<title>Accuracy of trajectory determination and prediction of ADEOS with RIS experiment</title>

Abstract

The advanced earth observing satellite (ADEOS) was launched on August 17th, 1996. The ADEOS carries a large aperture laser-reflector, referred as Retroreflector in Space (RIS). In order to hit laser properly onto the RIS, we need a trajectory prediction with accuracy of about 100 m. The flight-dynamics team at the NASDA ordinarily derives a satellite trajectory with range and range rate (RARR) measurements using S-band radio wave. However, the trajectory prediction is expected to be only as accurate as 1 km for ADEOS. This uncertainty is not acceptable for the RIS. Our main goal is to provide a trajectory prediction valid for three days with uncertainty of 100 meters or smaller with satellite laser ranging (SLR) method. This subject is being studied with the ADEOS/RIS experiment. As a result, our accuracy of a position prediction with the SLR method is about 80 meters or better, and therefore we believe performance of the SLR method will supersede our RARR method with at least a ten-fold improvement on its accuracy. In the future missions of the NASDA, a spacecraft needs higher accuracy in trajectory determination and prediction. A brief discussion on the post-ADEOS mission plan will be found in this paper as well.