Cancellation of Space-Based Interference in Radio Telescopes

A concept is presented that was developed at the National Astronomy and Ionosphere Center (NAIC) at Arecibo, Puerto Rico, for suppression of Global Positioning System (GPS) signals in the 305 m dish radio receiver path prior to back-end processing. The subsystem requires no auxiliary antenna and is intended for easy integration with virtually any radio telescope system. The design focuses on the GPS L3 signal at 1381.05 MHz which, during periodic tests, interferes with observations of objects in an important range of redshifts. The signal dynamically change modulation modes and our scheme has demonstrated, through simulations using actual telescope data, the ability to acquire and track the signal as well as detect mode changes in order to to apply cancellation or blanking, as appropriate. A follow-up is planned to develop a prototype to deploy and evaluate at NAIC.