## AAS 99-199

## Satellite Tracking Using Ambient RF (STAR) Part 2: Orbit Estimation

#### R.A. Racca, W.M. Rezzonico, C.T. Krinsky, M.F. Storz

## Abstract

The STAR initiative was proposed to demonstrate the ability to use ambient RF energy to reliably detect and track space objects in a "bistatic" configuration where the source of electromagnetic energy is physically displaced from a receiver which collects the reflected energy from the space object of interest. Bistatic range-rate and range observations were obtained for selected low-earth orbiting satellites and the previously known initial state vector was updated using a least-squares differential correction methodology to generate an improved state estimate. In some cases, truth data was available from laser-ranged measurements of the satellite's position. The results depend on many factors including the number of observation, the number of transmitters used, and the aspect angles associated with the viewing geometry. Optimization of these dependencies yields the state vector estimates which are within 100 meters of the laser-ranges truth values.