Real time prediction, detection and co-existing with satellite interference at GMRT

Modern radio telescopes were designed for wider bandwidth to use the interference free bands for radio astronomy. Many intentional radiations are directional and line of site, pointing can be avoided to prevent receiver saturation. About 35000 Satellites are in space to provide voice and data service, navigation, GPS, weather, military and various space programs. These satellite footprints are larger to cover wide area and produce interference to radio telescopes. These satellites are geo stationary, geo synchronous, low, and medium orbiting satellites whose locations and orbits have been characterized with the precise servo system of GMRT antennas. The individual satellite signals have been characterized for its frequency, power level and beam width using GMRT antenna and receiver. The antenna control and monitoring system of GMRT observatory is programmed to produce an alarm whenever the antenna beam is nearing a satellite. The software tools provide prediction of these satellite cross over with any scheduled radio astronomy observation, real time location of the antenna beam with adjacent line of site satellites on the sky and tools to post process the old astronomical data for flagging the duration of satellite signal overlap or saturation. The soft tools will be used to apply digital filtering techniques to mitigate these satellite signals in real time or during post processing. The paper presents the detail characterization of satellite interference to GMRT and the software tools developed to co-exist with satellite interference with detail analysis of the loss of signal or data for any given astronomical observation.