Performance Assessment of Radio Occultation Experiment on a Near Equatorial Orbit Microsatellite

The microsatellite, VELOX-CI, supported by Singapore's Economic Development Board, is designed to evaluate the navigation system and radio occultation experiment for the tropical environmental monitoring. The satellite, with the size of a mini-fridge, was launched on 16 December 2015, together with five other Singapore satellites from India's Satish Dhawan Space Centre, Sriharikota. The scope of VELOX-CI program is to develop the atmospheric measurement payload, GPS-based attitude determination, and star tracking algorithm for precise attitude determination. VELOX-CI carries a GPS receiver payload for measuring the atmospheric effect on the propagated GPS signals. This payload consists of three dual-frequency geodetic-grade GPS receivers for attitude determination experiment. Moreover, VELOX-CI was launched into near equatorial orbit (NEO) so that more radio occultation observations in tropical region could be obtained. In this paper, the VELOX-CI program and its radio occultation payload will be described. VELOX-CI operations as well as the analysis of receiver's performance and radio occultation experiment would also be highlighted. The success of the payload will provide atmospheric sounding for long term studies.