Fregat's successful qualification flight puts Cluster II in fine fettle
21 March 2000Preliminary analysis of Monday's Cluster II Mission Validation Flight showsthat the Fregat upper stage on the Russian Soyuz rocket has passed itssecond test with flying colours.The objectives of this flight were to confirm the re-ignition and orbitalmanoeuvring capabilities of the Fregat, and to validate the mission profileto be used by ESA's Cluster II scientific satellites. The newly developedFregat ('frigate' in English) is now ready to launch the Cluster II quartetthis summer.
The Soyuz-Fregat launch vehicle lifted off on 20 March at 11.28 p.m. local time (6.28 p.m. GMT). On board was a specially built payload called "Dumsat", which was developed by Aerospatiale Matra Lanceurs and NPO Lavotchkin.
This 2 400 kg dummy spacecraft consisted of a metallic cylindrical structure with the same mass and inertia as a pair of Cluster II satellites. Dumsat was also attached to the same type of payload adapter to be used for the Cluster II mission. This cone-shaped, skirt-type payload adapter is mounted directly to the Fregat upper stage.
Sensors and flux meters on board Dumsat were used to record what happened from lift-off through injection into orbit. They provided detailed information on the mechanical, thermal and acoustic environment of the satellites.
Less than nine minutes after the Soyuz left the pad, the Fregat separated from the booster's third stage. A few seconds later, the main engine on the Fregat fired for almost four minutes to place the upper stage and its payload into a circular parking orbit about 200 km above the Earth.
After one circuit of the planet, the Fregat engine was restarted. This second burn, which lasted for approximately 10 minutes, altered the Fregat's orbit to a highly elliptical track, whose altitude varied from 242 km to 18 000 km. A final obstacle was passed after a successful simulation of the Dumsat's separation.
Following hard on the heels of the previous successful qualification flight on 9 February, the way is now clear for the dual Cluster II launches in June and July.