<h2>AAS 99-177</h2>
<h2>Self Contained Autonomous Navigation System for Deep Space Missions                                                                              </h2>
<h4>Y. Guo                                                                                                                                                                              </h4>
Johns Hopkins University, APL, Laurel, MD                                                                                                                                 
<h2> Abstract </h2>
A new type of autonomous navigation system is proposed here fore deep space missions. It uses the sun as the reference body and determines the spacecraft orbit based on observations made on the sun using onboard instruments. Two types of observation data, the direction of the spacecraft relative to the sun as a function of time and the optical Doppler shifts due to the motion of the spacecraft relative to the sun, can e used for estimating and predicting the spacecraft trajectory. Unlike the ground-based system, this new system does not rely on the Deep Space Network and has the potential to guide the spacecraft into much deeper space.