Spanish antenna upgraded for Cluster II
18 March 1999Over the past few months, a major relocation exercise has been taking place in preparation for the Cluster II launches next year. The result is the creation of a new structure on the site of an elderly 15 metre dish antenna (VIL-1) at the European Space Agency's Villafranca del Castillo Satellite Tracking Station (VILSPA) in Spain.
VIL-1 has been largely rebuilt using equipment brought thousands of kilometres from the Odenwald, near Darmstadt in Germany. Formerly used for the International Ultraviolet Explorer (IUE) mission 1976 - 1996 and for the Infrared Space Observatory (ISO) 1996 - 1998, VIL-1 is now being refurbished and upgraded to meet the special mission requirements of the Cluster II mission. Communications are particularly challenging in the case of Cluster II, since the four satellites will follow highly elliptical orbits, require high velocity tracking and the same antenna will track each of the four spacecraft.
The upgrade of the S-band antenna started on 19 November 1998 with the arrival at Villafranca of 26 containers brought in by a convoy of giant lorries. The 23 tonnes of equipment from the Odenwald included antenna panels, cable twister, feed horn, gearboxes and electronic equipment. 14 of the boxes, which contained particularly fragile hardware, had to be stored in a heated, dry environment inside a special building near Madrid.
The Antenna Equipment Room (AER) cabin and the subreflector arrived at VILSPA by a special (3.2 m wide) road transporter. Special permission for this journey was required from the authorities in Germany, France and Spain. During the entire trip (which lasted more than two weeks), heating and dehydration systems were permanently switched on inside the cabin to avoid condensation on the equipment and waveguides.
The dish panels and AER have already been fitted to the original concrete base and metal structure, and the remaining installation work is expected to be completed by early summer. The refurbished antenna should be operational by September 1999.
VILSPA, located in Villanueva de la Caqada (some 28 km north west of Madrid) has been selected to be the prime Telemetry, Tracking and Command (TT&C) station for Cluster II. Data transmitted from the four satellites will be sent through two 128 Kbs dedicated links and one back-up ISDN link from VILSPA to the European Space Operations Centre (ESOC) at Darmstadt.
Two ground antennae, one at Odenwald and the other at Redu (Belgium), were intended for use during the original Cluster mission. However, since the new spacecraft are now equipped with solid state recorders capable of greater data storage capacity, a single antenna is now sufficient for the Cluster II mission.