Investigations of Doppler Collision Effects on NavIC

Abstract

Doppler collision is a very important effect that will limit the performance of the satellite navigation systems. Therefore, there is a need to analyze the effect on NavIC (Navigation with Indian Constellation). NavIC is the emerging regional satellite navigation system designed and developed by Indian Space Research Organization, India. This system having seven IRNSS (Indian Regional Navigation Satellite System) satellite constellation consists of three geostationary satellites (IRNSS 1C, 1F and 1G) and four geosynchronous satellites. As the NavIC constellation uses the geostationary satellites, the effect of Doppler collision is more, even though they have orbital inclination angle of about ±5°. In this paper, the effect of Doppler collision for NavIC constellation is analyzed by considering three months data acquired from IGS (IRNSS-GPS-SBAS) receiver. It is found that Doppler collision occurs between IRNSS 1C and 1G is more comparatively IRNSS 1C and 1F & IRNSS 1F and 1G. The Doppler collision period occurs twice in a one sidereal day for all IRNSS geostationary satellites combination. For IRNSS 1C and 1G, the Doppler collision period is about 4 hrs 52 min i.e 18.8% of the one day time (24hrs). These results are useful for changing the inclination of geostationary satellites for avoiding Doppler collision which will improve positional accuracy.