Session
Session 1: Advanced Concepts I
Abstract
In flight, the Near Earth Object Surveillance Satellite (NEOSSat) lost use of its single-string magnetometer that was necessary to coarsely solve the attitude problem and seed the satellite's star tracker for fine attitude determination. Unable to determine attitude, satellite control was lost and an ad-hoc, in-flight, solution was needed to recover operations. Building on existing GPS literature, NEOSSat's GPS receiver was augmented, in software, to estimate the antenna's look direction, in an inertial frame of reference. Matched with the known (mounting) vector in the body frame, a vector pair was successfully created that replaced the one from the magnetometer. This paper describes the mission context, algorithms, calibration methods, software implementation, testing (ground and flight) and optimizations that enabled the on-orbit GPS receiver to become a successful attitude sensor. The results, RMS errors within 10 degrees without mitigation of multipath effects, are generally applicable to satellites that have even just one GPS receiver and antenna and represent an alternate or back-up means of contributing to coarse attitude determination.
Single GPS Antenna Attitude Vector Pair - NEOSSat Recovery
In flight, the Near Earth Object Surveillance Satellite (NEOSSat) lost use of its single-string magnetometer that was necessary to coarsely solve the attitude problem and seed the satellite's star tracker for fine attitude determination. Unable to determine attitude, satellite control was lost and an ad-hoc, in-flight, solution was needed to recover operations. Building on existing GPS literature, NEOSSat's GPS receiver was augmented, in software, to estimate the antenna's look direction, in an inertial frame of reference. Matched with the known (mounting) vector in the body frame, a vector pair was successfully created that replaced the one from the magnetometer. This paper describes the mission context, algorithms, calibration methods, software implementation, testing (ground and flight) and optimizations that enabled the on-orbit GPS receiver to become a successful attitude sensor. The results, RMS errors within 10 degrees without mitigation of multipath effects, are generally applicable to satellites that have even just one GPS receiver and antenna and represent an alternate or back-up means of contributing to coarse attitude determination.
