Small Satellite Rendezvous and Characterization of Asteroid 99942 Apophis

摘要

The Measurement and Analysis of Apophis Trajectory (MAAT) concept study investigated a low-cost characterization mission to the asteroid 99942 Apophis that leverage small spacecraft architectures and technologies. The mission goals were to perform physical characterization and improve the orbital model. The MAAT mission uses a small spacecraft free flyer and a bi-propellant transfer stage that can be incorporated as a secondary payload on Evolved Expendable Launch Vehicles (EELVs), Atlas V or Delta IV launches. Using the innovative secondary architecture allows the system to be launched on numerous GTO or LTO opportunities such as NASA science missions or commercial communication satellites. The trajectory takes advantage of the reduced Delta-V requirement during the 2012-2015 time frame, with a large flexible launch opportunity, from January to November 2012 and heliocentric injection occurs in April 2013. Primary communications use the traditional Deep Space Network (DSN) with a secondary system using a laser link demonstrating the technology at greater than Earth-Moon distances. The spacecraft uses Commercial Off The Shelf (COTS) components and technologies in combination with a reduced Lunar CRater Observation and Sensing Satellite (LCROSS) instrument suite. The suite includes a high-resolution navigation camera, two visible mapping cameras, an infrared camera and a laser ranger. The study of both the physical and dynamical properties of Apophis requires a rendezvous mission, with the spacecraft operating for several months in close proximity. Physical characterization occurs over three months and includes determining the mass, density, dynamical state, topography, and geological context of the object that is difficult too determine or cannot be determined from ground based instruments. Tracking of the spacecraft over several months using the Deep Space Network (DSN) ensures increased accuracy in orbit determination and combined with physical characterization allows for the study of non-gravitational forces, such as the Yarkovsky effect. The science data and analysis can yield physical and orbital characteristics of Apophis several orders of magnitude better than currently estimated and provide science data that cannot be achieved with ground-based instruments.