AsteroidFinder/SSB: A German Mission for the Search of IEOs
Mottola, S.¹; Behrens, J.¹; Börner, A.¹; Gerene, S.²; Grundmann, J.T.¹; Hahn, G.¹; Hallmann, M.¹; Kührt, E.¹; Michaelis, H.¹; Scheibe, K.¹; Schmitz, N.¹; Spietz, P.^1
1DLR; ²JAQAR

Inner Earth Objects (IEOs) are a special group of NEOs (Near-Earth Objects) with orbits completely contained within the Earth orbit. Because of their low solar elongation they are only observable from the ground shortly after sunset or just before sunrise - analog to the planets Mercury and Venus - which makes them difficult to discover. As of writing, only 10 IEOs have been positively detected by ground-based surveys, out of an estimated population of about 1000 down to a size of 100m.

An Earth-orbiting search telescope capable of observing at small angular distances from the Sun is an efficient and cost-effective tool for discovering these objects and measuring their orbits. For this reason DLR, the German Aerospace Center, has selected AsteroidFinder as the first payload to be flown on its SSB satellite platform, in the frame of the German national compact satellite Program.

The primary scientific goals of AsteroidFinder are to contribute to the understanding of the dynamical evolution of the innermost region of the Solar System and of the cratering history of the inner planets. This is achieved by estimating the IEO population, their size-frequency distribution and their orbital properties. In addition to these primary goals, AsteroidFinder will contribute to the assessment of the impact hazard of NEOs and provide a test platform for the space-based detection of space debris and artificial satellites.

The mission concept consists of a 25cm wide-field telescope installed on the DLR compact satellite bus orbiting in LEO. The telescope continuously scans the region of the sky in the range of 30° to 60° solar elongation. Asteroids in the field are identified through their apparent motion across subsequent images. The telescope is body-mounted to the platform, and the necessary pointing is achieved through rotation of the spacecraft. The 2°x2° FOV camera makes use of novel detector technology and advanced software processing to enhance the detection capability for faint objects.

Simulations of the operations and of the detection process, based on a model of a debiased NEO population (Bottke et al. 2002, Icarus 156, 399-433), indicate an expected detection rate of a few tens of IEOs during one year of operation. Currently in preparation for phase B, the launch of AsteroidFinder/SSB is planned for 2012, for a one-year baseline mission with a possible extension.

This mission will contribute to different national and international efforts as the NASA's Spaceguard II goal, the NEO exploration activities in the frame of ESA's Cosmic Vision Program, and the upcoming ESA Space Situation Awareness initiative.