Double Asteroid Redirection Test
|Mission type||Asteroid impactor|
|Manufacturer||Applied Physics Laboratory|
|Launch mass||500 kg (1,100 lb)|
|Dimensions||12.5 m × 2.4 m|
|Start of mission|
|Launch date||2021 |
|Rocket||Piggyback on a commercial satellite launch|
|(65803) Didymos impactor|
|Impact date||October 2022|
Double Asteroid Redirection Test (DART) is a planned space probe that will demonstrate the kinetic effects of crashing an impactor spacecraft into an asteroid moon for planetary defense purposes. The mission is intended to test whether a spacecraft impact could successfully deflect an asteroid on a collision course with Earth.
A demonstration of an asteroid deflection is a key test that NASA and other agencies wish to perform before the actual need of planetary protection is present. DART is a joint project between NASA and the Johns Hopkins Applied Physics Laboratory (APL), and it is being developed under the auspices of NASA's Planetary Defense Coordination Office.
In August 2018 NASA approved the project to start the final design and assembly phase.
Originally, the European Space Agency (ESA) and NASA had independent plans for a mission to test asteroid deflection strategies, and by 2015 they struck a collaboration called AIDA —now cancelled— that would have had the two spacecraft launch separately but work in synergy. Under the proposal, the European spacecraft, AIM, would have launched in December 2020, and DART in July 2021. AIM would have orbited the larger asteroid and study its composition and that of its moon. DART would then impact the moon on October 2022, during a close approach to Earth. AIM would have studied the asteroid's strength, surface physical properties and its internal structure, as well as measure the effect on the asteroid moon's orbit around the larger asteroid. Since the AIM orbiter was cancelled, the full characterization of the asteroids will not be obtained, and the effects of the impact by DART will be monitored from ground-based telescopes and radar.
The spacecraft's solar arrays use a roll-up design called ROSA, and this was tested on the International Space Station in June 2017 as part of Expedition 52, delivered to the station by CRS-11 SpaceX Dragon unmanned space launch. In June 2017 NASA approved a move from concept development to the preliminary design phase, and in August 2018 NASA approved the project to start the final design and assembly phase.
Scientists estimate 25,000 large asteroids lurk in the Solar System, though to date, surveys have detected about 8,000, therefore NASA officials think it is imperative to develop an effective plan should a near-Earth object threaten Earth. DART is an impactor that hosts no scientific payload other than a Sun sensor, a star tracker, and 20 cm aperture camera to support autonomous navigation to impact the small asteroid's moon at its center. It is estimated that the impact of the 500 kg (1,100 lb) DART at 6 km/s (3.7 mi/s) will produce a velocity change on the order of 0.4 mm/s, which leads to a small change in trajectory of the asteroid system, but over time, it leads to a large shift of path. Overall, DART is expected to alter the speed of Didymos's orbit by about half a millimeter per second, resulting in an orbital period change of perhaps 10 minutes. Over a span of millions of kilometers, the cumulative trajectory change would turn a collision with a genuinely Earth-bound asteroid or comet into a safe outcome. The actual velocity change and orbital shift will be measured a few years later by a small spacecraft called Hera that would do a detailed reconnaissance and assessment.
DART spacecraft will use the NEXT ion thuster —with power from solar panels establishing solar electric propulsion- for primary propulsion. The DART impactor is also proposed to make a flyby observation of asteroid 3361 Orpheus during its trajectory to 65803 Didymos. It will obtain some images in the visible spectrum.
The low mass, and use of solar electric ion propulsion, is hoped to allow DART to be launched as a secondary payload on a commercial/scheduled launch and keep the total project cost down to $250 million.
The Italian Space Agency (ASI) proposes to include a secondary spacecraft called LICIA (Light Italian CubeSat for Imaging of Asteroids), a small CubeSat that would piggyback with DART and would separate shortly before impact to acquire images of the impact and ejecta as it drifts past the asteroid. LICIA will be able to communicate directly with Earth, sending back images of the ejecta after the Didymos flyby. It will have a design similar to ASI's ArgoMoon CubeSat, planned to be launched in 2020.
In a separate project, the European Space Agency is formulating Hera, a spacecraft that would be launched to Didymos a few years after DART's impact to do a detailed reconnaissance and assessment.
The mission's target is 65803 Didymos, a binary asteroid system in which one asteroid is orbited by a smaller one. The primary asteroid is about 800 m (2,600 ft) in diameter; its small satellite is about 150 m (490 ft) in diameter in an orbit about 1.1 km from the primary. DART will target the smaller asteroid's moon. Didymos is not an Earth-crossing asteroid, and there is no possibility that the deflection experiment could create an impact hazard.
- Asteroid impact avoidance
- B612 Foundation
- Don Quijote (spacecraft)
- Planetary defense against asteroids and comets
- The Spaceguard Foundation
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