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A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun (perihelion) is less than 1.3 times the Earth–Sun distance. This definition applies to the object's orbit around the Sun,rather than its current position,thus an object with such an orbit is considered an NEO even at times when it is far from making a close approach of Earth. If an NEO's orbit crosses the Earth's orbit,and the object is larger than 140 meters (460 ft) across,it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids,but about 0.35% are comets.
The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons,which carry momentum. It is usually considered in relation to meteoroids or small asteroids,as its influence is most significant for these bodies.
Asteroid impact avoidance comprises the methods by which near-Earth objects (NEO) on a potential collision course with Earth could be diverted away,preventing destructive impact events. An impact by a sufficiently large asteroid or other NEOs would cause,depending on its impact location,massive tsunamis or multiple firestorms,and an impact winter caused by the sunlight-blocking effect of large quantities of pulverized rock dust and other debris placed into the stratosphere. A collision 66 million years ago between the Earth and an object approximately 10 kilometers wide is thought to have produced the Chicxulub crater and triggered the Cretaceous–Paleogene extinction event that is understood by the scientific community to have caused the extinction of all non-avian dinosaurs.
The B612 Foundation is a private nonprofit foundation headquartered in Mill Valley,California,United States,dedicated to planetary science and planetary defense against asteroids and other near-Earth object (NEO) impacts. It is led mainly by scientists,former astronauts and engineers from the Institute for Advanced Study,Southwest Research Institute,Stanford University,NASA and the space industry.
99942 Apophis (provisional designation 2004 MN4) is a near-Earth asteroid and a potentially hazardous object with a diameter of 370 metres (1,210 feet) that caused a brief period of concern in December 2004 when initial observations indicated a probability up to 2.7% that it would hit Earth on April 13,2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth in 2029. Until 2006,a small possibility nevertheless remained that,during its 2029 close encounter with Earth,Apophis would pass through a gravitational keyhole of no more than about 800 kilometres (500 mi) in diameter,which would have set up a future impact exactly seven years later on April 13,2036. This possibility kept it at Level 1 on the Torino impact hazard scale until August 2006,when the probability that Apophis would pass through the keyhole was determined to be very small and Apophis's rating on the Torino scale was lowered to zero. By 2008,the keyhole had been determined to be less than 1 km wide. During the short time when it had been of greatest concern,Apophis set the record for highest rating ever on the Torino scale,reaching level 4 on December 27,2004.
2002 AT4 is a near-Earth object and potentially hazardous asteroid of the Amor group,approximately 350 meters (1,100 feet) in diameter. It has an eccentric orbit that brings it sometimes close to Earth's orbit,and sometimes halfway between Mars and Jupiter. It is a dark D-type asteroid which means that it may be reddish in color.
(10302) 1989 ML is an as yet unnamed near-Earth asteroid. It is approximately 0.6 km in diameter. An Amor asteroid,it orbits between Earth and Mars. It is an X-type asteroid,so its surface composition is yet unknown. It was discovered by Eleanor F. Helin and Jeff T. Alu at Palomar Observatory on 29 June 1989.
Advanced Concepts Team (ACT) is a research lab within the European Space Agency tasked to "... monitor and perform research on advanced space concepts and technologies,preparing ESA for any disruptive change to come.". Located at the European Space Research and Technology Centre,in the Netherlands,the team was instituted in 2002 with the objective of fostering advanced research on space systems,innovative concepts and working methods. It serves the function of a think tank providing decision makers the support of a highly multidisciplinary research group. Science and engineering research fellows,Young Graduate Trainee and interns form the bulk of the Team. They carry out research work on advanced topics and emerging technologies and perform highly skilled analysis on a wide range of topics.
A gravitational keyhole is a tiny region of space where a planet's gravity would alter the orbit of a passing asteroid such that the asteroid would collide with that planet on a given future orbital pass. The word "keyhole" contrasts the large uncertainty of trajectory calculations with the relatively narrow bundle(s) of critical trajectories. The term was coined by P. W. Chodas in 1999. It gained some public interest when it became clear,in January 2005,that the asteroid 99942 Apophis would miss the Earth in 2029 but may go through one or another keyhole leading to impacts in 2036 or 2037. Further research has since been done,however,which revealed the probability of Apophis passing through the keyhole was extremely low.
65803 Didymos is a sub-kilometer asteroid and binary system that is classified as a potentially hazardous asteroid and near-Earth object of the Apollo group. The asteroid was discovered in 1996 by the Spacewatch survey at Kitt Peak,and its small 160-meter minor-planet moon,named Dimorphos,was discovered in 2003. Due to its binary nature,the asteroid was then named Didymos,the Greek word for 'twin'.
3361 Orpheus is an Apollo asteroid that was discovered on 24 April 1982 by Carlos Torres at Cerro El Roble Astronomical Station. Its eccentric orbit crosses that of Mars and Earth,and approaches Venus as well. From 1900 to 2100 it passes closer than 30 Gm to Venus,11;Earth,33;and Mars,14 times. It passed by Earth at a distance of about 0.03 AU in 1937,1978,1982,and 2021,and will do so again in 2025.
(612600) 2003 SM84 is a sub-kilometer asteroid,classified as near-Earth object of the Amor group orbiting between Earth and Mars. It was first observed by the Lincoln Near-Earth Asteroid Research (LINEAR) at the Lincoln Laboratory ETS on 20 September 2003.
The Asteroid Impact and Deflection Assessment (AIDA) missions are a proposed pair of space probes which will study and demonstrate the kinetic effects of crashing an impactor spacecraft into an asteroid moon. The mission is intended to test and validate impact models of whether a spacecraft could successfully deflect an asteroid on a collision course with Earth.
Patrick Michel is a French planetary scientist,Senior Researcher at CNRS,leader of the team TOP of the CNRS and UniversitéCôte d'Azur Lagrange Laboratory at the Côte d'Azur Observatory in Nice (France),and also a Global Fellow of the University of Tokyo.
Double Asteroid Redirection Test (DART) was a NASA space mission aimed at testing a method of planetary defense against near-Earth objects (NEOs). It was designed to assess how much a spacecraft impact deflects an asteroid through its transfer of momentum when hitting the asteroid head-on. The selected target asteroid,Dimorphos,is a minor-planet moon of the asteroid Didymos;neither asteroid poses an impact threat to Earth,but their joint characteristics made them an ideal benchmarking target. Launched on 24 November 2021,the DART spacecraft successfully collided with Dimorphos on 26 September 2022 at 23:14 UTC about 11 million kilometers from Earth. The collision shortened Dimorphos' orbit by 32 minutes,greatly in excess of the pre-defined success threshold of 73 seconds. DART's success in deflecting Dimorphos was due to the momentum transfer associated with the recoil of the ejected debris,which was substantially larger than that caused by the impact itself.
Dimorphos is a natural satellite or moon of the near-Earth asteroid 65803 Didymos,with which it forms a binary system. The moon was discovered on 20 November 2003 by Petr Pravec in collaboration with other astronomers worldwide. Dimorphos has a diameter of 177 meters (581 ft) across its longest extent and it was the target of the Double Asteroid Redirection Test (DART),a NASA space mission that deliberately collided a spacecraft with the moon on 26 September 2022 to alter its orbit around Didymos. Before the impact by DART,Dimorphos had a shape of an oblate spheroid with a surface covered in boulders but virtually no craters. The moon is thought to have formed when Didymos shed its mass due to its rapid rotation,which formed an orbiting ring of debris that conglomerated into a low-density rubble pile that became Dimorphos today.
Light Italian CubeSat for Imaging of Asteroids is a six-unit CubeSat of the Italian Space Agency (ASI). LICIACube is a part of the Double Asteroid Redirection Test (DART) mission and carries out observational analysis of the Didymos asteroid binary system after DART's impact on Dimorphos. It communicates directly with Earth,sending back images of the ejecta and plume of DART's impact as well as having done asteroidal study during its flyby of the Didymos system from a distance of 56.7 km (35.2 mi),165 seconds after DART's impact. LICIACube is the first purely Italian autonomous spacecraft in deep space. Data archiving and processing is managed by the Space Science Data Center (SSDC) of the ASI.
Hera is a space mission in development at the European Space Agency in its Space Safety program. Its primary objective is to study the Didymos binary asteroid system that was impacted by DART and contribute to validation of the kinetic impact method to deviate a near-Earth asteroid in a colliding trajectory with Earth. It will measure the size and the morphology of the crater created and momentum transferred by an artificial projectile impacting an asteroid,which will allow measuring the efficiency of the deflection produced by the impact. It will also analyze the expanding debris cloud caused by the impact.
References
- 1 2 3 4 "Don Quixote concept". ESA. Archived from the original on 30 June 2015. Retrieved 17 June 2015.
- 1 2 3 4 5 6 "Sancho study: designing the minimum Earth escape spacecraft". ESA. 23 May 2012. Archived from the original on 15 May 2015. Retrieved 17 June 2015.
- 1 2 "Don Quijote mission". ESA . Retrieved 11 March 2023.
- ↑ "Don Quichotte". www.esa.int. Retrieved 2023-02-21.
- ↑ "NEO precursor studies". ESA. 26 February 2015. Archived from the original on 7 June 2015. Retrieved 17 June 2015.
- ↑ "N° 41–2005: ESA selects targets for asteroid-deflecting mission Don Quijote" (Press release). ESA. 26 September 2005. Retrieved 17 June 2015.
- ↑ "Asteroid Impact Deflection Assessment AIDA study". ESA. 26 February 2015. Archived from the original on 7 June 2015. Retrieved 17 June 2015.
- ↑ "Asteroid deflection mission seeks smashing ideas". ESA. 15 January 2013. Archived from the original on 21 June 2015. Retrieved 17 June 2015.
- ↑ "Asteroid Deflection Mission AIDA Set To Crash Two Spacecraft Into Space Rock In 2022". Huffington Post. 25 March 2013. Retrieved 17 June 2015.
