Asteroid Impact & Deflection Assessment (AIDA) study
The Asteroid Impact & Deflection Assessment (AIDA) mission is a joint effort of ESA, JHU/APL, NASA, OCA and DLR. The mission design foresees two independent spacecraft, one impactor (DART) and one rendezvous probe (AIM). As in the separate DART and AIM studies, the target of this mission is the binary asteroid system Didymos. For a successful joint mission, one spacecraft, DART, would impact the secondary of the Didymos binary system while AIM would observe and measure any the change in the relative orbit.
For this joint project, an equal timing of the experiment is set for both missions (additionally maximum proximity of the target to Earth allows ground-based characterisation of the experiment). Despite the joint procedure, both spacecraft are still able to pursue their missions fully independently. Therefore if for some reason one of the spacecraft cannot contribute to the joint campaign, the other will be able to achieve the individual mission goals.
The AIDA rendezvous spacecraft would be under responsibility of ESA. ESA's Future Preparation and Strategy Studies Office commissioned a preliminary assessment at the Agency’s Concurrent Design Facility (CDF) in April 2012.
The study concentrates on the design of a rendezvous mission. ESA’s spacecraft would arrive before APL’s impactor spacecraft in order to characterise the binary asteroid, and have the chance to observe the impact as well as the resulting ejecta and crater.
The main objectives of the AIDA orbiter are:
- Determine binary asteroid orbital and rotation state
- Analyse size, mass and shape of both binary asteroid components
- Analyse geology and surface properties
The assessment considered two concepts (DART and AIM) that have been developed as two self standing missions. Joining the two missions will bring additional value, given by addressing the following supplementary objective for the rendezvous spacecraft:
- Observe the impact crater and derive collision and impact properties
65803 Didymos (1996 GT) is an Apollo asteroid discovered on April 11, 1996 by Spacewatch at Kitt Peak. It has a satellite orbiting it with a period of 11.9 hours, hence the appellation "Didymos", meaning "twin". Following are some describing parameters:
- Semi-major axis: 1.644 AU
- Orbital Period: 770.14 days
- Allows to cheaply achieve a 2:1 resonance (2 s/c revolutions : 1 asteroid revolution)
- Eccentricity: 0.384
- Inclination: 3.4 deg
- Geometric albedo: 0.147
- Diameter primary: 800 m
- Diameter secondary: 150 m
- Separation: 1050 m
- Orbital period secondary: 11.9 h (almost circular orbit)
- Orientation of the mutual orbital plane is known (2 solutions)
Propulsion selection and interplanetary transfer
Within the study all major design trade-offs have been carried out. Given the demanding mass envelope imposed by the use of the VEGA LV, the selection of the spacecraft propulsion technology (chemical or electrical) was of particular importance. The analysis considered mostly the reference interplanetary trajectory (direct transfer or including swingbys) and the resulting mass at arrival. The requirement was for the spacecraft to arrive two months before the impactor spacecraft hits. Due to the low values of the arrival mass at the asteroid, chemical propulsion was discarded.
The resulting baseline trajectory involves an Earth swing-by and assumes a performance of a SNECMA PPS-1350 Hall-effect thruster, the one demonstrated by ESA’s SMART-1 lunar mission.
The ADIA rendezvous mission is designed to be compatible with the VEGA launch vehicle, which would require an additional “kick motor” (e.g. STAR-48) to perform the Earth escape burn. On arrival, the spacecraft would perform continuous observations from a serious of “station points” fixed point relative to the asteroid inertial frame and at a safe distance, out of the sphere of influence of both Didymos components. In order to be able to image the two bodies for precise measurements of the orbital state, distances of 13.5 to 17 km were considered for the 1st characterization point. The impact of the impactor spacecraft will be observed from a 2nd characterization point of 100 km to avoid any damage by debris generated in the impact.
The strawman payload for the characterization of the asteroid consists of a Narrow Angle Camera, a Micro laser Altimeter, a Thermal IR Imager and a NIR spectrometer.
The animation was produced by John Hopkins University, Applied Physics Laboratory (JHU/APL), click here to download (22.1 Mb)
For further information please contact:
General Studies Programme
Future Preparation and Stragic Studies Office (PPC-PF)
Tel: +33 1 5369 7623
Email: andres.galvez @ esa.int
Last update: 19 December 2012