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A satellite or artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation (GPS), broadcasting, scientific research, and Earth observation. Additional military uses are reconnaissance, early warning, signals intelligence and, potentially, weapon delivery. Other satellites include the final rocket stages that place satellites in orbit and formerly useful satellites that later become defunct.
A geosynchronous orbit is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds. The synchronization of rotation and orbital period means that, for an observer on Earth's surface, an object in geosynchronous orbit returns to exactly the same position in the sky after a period of one sidereal day. Over the course of a day, the object's position in the sky may remain still or trace out a path, typically in a figure-8 form, whose precise characteristics depend on the orbit's inclination and eccentricity. A circular geosynchronous orbit has a constant altitude of 35,786 km (22,236 mi).
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, peaking in number at an altitude around 800 km (500 mi), while the farthest in LEO, before medium Earth orbit (MEO), have an altitude of 2,000 kilometers, about one-third of the radius of Earth and near the beginning of the inner Van Allen radiation belt.
Space debris are defunct human-made objects in space – principally in Earth orbit – which no longer serve a useful function. These include derelict spacecraft, mission-related debris, and particularly numerous in-Earth orbit, fragmentation debris from the breakup of derelict rocket bodies and spacecraft. In addition to derelict human-made objects left in orbit, space debris includes fragments from disintegration, erosion, or collisions; solidified liquids expelled from spacecraft; unburned particles from solid rocket motors; and even paint flecks. Space debris represents a risk to spacecraft.
A laser broom is a proposed ground-based laser beam-powered propulsion system that sweeps space debris out of the path of artificial satellites to prevent collateral damage to space equipment. It heats up one side of the debris to shift its orbit trajectory, altering the path to hit the atmosphere sooner. Space researchers have proposed that a laser broom may help mitigate Kessler syndrome, a runaway cascade of collision events between orbiting objects. Additionally, laser broom systems mounted on satellites or space station have also been proposed.
Planetes is a Japanese hard science fiction manga written and illustrated by Makoto Yukimura. It was serialized in Kodansha's seinen manga magazine Morning between January 1999 to January 2004, with its chapters collected into four tankōbon volumes. It was adapted into a 26-episode anime television series by Sunrise, which was broadcast on NHK from October 2003 through April 2004. The story revolves around the crew of a space debris collection craft in the year 2075.
The Whipple shield or Whipple bumper, invented by Fred Whipple, is a type of spaced armor shielding to protect crewed and uncrewed spacecraft from hypervelocity impact / collisions with micrometeoroids and orbital debris whose velocities generally range between 3 and 18 kilometres per second. According to NASA, the Whipple shield is designed to withstand collisions with debris up to 1 cm.
Cerise was a French military reconnaissance satellite. Its main purpose was to intercept HF radio signals for French intelligence services. With a mass of 50 kg, it was launched by an Ariane 4 rocket from Kourou in French Guiana at 17:23 UT, 7 July 1995. Cerise's initial orbital parameters were period 98.1 min, apogee 675 km, perigee 666 km, and inclination 98.0 deg.
The Kessler syndrome, proposed by NASA scientists Donald J. Kessler and Burton G. Cour-Palais in 1978, is a scenario in which the density of objects in low Earth orbit (LEO) due to space pollution is numerous enough that collisions between objects could cause a cascade in which each collision generates space debris that increases the likelihood of further collisions. In 2009, Kessler wrote that modeling results had concluded that the debris environment was already unstable, "such that any attempt to achieve a growth-free small debris environment by eliminating sources of past debris will likely fail because fragments from future collisions will be generated faster than atmospheric drag will remove them". One implication is that the distribution of debris in orbit could render space activities and the use of satellites in specific orbital ranges difficult for many generations.
Spacecraft collision avoidance is the implementation and study of processes minimizing the chance of orbiting spacecraft inadvertently colliding with other orbiting objects. The most common subject of spacecraft collision avoidance research and development is for human-made satellites in geocentric orbits. The subject includes procedures designed to prevent the accumulation of space debris in orbit, analytical methods for predicting likely collisions, and avoidance procedures to maneuver offending spacecraft away from danger.
5185 Alerossi, provisional designation 1990 RV2, is a background asteroid from the central region of the asteroid belt, approximately 13 miles (21 kilometers) in diameter. It was discovered on 15 September 1990, by American astronomer Henry Holt at Palomar Observatory in California, United States. The asteroid was later named for Italian geodesist Alessandro Rossi.
Kosmos-2251 was a Russian Strela-2M military communications satellite. It was launched into Low Earth orbit from Site 132/1 at the Plesetsk Cosmodrome at 04:17 UTC on 16 June 1993, by a Kosmos-3M carrier rocket. The Strela satellites had a lifespan of 5 years, and the Russian government reported that Kosmos-2251 ceased functioning in 1995. Russia was later criticised by The Space Review for leaving a defunct satellite in a congested orbit, rather than deorbiting it. In response, Russia noted that they were not required to do so under international law. In any case, the KAUR-1 satellites had no propulsion system, which is usually required for deorbiting.
Iridium 33 was a communications satellite launched by Russia for Iridium Communications. It was launched into low Earth orbit from Site 81/23 at the Baikonur Cosmodrome at 01:36 UTC on 14 September 1997, by a Proton-K rocket with a Block DM2 upper stage. The launch was arranged by International Launch Services (ILS). It was operated in Plane 3 of the Iridium satellite constellation, with an ascending node of 230.9°.
Strictly speaking, a satellite collision is when two satellites collide while in orbit around a third, much larger body, such as a planet or moon. This definition is typically loosely extended to include collisions between sub-orbital or escape-velocity objects with an object in orbit. Prime examples are the anti-satellite weapon tests. There have been no observed collisions between natural satellites, but impact craters may show evidence of such events. Both intentional and unintentional collisions have occurred between man-made satellites around Earth since the 1980s. Anti-satellite weapon tests and failed rendezvous or docking operations can result in orbital space debris, which in turn may collide with other satellites.
On February 10, 2009, two communications satellites—the active commercial Iridium 33 and the derelict Russian military Kosmos 2251—accidentally collided at a speed of 11.7 km/s (26,000 mph) and an altitude of 789 kilometres (490 mi) above the Taymyr Peninsula in Siberia. It was the first time a hypervelocity collision occurred between two satellites; previous incidents had involved a satellite and a piece of space debris.
The Space Surveillance Telescope (SST) is a Southern Hemisphere-based United States Space Force telescope used for detecting, tracking, and cataloguing satellites, near-Earth objects, and space debris.
WT1190F was a small temporary satellite of Earth that impacted Earth on 13 November 2015 at 06:18:21.7 UTC. It is thought to have been space debris from the trans-lunar injection stage of the 1998 Lunar Prospector mission. It was first discovered on 18 February 2013 by the Catalina Sky Survey. It was then lost, and reacquired on 29 November 2013. It was again discovered on 3 October 2015 by astronomer Rose Garcia with the Catalina Sky Survey 60-inch telescope, and the object was soon identified to be the same as the two objects previously sighted by the team, who have been sharing their data through the International Astronomical Union's Minor Planet Center (MPC). An early orbit calculation showed that it was orbiting Earth in an extremely elliptical orbit, taking it from within the geosynchronous satellite ring to nearly twice the distance of the Moon. It was also probably the same object as 9U01FF6, another object on a similar orbit discovered on 26 October 2009.
Jeanne Lee Crews was an American aerospace engineer at NASA, and also one of the first female engineers to join the agency. She retired in November 2002 and is now living in Satellite Beach, Florida. In order to protect spacecraft from debris, she designed a "flexible multi-shock shield to protect spacecraft from debris," which is still in use on the International Space Station today. Jeanne Lee Crews is also one of the first women at NASA to participate on a zero-G flight. She has more recently been working on a way to gather and accumulate orbital debris, through a large balloon that will return to Earth once full. Jeanne Lee Crews has been awarded with Aerospace Lifetime Achievement Award, the NASA Exceptional Service Medal, and the NASA Exceptional Achievement Medal.
Space sustainability aims to maintain the safety and health of the space environment, as well as planetary environments.
References
- ↑ "Don Kessler". International Association for the Advancement of Space Safety. 2020. Retrieved 11 October 2020.
- 1 2 "11267 Donaldkessler (1981 UE28)". Minor Planet Center. Retrieved 23 April 2017.
- 1 2 Khatchadourian, Raffi (18 September 2020). "The Elusive Peril of Space Junk". The New Yorker. Retrieved 2020-10-11.
- 1 2 3 4 Schwartz, Evan I., "Waste MGMT", Wired , vol. 18, no. 6, pp. 172–180.
- ↑ Donald J. Kessler and Burton G. Cour-Palais (1978). "Collision Frequency of Artificial Satellites: The Creation of a Debris Belt". Journal of Geophysical Research. 83 (A6): 2637–2646. Bibcode:1978JGR....83.2637K. doi:10.1029/JA083iA06p02637.
- ↑ Video of address
- ↑ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 23 April 2017.
