Session
Technical Session V: Existing Missions - What's Flying
Abstract
SNAP-1 is the first 3-axis stabilised nanosatellite in orbit. The satellite is stabilised by a single Ymomentum wheel and 3-axis magnetorquer rods, used for nutation damping and wheel momentum management. The primary attitude sensor used for attitude and rate estimation, is a miniature 3-axis magnetometer. This paper will show the attitude performance results during pointing of the CMOS cameras. One of the challenges was how to handle a large residual magnetic moment disturbance on the satellite. This disturbance was caused by an unforseen permanent magnetisation dipole from the thruster solenoids, which could not be fully cancelled by the magnetorquer rods. To enable the onboard attitude and rate Kalman filter to give accurate state estimates, the magnetic disturbance was first characterised and then partially compensated for, using the magnetorquer rods. The paper will explain how this problem was solved, before the Y-momentum wheel could be utilised to stabilise and point the imaging payload. The attitude disturbances during firings of the butane gas thruster will also be presented and characterised. The effect of these firings on the orbit will be shown as measured by the GPS receiver on SNAP-1. The lessons learned from the AODCS design of a SSTL nanosatellite are summarised.
In-Orbit Attitude Performance of the 3-Axis Stabilised SNAP-1 Nanosatellite
SNAP-1 is the first 3-axis stabilised nanosatellite in orbit. The satellite is stabilised by a single Ymomentum wheel and 3-axis magnetorquer rods, used for nutation damping and wheel momentum management. The primary attitude sensor used for attitude and rate estimation, is a miniature 3-axis magnetometer. This paper will show the attitude performance results during pointing of the CMOS cameras. One of the challenges was how to handle a large residual magnetic moment disturbance on the satellite. This disturbance was caused by an unforseen permanent magnetisation dipole from the thruster solenoids, which could not be fully cancelled by the magnetorquer rods. To enable the onboard attitude and rate Kalman filter to give accurate state estimates, the magnetic disturbance was first characterised and then partially compensated for, using the magnetorquer rods. The paper will explain how this problem was solved, before the Y-momentum wheel could be utilised to stabilise and point the imaging payload. The attitude disturbances during firings of the butane gas thruster will also be presented and characterised. The effect of these firings on the orbit will be shown as measured by the GPS receiver on SNAP-1. The lessons learned from the AODCS design of a SSTL nanosatellite are summarised.
