Callisto has developed a number of bespoke simulators for testing ground equipment prior to a satellite launch.
Electrically De-spun Antenna Simulator
The METEOSAT series satellite are spin stabilised and are equipped with Electrically De-spun Antennas, for the communication links to the ground stations. Callisto has designed simulators to produce parasitic AM and PM ripple on data-modulated RF signals in order to test ground station receivers.
Many satellite missions start with an In Orbit Test (IOT) prior to the start of operations. Dedicated IOT equipment is installed in ground stations to undertake these tests. However, how can the ground IOT equipment be verified and the test procedures validated before satellite launch? Callisto has designed an L band transponder simulator for validation of the METEOSAT Second Generation ground stations IOT capability prior to the satellite launch.
Verification that ground station equipment can operate with Doppler effects due to satellite motion is important, particular for LEO missions when Doppler shifts and rates of frequency change can be high. Callisto has designed and developed equipment which can accurately simulate the change in frequency on a downlink RF signal as if coming from a satellite pass.
The Doppler profile is updated in real-time to simulate a satellite pass. Care has been taken in the design to ensure that the frequency changes are phase continuous, as will be the case with a real satellite signal.
Callisto has developed a TM Recorder based on a PC. The unit can record either a video signal (modulated sub-carrier for example) or a PCM serial data stream. The length of data recording is limited only by the amount of free space on the PC hard drive.
Diagram showing a conscan superimposed on an antenna tracking trajectory
Testing of Spacecraft Launch Tracking Simulation
In association with the CNES (France Centre National d'Etudes Spatiales), Callisto has developed a software solution based on SCILAB to simulate the tracking of a spacecraft target from a ground station.
The aim is to simulate the tracking of ESA launchers for typical orbits like Galileo or GTO/GTO+ from ESA New Norcia (NNO) ground station (antenna diameter 35m needed).
It is therefore possible to anticipate the feasibility of the target tracking and analyse any possible problems that could occur.
Tracking algorithms can be tested according to the ground station and the target parameters.