A Back-up Orbit Determination System for Small Satellite Missions
- Paper number
IAC-08.B4.3.13
- Author
Dr. Narayanasetti Venkata Vighnesam, Indian Space Research Organization (ISRO), India
- Coauthor
Mr. Anatta Sonney, Indian Space Research Organization (ISRO), India
- Year
2008
- Abstract
Indian Space Research Organization (ISRO) has launched a series of IRS satellites under the Indian Remote Sensing Programme for the development of earth resources of the country. With the experience and expertise gained over the last two decades in the remote sensing technology, India is playing a lead role in Third world and would like to extend these services of providing remote sensing data from an Indian satellite to students/scientists in the developing countries. ISRO has developed a small remote sensing micro satellite weighing about 75kg, called TWSAT carrying an optical camera to provide multi-spectral data to the Third world countries. TWSAT, an Indian multi-spectral imaging micro-satellite for developing nations, will be flown in the first quarter of 2008 as an auxiliary satellite on PSLV along with CARTOSAT-2A. Satellite Position System (SPS) 12-channel GPS receiver (C/A code) onboard provides instantaneous state vectors of TWSAT. The SPS data consists of the SPS solution as well as measurements and GPS ephemeris. The on-board computed state vector and measurements are received in three data streams namely Real Time (RT), Play Back (PB) and LBT (HK-TLM). The SPS-PB data is the prime source for TWSAT orbit determination. In view of non availability of S-band transponder onboard and due to possibility of getting one-way Doppler data from the satellite, it is planned to have a back-up orbit determination system using S-band one-way Doppler data. At present, before TWSAT launch, Flight Dynamics System (FDS) activities are under test and evaluation at mission operations centre. Achievable orbit determination accuracy was demonstrated using simulated tracking data. Orbit determinations were carried out with non-nominal initial states and also assuming very high system noise. Range rate measurements are converted from Doppler shift by estimating central frequency. ISRO’s operational orbit determination program (ODP) derives the solution of 'equations of motion' through numerical integration. The orbit generator is based on Cowell’s method. For integrating the second order differential equations of motion, the method based on double integration “Gauss Jackson Merson Second Sum” method is employed. The partial derivatives of measurements with respect to state parameters are computed using increment method. Table –I and Table –II describes about orbit determination summary and achievable OD accuracy. This paper describes about the method of orbit determination using only one-way Doppler tracking data, achievable orbit determination (OD) accuracy using simulated as well as live tracking data (one way Doppler) of on-orbit IRS satellites and achieved OD accuracy using TWSAT tracking data. This paper also highlights tracking system performance form different tracking stations ( Bangalore, Lucknow and Mauritius) configured for the mission along with comparisons of S-band one-way Doppler OD results with GPS based OD results during initial phase of the mission.
- Abstract document
- Manuscript document
(absent)