NASA joins forces with its European counterpart ESA to build a probe for asteroid deflection test. The Asteroid Impact and Deflection Assessment (AIDA) mission will test our ability to perform a spacecraft impact on a potentially hazardous near-Earth asteroid. The target chosen by scientists, nicknamed "Didymoon", is the natural satellite orbiting the asteroid Didymos.

AIDA is made up of two "sub-missions": the ESA-led Asteroid Impact Mission (AIM) and NASA-led Double Asteroid Redirection Test (DART). DART will impact with Didymoon and AIM will assess the mission's effectiveness in diverting the moon's orbit around Didymos.

"AIDA will help us gain important knowledge regarding [asteroid] hazard mitigation," Patrick Michel of the Cote d'Azur Observatory (OCA), the lead of the AIM Investigation Team, told astrowatch.net.

"Once we validate our understanding of the impact physics and the kinetic impactor techniques, we can design the next kinetic impactor with a more reliable way," he added.

The AIM probe will be launched in October 2020 onboard a Russian Soyuz 2.1b launch vehicle from the European spaceport in Kourou, French Guiana. After the launch and a deep-space maneuver, AIM will arrive at Didymos in June 2022, some months before DART impact.

After arrival, the AIM spacecraft will transition into a heliocentric co-flying orbit, from which it will observe the binary system to derive a high-resolution 3D model of the asteroid, to determine its mass and dynamical state, and characterize its surface and shallow sub-surface properties by means of a thermal infrared imager and high-frequency radar.

"AIM will provide first direct measurement of the internal structure of a small asteroid. The internal structure of such small bodies is a great source of debates and it is the outcome of their collisional history, as most bodies at this size are fragments of bigger ones. We have various internal structure models but none is complete and has been validated yet, and they all tell us a different story on the formation of binary asteroids, and on the solar system collisional evolution," Michel said.

This first characterization phase will last for a couple of months and will be conducted from a distance between 22 to 6 miles from the asteroid. Following this, the AIM spacecraft will release a number of CubeSats and a lander which is based on the German Aerospace Center's (DLR) MASCOT lander.

"It will be the first direct interaction of a small lander with a surface in a very low gravitational environment, much lower than comet 67P/Churyumov-Gerasimenko [ESA's Rosetta spacecraft target]," Michel noted.

"This will make us improve drastically our understanding of the mechanical response of a surface in low-g, with implications on our interpretation of surface images and great relevance for a good design of tools aimed at interacting with a small asteroid's surface."

The landing of the MASCOT-2 spacecraft on Didymoon will be one of the most difficult tasks to complete. The lander will allow for a detailed characterization of the deep-interior structure of the asteroid by means of a low-frequency bistatic radar.

"One difficulty with AIM is landing the MASCOT-2 on the small and Didymoon's low gravity. It will require the AIM spacecraft getting close, about 650 ft. to the surface of the secondary body," Michael Kuppers, ESA's Project Scientist for the AIDA/AIM mission, told SpaceFlight Insider.

The CubeSats will assist with observations and will test new science and technology capabilities, including intersatellite communications links in deep space.

The impact of the approximately 700 lbs. DART spacecraft at 6.25 km/s will produce a velocity change on the order of 0.4 mm/s, which leads to a significant change in the mutual orbit of these two objects, but only a minimal change in the heliocentric orbit of the system.

Approximately two weeks before DART impact, the AIM spacecraft will be placed at 60 miles from the asteroid for impact observation. According to Michel, AIM will go to a safe position during the impact, observing the ejecta curtain and then come closer once the environment is safe to measure the outcome. It's also possible that some CubeSats that AIM will deploy before DART impact will observe the event from close range. After the impact a second characterization phase will conclude the mission.

"Having such a fully documented experiment, which requires the measurements of the initial conditions with AIM, including both the DART impact conditions and target's structure, and the outcome, is priceless. It will definitely allow us to either validate our understanding or revise it according to what will happen," Michel concluded.

The AIDA mission is a joint international collaboration of ESA, DLR, OCA, NASA, and the John Hopkins University Applied Physics Laboratory (JHU/APL).

"The cooperation works excellent on project level as well, with participation of the NASA side in all relevant ESA meetings and vice versa," Kuppers said.

The AIDA collaboration was discussed last week at the European Planetary Science Congress (EPSC) 2015 in Nantes, France. The mission is currently in the conceptual phase.