ESA's 15 m-diameter dish antenna at the European Space Astronomy Centre (ESAC), near Madrid, which has been upgraded to use the new SARAS technology (Photo: ESA/Isdefe)
Image Gallery (2 images)
As you might expect, acquiring a signal from a satellite traveling at speeds of over 28,000 km/h (17,400 mph) can be a tricky business. A new system called SARAS, which is a Spanish acronym for "Fast Acquisition of Satellites and Launchers," more than doubles the effective area of the receiving dish antenna, allowing the signal to be acquired much faster.
When a satellite begins transmitting signals after separating from its rocket, the receiving station on the ground needs to be pointing at precisely the right spot to catch the highly focused and narrow beam transmitted by the fast-moving satellite.
"If the antenna is not pointed perfectly, or if the satellite zips by out of its 'field of view' before acquisition, the signal could be missed altogether," says Magdalena Martinez de Mendijur, a systems engineer at ESA’s Operations Centre in Germany. "Traditionally, even the best stations – like ESA’s 15 m (49 ft) and 35 m (115 ft)-diameter dishes – are only sensitive across an arc of just a few degrees."
The new SARAS system, which was developed by Spanish company Isdefe with support from the ESA's General Support Technology Program, sees eight small radio-frequency sensors mounted in a circular array around the rim of an existing dish antenna.
"The signals received by these eight are combined, and the system can estimate the direction of arrival of the incoming radio beam, and the entire dish can be repointed directly at the satellite with great precision and accuracy, even when the incoming signal is weak or distorted," says Magdalena.
Klaus Juergen Schulz, who is responsible for ground station engineering, adds that the system more than doubles the size of the dish's window and can acquire a signal from a new satellite in less than 12 seconds, with a future version expected to improve this to just two seconds.
The SARAS system was fitted to the 15 m dish at ESA's Space Astronomy Center in Spain last year and in testing has caught signals from various missions, including CryoSat-2, XMM, GOCE and SWARM.
The plan is to develop the system into a full commercial product. It has already been patented in Spain and is currently being patented in Europe.
No comments:
Post a Comment