Satellite System Validation Test

Project SMOS has just passed an important stage in the validation process of its complete system by carrying out the first ground to flight contact test with the real satellite.

This test, called SSVT (Satellite System Validation Test) proceeded from the 5 to March 7 under CNES management. It is an heavy test which implied several teams in different centers:

• operation team of CNES in the satellite control center in Toulouse
• satellite integration team at Thalès Alenia Space in Cannes
• programming and operation payload team ESA/CASA in Villafranca in Spain

The process of validation of the system is mainly based on the use of simulators (PRESTO for the satellite and MIRASIM for the payload); it implies nevertheless a certain number of appointments between the satellite and the ground, in particular with regard to:

• the operations which the simulator cannot represent accurately
• particularly important operations (critical) or innovative for the mission
• the validation of the complete chain of command controls.

For SMOS, mission based on system PROTEUS, the validation of the platform parts profits largely from the experimence obtained on the preceding missions (Calipso and Corot): that reduces the need of testing with the true satellite (saving of time & budget).

Test plan of this first contact was the following activities:

• test of the platform commands not validated on PRESTO for lack of observable
• test of modification of the microprogram of the star sensor (STR)
• validation of the procedures of deployment of the arms of the payload and of its powering
• sending of commands towards the payload (direct and programmed mode) for its setting in configuration in all its modes.

Chronological course of the test:

• Before the test: generation of the command plans (ESA and CNES) and validations of those on the simulators. Test Readiness Review.
• During the test: setting in configuration of the satellite by Thales then sending of the plans of remote controls from Toulouse; these remote controls are sent to the satellite by a simulator of Sband station connected to the antenna of SMOS. Telemetries are recovered in the same way (band S for the platform, band X for the instrument)
• After the test: transmission and analysis of telemetries by using the real components of the "system". Test Review Board.

Whole of the objectives of the test were reached : in particular, one could check, from end to end, the procedure of deployment by correlating the orders and the real electrical measurements obtained at the points of die stacking on the satellite.
It is already envisaged a second test between ground and satellite (SSVT2) at the end of May, to check the capacity of the ground in particular to upload modifications of the payload software.

    
Teams of CNES and ESA in the Toulouse control center during the test.