Wednesday, 8 August 2012

Beacon satellites revisited

Beacon satellite signal power measured using a stationary beam pointed towards the point of closes approach. Both the full beamformed signal power and the power of all the individual tiles is plotted. As expected, the power recorded on all individual tiles is nearly the same -- also showing the sidelobe. The full beamformed beam is more narrow but contains some irregualrities that we will hopefully get rid of after performing a new calibration. 
A lot has happened after the first beacon satellite measurement, which seemingly was successful. However, when more satellites were measured, the signal didn't peak at the time when the satellite was transiting the beam. Even the beams of the individual tiles indicated that analog beamforming was not pointed in the correct direction. After several days of work, we have tracked the problem down to a small error in the antenna coordinate files, which caused the azimuths to be rotated 90 degrees clockwise. After fixing this minor problem, everything seems to be working more or less as expected and we will soon be ready for the first EISCAT measurement.

In other news: after replacing the quad gigabit ethernet card on the measurement PC, we can now receive all 244 beamlets simultaneously without dropping samples anymore. This amounts to about 400 MB/s! With the previous card, which from outside appearance looks nearly the same, we could only get 124 beamlets.

The next steps will be to redo the calibration with the corrected antenna coordinates and perform some incoherent scatter radar experiments with the Tromsø VHF system.

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