DART, the Double Asteroid Redirection Test, is the first mission to test a potential method of deflecting an asteroid on course to hit Earth. Launching in 2021 and arriving at asteroid 65803 Didymos in 2022, it will intentionally crash into the asteroid's small moon (informally known as Didymoon).
The crash should change Didymoon’s orbital period around Didymos by 4.2 minutes, a large enough change to measure from Earth-based telescopes. Such a change would show that if we spot a potentially hazardous asteroid in time, a DART-like impact could change its course enough to miss Earth.
DART is NASA's contribution to the Asteroid Impact and Deflection Assessment (AIDA) mission, a NASA-ESA collaboration. After DART’s impact, in 2025, ESA would send a follow-on spacecraft called Hera to Didymos to observe the crater DART created.
En route to Didymos, DART may fly past asteroid 2001 CB21. Shortly before DART strikes Didymoon, it may also deploy an Italian Space Agency-built CubeSat to observe the impact.
Fourteen Arecibo radar images of the near-Earth asteroid (65803) Didymos and its moonlet, taken on 23, 24 and 26 November 2003. NASA’s planetary radar capabilities enable scientists to resolve shape, concavities, and possible large boulders on the surfaces of these small worlds. Photometric lightcurve data indicate that Didymos is a binary system, and radar imagery distinctly shows the secondary body.
65803 Didymos (Greek for "twin") is a binary, S-type near-Earth asteroid system. The system was discovered in 1996 by Spacewatch at Kitt Peak, Arizona, and confirmed as a binary asteroid in 2003.
Asteroid Didymos roughly travels between Earth's orbit and beyond Mars' orbit.
Aphelion: 2.28 AU
Perihelion: 1.01 AU
Close approaches to Earth: 04 October 2022 (0.071 AU / 10.6 million kilometers / 27 lunar distances), 01 September 2041 (0.354 AU / 53 million kilometers / 138 lunar distances)
Didymos A (parent body)
Diameter: 750 meters
Rotation period: 2.26 hours (rapid rotator)
Didymos B (Didymoon)
Diameter: 160 meters
Orbital period: 11.90 hours (tidally locked). After the DART impact, Didymos B's orbital period is expected to drop from 11.90 to 11.83 hours, a difference of 4.2 minutes.
Dimensions: Bus box 1.14 meters wide, 1.24 meters tall, 1.32 meters deep. DART's 2 roll-out solar arrays give the spacecraft a width of 12.5 meters when deployed.
Didymos arrival mass: 500 kg
DART has a single science instrument called DRACO (Didymos Reconnaissance & Asteroid Camera for OpNav), a dual-purpose telescope for observing the asteroid in high-resolution and for autonomous navigation. New Horizons LORRI heritage, built by JHUAPL. 208 mm aperture, f/12.6, 0.29-degree field of view. Panchromatic CMOS image sensor with 2560 x 2160 pixel resolution. Fletcher et. al (2018)
When DART is about 4 hours away from impact, its Small-body Maneuvering Autonomous Real-Time (SMART) navigation system will guide the spacecraft the rest of the way to Didymoon. Using images from DRACO, SMART will differentiate between Didymos A and B and steer toward Didymos B.
NEXT-C (NASA Evolutionary Xenon Thruster – Commercial) solar electric propulsion system: DART's solar-electric propulsion system gives it launch window flexibility, since it will make multiple phasing loops around Earth before reaching escape velocity and heading on to Didymos. Dawn heritage, developed at NASA Glenn. Can be throttled from 25 to 235 mN, input power up to 7.4 kW. Fact sheet (2018)
Roll Out Solar Arrays (ROSA): DART's 2 large, roll-out solar arrays are necessary to provide power for the solar-electric propulsion system. The roll-out technology was successfully tested in space from the International Space Station in 2017. Beginning-of-life power: 6.6 kW. Manufacturer: Deployable Space Systems (DSS)
11 April 2019: NASA announces $69 million launch contract for DART to launch on SpaceX Falcon 9 from Vandenberg Air Force Base
2017: ESA refines AIM concept, re-brands mission proposal as Hera
23 June 2017: DART moves from concept to preliminary design phase
December 2016: ESA council declines to fund its portion of the mission, AIM. NASA continues work on DART, noting that ground-based telescopes can observe Didymoon's orbital change around Didymos instead.
2005: ESA begins considering a two-spacecraft asteroid deflection mission called Don Quijote, which would send a spacecraft called Sancho to orbit the target asteroid before a second spacecraft named Hidalgo impacts the asteroid. Two asteroid targets were considered: 2002 AT4 and 1989 ML.
DART's planned budget is $313.9 million spread out over 8 years. This covers spacecraft development, launch vehicle, and operations through the end of its primary mission in late 2022.
Double Asteroid Redirection Test costs per fiscal year. Amounts after the current year are official projections. Source: Planetary Science Budget Dataset, compiled by Casey Dreier for The Planetary Society (accessible on Google Sheets or downloadable as an Excel file).