The UKS orbit was determined using tracking data from the RAL's Chilton ground station, which was used for uplink of commands to, and downlink of low-bit rate data from, UKS. These data were processed using the GEODYN orbit software package supplied by NASA. This software took in an initial set of orbit elements and then compared the predicted azimuth and elevation of the spacecraft and with the observed values obtained from tracking. It then adjusted the orbit elements to obtain a better fit between prediction and observation. Several iterations were usually needed to obtain good convergence.
The uncertainties in the position data are described in the position data caveats.
The UKS-IRM separation was measured directly by a VHF pulsed-radar transceiver on UKS together with an echoing transponder on IRM. Unfortunately, the transponder failed on 23 September 1984, about one month into the mission. Following this failure, effort was devoted to finding another method to determine the separation. This led to the development of the method of inertial tracking in which the ground-station antenna tracked a fixed (inertial) point on the orbit and measured the time delay between the peak signals from UKS and IRM. This time delay yielded a measure of the along-track component of the UKS-IRM separation. The method of inertial tracking was successfully tested on 21 November 1984 and was then used to provide separation data through to the end of the mission.
The varying uncertainties in the separation data are described in the separation data caveats.
For a detailed description of the AMPTE orbit work carried out at RAL, please consult:
G.H. Spalding, "Orbit determination and control for the AMPTE UK
Satellite", AAS/AIAA Astrodynamics Specialist Conference, Vail,
Colorado, August 12-15, 1985,
Paper AAS 85-409.
A HTML version of this paper is
available.
Full details of the method of inertial tracking can be found in:
R.H. Holdaway, "Quasi-inertial tracking for finding satellites", AAS/AIAA Astrodynamics Specialist Conference, Vail, Colorado, August 12-15, 1985, Paper AAS 85-384.
For more information on AMPTE orbit analysis, contact George Spalding (Email: G.Spalding@rl.ac.uk)