Scientific Goals
The primary goal of the mission is to search for Inner-Earth Objects (IEOs), a particular class of near-Earth objects (NEOs) with orbits lying completely within the Earth’s orbit. Due to their proximity on the sky to the Sun, IEOs are extremely difficult to discover from the ground. About 6000 NEOs have been discovered, of which only 10 are IEOs. However, it is thought that more than 1000 such objects with diameters > 100 m exist. Simulations have shown that AsteroidFinder may detect some tens of IEOs in an operational period of at least one year and be able to characterize the population in terms of total number, orbit and size distribution. Information on IEOs is key to understanding the contribution of these bodies to the terrestrial impact hazard and for verifying or excluding theories of planetesimal reservoirs and their orbital evolution histories. A secondary goal of the mission is to demonstrate that the detection of cm-sized pieces of space debris is in principle feasible with a satellite-based optical instrument.
Technical Implementation
To achieve its goals the mission has to detect small objects of various surface albedos, including extremely dark ones, near the direction of the Sun. This requires a limiting sensitivity of > 18.5 mag. To achieve this sensitivity long exposure times (~ 1 min) and a high pointing stability (~ 1 arcsec/s) are needed. Since the stability requirement is beyond the capability of the SSB, an order of magnitude improvement must be achieved at payload level. Furthermore, stray light from the Sun, Earth and other objects must be effectively suppressed.
The baseline payload of the AsteroidFinder mission consists of two main elements. The telescope has an aperture of 25 cm and a focal length of 76 cm. The electronic unit (EU) contains the focal-plane array (EMCCD detector) with 2000 x 2000 pixels, the corresponding front-end electronics, the digital-processing unit and power-supply unit. The data produced by the EU are stored in the mass memory of the satellite.
Summary
AsteroidFinder is a technically challenging, scientifically fascinating low-budget DLR space mission with international support. By operating at the cutting edge of present research, AsteroidFinder will greatly increase our knowledge of IEOs and of NEOs in general. It will help us to better quantify the asteroidal impact risk for the Earth. It will enable DLR to develop new technologies and gain experience with existing ones.