
4.
United States
–
Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean. The U. S. territories are scattered about the Pacific Ocean, the geography, climate and wildlife of the country are extremely diverse. At 3.8 million square miles and with over 324 million people, the United States is the worlds third- or fourth-largest country by area, third-largest by land area. It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15,000 years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast. Numerous disputes between Great Britain and the following the Seven Years War led to the American Revolution. On July 4,1776, during the course of the American Revolutionary War, the war ended in 1783 with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power. The current constitution was adopted in 1788, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in 1791 and designed to guarantee many fundamental civil liberties. During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean. The Spanish–American War and World War I confirmed the status as a global military power. The end of the Cold War and the dissolution of the Soviet Union in 1991 left the United States as the sole superpower. The U. S. is a member of the United Nations, World Bank, International Monetary Fund, Organization of American States. The United States is a developed country, with the worlds largest economy by nominal GDP. It ranks highly in several measures of performance, including average wage, human development, per capita GDP. While the U. S. economy is considered post-industrial, characterized by the dominance of services and knowledge economy, the United States is a prominent political and cultural force internationally, and a leader in scientific research and technological innovations. In 1507, the German cartographer Martin Waldseemüller produced a map on which he named the lands of the Western Hemisphere America after the Italian explorer and cartographer Amerigo Vespucci
5.
NASA
–
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
6.
Photovoltaic system
–
A photovoltaic system, also PV system or solar power system, is a power system designed to supply usable solar power by means of photovoltaics. It may also use a tracking system to improve the systems overall performance and include an integrated battery solution. Strictly speaking, a solar array only encompasses the ensemble of solar panels, the part of the PV system. Moreover, PV systems convert light directly into electricity and shouldnt be confused with other technologies, such as concentrated solar power or solar thermal, used for heating and cooling. PV systems range from small, rooftop-mounted or building-integrated systems with capacities from a few to tens of kilowatts. Nowadays, most PV systems are grid-connected, while off-grid or stand-alone systems only account for a portion of the market. A rooftop system recoups the energy for its manufacturing and installation within 0.7 to 2 years. Due to the growth of photovoltaics, prices for PV systems have rapidly declined in recent years. However, they vary by market and the size of the system, a photovoltaic system converts the suns radiation into usable electricity. It comprises the solar array and the balance of system components, other distinctions may include, systems with microinverters vs. central inverter, systems using crystalline silicon vs. thin-film technology, and systems with modules from Chinese vs. About 99 percent of all European and 90 percent of all U. S. solar power systems are connected to the grid, while off-grid systems are somewhat more common in Australia. PV systems rarely use battery storage and this may change soon, as government incentives for distributed energy storage are being implemented and investments in storage solutions are gradually becoming economically viable for small systems. A solar array of a typical residential PV system is rack-mounted on the roof, rather than integrated into the roof or facade of the building, utility-scale solar power stations are ground-mounted, with fixed tilted solar panels rather than using expensive tracking devices. Crystalline silicon is the predominant material used in 90 percent of worldwide produced solar modules, about 70 percent of all solar cells and modules are produced in China and Taiwan, leaving only 5 percent to European and US-manufacturers. S. Which are less opposed to ground-mounted solar farms and cost-effectiveness is more emphasized by investors, driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics is declining continuously. There are several million PV systems distributed all over the world, mostly in Europe, in exceptionally irradiated locations, or when thin-film technology is used, the so-called energy payback time decreases to one year or less. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have greatly supported installations of PV systems in many countries. As of 2015, the fast-growing global PV market is approaching the 200 GW mark – about 40 times the installed capacity of 2006
7.
Radioisotope thermoelectric generator
–
This generator has no moving parts. RTGs have been used as sources in satellites, space probes. Safe use of RTGs requires containment of the radioisotopes long after the life of the unit. The RTG was invented in 1954 by Mound Laboratories scientists Ken Jordan and they were inducted into the National Inventors Hall of Fame in 2013. RTGs were developed in the US during the late 1950s by Mound Laboratories in Miamisburg, the project was led by Dr. Bertram C. The first RTG launched into space by the United States was SNAP 3B in 1961 powered by 96 grams of plutonium-238 metal, one of the first terrestrial uses of RTGs was in 1966 by the US Navy at uninhabited Fairway Rock in Alaska. RTGs were used at that site until 1995, a common RTG application is spacecraft power supply. Systems for Nuclear Auxiliary Power units were used for probes that traveled far from the Sun rendering solar panels impractical. As such, they were used with Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, Galileo, Ulysses, Cassini, New Horizons and the Mars Science Laboratory. RTGs were used to power the two Viking landers and for the scientific experiments left on the Moon by the crews of Apollo 12 through 17. Because the Apollo 13 moon landing was aborted, its RTG rests in the South Pacific Ocean, RTGs were also used for the Nimbus, Transit and LES satellites. By comparison, only a few vehicles have been launched using full-fledged nuclear reactors, the Soviet RORSAT series. In addition to spacecraft, the Soviet Union constructed many unmanned lighthouses, powered by strontium-90, they are very reliable and provide a steady source of power. In one instance, the compartments were opened by a thief. In another case, three woodsmen in Tsalendzhikha Region, Georgia came across two ceramic RTG heat sources that had stripped of their shielding. Two of the three were hospitalized with severe radiation burns after carrying the sources on their backs. The units were eventually recovered and isolated, there are approximately 1,000 such RTGs in Russia. All of them have long exhausted their 10-year engineered life spans and they are likely no longer functional, and may be in need of dismantling
8.
Viking 1
–
Viking 1 was the first of two spacecraft sent to Mars as part of NASAs Viking program. On July 20,1976, it became the first spacecraft to land successfully on Mars, Viking 1 held the record for the longest Mars surface mission of 2307 days or 2245 sols until that record was broken by Opportunity on May 19,2010. Following launch using a Titan/Centaur launch vehicle on August 20,1975, and a 10-month cruise to Mars, the orbiter began returning global images of Mars about 5 days before orbit insertion. The Viking 1 Orbiter was inserted into Mars orbit on June 19,1976, landing on Mars was planned for July 4,1976, the United States Bicentennial, but imaging of the primary landing site showed it was too rough for a safe landing. The landing was delayed until a site was found, and took place instead on July 20. The lander separated from the orbiter at 08,51 UTC and it was the first attempt by the United States at landing on Mars. The instruments of the orbiter consisted of two cameras for imaging, an infrared spectrometer for water vapor mapping and infrared radiometers for thermal mapping. The orbiter primary mission ended at the beginning of solar conjunction on November 5,1976, the extended mission commenced on December 14,1976, after solar conjunction. Operations included close approaches to Phobos in February 1977, the periapsis was reduced to 300 km on March 11,1977. Operations were terminated on August 17,1980, after 1485 orbits, a 2009 analysis concluded that, while the possibility that Viking 1 had impacted mars could not be ruled out, it was most likely still in orbit. The lander and its aeroshell separated from the orbiter on July 20 at 08,51 UTC, at the time of separation, the lander was orbiting at about 5 kilometres per second. The aeroshells retrorockets fired to begin the lander de-orbit maneuver, after a few hours at about 300 kilometres altitude, the lander was reoriented for atmospheric entry. The aeroshell with its heat shield slowed the craft as it plunged through the atmosphere. During this time, entry science experiments were performed by using a retarding potential analyzer, a spectrometer, as well as pressure, temperature. At 6 km altitude, traveling at about 250 metres per second, seven seconds later the aeroshell was jettisoned, and 8 seconds after that the three lander legs were extended. In 45 seconds the parachute had slowed the lander to 60 metres per second, at 1.5 km altitude, retrorockets on the lander itself were ignited and,40 seconds later at about 2.4 m/s, the lander arrived on Mars with a relatively light jolt. The legs had honeycomb aluminum shock absorbers to soften the landing, the landing rockets used an 18-nozzle design to spread the hydrogen and nitrogen exhaust over a large area. NASA calculated that this approach would mean that the surface would not be heated by more than one 1°C, since most of Vikings experiments focused on the surface material a more straightforward design would not have served
9.
Viking 2
–
The Viking 2 mission was part of the American Viking program to Mars, and consisted of an orbiter and a lander essentially identical to that of the Viking 1 mission. The Viking 2 lander operated on the surface for 1316 days, or 1281 sols, the orbiter worked until July 25,1978, returning almost 16,000 images in 706 orbits around Mars. The craft was launched on September 9,1975, following launch using a Titan/Centaur launch vehicle and a 333-day cruise to Mars, the Viking 2 Orbiter began returning global images of Mars prior to orbit insertion. Imaging of candidate sites was begun and the site was selected based on these pictures. The lander separated from the orbiter on September 3,1976 at 22,37,50 UT, the orbit inclination was raised to 75 degrees on 30 September 1976. The orbiter primary mission ended at the beginning of solar conjunction on October 5,1976, the extended mission commenced on 14 December 1976 after solar conjunction. On 20 December 1976 the periapsis was lowered to 778 km, operations included close approaches to Deimos in October 1977 and the periapsis was lowered to 300 km and the period changed to 24 hours on 23 October 1977. The orbiter developed a leak in its system that vented its attitude control gas. It was placed in a 302 ×33,176 km orbit, the lander and its aeroshell separated from the orbiter on 3 September 19,39,59 UT. At the time of separation, the lander was orbiting at about 4 km/s, after separation, rockets fired to begin lander deorbit. After a few hours, at about 300 km attitude, the lander was reoriented for entry, the aeroshell with its ablative heat shield slowed the craft as it plunged through the atmosphere. Approximately 22 kg of propellants were left at landing, due to radar misidentification of a rock or highly reflective surface, the thrusters fired an extra time 0.4 second before landing, cracking the surface and raising dust. The lander settled down with one leg on a rock, tilted at 8.2 degrees, the cameras began taking images immediately after landing. The Viking 2 lander was powered by generators and operated on the surface until April 11,1980. The soil resembled those produced from the weathering of basaltic lavas, the tested soil contained abundant silicon and iron, along with significant amounts of magnesium, aluminum, sulfur, calcium, and titanium. Trace elements, strontium and yttrium, were detected, the amount of potassium was one fifth of the average for the Earths crust. Some chemicals in the soil contained sulfur and chlorine that were like those remaining after the evaporation of sea water, Sulfur was more concentrated in the crust on top of the soil than in the bulk soil beneath. The Sulfur may be present as sulfates of sodium, magnesium, calcium, a sulfide of iron is also possible
10.
Space probe
–
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
11.
Mars
–
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is referred to as the Red Planet because the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet, Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan, there are ongoing investigations assessing the past habitability potential of Mars, as well as the possibility of extant life. Future astrobiology missions are planned, including the Mars 2020 and ExoMars rovers, liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is about 6⁄1000 that of the Earths, except at the lowest elevations for short periods. The two polar ice caps appear to be largely of water. The volume of ice in the south polar ice cap, if melted. On November 22,2016, NASA reported finding a large amount of ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior, Mars can easily be seen from Earth with the naked eye, as can its reddish coloring. Its apparent magnitude reaches −2.91, which is surpassed only by Jupiter, Venus, the Moon, optical ground-based telescopes are typically limited to resolving features about 300 kilometers across when Earth and Mars are closest because of Earths atmosphere. Mars is approximately half the diameter of Earth with an area only slightly less than the total area of Earths dry land. Mars is less dense than Earth, having about 15% of Earths volume and 11% of Earths mass, the red-orange appearance of the Martian surface is caused by iron oxide, or rust. It can look like butterscotch, other common colors include golden, brown, tan. Like Earth, Mars has differentiated into a metallic core overlaid by less dense materials. Current models of its interior imply a core with a radius of about 1,794 ±65 kilometers, consisting primarily of iron and this iron sulfide core is thought to be twice as rich in lighter elements than Earths. The core is surrounded by a mantle that formed many of the tectonic and volcanic features on the planet
12.
Spacecraft
–
A spacecraft is a vehicle, or machine designed to fly in outer space. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, space colonization, planetary exploration, on a sub-orbital spaceflight, a spacecraft enters space and then returns to the surface, without having gone into an orbit. For orbital spaceflights, spacecraft enter closed orbits around the Earth or around other celestial bodies, robotic spacecraft used to support scientific research are space probes. Robotic spacecraft that remain in orbit around a body are artificial satellites. Only a handful of interstellar probes, such as Pioneer 10 and 11, Voyager 1 and 2, orbital spacecraft may be recoverable or not. By method of reentry to Earth they may be divided in non-winged space capsules, Sputnik 1 was the first artificial satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957, the launch ushered in new political, military, technological, and scientific developments, while the Sputnik launch was a single event, it marked the start of the Space Age. Apart from its value as a technological first, Sputnik 1 also helped to identify the upper atmospheric layers density and it also provided data on radio-signal distribution in the ionosphere. Pressurized nitrogen in the satellites false body provided the first opportunity for meteoroid detection, Sputnik 1 was launched during the International Geophysical Year from Site No. 1/5, at the 5th Tyuratam range, in Kazakh SSR. The satellite travelled at 29,000 kilometers per hour, taking 96.2 minutes to complete an orbit and this altitude is called the Kármán line. In particular, in the 1940s there were several test launches of the V-2 rocket, as of 2016, only three nations have flown manned spacecraft, USSR/Russia, USA, and China. The first manned spacecraft was Vostok 1, which carried Soviet cosmonaut Yuri Gagarin into space in 1961, there were five other manned missions which used a Vostok spacecraft. The second manned spacecraft was named Freedom 7, and it performed a sub-orbital spaceflight in 1961 carrying American astronaut Alan Shepard to an altitude of just over 187 kilometers, there were five other manned missions using Mercury spacecraft. Other Soviet manned spacecraft include the Voskhod, Soyuz, flown unmanned as Zond/L1, L3, TKS, China developed, but did not fly Shuguang, and is currently using Shenzhou. Except for the shuttle, all of the recoverable manned orbital spacecraft were space capsules. Manned space capsules The International Space Station, manned since November 2000, is a joint venture between Russia, the United States, Canada and several other countries, some reusable vehicles have been designed only for manned spaceflight, and these are often called spaceplanes. The first example of such was the North American X-15 spaceplane, the first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19,1963. The first partially reusable spacecraft, a winged non-capsule, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarins flight
13.
Orbit
–
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet about a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating path around a body, to a close approximation, planets and satellites follow elliptical orbits, with the central mass being orbited at a focal point of the ellipse, as described by Keplers laws of planetary motion. For ease of calculation, in most situations orbital motion is adequately approximated by Newtonian Mechanics, historically, the apparent motions of the planets were described by European and Arabic philosophers using the idea of celestial spheres. This model posited the existence of perfect moving spheres or rings to which the stars and it assumed the heavens were fixed apart from the motion of the spheres, and was developed without any understanding of gravity. After the planets motions were accurately measured, theoretical mechanisms such as deferent. Originally geocentric it was modified by Copernicus to place the sun at the centre to help simplify the model, the model was further challenged during the 16th century, as comets were observed traversing the spheres. The basis for the understanding of orbits was first formulated by Johannes Kepler whose results are summarised in his three laws of planetary motion. Second, he found that the speed of each planet is not constant, as had previously been thought. Third, Kepler found a relationship between the orbital properties of all the planets orbiting the Sun. For the planets, the cubes of their distances from the Sun are proportional to the squares of their orbital periods. Jupiter and Venus, for example, are respectively about 5.2 and 0.723 AU distant from the Sun, their orbital periods respectively about 11.86 and 0.615 years. The proportionality is seen by the fact that the ratio for Jupiter,5. 23/11.862, is equal to that for Venus,0. 7233/0.6152. Idealised orbits meeting these rules are known as Kepler orbits, isaac Newton demonstrated that Keplers laws were derivable from his theory of gravitation and that, in general, the orbits of bodies subject to gravity were conic sections. Newton showed that, for a pair of bodies, the sizes are in inverse proportion to their masses. Where one body is more massive than the other, it is a convenient approximation to take the center of mass as coinciding with the center of the more massive body. Lagrange developed a new approach to Newtonian mechanics emphasizing energy more than force, in a dramatic vindication of classical mechanics, in 1846 le Verrier was able to predict the position of Neptune based on unexplained perturbations in the orbit of Uranus. This led astronomers to recognize that Newtonian mechanics did not provide the highest accuracy in understanding orbits, in relativity theory, orbits follow geodesic trajectories which are usually approximated very well by the Newtonian predictions but the differences are measurable. Essentially all the evidence that can distinguish between the theories agrees with relativity theory to within experimental measurement accuracy
14.
Lander (spacecraft)
–
A lander is a spacecraft which descends toward and comes to rest on the surface of an astronomical body. For bodies with atmospheres, the landing occurs after atmospheric entry, in these cases, landers may employ parachutes to slow down and to maintain a low terminal velocity. Sometimes small landing rockets are fired just before impact to reduce the impact velocity, landing may be accomplished by controlled descent and setdown on landing gear, with the possible addition of a post-landing attachment mechanism for celestial bodies with low gravity. Some missions used inflatable airbags to cushion the landers impact rather than a traditional landing gear. When a high velocity impact is planned not for just achieving the surface but for study of consequences of impact, the spacecraft is called an impactor. Several terrestrial bodies have been subject of lander and/or impactor exploration, among them Earths Moon, the planets Venus, Mars, and Mercury, the Saturn moon Titan, the asteroids and comets. A number of Moon probes, such as members of the Soviet Luna program. In 1959 the first impact on Moon intended to be by Luna 1 probe but occurred by Luna 2 probe, the Soviet Luna 9 was in 1966 the first spacecraft to achieve a lunar soft landing and to transmit photographic data to Earth. The Altair spacecraft, previously known as the Lunar Surface Access Module or LSAM, was the lander for Project Constellation. As of August 2012 NASA is developing vehicles that use a rocket descent engine permitting them land on the Moon and these vehicles include the Mighty Eagle lander and the Morpheus lander. The Project Morpheus lander may have sufficient thrust to propel a manned ascent stage, a first Boomerang-class lunar sample return mission plans under open source OpenLuna program. Russia has plans for Luna-Grunt mission to return samples from the Moon by 2021, the Chinese Change 3 mission and its Jade Rabbit rover landed on 14 December 2013. Then China plans to repeat lander with rover in Change 4 mission after 2015 that will followed by Change 5 and Change 6 sample return missions in 2017 and before 2020. The Soviet Venera program included a number of Venus landers, some of which were crushed during descent much as Galileos Jupiter lander, Venera 3 in 1966 and Venera 7 in 1970 became the first impact and soft landing on Venus. The Soviet Vega program also placed in 1985 two balloons in the Venusian atmosphere, they were the first aerial tools on other planets, the Soviet Unions Mars 1962B was the first Earth based mission intended to reach the surface as impact on Mars in 1962. Three other landers, Mars 2 in 1971 and Mars 5, Mars 6 in 1973, all four landers used an aeroshell-like heat shield during atmospheric entry. Mars 2 and Mars 3 landers carried the first small skis-walking Martian rovers that did not work on the planet. The Soviet Union planned the heavy Marsokhod Mars 4NM mission Mars sample return Mars 5NM mission, a double-launching Soviet Mars 5M sample return mission was planned for 1979 but cancelled due to complexity and technical problems
15.
Voyager program (Mars)
–
The Voyager Mars Program was a planned series of unmanned NASA probes to the planet Mars. The missions were planned, as part of the Apollo Applications Program, the probes were conceived as precursors for a manned Mars landing in the 1980s. Originally, NASA had proposed a direct lander using a variant of the Apollo Command Module launched atop of a Saturn IB rocket with a Centaur upper stage. With the discovery by Mariner 4 in 1965 that Mars had only a tenuous atmosphere and this required the use of a Saturn V to launch two probes at once. Despite the cancellation, the planning and development of the Voyager Mars program was carried out by NASAs Viking program in the mid-1970s. Cheaper and simpler than the Voyager Mars program, the Viking 1 and Viking 2 probes were launched to Mars on separate Titan IIIE/Centaur rockets in 1975, the Saturn V had also been planned at one point as the launch vehicle for an upscaled probe for this mission. List of NASA cancellations Voyager 1973 at Astronautix. com
16.
Voyager program
–
The Voyager program is a continuing American scientific program that employs two robotic probes, Voyager 1 and Voyager 2, to study the outer Solar System. They were launched in 1977 to take advantage of an alignment of Jupiter, Saturn, Uranus, and Neptune. Their mission has been extended three times, and both continue to collect and relay useful scientific data. Neither Uranus nor Neptune has been visited by any other than Voyager 2. On August 25,2012, data from Voyager 1 indicated that it had become the first human-made object to enter space, traveling further than anyone, or anything. As of 2013, Voyager 1 was moving with a velocity of 17 kilometers per second relative to the Sun, Data and photographs collected by the Voyagers cameras, magnetometers, and other instruments revealed previously unknown details about each of the giant planets and their moons. Close-up images from the spacecraft charted Jupiter’s complex cloud forms, winds, saturn’s rings were found to have enigmatic braids, kinks, and spokes and to be accompanied by myriad ringlets. At Uranus Voyager 2 discovered a magnetic field around the planet and 10 additional moons. Its flyby of Neptune uncovered three complete rings and six hitherto unknown moons as well as a magnetic field and complex. Voyager 2 is still the only spacecraft to have visited the ice giants, the two Voyager space probes were originally conceived as part of the Mariner program, and they were thus initially named Mariner 11 and Mariner 12. The Voyager Program was similar to the Planetary Grand Tour planned during the late 1960s, the Grand Tour would take advantage of an alignment of the outer planets discovered by Gary Flandro, an aerospace engineer at the Jet Propulsion Laboratory. This alignment, which occurs once every 175 years, would occur in the late 1970s and make it possible to use gravitational assists to explore Jupiter, Saturn, Uranus, Neptune, and Pluto. The Planetary Grand Tour was to several pairs of probes to fly by all the outer planets along various trajectories, including Jupiter-Saturn-Pluto. Limited funding ended the Grand Tour program, but elements were incorporated into the Voyager Program, Voyager 2 was the first to launch. Its trajectory was designed to allow flybys of Jupiter, Saturn, Uranus and this encounter sent Voyager 1 out of the plane of the ecliptic, ending its planetary science mission. Had Voyager 1 been unable to perform the Titan flyby, the trajectory of Voyager 2 could have altered to explore Titan, forgoing any visit to Uranus. Voyager 1 was not launched on a trajectory that would have allowed it to continue to Uranus and Neptune, but could have continued from Saturn to Pluto without exploring Titan. The New Horizons probe, which had a higher velocity than Voyager 1, is traveling more slowly due to the extra speed Voyager 1 gained from its flybys of Jupiter
17.
Titan (rocket family)
–
Titan is a family of U. S. expendable rockets used between 1959 and 2005. A total of 368 rockets of this family were launched, including all the Project Gemini manned flights of the mid-1960s, titans also were used to send highly successful interplanetary scientific probes throughout the Solar System. The HGM-25A Titan I was the first version of the Titan family of rockets and it began as a backup ICBM project in case the Atlas was delayed. It was a rocket whose LR-87 engine was powered by RP-1. It was operational from early 1962 to mid-1965, the ground guidance for the Titan was the UNIVAC ATHENA computer, designed by Seymour Cray, based in a hardened underground bunker. Using radar data, it made course corrections during the burn phase, most of the Titan rockets were the Titan II ICBM and their civilian derivatives for NASA. The first Titan II guidance system was built by AC Spark Plug and it used an Inertial measurement unit made by AC Spark Plug derived from original designs from the Charles Stark Draper Laboratory at MIT. The missile guidance computer was the IBM ASC-15, when spares for this system became hard to obtain, it was replaced by a more modern guidance system, the Delco Electronics Universal Space Guidance System. The USGS used a Carousel IV IMU and a Magic 352 computer, the USGS was already in use on the Titan III space launcher when work began in March 1978 to replace the Titan II guidance system. The main reason was to reduce the cost of maintenance by $72 million per year, the most famous use of the civilian Titan II was in the NASA Gemini program of manned space capsules in the mid-1960s. Twelve Titan II GLVs were used to launch two U. S. unmanned Gemini test launches and ten manned capsules with two-man crews, all of the launches were successes. Also, in the late 1980s some of the deactivated Titan IIs were converted into space launch vehicles to be used for launching U. S. Government payloads. The final such vehicle launched a Defense Meteorological Satellite Program weather satellite from Vandenberg Air Force Base, California, the Titan III was a modified Titan II with optional solid rocket boosters. The Titan III core was similar to the Titan II, but had a few differences, the Titan IIIA was a prototype rocket booster, which consisted of a standard Titan II rocket with a Transtage upper stage. The Titan IIIB with its different versions had the Titan III core booster with an Agena D upper stage and this combination was used to launch the KH-8 GAMBIT series of intelligence-gathering satellites. They were all launched from Vandenberg Air Force Base, California and their maximum payload mass was about 7,500 lb. The powerful Titan IIIC used a Titan III core rocket with two large strap-on solid-fuel boosters to increase its launch thrust, and hence the maximum payload mass capability. The Titan IIID was a derivative of the Titan IIIC, without the upper transtage, the first guidance system for the Titan III used the AC Spark Plug company IMU and an IBM ASC-15 guidance computer from the Titan II
18.
Centaur (rocket stage)
–
To keep the tanks from collapsing prior to propellant loading, they were either kept in stretch or pressurized with nitrogen gas. Centaur is powered by one or two RL10 rocket engines, in 1956 Krafft Ehricke of Convair began to study a liquid hydrogen upper stage rocket. In 1958 the project started through a joint between Convair, Advanced Research Projects Agency and U. S. Air Force, in 1959 NASA assumed ARPAs role. Development started at NASAs Marshall Space Flight Center and then at Lewis Research Center, now the Glenn Research Center, however, Centaur never flew on any Saturn vehicle, though the Saturn I used a cluster of six RL10 engines on its second stage. The Centaur was originally designed for use with the Atlas launch vehicle family, Centaur was considered essential for the launch of the Surveyor probes, as well as proving the viability of liquid hydrogen as a high energy fuel. Initial Atlas-Centaur launches used developmental versions, labeled Centaur-A through C, the first launch on May 8,1962 ended in an explosion 54 seconds after launch when insulation panels on the Centaur failed and caused the LH2 tank to rupture. After extensive redesigns, the next test took place on November 26,1963 and was successful, on May 30,1966, an Atlas-Centaur boosted the first Surveyor lander towards the Moon. The soft landing of Surveyor 1 in the Ocean of Storms was NASAs first landing on any extraterrestrial body and this was followed by six more Surveyor missions over the next two years, four of which were successful, though Atlas-Centaur performed as expected for each launch. Further, these missions demonstrated the feasibility of reigniting a hydrogen engine in space, a capability vital to Apollo, by the 1970s, Centaur was fully mature and had become the standard rocket stage for launching larger civilian payloads into high earth orbit. In addition, it replaced the Atlas-Agena vehicle for NASA planetary probe missions, the Department of Defense meanwhile preferred to use the Titan booster family for its heavy lift needs. Through 1989, the Centaur-D was used as the stage for 63 Atlas rocket launches,55 of which were successful. The Centaur stage was mated with the far more powerful Titan III booster in 1974, producing the Titan IIIE or Titan III-Centaur, Centaur would also feature improved thermal insulation, allowing it to coast up to five hours in orbit, up from Atlas-Centaurs 30 minute maximum. The first launch of Titan-Centaur in February 1974 was unsuccessful, with Centaurs engines failing to ignite after separation from the Titan booster, without power, the Centaur was ordered to self-destruct by a range safety command. It was eventually determined that Centaurs engines had ingested an incorrectly installed clip from the oxygen tank, the next Titan-Centaur flew in December 1974 and carried the joint German-American Helios 1 probe to study the sun at close range. Centaur completed a further two burns after separation, proving the stages in-space multi-restart capability, in 1975, Titan-Centaur launched the Viking 1 and Viking 2 spacecraft to Mars. Originally planned to be launched on the Saturn V, the Vikings would be the most massive interplanetary missions to that time and these launches were followed by the 1976 launch of Helios 2, another German solar probe, which approached the sun even more closely than Helios 1. Helios 2 still holds the record for the highest speed of any spacecraft, Voyager 2 was launched on August 20,1977, followed 16 days later by Voyager 1. Voyager 2 is the spacecraft to have visited Uranus and Neptune
19.
Atmosphere
–
An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is likely to be retained if the gravity it is subject to is high. The atmosphere of Earth is mostly composed of nitrogen, oxygen, argon with carbon dioxide, the atmosphere helps protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of modification of the paleoatmosphere by living organisms. The term stellar atmosphere describes the region of a star. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere, Atmospheric pressure is the force per unit area that is applied perpendicularly to a surface by the surrounding gas. It is determined by a gravitational force in combination with the total mass of a column of gas above a location. On Earth, units of air pressure are based on the recognized standard atmosphere. It is measured with a barometer, the pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above. The height at which the pressure from an atmosphere declines by a factor of e is called the height and is denoted by H. For such an atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the determination of the atmospheric pressure at any particular altitude is more complex. Surface gravity, the force that holds down an atmosphere, differs significantly among the planets, for example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from objects with lower gravity. Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite their relatively low gravities, rogue planets, theoretically, may also retain thick atmospheres. Since a collection of gas molecules may be moving at a range of velocities. Lighter molecules move faster than ones with the same thermal kinetic energy. It is thought that Venus and Mars may have lost much of their water when, after being photo dissociated into hydrogen and oxygen by solar ultraviolet, Earths magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the polar regions due to auroral activity
20.
Soft landing (rocketry)
–
A soft landing is any type of aircraft, rocket or spacecraft-lander landing that does not result in damage to/the destruction of the vehicle or anything on board. This can be achieved by parachute —often this is into water, vertical rocket powered landing, often referred to as VTVL. Horizontal landing such as with the Space Shuttle also known as VTHL, being caught as attempted with Genesis and followed by some other form of landing. Soft landing can be contrasted with the hard landing
21.
Measuring instrument
–
A measuring instrument is a device for measuring a physical quantity. In the physical sciences, quality assurance, and engineering, measurement is the activity of obtaining and comparing physical quantities of objects and events. Established standard objects and events are used as units, and the process of measurement gives a number relating the item under study, measuring instruments, and formal test methods which define the instruments use, are the means by which these relations of numbers are obtained. All measuring instruments are subject to varying degrees of instrument error, scientists, engineers and other humans use a vast range of instruments to perform their measurements. These instruments may range from simple objects such as rulers and stopwatches to electron microscopes, virtual instrumentation is widely used in the development of modern measuring instruments. In the past, a common time measuring instrument was the sundial, today, the usual measuring instruments for time are clocks and watches. For highly accurate measurement of time a clock is used. Stop watches are used to measure time in some sports. Energy is measured by an energy meter, examples of energy meters include, An electricity meter measures energy directly in kilowatt hours. A gas meter measures energy indirectly by recording the volume of gas used and this figure can then be converted to a measure of energy by multiplying it by the calorific value of the gas. A physical system that exchanges energy may be described by the amount of energy exchanged per time-interval, for the ranges of power-values see, Orders of magnitude. Action describes energy summed up over the time a process lasts and its dimension is the same as that of an angular momentum. A phototube provides a measurement which permits the calculation of the quantized action of light. This includes basic quantities found in classical- and continuum mechanics, dumpy level Laser line level Spirit level Gyroscope Ballistic pendulum, indirectly by calculation and or gauging Considerations related to electric charge dominate electricity and electronics. Electrical charges interact via a field and that field is called electric if the charge doesnt move. If the charge moves, thus realizing an electric current, especially in a neutral conductor. Electricity can be given a quality — a potential, and electricity has a substance-like property, the electric charge. Energy in elementary electrodynamics is calculated by multiplying the potential by the amount of charge found at that potential, potential times charge, electrometer is often used to reconfirm the phenomenon of contact electricity leading to triboelectric sequences
22.
Life on Mars
–
The possibility of life on Mars is a subject of significant interest to astrobiology due to the planets proximity and similarities to Earth. To date no proof has been found of past or present life on Mars, however, cumulative evidence is now building that the ancient surface environment of Mars had liquid water and may have been habitable for microorganisms. The existence of habitable conditions does not necessarily indicate the presence of life, scientific searches for evidence of life began in the 19th century, and they continue today via telescopic investigations and landed missions. On November 22,2016, NASA reported finding a large amount of ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior, Mars is of particular interest for the study of the origins of life because of its similarity to the early Earth. This is especially so since Mars has a climate, and lacks plate tectonics or continental drift. The search for evidence of habitability, taphonomy, and organic carbon on the planet Mars is now a primary NASA objective, Mars polar ice caps were discovered in the mid-17th century. In the latter part of the 18th century, William Herschel proved they grow and shrink alternately, in the summer and winter of each hemisphere. By the mid-19th century, astronomers knew that Mars had certain similarities to Earth. They also knew that its axial tilt was similar to Earths and these observations led to the increase in speculation that the darker albedo features were water, and brighter ones were land. It was therefore natural to suppose that Mars may be inhabited by some form of life, in 1853, William Whewell, a fellow of Trinity College, Cambridge, who popularized the word scientist, theorized that Mars had seas, land and possibly life forms. Speculation about life on Mars exploded in the late 19th century, despite this, in 1895, American astronomer Percival Lowell published his book Mars, followed by Mars and its Canals in 1906, proposing that the canals were the work of a long-gone civilization. This idea led British writer H. G. Wells to write The War of the Worlds in 1897, telling of an invasion by aliens from Mars who were fleeing the planets desiccation. Spectroscopic analysis of Mars atmosphere began in earnest in 1894, when U. S. astronomer William Wallace Campbell showed that neither water nor oxygen were present in the Martian atmosphere. By 1909 better telescopes and the best perihelic opposition of Mars since 1877 conclusively put an end to the canal hypothesis, chemical, physical, geological, and geographic attributes shape the environments on Mars. Isolated measurements of these factors may be insufficient to deem an environment habitable, scientists do not know the minimum number of parameters for determination of habitability potential, but they are certain it is greater than one or two of the factors in the table below. Similarly, for group of parameters, the habitability threshold for each is to be determined. Laboratory simulations show that whenever multiple lethal factors are combined, the survival rates plummet quickly, there are no full-Mars simulations published yet that include all of the biocidal factors combined
23.
Mariner 9
–
Mariner 9 was an unmanned NASA space probe that contributed greatly to the exploration of Mars and was part of the Mariner program. After months of dust storms it managed to send clear pictures of the surface. Mariner 9 returned 7329 images over the course of its mission, an infrared radiometer was included to detect heat sources in search of evidence of volcanic activity. It was to study changes in the Martian atmosphere and surface. Mars two moons were also to be analyzed, Mariner 9 more than met its objectives. NASA still held out hope that another Mariner probe and Atlas-Centaur could be readied before the 1971 Mars launch window closed, Convair also had an available Centaur stage on hand and could have an Atlas readied in time, but the idea was ultimately abandoned for lack of funding. Mariner 9 was mated to Atlas-Centaur AC-23 on May 9 with investigation into Mariner 8s failure ongoing, all testing came back negative and on May 22, a tested and verified rate gyro package arrived from Convair and was installed in the Centaur. Liftoff took place on May 30 at 5,23 PM EST, all launch vehicle systems performed normally and the Mariner separated from the Centaur at 13 minutes and 18 seconds after launch. Mariner 9 was the first spacecraft to orbit another planet, when Mariner 9 arrived at Mars on November 14,1971, planetary scientists were surprised to find the atmosphere was thick with a planet-wide robe of dust, the largest storm ever observed. Mariner 9s computer was reprogrammed from Earth to delay imaging of the surface for a couple of months until the dust settled. The main surface imaging did not get underway until mid-January 1972 and this unexpected situation made a strong case for the desirability of studying a planet from orbit rather than merely flying past. It also highlighted the importance of flexible mission software, the images revealed river beds, craters, massive extinct volcanoes, canyons, evidence of wind and water erosion and deposition, weather fronts, fogs, and more. Mars small moons, Phobos and Deimos, were also photographed, the findings from the Mariner 9 mission underpinned the later Viking program. The enormous Valles Marineris canyon system is named after Mariner 9 in honor of its achievements, after depleting its supply of attitude control gas, the spacecraft was turned off on October 27,1972. The ultraviolet spectrometer aboard Mariner 9 was constructed by the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder, the ultraviolet spectrometer team was led by Professor Charles Barth. The Infrared Interferometer Spectrometer team was led by Dr. Rudolf A. Hanel from NASA Goddard Spaceflight Center, the IRIS instrument was built by Texas Instruments, Dallas, Texas. The Infrared Radiometer team was led by Professor Gerald Neugebauer from the California Institute of Technology, to control for errors in the reception of the grayscale image data sent by Mariner 9, the data had to be encoded before transmission using a so-called error-correcting code. Each image pixel was represented as a 6-bit binary value, which had 64 possible grayscale levels, because of limitations of the transmitter, the maximum useful data length was about 30 bits
24.
Octagon
–
In geometry, an octagon is an eight-sided polygon or 8-gon. A regular octagon has Schläfli symbol and can also be constructed as a truncated square, t. A truncated octagon, t is a hexadecagon, t, the sum of all the internal angles of any octagon is 1080°. As with all polygons, the external angles total 360°, the midpoint octagon of a reference octagon has its eight vertices at the midpoints of the sides of the reference octagon. A regular octagon is a figure with sides of the same length. It has eight lines of symmetry and rotational symmetry of order 8. A regular octagon is represented by the Schläfli symbol, the internal angle at each vertex of a regular octagon is 135°. The area of an octagon of side length a is given by A =2 cot π8 a 2 =2 a 2 ≃4.828 a 2. In terms of the circumradius R, the area is A =4 sin π4 R2 =22 R2 ≃2.828 R2. In terms of the r, the area is A =8 tan π8 r 2 =8 r 2 ≃3.314 r 2. These last two coefficients bracket the value of pi, the area of the unit circle. The area can also be expressed as A = S2 − a 2, where S is the span of the octagon, or the second-shortest diagonal, and a is the length of one of the sides, or bases. This is easily proven if one takes an octagon, draws a square around the outside and then takes the corner triangles and places them with right angles pointed inward, the edges of this square are each the length of the base. Given the length of a side a, the span S is S = a 2 + a + a 2 = a ≈2.414 a. The area is then as above, A =2 − a 2 =2 a 2 ≈4.828 a 2, expressed in terms of the span, the area is A =2 S2 ≈0.828 S2. Another simple formula for the area is A =2 a S, more often the span S is known, and the length of the sides, a, is to be determined, as when cutting a square piece of material into a regular octagon. From the above, a ≈ S /2.414, the two end lengths e on each side, as well as being e = a /2, may be calculated as e = /2. The circumradius of the octagon in terms of the side length a is R = a
25.
Mass
–
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
26.
Attitude control
–
Attitude control is controlling the orientation of an object with respect to an inertial frame of reference or another entity. The integrated field that studies the combination of sensors, actuators and algorithms is called Guidance, Navigation, a spacecrafts attitude must typically be stabilized and controlled for a variety of reasons. Propulsion system thrusters are fired only occasionally to make desired changes in spin rate, if desired, the spinning may be stopped through the use of thrusters or by yo-yo de-spin. The Pioneer 10 and Pioneer 11 probes in the solar system are examples of spin-stabilized spacecraft. Three-axis stabilization is a method of spacecraft attitude control in which the spacecraft is held fixed in the desired orientation without any rotation. One method is to use thrusters to continually nudge the spacecraft back. Thrusters may also be referred to as control systems, or reaction control systems. The space probes Voyager 1 and Voyager 2 employ this method, another method for achieving three-axis stabilization is to use electrically powered reaction wheels, also called momentum wheels, which are mounted on three orthogonal axes aboard the spacecraft. They provide a means to trade angular momentum back and forth between spacecraft and wheels, to rotate the vehicle on a given axis, the reaction wheel on that axis is accelerated in the opposite direction. To rotate the back, the wheel is slowed. This is done during maneuvers called momentum desaturation or momentum unload maneuvers, most spacecraft use a system of thrusters to apply the torque for desaturation maneuvers. A different approach was used by the Hubble Space Telescope, which had sensitive optics that could be contaminated by thruster exhaust, there are advantages and disadvantages to both spin stabilization and three-axis stabilization. Many spacecraft have components that require articulation, Voyager and Galileo, for example, were designed with scan platforms for pointing optical instruments at their targets largely independently of spacecraft orientation. Many spacecraft, such as Mars orbiters, have solar panels that must track the Sun so they can provide power to the spacecraft. Cassinis main engine nozzles are steerable, knowing where to point a solar panel, or scan platform, or a nozzle — that is, how to articulate it—requires knowledge of the spacecrafts attitude. Because AACS keeps track of the attitude, the Suns location. It logically falls to one subsystem, then, to manage both attitude and articulation, the name AACS may even be carried over to a spacecraft even if it has no appendages to articulate. Many sensors generate outputs that reflect the rate of change in attitude and these require a known initial attitude, or external information to use them to determine attitude
27.
Coordinate axis
–
The order of the coordinates is significant, and they are sometimes identified by their position in an ordered tuple and sometimes by a letter, as in the x-coordinate. The coordinates are taken to be real numbers in elementary mathematics, the use of a coordinate system allows problems in geometry to be translated into problems about numbers and vice versa, this is the basis of analytic geometry. The simplest example of a system is the identification of points on a line with real numbers using the number line. In this system, an arbitrary point O is chosen on a given line. The coordinate of a point P is defined as the distance from O to P. Each point is given a unique coordinate and each number is the coordinate of a unique point. The prototypical example of a system is the Cartesian coordinate system. In the plane, two lines are chosen and the coordinates of a point are taken to be the signed distances to the lines. In three dimensions, three perpendicular planes are chosen and the three coordinates of a point are the distances to each of the planes. This can be generalized to create n coordinates for any point in n-dimensional Euclidean space, depending on the direction and order of the coordinate axis the system may be a right-hand or a left-hand system. This is one of many coordinate systems, another common coordinate system for the plane is the polar coordinate system. A point is chosen as the pole and a ray from this point is taken as the polar axis, for a given angle θ, there is a single line through the pole whose angle with the polar axis is θ. Then there is a point on this line whose signed distance from the origin is r for given number r. For a given pair of coordinates there is a single point, for example, and are all polar coordinates for the same point. The pole is represented by for any value of θ, there are two common methods for extending the polar coordinate system to three dimensions. In the cylindrical coordinate system, a z-coordinate with the meaning as in Cartesian coordinates is added to the r and θ polar coordinates giving a triple. Spherical coordinates take this a further by converting the pair of cylindrical coordinates to polar coordinates giving a triple. A point in the plane may be represented in coordinates by a triple where x/z and y/z are the Cartesian coordinates of the point
28.
Spacecraft propulsion
–
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. Each method has drawbacks and advantages, and spacecraft propulsion is an area of research. However, most spacecraft today are propelled by forcing a gas from the back/rear of the vehicle at high speed through a supersonic de Laval nozzle. This sort of engine is called a rocket engine, all current spacecraft use chemical rockets for launch, though some have used air-breathing engines on their first stage. Most satellites have simple reliable chemical thrusters or resistojet rockets for orbital station-keeping, soviet bloc satellites have used electric propulsion for decades, and newer Western geo-orbiting spacecraft are starting to use them for north-south stationkeeping and orbit raising. Interplanetary vehicles mostly use chemical rockets as well, although a few have used ion thrusters, artificial satellites must be launched into orbit and once there they must be placed in their nominal orbit. Once in the orbit, they often need some form of attitude control so that they are correctly pointed with respect to Earth, the Sun. They are also subject to drag from the atmosphere, so that to stay in orbit for a long period of time some form of propulsion is occasionally necessary to make small corrections. Many satellites need to be moved from one orbit to another time to time. A satellites useful life is usually over once it has exhausted its ability to adjust its orbit, spacecraft designed to travel further also need propulsion methods. They need to be launched out of the Earths atmosphere just as satellites do, once there, they need to leave orbit and move around. For interplanetary travel, a spacecraft must use its engines to leave Earth orbit, once it has done so, it must somehow make its way to its destination. Current interplanetary spacecraft do this with a series of short-term trajectory adjustments, in between these adjustments, the spacecraft simply falls freely along its trajectory. The most fuel-efficient means to move from one orbit to another is with a Hohmann transfer orbit. The spacecraft falls freely along this elliptical orbit until it reaches its destination, special methods such as aerobraking or aerocapture are sometimes used for this final orbital adjustment. The concept has been tested by the Japanese IKAROS solar sail spacecraft. Spacecraft for interstellar travel also need propulsion methods, no such spacecraft has yet been built, but many designs have been discussed. Because interstellar distances are great, a tremendous velocity is needed to get a spacecraft to its destination in a reasonable amount of time
29.
Satellite bus
–
A satellite bus or spacecraft bus is the general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of a spacecraft, usually providing locations for the payload, a bus-derived satellite would be used as opposed to a one-off, or specially produced satellite, such as Prospero X-3. Bus-derived satellites are usually customized to customer requirements, for example with specialized sensors or transponders, comparison of satellite buses Service module Satellite Glossary JWST Observatory, The Spacecraft Bus Spitzers Spacecraft Bus Gunters Space Page, Spacecraft buses
30.
Liquid-propellant rocket
–
A liquid-propellant rocket or liquid rocket is a rocket engine that uses liquid propellants. This permits the use of low-mass propellant tanks, resulting in a mass ratio for the rocket. An inert gas stored in a tank at a pressure is sometimes used instead of pumps in simpler small engines to force the propellants into the combustion chamber. These engines may have a mass ratio, but are usually more reliable. And are therefore used widely in satellites for orbit maintenance, some designs are throttleable for variable thrust operation and some may be restarted after a previous in-space shutdown. Liquid propellants are used in hybrid rockets, in which a liquid oxidizer is generally combined with a solid fuel. This seminal treatise on astronautics was published in 1903, but was not distributed outside Russia until years later, german V-2 inventor Wernher von Braun considered Paulet one of the fathers of aeronautics. The National Air & Space Museum in Washington, D. C. has a plaque honoring the memory of Paulet. He was the only known developer of liquid-propellant rocket engine experiments in the 19th century, however, he did not publish his work. In 1927 he wrote a letter to a newspaper in Lima, historians of early rocketry experiments, among them Max Valier, Willy Ley, and John D. Clark, have given differing amounts of credence to Paulets report. Paulet described laboratory tests of, but did not claim to have launched a liquid rocket. Wernher von Braun, in his book World History of Aeronautics states, Pedro Paulet was in Paris in those years, experimenting with his tiny two-and-a-half kilogram motor, by this act, Paulet should be considered the pioneer of the liquid fuel propulsion motor. Further, in his History of Rocketry and Space Travel, von Braun recognizes that by his efforts, Paulet helped man reach the Moon. The rocket, which was dubbed Nell, rose just 41 feet during a 2. 5-second flight that ended in a cabbage field, goddard proposed liquid propellants about fifteen years earlier and began to seriously experiment with them in 1921. In Germany, engineers and scientists became enthralled with liquid-fuel rockets and this amateur rocket group, the VfR, included Wernher von Braun, who became the head of the army research station that secretly built the V-2 rocket weapon for the Nazis. The German-Romanian Hermann Oberth published a book in 1922 suggesting the use of liquid propellants, after World War II the American government and military finally seriously considered liquid-propellant rockets as weapons and began to fund work on them. The Soviet Union did likewise, and thus began the Space Race, bipropellant liquid rockets generally use a liquid fuel, such as liquid hydrogen or a hydrocarbon fuel such as RP-1, and a liquid oxidizer, such as liquid oxygen. The engine may be a rocket engine, where the fuel and oxidizer
31.
Dinitrogen tetroxide
–
Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide, is the chemical compound N2O4. It is a reagent in chemical synthesis. It forms a mixture with nitrogen dioxide. Dinitrogen tetroxide is an oxidizer that is hypergolic upon contact with various forms of hydrazine. Dinitrogen tetroxide could be regarded as two nitro groups bonded together and it forms an equilibrium mixture with nitrogen dioxide. The molecule is planar with an N-N bond distance of 1.78 Å, the N-N distance corresponds to a weak bond, since it is significantly longer than the average N-N single bond length of 1.45 Å. Unlike NO2, N2O4 is diamagnetic since it has no unpaired electrons, inevitably, some dinitrogen tetroxide is a component of smog containing nitrogen dioxide. Nitrogen tetroxide is made by the oxidation of ammonia, steam is used as a diluent to reduce the combustion temperature. The gas is essentially pure nitrogen dioxide, which is condensed into dinitrogen tetroxide in a brine-cooled liquefier, dinitrogen tetroxide can also be made through the reaction of concentrated nitric acid and metallic copper. This synthesis is more practical in a setting and is commonly used as a demonstration or experiment in undergraduate chemistry labs. The unstable species further react to form nitrogen dioxide which is purified and condensed to form dinitrogen tetroxide. Nitrogen tetroxide is used as an oxidizer in one of the more important rocket propellants because it can be stored as a liquid at room temperature and it became the storable oxidizer of choice for many rockets in both the United States and USSR by the late 1950s. It is a propellant in combination with a hydrazine-based rocket fuel. One of the earliest uses of this combination was on the Titan family of rockets used originally as ICBMs and then as launch vehicles for many spacecraft. Used on the U. S. Gemini and Apollo spacecraft and also on the Space Shuttle, it continues to be used as stationkeeping propellant on most geo-stationary satellites, and many deep-space probes. It now seems likely that NASA will continue to use this oxidizer in the next-generation crew-vehicles which will replace the shuttle and it is also the primary oxidizer for Russias Proton rocket. When used as a propellant, dinitrogen tetroxide is usually referred to simply as Nitrogen Tetroxide, most spacecraft now use MON instead of NTO, for example, the Space Shuttle reaction control system used MON3. On 24 July 1975, NTO poisoning affected the three U. S. astronauts on board the Apollo-Soyuz Test Project during its final descent, one crew member lost consciousness during descent
32.
Rocket engine
–
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
33.
Gimbal
–
A gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of three gimbals, one mounted on the other with orthogonal axes, may be used to allow an object mounted on the innermost gimbal to remain independent of the rotation of its support. The gimbal suspension used for mounting compasses and the like is sometimes called a Cardan suspension after Italian mathematician, however, Cardano did not invent the gimbal, nor did he claim to. The device has been known since antiquity, first described in the 3rd c, BCE by Philo of Byzantium, although some modern authors support it may not have a single identifiable inventor. The gimbal was first described by the Greek inventor Philo of Byzantium and this was done by the suspension of the inkwell at the center, which was mounted on a series of concentric metal rings so that it remained stationary no matter which way the pot is turned. Thus, the sinologist Joseph Needham suspected Arab interpolation as late as 1965, however, Carra de Vaux, author of the French translation which still provides the basis for modern scholars, regards the Pneumatics as essentially genuine. The historian of technology George Sarton also asserts that it is safe to assume the Arabic version is a copying of Philos original. So does his colleague Michael Lewis, after antiquity, gimbals remained widely known in the Near East. In the Latin West, reference to the device appeared again in the 9th century recipe book called the Little Key of Painting Mappae clavicula, the French inventor Villard de Honnecourt depicts a set of gimbals in his famous sketchbook. In the early period, dry compasses were suspended in gimbals. In China, the Han Dynasty inventor Ding Huan created a gimbal incense burner around 180 CE, there is a hint in the writing of the earlier Sima Xiangru that the gimbal existed in China since the 2nd century BCE. There is mention during the Liang Dynasty that gimbals were used for hinges of doors and windows, extant specimens of Chinese gimbals used for incense burners date to the early Tang Dynasty, and were part of the silver-smithing tradition in China. In this application, the measurement unit is equipped with three orthogonally mounted gyros to sense rotation about all axes in three-dimensional space. The gyro outputs are kept to a null through drive motors on each gimbal axis, to accomplish this, the gyro error signals are passed through resolvers mounted on the three gimbals, roll, pitch and yaw. These resolvers perform an automatic matrix transformation according to each gimbal angle, the yaw torques must be resolved by roll and pitch transformations. The gimbal angle is never measured, similar sensing platforms are used on aircraft. In inertial navigation systems, gimbal lock may occur when vehicle rotation causes two of the three rings to align with their pivot axes in a single plane. When this occurs, it is no longer possible to maintain the sensing platforms orientation, to control roll, twin engines with differential pitch or yaw control signals are used to provide torque about the vehicles roll axis
34.
Degree (angle)
–
A degree, usually denoted by °, is a measurement of a plane angle, defined so that a full rotation is 360 degrees. It is not an SI unit, as the SI unit of measure is the radian. Because a full rotation equals 2π radians, one degree is equivalent to π/180 radians, the original motivation for choosing the degree as a unit of rotations and angles is unknown. One theory states that it is related to the fact that 360 is approximately the number of days in a year. Ancient astronomers noticed that the sun, which follows through the path over the course of the year. Some ancient calendars, such as the Persian calendar, used 360 days for a year, the use of a calendar with 360 days may be related to the use of sexagesimal numbers. The earliest trigonometry, used by the Babylonian astronomers and their Greek successors, was based on chords of a circle, a chord of length equal to the radius made a natural base quantity. One sixtieth of this, using their standard sexagesimal divisions, was a degree, Aristarchus of Samos and Hipparchus seem to have been among the first Greek scientists to exploit Babylonian astronomical knowledge and techniques systematically. Timocharis, Aristarchus, Aristillus, Archimedes, and Hipparchus were the first Greeks known to divide the circle in 360 degrees of 60 arc minutes, eratosthenes used a simpler sexagesimal system dividing a circle into 60 parts. Furthermore, it is divisible by every number from 1 to 10 except 7 and this property has many useful applications, such as dividing the world into 24 time zones, each of which is nominally 15° of longitude, to correlate with the established 24-hour day convention. Finally, it may be the case more than one of these factors has come into play. For many practical purposes, a degree is a small enough angle that whole degrees provide sufficient precision. When this is not the case, as in astronomy or for geographic coordinates, degree measurements may be written using decimal degrees, with the symbol behind the decimals. Alternatively, the sexagesimal unit subdivisions can be used. One degree is divided into 60 minutes, and one minute into 60 seconds, use of degrees-minutes-seconds is also called DMS notation. These subdivisions, also called the arcminute and arcsecond, are represented by a single and double prime. For example,40. 1875° = 40° 11′ 15″, or, using quotation mark characters, additional precision can be provided using decimals for the arcseconds component. The older system of thirds, fourths, etc. which continues the sexagesimal unit subdivision, was used by al-Kashi and other ancient astronomers, but is rarely used today
35.
Newton (unit)
–
The newton is the International System of Units derived unit of force. It is named after Isaac Newton in recognition of his work on classical mechanics, see below for the conversion factors. One newton is the force needed to one kilogram of mass at the rate of one metre per second squared in direction of the applied force. In 1948, the 9th CGPM resolution 7 adopted the name newton for this force, the MKS system then became the blueprint for todays SI system of units. The newton thus became the unit of force in le Système International dUnités. This SI unit is named after Isaac Newton, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, section 5.2. Newtons second law of motion states that F = ma, where F is the applied, m is the mass of the object receiving the force. The newton is therefore, where the symbols are used for the units, N for newton, kg for kilogram, m for metre. In dimensional analysis, F = M L T2 where F is force, M is mass, L is length, at average gravity on earth, a kilogram mass exerts a force of about 9.8 newtons. An average-sized apple exerts about one newton of force, which we measure as the apples weight, for example, the tractive effort of a Class Y steam train and the thrust of an F100 fighter jet engine are both around 130 kN. One kilonewton,1 kN, is 102.0 kgf,1 kN =102 kg ×9.81 m/s2 So for example, a platform rated at 321 kilonewtons will safely support a 32,100 kilograms load. Specifications in kilonewtons are common in safety specifications for, the values of fasteners, Earth anchors. Working loads in tension and in shear, thrust of rocket engines and launch vehicles clamping forces of the various moulds in injection moulding machines used to manufacture plastic parts
36.
Delta-v
–
It is a scalar that has the units of speed. As used in context, it is not the same as the physical change in velocity of the vehicle. For multiple maneuvers, delta-v sums linearly, for interplanetary missions delta-v is often plotted on a porkchop plot which displays the required mission delta-v as a function of launch date. Δ v = ∫ t 0 t 1 | T | m d t where T is the instantaneous thrust at time, M is the instantaneous mass at time, t. In the absence of forces, Δ v = ∫ t 0 t 1 | v ˙ | d t where v ˙ is the coordinate acceleration. When thrust is applied in a constant direction this simplifies to, orbit maneuvers are made by firing a thruster to produce a reaction force acting on the spacecraft. e. If for example 20% of the mass is fuel giving a constant v exh of 2100 m/s the capacity of the reaction control system is Δ v =2100 ln m/s =460 m/s. But for many purposes, typically for studies or for maneuver optimization, like this one can for example use a patched conics approach modeling the maneuver as a shift from one Kepler orbit to another by an instantaneous change of the velocity vector. This approximation with impulsive maneuvers is in most cases very accurate, for low thrust systems, typically electrical propulsion systems, this approximation is less accurate. But even for geostationary spacecraft using electrical propulsion for out-of-plane control with thruster burn periods extending over several hours around the nodes this approximation is fair, delta-v is typically provided by the thrust of a rocket engine, but can be created by other engines. The time-rate of change of delta-v is the magnitude of the caused by the engines. The actual acceleration vector would be found by adding thrust per mass on to the gravity vector, the total delta-v needed is a good starting point for early design decisions since consideration of the added complexities are deferred to later times in the design process. The rocket equation shows that the amount of propellant dramatically increases with increasing delta-v. Which is just the rocket equation applied to the sum of the two maneuvers and this is convenient since it means that delta-v’s can be calculated and simply added and the mass ratio calculated only for the overall vehicle for the entire mission. Thus delta-v is commonly quoted rather than mass ratios which would require multiplication, when designing a trajectory, delta-v budget is used as a good indicator of how much propellant will be required. Propellant usage is a function of delta-v in accordance with the rocket equation. For example, most spacecraft are launched in an orbit with inclination fairly near to the latitude at the launch site, for examples of calculating delta-v, see Hohmann transfer orbit, gravitational slingshot, and Interplanetary Transport Network. It is also notable that large thrust can reduce gravity drag, delta-v is also required to keep satellites in orbit and is expended in propulsive orbital stationkeeping maneuvers
37.
Sun sensor
–
A sun sensor is a navigational instrument used by spacecraft to detect the position of the sun. Sun sensors are used for control, solar array pointing, gyro updating. In addition to spacecraft, sun sensors find use in ground-based weather stations and sun-tracking systems, there are various types of sun sensors, which differ in their technology and performance characteristics. Sun presence sensors provide an output, indicating when the sun is within the sensors field of view. Analog and digital sun sensors, in contrast, indicate the angle of the sun by continuous and discrete signal outputs, respectively. In typical sun sensors, a slit at the top of a rectangular chamber allows a line of light to fall on an array of photodetector cells at the bottom of the chamber. A voltage is induced in these cells, which is registered electronically, by orienting two sensors perpendicular to each other, the direction of the sun can be fully determined. Often, multiple sensors will share processing electronics
38.
Canopus
–
Canopus, also designated Alpha Carinae, is the brightest star in the southern constellation of Carina, and the second brightest star in the night-time sky, after Sirius. Canopuss visual magnitude is −0.74, and it has a magnitude of −5.71. Canopus is a giant of spectral type A9, so it is essentially white when seen with the naked eye. It is located in the far southern sky, at a year 2000 declination of −52° 42′ and its name is generally considered to originate from the mythological Canopus, who was a navigator for Menelaus, king of Sparta. In Indian Vedic literature, the star Canopus is associated with the sage Agastya, Agastya, the star, is said to be the cleanser of waters and its rising coincides with the calming of the waters of the Indian Ocean. It is considered the son of Pulasthya, son of Brahma, Canopus was not visible to the mainland ancient Greeks and Romans, it was, however, visible to the ancient Egyptians. Hence Aratus did not write of the star as it remained below the horizon, while Eratosthenes and Ptolemy—observing from Alexandria—did, the Navajo named it Ma’ii Bizò‘. The Bedouin people of the Negev and Sinai also knew it as Suhayl, due to the fact that it disappears below the horizon in those regions, it became associated with a changeable nature, as opposed to always-visible Polaris, which was circumpolar and hence steadfast. It is also referred to by its Arabic name, سهيل, called the Old Man of the South Pole in Chinese, Canopus appears on the medieval Chinese manuscript the Dunhuang star chart, despite not being visible from the Chinese capital of Changan. The Chinese astronomer Yi Xing had journeyed south to chart Canopus, however, it was already mentioned by Sima Qian in the second century BC, drawing on sources from the Warring States period, as the southern counterpart of Sirius. Bright stars were important to the ancient Polynesians for navigation between the islands and atolls of the Pacific Ocean. Low on the horizon, they acted as stellar compasses to assist mariners in charting courses to particular destinations. The Hawaiian people called Canopus Ke Alii-o-kona-i-ka-lewa, The chief of the expanse, it was one of the stars used by Hawaii-loa. The Māori people of New Zealand/Aotearoa had several different names for Canopus, ariki, was known as a solitary star that appeared in the east, prompting people to weep and chant. They also named it Atutahi, Aotahi or Atuatahi, Stand Alone and its solitary nature indicates it is a tapu star, as tapu people are often solitary. Its appearance at the beginning of the Maruaroa season foretells the coming winter, light rays to the south indicate a cold wet winter, food was offered to the star on its appearance. This name has several different mythologies attached to it as well, one story tells of how Atutahi was left outside of the basket representing the Milky Way when Tāne wove it. Another related myth surrounding the star says that Atutahi was the child of Rangi
39.
Star tracker
–
A star tracker is an optical device that measures the position of star using photocell or a camera. A star tracker may include a processor to identify stars by comparing the pattern of observed stars with the pattern of stars in the sky. Star trackers, which require high sensitivity, may become confused by sunlight reflected from the spacecraft, star trackers are also susceptible to a variety of errors in addition to a variety of optical sources of error. There are also many sources of confusion for the star identification algorithm. There are roughly 57 bright navigational stars in common use, however, for more complex missions, entire star field databases are used to determine spacecraft orientation. These types of star catalogs can have thousands of stored in memory on board the spacecraft, or else processed using tools at the ground station
40.
Gyroscope
–
A gyroscope is a spinning wheel or disc in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum, because of this, gyroscopes are useful for measuring or maintaining orientation. Due to their precision, gyroscopes are used in gyrotheodolites to maintain direction in tunnel mining. Gyroscopes can be used to construct gyrocompasses, which complement or replace magnetic compasses, a gyroscope is a wheel mounted in two or three gimbals, which are a pivoted supports that allow the rotation of the wheel about a single axis. In the case of a gyroscope with two gimbals, the gimbal, which is the gyroscope frame, is mounted so as to pivot about an axis in its own plane determined by the support. This outer gimbal possesses one degree of freedom and its axis possesses none. The inner gimbal is mounted in the frame so as to pivot about an axis in its own plane that is always perpendicular to the pivotal axis of the gyroscope frame. This inner gimbal has two degrees of rotational freedom, the axle of the spinning wheel defines the spin axis. The rotor is constrained to spin about an axis, which is perpendicular to the axis of the inner gimbal. So the rotor possesses three degrees of freedom and its axis possesses two. The wheel responds to a force applied to the axis by a reaction force to the output axis. The behaviour of a gyroscope can be most easily appreciated by consideration of the front wheel of a bicycle. If the wheel is leaned away from the vertical so that the top of the moves to the left. In other words, rotation on one axis of the turning wheel produces rotation of the third axis, a gyroscope flywheel will roll or resist about the output axis depending upon whether the output gimbals are of a free or fixed configuration. Examples of some free-output-gimbal devices would be the attitude reference gyroscopes used to sense or measure the pitch, roll, the centre of gravity of the rotor can be in a fixed position. Some gyroscopes have mechanical equivalents substituted for one or more of the elements, for example, the spinning rotor may be suspended in a fluid, instead of being pivotally mounted in gimbals. In some special cases, the outer gimbal may be omitted so that the rotor has two degrees of freedom. Essentially, a gyroscope is a top combined with a pair of gimbals, Tops were invented in many different civilizations, including classical Greece, Rome, and China
41.
Accelerometer
–
An accelerometer is a device that measures proper acceleration, proper acceleration is not the same as coordinate acceleration. For example, an accelerometer at rest on the surface of the Earth will measure an acceleration due to Earths gravity, by contrast, accelerometers in free fall will measure zero. Accelerometers have multiple applications in industry and science, highly sensitive accelerometers are components of inertial navigation systems for aircraft and missiles. Accelerometers are used to detect and monitor vibration in rotating machinery, accelerometers are used in tablet computers and digital cameras so that images on screens are always displayed upright. Accelerometers are used in drones for flight stabilisation, coordinated accelerometers can be used to measure differences in proper acceleration, particularly gravity, over their separation in space, i. e. gradient of the gravitational field. This gravity gradiometry is useful because absolute gravity is a weak effect, micromachined accelerometers are increasingly present in portable electronic devices and video game controllers, to detect the position of the device or provide for game input. An accelerometer measures proper acceleration, which is the acceleration it experiences relative to freefall and is the acceleration felt by people and objects. Put another way, at any point in spacetime the equivalence principle guarantees the existence of an inertial frame. Such accelerations are popularly denoted g-force, i. e. in comparison to standard gravity, an accelerometer at rest relative to the Earths surface will indicate approximately 1 g upwards, because any point on the Earths surface is accelerating upwards relative to the local inertial frame. The reason for the appearance of an offset is Einsteins equivalence principle. For similar reasons, an accelerometer will read zero during any type of free fall and this includes use in a coasting spaceship in deep space far from any mass, a spaceship orbiting the Earth, an airplane in a parabolic zero-g arc, or any free-fall in vacuum. Another example is free-fall at a high altitude that atmospheric effects can be neglected. However this does not include a fall in air resistance produces drag forces that reduce the acceleration. At terminal velocity the accelerometer will indicate 1 g acceleration upwards, Acceleration is quantified in the SI unit metres per second per second, in the cgs unit gal, or popularly in terms of standard gravity. For the practical purpose of finding the acceleration of objects with respect to the Earth, such as for use in a navigation system. This can be obtained either by calibrating the device at rest, conceptually, an accelerometer behaves as a damped mass on a spring. When the accelerometer experiences an acceleration, the mass is displaced to the point that the spring is able to accelerate the mass at the rate as the casing. The displacement is measured to give the acceleration
42.
Hertz
–
The hertz is the unit of frequency in the International System of Units and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide proof of the existence of electromagnetic waves. Hertz are commonly expressed in SI multiples kilohertz, megahertz, gigahertz, kilo means thousand, mega meaning million, giga meaning billion and tera for trillion. Some of the units most common uses are in the description of waves and musical tones, particularly those used in radio-. It is also used to describe the speeds at which computers, the hertz is equivalent to cycles per second, i. e. 1/second or s −1. In English, hertz is also used as the plural form, as an SI unit, Hz can be prefixed, commonly used multiples are kHz, MHz, GHz and THz. One hertz simply means one cycle per second,100 Hz means one hundred cycles per second, and so on. The unit may be applied to any periodic event—for example, a clock might be said to tick at 1 Hz, the rate of aperiodic or stochastic events occur is expressed in reciprocal second or inverse second in general or, the specific case of radioactive decay, becquerels. Whereas 1 Hz is 1 cycle per second,1 Bq is 1 aperiodic radionuclide event per second, the conversion between a frequency f measured in hertz and an angular velocity ω measured in radians per second is ω =2 π f and f = ω2 π. This SI unit is named after Heinrich Hertz, as with every International System of Units unit named for a person, the first letter of its symbol is upper case. Note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, the hertz is named after the German physicist Heinrich Hertz, who made important scientific contributions to the study of electromagnetism. The name was established by the International Electrotechnical Commission in 1930, the term cycles per second was largely replaced by hertz by the 1970s. One hobby magazine, Electronics Illustrated, declared their intention to stick with the traditional kc. Mc. etc. units, sound is a traveling longitudinal wave which is an oscillation of pressure. Humans perceive frequency of waves as pitch. Each musical note corresponds to a frequency which can be measured in hertz. An infants ear is able to perceive frequencies ranging from 20 Hz to 20,000 Hz, the range of ultrasound, infrasound and other physical vibrations such as molecular and atomic vibrations extends from a few femtoHz into the terahertz range and beyond. Electromagnetic radiation is described by its frequency—the number of oscillations of the perpendicular electric and magnetic fields per second—expressed in hertz. Radio frequency radiation is measured in kilohertz, megahertz, or gigahertz
43.
Transmitter
–
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which generates a radio frequency alternating current. When a connected antenna is excited by this current, the antenna emits radio waves. The term transmitter is usually limited to equipment that generates radio waves for communication purposes, or radiolocation, such as radar and navigational transmitters. Generators of radio waves for heating or industrial purposes, such as ovens or diathermy equipment, are not usually called transmitters even though they often have similar circuits. The term is used more specifically to refer to a broadcast transmitter. This usage typically includes both the proper, the antenna, and often the building it is housed in. A transmitter can be a piece of electronic equipment, or an electrical circuit within another electronic device. A transmitter and a receiver combined in one unit is called a transceiver, the term transmitter is often abbreviated XMTR or TX in technical documents. The purpose of most transmitters is radio communication of information over a distance, the transmitter combines the information signal to be carried with the radio frequency signal which generates the radio waves, which is called the carrier signal. The information can be added to the carrier in several different ways, in an amplitude modulation transmitter, the information is added to the radio signal by varying its amplitude. In a frequency modulation transmitter, it is added by varying the signals frequency slightly. Many other types of modulation are used, the radio signal from the transmitter is applied to the antenna, which radiates the energy as radio waves. The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as phones, walkie-talkies. In more powerful transmitters, the antenna may be located on top of a building or on a tower, and connected to the transmitter by a feed line. The first primitive radio transmitters were built by German physicist Heinrich Hertz in 1887 during his investigations of radio waves. These generated radio waves by a high voltage spark between two conductors, beginning in 1895 Guglielmo Marconi developed the first practical radio communication systems using spark transmitters. These spark-gap transmitters were used during the first three decades of radio, called the wireless telegraphy or spark era, vacuum tube transmitters took over because they were inexpensive and produced continuous waves, which could be modulated to transmit audio using amplitude modulation. This made possible commercial AM radio broadcasting, which began in about 1920, experimental television transmission had been conducted by radio stations since the late 1920s, but practical television broadcasting didnt begin until the 1940s
44.
Traveling-wave tube
–
A traveling-wave tube or traveling-wave tube amplifier is a specialized vacuum tube that is used in electronics to amplify radio frequency signals in the microwave range. The TWT belongs to a category of linear beam tubes, such as the klystron, although there are various types of TWT, two major categories are, Helix TWT In which the radio waves interact with the electron beam while traveling down a wire helix which surrounds the beam. These have wide bandwidth, but output power is limited to a few hundred watts, coupled cavity TWT In which the radio wave interacts with the beam in a series of cavity resonators through which the beam passes. These function as narrowband power amplifiers, a major advantage of the TWT over some other microwave tubes is its ability to amplify a wide range of frequencies, a wide bandwidth. The bandwidth of the helix TWT can be as high as two octaves, while the cavity versions have bandwidths of 10–20%, operating frequencies range from 300 MHz to 50 GHz. The power gain of the tube is on the order of 40 to 70 decibels, TWTs account for over 50% of the sales volume of all microwave vacuum tubes. They are widely used as the power amplifiers and oscillators in radar systems, communication satellite and spacecraft transmitters, the TWT is an elongated vacuum tube with an electron gun at one end. A voltage applied across the cathode and anode accelerates the electrons towards the far end of the tube, at the other end of the tube the electrons strike the collector, which returns them to the circuit. Wrapped around the inside of the tube, just outside the path, is a helix of wire. The RF signal to be amplified is fed into the helix at a point near the end of the tube. The signal is fed into the helix via a waveguide or electromagnetic coil placed at one end, forming a one-way signal path. By controlling the voltage, the speed of the electrons flowing down the tube is set to be similar to the speed of the RF signal running down the helix. The signal in the causes an magnetic field to be induced in the center of the helix. Depending on the phase of the signal, the electrons will either be sped up or slowed down as they pass the windings and this causes the electron beam to bunch up, known technically as velocity modulation. The resulting pattern of electron density in the beam is an analog of the original RF signal, because the beam is passing the helix as it travels, and that signal varies, it causes induction in the helix, amplifying the original signal. By the time it reaches the end of the tube. A second directional coupler, positioned near the collector, receives an amplified version of the signal from the far end of the RF circuit. Attenuators placed along the RF circuit prevent the wave from traveling back to the cathode
Interactive imagemap of the global topography of Mars, overlain with locations of Mars landers and rovers (Red label = Rover; Blue label = Lander; bold red/blue = currently active). Hover your mouse to see the names of over 25 prominent geographic features, and click to link to them. Coloring of the base map indicates relative elevations, based on data from the Mars Orbiter Laser Altimeter on NASA's Mars Global Surveyor. Reds and pinks are higher elevation (+3 km to +8 km); yellow is 0 km; greens and blues are lower elevation (down to −8 km). Whites (>+12 km) and browns (>+8 km) are the highest elevations. Axes are latitude and longitude; Poles are not shown. 
.jpg)
.jpg)
