The Deep Space 4/Champollion Comet Rendezvous and Lander Technology Demonstration Mission

Introduction: The Deep Space 4/Champollion mission is designed to test and validate technologies for landing on and anchoring to small bodies, and sample collection and transfer, in preparation for future sample return missions from comets, asteroids, and satellites. In addition, DS-4 will test technologies for advanced, multi-engine solar electric propulsion (SEP) systems, inflatablerigidizable solar arrays, autonomous navigation and precision guidance for landing, autonomous hazard detection and avoidance, and advanced integrated avionics and packaging concepts. Deep Space-4/Champollion consists of two spacecraft: an orbiter/carrier vehicle which includes the multi-engine SEP stage, and a lander, called Champollion, which will descend to the surface of the cometary nucleus (Jean Francois Champollion was the Egyptologist who translated the Rosetta stone in 1824). Deep Space 4/Champollion is a joint project between NASA and CNES, the French space agency. Trajectory: The Deep Space 4/Champollion trajectory is shown in Figure 1. DS-4/Champollion will be launched in April, 2003 on a Delta 7925 expendable vehicle. The spacecraft will rendezvous with and orbit periodic comet Tempel 1 in April 2006, and will deploy a 160 kg lander to the nucleus surface in September, 2006. Rendezvous occurs post-perihelion at a heliocentric distance of 2.8 AU, and the landing occurs at 3.4 AU. The lander will operate for approximately 80 hours on the nucleus surface, making measurements with its suite of scientific instruments. Target: Periodic comet 46P/Tempel 1 is a typical Jupiter-family, short-period comet with a perihelion distance of 1.50 AU and an orbital period of 5.50 years. The comet nucleus is believed to be approximately 7.8 × 5.6 km, assuming an albedo of 0.04 [1], and rotates in 25 40 hours. Gas production near perihelion has been measured at 1.1 × 10 molecules sec [2]. An observational program to further characterize the comet is underway. Mission options: Several options are available for the DS-4/Champollion mission. Given sufficient resources (i.e., funding, launch vehicle payload capability), the spacecraft could collect a sample of cometary material for return to Earth. The lander is capable of taking off from the nucleus surface carrying a sample return cannister, and then autonomously rendezvousing with the orbiter/carrier vehicle in orbit around the nucleus. The sample would be maintained at cryogenic temperatures and would be returned in a hermetically sealed re-entry capsule. A somewhat lesser goal is to take off from the nucleus surface and rendezvous with the carrier spacecraft in orbit around the nucleus in order to demonstrate some but not all of the elements of a sample return technology program. At present, both of these options are under consideration. Payload: The Champollion lander carries four instruments selected by a joint NASA/CNES AO. They are: CHARGE, a gas chromatograph/mass spectrometer which will analyze samples of cometary ices and organics (PI: Paul Mahaffy/NASA GSFC); CIRCLE, 3 near-field cameras and a microscope/IR spectrometer for examining comet samples (PI: Roger Yelle/Boston Univ.); CIVA, 6 panoramic cameras including one stereo pair (PI: J.-P. Bibring/ IAS); and CPPP, a pair of physical properties probes which will be driven into the comet’s surface (PI: Thomas Ahrens/Caltech). The lander will also include a descent camera which is part of the autonomous landing technology demonstration, and a