<h2>AAS 99-187</h2>
<h2>GNSS- and Accelerometry-Based Precise orbit Determination of Low-Earth Satellites                                                                </h2>
<h4>S. Casotto, A. Zin                                                                                                                                                                  </h4>
University di Padova, Italy                                                                                                                                               
<h2> Abstract </h2>
It is the purpose of the present paper to address the performance of an orbit restitution system based on the use of combined GPS and GLONASS dual-frequency carrier phase and accelerometer data. This data synergy is anticipated for bother the ESA GOCE mission and the ASI SAGE mission, as well as for other missions flying in the 300-400 km altitude range. The investigation has been carried out by simulating realistic error sources including accelerometer measurement error, transmitter and receiver clock errors and propagation errors. Special attention has been given to simulating the accelerometer error at lower frequencies than the operational bandwidth so as to obtain the sensitivity of the recovered orbit accuracy to the length of the data arc. A peculiar aspect of the investigation regards the simulation of the S/A d-process and the assessment of its impact on the restitution.