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Communications & Tracking
Spacecraft telemetry, command and tracking is carried out primarily by the ESA ground station in Villafranca, Spain, with support from NASA's Deep Space Network. In the critical early stages between launch and final orbit insertion, additional ground stations in Kourou (French Guiana), Perth (Australia) and Kiruna (Sweden) were used.
The ESA Ground Stations and Communications Network (ESTRACK) performs the telemetry, command and tracking operations in the S-band radio frequencies via the Villafranca ground station. Wide band data acquisition is also possible via the NASA Deep Space Network ground stations in California, Spain and Australia.
The Villafranca ground station
ESA's Villafranca del Castillo Satellite Tracking Station (VILSPA), which is located in Villanueva de la Caqada (some 28 km northwest of Madrid), is the prime Telemetry, Tracking and Command (TT&C) station for Cluster.
The antenna used is an S-band, 15 metre dish (VIL-1) which was formerly used for the International Ultraviolet Explorer (IUE) mission from 1976 to 1996 and for the Infrared Space Observatory (ISO) mission from 1996 to 1998. VIL-1 was refurbished and upgraded to meet the requirements of the Cluster mission, using many parts from the Odenwald antenna in Germany, which was originally to be used for the first Cluster spacecraft.
Since IUE and ISO were slow-moving satellites, the antenna servo speed and tracking receiver response were not considered to be of major importance. However, the Cluster satellites have highly elliptical orbits and require high velocity tracking, so the modifications to the VIL-1 antenna included replacement of the old servo and tracking systems.
The Cluster antenna at Villafranca
A major upgrade of the antenna started on 19 November 1998 with the arrival at Villafranca of 26 boxes, transported by truck from Odenwald (Germany). They contained antenna dish panels, cable twister, feed horn, servo gearboxes and electronic equipment weighing more than 23 tonnes.
The Antenna Equipment Room (AER) cabin and the subreflector arrived by a special 3.2 metre wide transport. Special permission for this transfer was required from authorities of Germany, France and Spain. During the entire journey, which lasted more than two weeks, the cabin heating and dehydrator systems had to be powered up to avoid condensation on the equipment and waveguides.
The VIL-1 upgrade featured replacement of the following:
In April 1999, ground station telemetry, telecommand, ranging and communications equipment arrived from the ex-Odenwald antenna. The VIL-1 upgrade activities were completed in autumn 1999 and supported the ground system validation prior to launch.
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