East–West Station-Keeping maneuver strategy for COMS satellite using iterative process

Abstract

The first Korean multi-mission geostationary satellite, Communication, Ocean, and Meteorological Satellite (COMS) will be launched in 2010. The missions of this satellite will be Ka-band communications, ocean color monitoring, and meteorological imaging. The satellite was designed with only one solar array on the south panel. This novel configuration will keep imaging instruments on the north side from heating up. Asymmetry of the spacecraft configuration requires twice-a-day thruster-based Wheel Off-Loading (WOL) operations to keep the satellite attitude for imaging and communication. Thruster firings during the WOL operations cause the satellite orbit to change two times a day. Weekly East–West Station-Keeping (EWSK) and North–South Station-Keeping (NSSK) maneuver operations are planned for the COMS satellite in order to maintain the satellite in ±0.05° box at 128.2°E longitude. The EWSK maneuver is planned to be performed two days after the NSSK maneuver to correct small side effects in East–West direction due to plume impingement against the solar array during NSSK maneuver. Normally thruster firings during the WOL operation affect the satellite orbit only in the North–South direction, but there are also small perturbations in the East–West direction. In this paper, EWSK maneuver strategy for the COMS satellite is presented. This strategy takes twice-a-day thruster-based WOL operations and plume impingement effect of the NSSK maneuver into account. And an iterative process to calculate the velocity changes and maneuver time for the EWSK maneuver is applied. One year of the EWSK and NSSK maneuver simulations are performed with twice-a-day WOL to verify the proposed strategy. The proposed strategy showed that the mean longitude of the satellite is controlled at 128.2° ± 0.007° which is three times tighter than that of non-iterative process. Required Delta velocity (Δ V) for EWSK maneuver is also slightly smaller for iterative process. Tightly controlled mean longitude guarantees a better quality of satellite communications and Earth imaging when the spacecraft attitude is well maintained by on-board control.