National Radio Astronomy Observatory Green Bank, West Virginia ELECTRONICS DIVISION INTERNAL REPORT NO. 316 —— A Study of Radar Signals Received by the Green Bank Telescope
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چکیده
The strongest interfering signals received in the passband of the Green Bank Telescope’s (GBT) 1.15-1.7 GHz receiver are radar pulses at 1256 and 1292 MHz. These pulses are transmitted by an ARSR-3 FAA Air Surveillance Radar on Apple Orchard Mountain near Bedford, VA, longitude 79.510W, latitude 37.517N, elevation 1288 meters (4225 feet). This radar antenna is about 106 km south-southeast of the GBT at an azimuth of 164 degrees. The radar transmits a 2-microsecond pulse with an average repetition rate of 341 pulses per second. The radar antenna has an azimuthal beamwidth of about 1 degree and an azimuthal sweep rate of 5 rpm (12 second rotation period). When the radar beam is pointed near the direction of the GBT the 1.15-1.72 GHz Gregorian receiver is saturated during the radar pulse unless a notch filter is inserted after the cooled RF amplifiers. This report presents the results of a study of the characteristics of the received radar signals and what can be learned from them about the propagation of RFI in the mountainous terrain surrounding Green Bank. Long-delay echoes from aircraft and rain showers are shown. These results are then used to develop and test algorithms for removing the radar signals from the receiver output so that astronomical observations can be made at the frequencies of the radar signals.
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تاریخ انتشار 2006