A LITERAL ANALYSIS OF POTENTIAL INTERFERENCE FROM SATELLITES WITH THE PROPOSED PFD INCREASE

Abstract

An increase in the maximum power flux-density (pfd) permitted from satellites in the 2025 to 2300 MHz band is currently under consideration by IRAC. This analysis assumes the worst case conditions for interference to telemetry operations at the missile test ranges as a result of current and proposed satellite pfd levels. Assumptions in the analysis include the maximum permitted power flux-density with uniform energy distribution over the band of interest, polarization compatibility, and alignment of the telemetry station, the missile and the satellite. It was found that the performance of essentially all missile telemetry receiving systems may be appreciably degraded by even the lowest pfd limits currently permitted. For the higher pfd limits under consideration, degradations in the order of 40 dB are to be expected at stations with dish antennas of only five foot diameter. An increase in the size or gain of an antenna will reduce the probability of interference, because of its decreased beamwidth, but will also increase the performance degradation because of the station’s increased figure of merit, G/T. For satisfactory missile telemetry operation under these conditions, the normal missile’s telemetry received signal-to-noise ratio would have to be well over 40 dB to overcome satellite interference. The results of the analysis are actually independent of all receiving station parameters except the station’s figure of merit, G/T. Probability of interference is not addressed because of the variation of conditions and missions of the various test ranges as well as the unknown number of satellites and their characteristics - present and future. If missile and satellite telemetry is to coexist in the 2200 to 2290 MHz band, the implementation of several recommendations is considered necessary. The recommendations are; 1) Satellite pfd levels should remain at the current limits; 2) Coordination between the satellite controllers and the range operations must be established; and 3) Multiple telemetry receiving stations with significantly different aspect angles with respect to the test vehicle during the test should be used.