Radioisotope thermoelectric generator
A radioisotope thermoelectric generator is an electrical generator that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This generator has no moving parts. RTGs have been used as power sources in satellites, space probes, unmanned remote facilities such as a series of lighthouses built by the former Soviet Union inside the Arctic Circle. RTGs are the most desirable power source for unmaintained situations that need a few hundred watts of power for durations too long for fuel cells, batteries, or generators to provide economically, in places where solar cells are not practical. Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit. Notably, RTGs tend to be prohibitively expensive for most things they might otherwise find applications for; the RTG was invented in 1954 by John Birden. They were inducted into the National Inventors Hall of Fame in 2013.
Jordan and Birden worked on an Army Signal Corps contract beginning on January 1, 1957, to conduct research on radioactive materials and thermocouples suitable for the direct conversion of heat to electrical energy using polonium-210 as the heat source. RTGs were developed in the US during the late 1950s by Mound Laboratories in Miamisburg, under contract with the United States Atomic Energy Commission; the project was led by Dr. Bertram C. Blanke; the first RTG launched into space by the United States was SNAP 3B in 1961 powered by 96 grams of plutonium-238 metal, aboard the Navy Transit 4A spacecraft. 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, Ulysses, 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, in the vicinity of the Tonga Trench. RTGs were used for the Nimbus, Transit and LES satellites. By comparison, only a few space vehicles have been launched using full-fledged nuclear reactors: the Soviet RORSAT series and the American SNAP-10A. In addition to spacecraft, the Soviet Union constructed many unmanned lighthouses and navigation beacons powered by RTGs. Powered by strontium-90 they are reliable and provide a steady source of power. Most have no protection, not fences or warning signs, the locations of some of these facilities are no longer known due to poor record keeping. In one instance, the radioactive compartments were opened by a thief. In another case, three woodsmen in Tsalendzhikha Region, Georgia found two ceramic RTG heat sources, stripped of their shielding.
The units were recovered and isolated. There are 1,000 such RTGs in Russia, all of which have long since exceeded their design operational lives of ten years. Most of these RTGs no longer function, may need to be dismantled; some of their metal casings have been stripped by metal hunters, despite the risk of radioactive contamination. The United States Air Force uses RTGs to power remote sensing stations for Top-ROCC and SEEK IGLOO radar systems predominantly located in Alaska. In the past, small "plutonium cells" were used in implanted heart pacemakers to ensure a long "battery life"; as of 2004, about ninety were still in use. By the end of 2007, the number was reported to be down to just nine; the Mound Laboratory Cardiac Pacemaker program began on June 1, 1966, in conjunction with NUMEC. When it was recognized that the heat source would not remain intact during cremation, the program was cancelled in 1972 because there was no way to ensure that the units would not be cremated with their users' bodies.
The design of an RTG is simple by the standards of nuclear technology: the main component is a sturdy container of a radioactive material. Thermocouples are placed in the walls of the container, with the outer end of each thermocouple connected to a heat sink. Radioactive decay of the fuel produces heat, it is the temperature difference between the fuel and the heat sink that allows the thermocouples to generate electricity. A thermocouple is a thermoelectric device that can convert thermal energy directly into electrical energy, using the Seebeck effect, it is made of two kinds of metal. They are connected to each other in a closed loop. If the two junctions are at different temperatures, an electric current will flow in the loop; the radioactive material used in RTGs must have several characteristics: Its half-life must be long enough so that it will release energy at a constant rate for a reasonable amount of time. The amount of energy released per time of a given quantity is inversely proportional to half-life.
An isotope with twice the half-life and the same energy per decay will release power at half the rate per mole. Typical half-lives for radioisotopes used in RTGs are therefore several decades, although isotopes with shorter half-lives could be used for specialized applications. For spaceflight use, the fuel must produce a l
Masten Space Systems
Masten Space Systems is an aerospace manufacturer startup company in Mojave, California, developing a line of vertical takeoff, vertical landing rockets for uncrewed research sub-orbital spaceflights and intended to support robotic orbital spaceflight launches. Masten Space Systems is a Mojave, California based rocket company, developing a line of reusable VTVL spacecraft, related rocket propulsion hardware. Masten Space Systems competed in the NASA and Northrop Grumman Lunar Lander Challenge X Prize in 2009, winning the level one second prize of $150,000 and the level two first prize of $1,000,000. On November 2, 2009 it was announced that Masten Space Systems had won first place in the level two category, with Armadillo Aerospace coming in second. Masten's Xombie won the US$150,000 second prize in the Level One competition of the Lunar Lander Challenge on October 7, 2009 with an average landing accuracy of 16 centimetres; the primary goal of these two airframes was to demonstrate stable, controlled flight using a GN&C system developed in-house at Masten.
XA-0.1B featured four engines with 1,000 pounds-force thrust, but was converted in Spring 2009 to be powered by one engine of 750 pounds-force thrust. By October 2009, the regeneratively cooled isopropyl alcohol and liquid oxygen rocket engine was running at around 900 pounds-force. XA-0.1B, nicknamed "Xombie", first flew free of tether September 19, 2009 and qualified for the Lunar Lander Challenge Level One second prize of $150,000 on October 7, 2009. In October 2016, NASA reported using Xombie to test the Landing Vision System, as part of the Autonomous Descent and Ascent Powered-flight Testbed experimental technologies, for the Mars 2020 mission landing; as of 7 March 2017 Xombie has flown 224 times. Masten's Xoie won the US$1,000,000 Level Two prize of the Lunar Lander Challenge on October 30, 2009, they beat Armadillo Aerospace by just a bit more than 24 inches of total landing accuracy, with an average accuracy of about 7.5 inches on the two landings in the round-trip competition flight.
Xoie has an aluminum frame and features a version of Masten's 750 pounds-force thrust engine that produces around 1,000 pounds-force of thrust. "Xoie", as the craft is nicknamed, qualified for the Lunar Lander Challenge level two on October 30, 2009. The Xaero reusable launch vehicle is a vertical-takeoff, vertical-landing rocket, being developed by Masten in 2010–2011, it has been proposed to NASA as a potential suborbital reusable launch vehicle for carrying research payloads under NASA's Flight Opportunities Program, projecting 30 km altitude in initial flights of five to six minutes duration, while carrying a 10 kg research payload. It is propelled by the 1,150 pounds-force Cyclops-AL-3 rocket engine burning isopropyl alcohol and liquid oxygen; the first Xaero test vehicle flew 110 test flights before being destroyed in its 111th flight. During the record-setting flight on Sep 11, 2012, an engine valve stuck open during descent, was sensed by the control system; as designed, the flight termination system was triggered, destroying the vehicle before it could create a range safety problem.
The final test flight was intended to test the vehicle at higher wind loads and altitudes, flying to an altitude of one kilometer while testing the flight controls at higher ascent and descent velocities before returning to a precise landing point. The ascent and initial portion of the descent was nominal, prior to the stuck throttle valve which resulted in termination of the flight prior to the planned precision landing. A follow up to Xaero with the ability to reach 6 km altitude with engine on throughout. Xaero-B is between 16 feet tall where Xaero was 12 feet tall. Xaero-B is proceeding through hot-fire testing, it will be used for the bulk of research flights up to initial altitudes between 20 km to 30 km. The vehicle has now been retired due to damage on a test flight in April 2017, it flew 75 times. The Xodiac is a VTVL rocket introduced in 2016, it features pressure-fed LOX/IPA propellant, a regeneratively cooled engine. Flights can simulate landing on the Mars. Video of Xodiac performing in-flight air flow tests Tuft strings.
Xeus is a vertical-takeoff lunar lander demonstrator. Xeus consists of a Centaur upper stage with RL-10 main engine to which four Katana vertical thrusters have been added. Production Xeus are estimated to be able to land on the Moon with up to 14 tonnes payload when using the expendable version or 5 tonnes payload when using the reusable version; the damaged Centaur on the demonstrator Xeus limits it to Earth flights. The production versions would have to be manufacturing fault free and certified for space operations. Man rating may be needed. United Launch Alliance, supplier of the Centaur, refer to Xeus as an abbreviation for eXperimental Enhanced Upper Stage. Further details of the proposed design are given in the paper "Experimental Enhanced Upper Stage: An affordable large lander system."Each of the Katanas used on a Xeus lander are to produce 3,500 pounds-force when performing a horizontal touchdown. In December 2012, Masten demonstrated their all-aluminum 2,800 pounds-force regeneratively-cooled engine, the KA6A.
The talk in this video announced the Xeus shows NASA's Space Exploration Vehicle rover with its two astronauts as a possible payload for the XEUS. On April 30, 2014 NASA announced that Masten Space Systems Inc. was one of
A sample-return mission is a spacecraft mission with the goal of collecting and returning samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back atoms and molecules or a deposit of complex compounds such as loose material and rocks; these samples may be obtained in a number of ways, such as soil and rock excavation or a collector array used for capturing particles of solar wind or cometary debris. To date, samples of Moon rock from Earth's Moon have been collected by robotic and crewed missions, the comet Wild 2 and the asteroid 25143 Itokawa have been visited by a robotic spacecraft which returned samples to Earth, samples of the solar wind have been returned by a robotic mission. In addition to sample-return missions, samples from three identified non-terrestrial bodies have been collected by means other than sample-return missions: samples from the Moon in the form of Lunar meteorites, samples from Mars in the form of Martian meteorites, samples from Vesta in the form of HED meteorites.
Samples available on Earth can be analyzed in laboratories, so we can further our understanding and knowledge as part of the discovery and exploration of the Solar System. Until now many important scientific discoveries about the Solar System were made remotely with telescopes, some Solar System bodies were visited by orbiting or landing spacecraft with instruments capable of remote sensing or sample analysis. While such an investigation of the Solar System is technically easier than a sample-return mission, the scientific tools available on Earth to study such samples are far more advanced and diverse than those that can go on spacecraft. Analysis of samples on Earth allows to follow up any findings with different tools, including tools that have yet to be developed. Samples analyzed on Earth can be matched against findings of remote sensing, for more insight into the processes that formed the Solar System; this was done, for example, with findings by the Dawn spacecraft, which visited the asteroid Vesta from 2011 to 2012 for imaging, samples from HED meteorites, which were compared to data gathered by Dawn.
These meteorites could be identified as material ejected from the large impact crater Rheasilvia on Vesta. This allowed deducing the composition of crust and core of Vesta; some differences in composition of asteroids can be discerned by imaging alone. However, for a more precise inventory of the material on these different bodies, more samples will be collected and returned in the future, to match their compositions with the data gathered through telescopes and astronomical spectroscopy. One further focus of such investigation—besides the basic composition and geologic history of the various Solar System bodies—is the presence of the building blocks of life on comets, Mars or the moons of the gas giants. Several sample-return missions to asteroids and comets are in the works. More samples from asteroids and comets will help determine whether life formed in space and was carried to Earth by meteorites. Another question under investigation is whether extraterrestrial life formed on other Solar System bodies like Mars or on the moons of the gas giants, whether life might exist there.
The result of NASA's last "Decadal Survey" was to prioritize a Mars sample-return mission, as Mars has a special importance: it is comparatively "nearby", might have harbored life in the past, might continue to sustain life. Jupiter's moon Europa is another important focus in the search for life in the Solar System. However, due to the distance and other constraints, Europa might not be the target of a sample-return mission in the foreseeable future. Planetary protection aims to prevent biological contamination of both the target celestial body and the Earth—in the case of sample-return missions. No sample has yet been returned with alien life in it. A sample-return from Mars or other location with potential to host life, is a category V mission under COSPAR which directs to containment of any unsterilized sample returned to Earth; this is because it is unknown the effects of such hypothetical life would be on humans or on the biosphere of Earth. For this reason, Carl Sagan and Joshua Lederberg argued in the 1970s that we should do sample-return missions classified as category V missions with extreme caution, studies by the NRC and ESF agreed.
The Apollo program returned over 382 kg of lunar rocks and regolith to the Lunar Receiving Laboratory in Houston. Today, 75% of the samples are stored at the Lunar Sample Laboratory Facility built in 1979. In July 1969, Apollo 11 achieved the first successful sample return from another Solar System body, it returned 22 kilograms of Lunar surface material. This was followed by 34 kilograms of material from Apollo 12, 42.8 kilograms of material from Apollo 14, 76.7 kilograms of material from Apollo 15, 94.3 kilograms of material from Apollo 16, 110.4 kilograms of material from Apollo 17. One of the most significant advances in sample-return missions occurred in 1970 when the robotic Soviet mission known as Luna 16 returned 101 grams of lunar soil. Luna 20 returned 55 grams in 1974, Luna 24 returned 170 grams in 1976. Although they recovered far less than the Apollo missions, they did this automatically. Apart from these three successes, other attempts under the Luna programme failed; the first two missions were intended to outstrip Apollo 11 and wer
A magnetometer or magnetic sensor is an instrument that measures magnetism—either the magnetization of a magnetic material like a ferromagnet, or the direction, strength, or relative change of a magnetic field at a particular location. A compass is a simple type of magnetometer, one that measures the direction of an ambient magnetic field; the first magnetometer capable of measuring the absolute magnetic intensity was invented by Carl Friedrich Gauss in 1833 and notable developments in the 19th century included the Hall effect, still used. Magnetometers are used for measuring the Earth's magnetic field and in geophysical surveys to detect magnetic anomalies of various types, they are used in the military to detect submarines. Some countries, such as the United States and Australia, classify the more sensitive magnetometers as military technology, control their distribution. Magnetometers can be used as metal detectors: they can detect only magnetic metals, but can detect such metals at a much larger depth than conventional metal detectors.
In recent years, magnetometers have been miniaturized to the extent that they can be incorporated in integrated circuits at low cost and are finding increasing use as miniaturized compasses. Magnetic fields are vector quantities characterized by both direction; the strength of a magnetic field is measured in units of tesla in the SI units, in gauss in the cgs system of units. 10,000 gauss are equal to one tesla. Measurements of the Earth's magnetic field are quoted in units of nanotesla called a gamma; the Earth's magnetic field can vary from 20,000 to 80,000 nT depending on location, fluctuations in the Earth's magnetic field are on the order of 100 nT, magnetic field variations due to magnetic anomalies can be in the picotesla range. Gaussmeters and teslameters are magnetometers that measure in units of gauss or tesla, respectively. In some contexts, magnetometer is the term used for an instrument that measures fields of less than 1 millitesla and gaussmeter is used for those measuring greater than 1 mT.
There are two basic types of magnetometer measurement. Vector magnetometers measure the vector components of a magnetic field. Total field magnetometers or scalar magnetometers measure the magnitude of the vector magnetic field. Magnetometers used to study the Earth's magnetic field may express the vector components of the field in terms of declination and the inclination. Absolute magnetometers measure the absolute magnitude or vector magnetic field, using an internal calibration or known physical constants of the magnetic sensor. Relative magnetometers measure magnitude or vector magnetic field relative to a fixed but uncalibrated baseline. Called variometers, relative magnetometers are used to measure variations in magnetic field. Magnetometers may be classified by their situation or intended use. Stationary magnetometers are installed to a fixed position and measurements are taken while the magnetometer is stationary. Portable or mobile magnetometers are meant to be used while in motion and may be manually carried or transported in a moving vehicle.
Laboratory magnetometers are used to measure the magnetic field of materials placed within them and are stationary. Survey magnetometers are used to measure magnetic fields in geomagnetic surveys; the performance and capabilities of magnetometers are described through their technical specifications. Major specifications include; the inverse is the cycle time in seconds per reading. Sample rate is important in mobile magnetometers. Bandwidth or bandpass characterizes. For magnetometers with no onboard signal processing, bandwidth is determined by the Nyquist limit set by sample rate. Modern magnetometers may perform averaging over sequential samples. Achieving a lower noise in exchange for lower bandwidth. Resolution is the smallest change in a magnetic field. A magnetometer should have a resolution a good deal smaller than the smallest change one wishes to observe. Quantization error is caused by recording roundoff and truncation of digital expressions of the data. Absolute error is the difference between the readings of a magnetometer true magnetic field.
Drift is the change in absolute error over time. Thermal stability is the dependence of the measurement on temperature, it is given as a temperature coefficient in units of nT per degree Celsius. Noise is the random fluctuations generated by electronics. Noise is given in units of n T / H z. Sensitivity is the larger of the resolution. Heading error is the change in the measurement due to a change in orientation of the instrument in a constant magnetic field; the dead zone is the angular region of magnetometer orientation in which the instrument produces poor or no measurements. All optically pumped, proton-free precession, Overhauser magnetometers experience some dead zone effects. Gradient tolerance is the ability of a ma
Lidar is a surveying method that measures distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can be used to make digital 3-D representations of the target; the name lidar, now used as an acronym of light detection and ranging, was a portmanteau of light and radar. Lidar sometimes is called 3D laser scanning, a special combination of a 3D scanning and laser scanning, it has terrestrial and mobile applications. Lidar is used to make high-resolution maps, with applications in geodesy, archaeology, geology, seismology, atmospheric physics, laser guidance, airborne laser swath mapping, laser altimetry; the technology is used in control and navigation for some autonomous cars. Lidar originated in the early 1960s, shortly after the invention of the laser, combined laser-focused imaging with the ability to calculate distances by measuring the time for a signal to return using appropriate sensors and data acquisition electronics.
Its first applications came in meteorology, where the National Center for Atmospheric Research used it to measure clouds. The general public became aware of the accuracy and usefulness of lidar systems in 1971 during the Apollo 15 mission, when astronauts used a laser altimeter to map the surface of the moon. Although now most sources treat the word "lidar" as an acronym, the term originated as a combination of "light" and "radar"; the first published mention of lidar, in 1963, makes this clear: "Eventually the laser may provide an sensitive detector of particular wavelengths from distant objects. Meanwhile, it is being used to study the moon by'lidar'..." The Oxford English Dictionary supports this etymology. The interpretation of "lidar" as an acronym came beginning in 1970, based on the assumption that since the base term "radar" started as an acronym for "Radio Detection And Ranging", "LIDAR" must stand for "Light Detection And Ranging", or for "Laser Imaging, Detection And Ranging". Although the English language no longer treats "radar" as an acronym and printed texts universally present the word uncapitalized, the word "lidar" became capitalized as "LIDAR" or "LiDAR" in some publications beginning in the 1980s.
No consensus exists on capitalization, reflecting uncertainty about whether or not "lidar" is an acronym, if it is an acronym, whether it should appear in lower case, like "radar". Various publications refer to lidar as "LIDAR", "LiDAR", "LIDaR", or "Lidar"; the USGS uses both "LIDAR" and "lidar", sometimes in the same document. Lidar uses ultraviolet, near infrared light to image objects, it can target a wide range of materials, including non-metallic objects, rain, chemical compounds, aerosols and single molecules. A narrow laser beam can map physical features with high resolutions; the essential concept of lidar was originated by EH Synge in 1930, who envisaged the use of powerful searchlights to probe the atmosphere. Indeed, lidar has since been used extensively for atmospheric meteorology. Lidar instruments fitted to aircraft and satellites carry out surveying and mapping – a recent example being the U. S. Geological Survey Experimental Advanced Airborne Research Lidar. NASA has identified lidar as a key technology for enabling autonomous precision safe landing of future robotic and crewed lunar-landing vehicles.
Wavelengths vary to suit the target: from about 10 micrometers to the UV. Light is reflected via backscattering, as opposed to pure reflection one might find with a mirror. Different types of scattering are used for different lidar applications: most Rayleigh scattering, Mie scattering, Raman scattering, fluorescence. Suitable combinations of wavelengths can allow for remote mapping of atmospheric contents by identifying wavelength-dependent changes in the intensity of the returned signal; the two kinds of lidar detection schemes are "incoherent" or direct energy detection and coherent detection. Coherent systems use optical heterodyne detection; this is more sensitive than direct detection and allows them to operate at much lower power, but requires more complex transceivers. Both types employ pulse models: either high energy. Micropulse systems utilize intermittent bursts of energy, they developed as a result of ever-increasing computer power, combined with advances in laser technology. They use less energy in the laser on the order of one microjoule, are "eye-safe", meaning they can be used without safety precautions.
High-power systems are common in atmospheric research, where they are used for measuring atmospheric parameters: the height and densities of clouds, cloud particle properties, pressure, wind and trace gas concentration. Lidar systems consist of several major components. 600–1000 nm lasers are most common for non-scientific applications. The maximum power of the laser is limited, or an automatic shut off system which turns the laser off at specific altitudes is used in order to make it ey
Resource Prospector (rover)
Resource Prospector is a cancelled mission concept by NASA of a rover that would have performed a survey expedition on a polar region of the Moon. The rover was to attempt to detect and map the location of volatiles such as hydrogen and lunar water which could foster more affordable and sustainable human exploration to the Moon and other Solar System bodies; the mission concept was still in its pre-formulation stage, when it was scrapped in April 2018. The Resource Prospector mission was proposed to be launched in 2022, its science instruments will be flown on several commercial lander missions contracted with NASA's new Commercial Lunar Payload Services program. In February 1976 the Soviet lander Luna 24 sent a sample of lunar soil to Earth, where it was found to contain about 0.1% water. Data obtained by the Lunar Reconnaissance Orbiter, Chandrayaan-1, the Lunar Crater Observation and Sensing Satellite, revealed that lunar water is distributed across the Moon's surface; the Resource Prospector mission concept proposes a NASA-led collaboration that seeks international space agencies and private industry partners to maximize the value.
However, it is unclear if the use of lunar resources is permitted under the 1967 Outer Space Treaty signed by the United States, 90 other countries. Hydrogen and oxygen can be used to make vital consumables, but to make rocket fuel, basic materials required for in-space manufacturing; the technical process is called in situ resource utilization or ISRU. The rover would have use a drill to extract samples of the lunar soil from as deep as one meter below the surface. In September 2015, the rover prototype underwent field testing, in May 2016, the prototype rover underwent thermal vacuum and thermal testing at NASA's Johnson Space Center in Houston. Before its cancellation, NASA officials were exploring various launch options, including to fly it as a secondary payload on board the second flight of the Space Launch System, called the Exploration Mission 2 in 2022. Another reported launch option was the Falcon Heavy rocket; the Resource Prospector team was notified on 23 April 2018 to cease all work on the project by the end of May.
The concept was going to be submitted for a major design review by the end of 2018 for funding and launch. This rover was the only mission in conceptual development by NASA to explore the surface of the Moon in situ; the cancellation stemmed from the program being moved to another Division with an insufficient budget to fund this mission. $100 million were spent on the rover's instruments over ten years. Scientists involved in the Lunar Exploration Analysis Group sent a letter on 26 April to the NASA administrator, James Bridenstine laying their case to reverse the decision, remarked that other nations are preparing landers to stake claim on the natural resources on the south polar region of the Moon. In a 3 May 2018 statement, NASA officials explained that lunar surface exploration will continue in the future, but using commercial lander services under a new Commercial Lunar Payload Services program; some of these commercial landers will be equipped with the ice drill and scientific instruments developed for the Resource Prospector.
NASA officials stated that under this program, Resource Prospector instruments will go forward in an expanded lunar surface campaign, instead of the original two weeks. Preliminary studies call for a rover of about 300 kg, it was suggested to be launched with a Falcon 9 rocket. The mission life would have been between 14 Earth days; the motivation and purpose of the mission was to characterize the nature and distribution of lunar water and other volatiles in lunar polar sub-surface materials, to demonstrate in situ resource utilization processing of lunar soil by heating samples in an oven and isolating the resulting volatiles. The conceptual payload includes: Neutron spectrometer Infrared spectrometer One meter long core drill Oven Luna-Glob, a current Russian lander program Lunar Prospector, a lunar orbiter launched in 1998 Prospector, a lander mission concept cancelled in 1962
A robotic spacecraft is an uncrewed spacecraft under telerobotic control. A robotic spacecraft designed to make scientific research measurements is called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn and Neptune are too distant to reach with current crewed spacecraft technology, so telerobotic probes are the only way to explore them. Many artificial satellites are robotic spacecraft, as are many rovers; the first robotic spacecraft was launched by the Soviet Union on 22 July 1951, a suborbital flight carrying two dogs Dezik and Tsygan. Four other such flights were made through the fall of 1951; the first artificial satellite, Sputnik 1, was put into a 215-by-939-kilometer Earth orbit by the USSR) on 4 October 1957. On 3 November 1957, the USSR orbited Sputnik 2.
Weighing 113 kilograms, Sputnik 2 carried the first living animal into the dog Laika. Since the satellite was not designed to detach from its launch vehicle's upper stage, the total mass in orbit was 508.3 kilograms. In a close race with the Soviets, the United States launched its first artificial satellite, Explorer 1, into a 193-by-1,373-nautical-mile orbit on 31 January 1958. Explorer I was a 80.75-inch long by 6.00-inch diameter cylinder weighing 30.8 pounds, compared to Sputnik 1, a 58-centimeter sphere which weighed 83.6 kilograms. Explorer 1 carried sensors which confirmed the existence of the Van Allen belts, a major scientific discovery at the time, while Sputnik 1 carried no scientific sensors. On 17 March 1958, the US orbited its second satellite, Vanguard 1, about the size of a grapefruit, remains in a 360-by-2,080-nautical-mile orbit as of 2016. Nine other countries have launched satellites using their own launch vehicles: France and China, the United Kingdom, Israel, North Korea, New Zealand.
In spacecraft design, the United States Air Force considers a vehicle to consist of the mission payload and the bus. The bus provides physical structure, thermal control, electrical power, attitude control and telemetry and commanding. JPL divides the "flight system" of a spacecraft into subsystems; these include: This is the physical backbone structure. It: provides overall mechanical integrity of the spacecraft ensures spacecraft components are supported and can withstand launch loads This is sometimes referred to as the command and data subsystem, it is responsible for: command sequence storage maintaining the spacecraft clock collecting and reporting spacecraft telemetry data collecting and reporting mission data This system is responsible for the correct spacecraft's orientation in space despite external disturbance-gravity gradient effects, magnetic-field torques, solar radiation and aerodynamic drag. In planetary exploration missions involving robotic spacecraft, there are three key parts in the processes of landing on the surface of the planet to ensure a safe and successful landing.
This process includes a entry into the planetary gravity field and atmosphere, a descent through that atmosphere towards a intended/targeted region of scientific value, a safe landing that guarantees the integrity of the instrumentation on the craft is preserved. While the robotic spacecraft is going through those parts, it must be capable of estimating its position compared to the surface in order to ensure reliable control of itself and its ability to maneuver well; the robotic spacecraft must efficiently perform hazard assessment and trajectory adjustments in real time to avoid hazards. To achieve this, the robotic spacecraft requires accurate knowledge of where the spacecraft is located relative to the surface, what may pose as hazards from the terrain, where the spacecraft should presently be headed. Without the capability for operations for localization, hazard assessment, avoidance, the robotic spacecraft becomes unsafe and can enter dangerous situations such as surface collisions, undesirable fuel consumption levels, and/or unsafe maneuvers.
Integrated sensing incorporates an image transformation algorithm to interpret the immediate imagery land data, perform a real-time detection and avoidance of terrain hazards that may impede safe landing, increase the accuracy of landing at a desired site of interest using landmark localization techniques. Integrated sensing completes these tasks by relying on pre-recorded information and cameras to understand its location and determine its position and whether it is correct or needs to make any corrections; the cameras are used to detect any possible hazards whether it is increased fuel consumption or it is a physical hazard such as a poor landing spot in a crater or cliff side that would make landing not ideal. Components in the telecommunications subsystem include radio antennas and receivers; these may be used to communicate with other spacecraft. The supply of electric power on spacecraft come from photovoltaic cells or from a radioisotope thermoelectric generator. Other components of the subsystem include batteries for storing power and distribution circuitry that conne