Antenna Test Facilities
What are they for?
Antennas are the way that a satellite maintains communications with Earth. They are expressly designed for transmitting and receiving EM radiation. On the ground, other antennas are the counterparts that relay the satellite signals to base stations.
Antennas also enable global navigation services like GPS or GALILEO, global broadcasting and communications services provided by telecommunication satellites. And antennas have evolved into an important tool for radio-based space exploration and Earth observation, employed for imaging radar, scatterometry and radiometry.
To serve this variety of applications, a broad number of different antenna types have been developed, from small GPS antennas, overlooking the whole sky todish-shaped 'high-gain' antennas, concentrating the radio signals they send or receive into a very small area to maximise signal strength. Typically operating across thousands of kilometres, if their pointing direction is off by even a tiny fraction of a degree then their radio beam may end up weakened, or hundreds of kilometres away from their intended target.
Modern antennas are often extremely complex: the current generation of telecommunication satellites transmit multiple small beams instead of a single main beam. Antenna dishes are carefully shaped to optimise signal strength across the region being served and enable frequency reuse for diferent channels without 'cross-talking'.
The antenna itself can be an array of smaller antennas, each antenna element having its own amplifier to boost an individual channel or all elements working together to shape or steer the beam.
The Antenna Test Facilities meet the challenging task of testing space antenna designs. They are made up of two test facilities, the Compact Antenna Test Range (CATR) Laboratory and the Compact Payload Test Range (CPTR).
Both CATR and CPTR are screened against external EM radiation and their inside walls are covered with pyramid-shaped 'anechoic' or non-reflective foam to absorb signals and prevent unwanted reflections. The CATR can handle antennas of up to 1m in diameter while the CPTR performs measurements on larger antennas or complete satellite payloads. The CPTR is also located within a clean room area to allow testing of flight hardware.
Last update: 9 October 2012
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