INDIA'S FIRST LUNAR MISSION CHANDRAYAAN-1 LAUNCH AND EARLY ORBIT PHASE ORBIT DETERMINATION

摘要

India's first Moon mission Chandrayaan-1 carrying eleven scientific instruments for the purpose of expanding scientific knowledge about the Moon was launched on 22nd October 2008 from Satish Dhawan Space Centre, Sriharikota, India by India's Polar Satellite Launch Vehicle PSLV-C11. The main objective of the mission is a simultaneous chemical, mineralogical and photo geologic mapping of the whole Moon with high spatial resolution using high-resolution state of the art sensors. The spacecraft was put into Moon's polar, circular orbit of about (102 X102) km on 12th November 2008 by carrying out sequence of five Earth bound maneuvers, one trajectory correction, Lunar orbit insertion maneuver and four Lunar bound maneuvers. The orbit of the satellite had to be determined continuously at a brisk pace to a good degree of accuracy to meet the requirements of the mission operations. Precise orbit determinations were carried out during each phase of the mission using tracking data collected from network of tracking stations configured for the mission. Tracking data was collected from NASA's DSN (Deep Space Network), APL as well as ISRO's DSN (IDSN) and non-DSN tracking stations. NASA's DSN stations namely Goldstone, Canberra, Madrid have supported the mission during initial phase of the mission. The determined daily orbital estimates were used for spacecraft navigation, mission planning, and science data processing. Robust Orbit determination strategy, characterized by accurate solutions and fast-turnaround to minimize fuel penalties, resulting from delays in implementation of required maneuvers will play an important factor that contribute to maneuver targeting accuracy and low propellant consumption for the mission. ISRO's operational Orbit Determination Program used for low earth missions was suitably updated and validated with simulated as well as live tracking data of Lunar Prospector mission before the launch of Chandrayaan-1 mission to cater the need aspect of meeting Lunar Mission 'Orbit Determination System' requirement during its different phases of the mission. This paper describes the Orbit Determination System for Chandrayaan-1 during different phases of the mission. The purpose of this paper is to describe the methodology and the performance of Chandrayaan-1 orbit determination system during initial phase of the mission along with achieved orbit determination accuracy in the early normal phase.