Session
Technical Session VIII: The Horizion-- New Small Satellite Missions or Sensors to Broaden Our Understanding of Space: Section I
Abstract
ROCSAT-3 mission is an international collaboration of Taiwan and the United States to deploy in 2005 a constellation of six microsatellites equipped with GPS occultation receivers in low Earth orbits to collect the GPS signal as passing through the atmosphere. The satellites would generate thousands of sounding data everyday uniformly distributed over the world. The satellites will then downlink the GPS occultation measurements to the ground receiving stations for processing and assimilated into the weather forecast model with minimal delay. The design of ROCSAT-3 constellation takes into consideration factors such as the capability of the available launch vehicle, the mass of the propellant, the locations of ground receiving stations, and the deployment period to achieve the final constellation. The six ROCSAT-3 satellites will be delivered by a single Minotaur launch into the same orbit plane initially. The dispersion of the satellites into the target constellation utilizes the principle that satellites at different altitudes will precess into different orbits over the time. By adjusting the altitude profiles, the six ROCSAT-3 microsatellites would be placed into six orbit planes. Considering ionospheric research, the fuel constraint, and the launcher lifting capability, the mission orbit of 800 km is selected. The inclination angle of 72 degrees is selected as the results of the trade studies involving the location of receiving stations and the precession rate of the orbit. The dominant factor in the selection of the separation angle among orbit planes is the requirement of distribution of the sounding data uniformly. With the constraint of the deployment period, the separation angle is currently defined as 24 degrees. Furthermore, in order to minimize the downlink confliction among satellite passes at the ground stations, a true anomaly separation of 52.5 degrees between satellites in adjacent orbit planes is selected. The mission life of ROCSAT-3 is 2 years. The constellation will be achieved 13 months after launch. An early phase mission plan has also been developed for the deployment period when the satellites are at lower altitudes. At altitude below 500 km, a pitch-biased attitude control can be used to point either the forward or aft occultation antenna at the desired angle for conducting the experiment.
Presentation Slides
ROCSAT-3 Constellation Mission
ROCSAT-3 mission is an international collaboration of Taiwan and the United States to deploy in 2005 a constellation of six microsatellites equipped with GPS occultation receivers in low Earth orbits to collect the GPS signal as passing through the atmosphere. The satellites would generate thousands of sounding data everyday uniformly distributed over the world. The satellites will then downlink the GPS occultation measurements to the ground receiving stations for processing and assimilated into the weather forecast model with minimal delay. The design of ROCSAT-3 constellation takes into consideration factors such as the capability of the available launch vehicle, the mass of the propellant, the locations of ground receiving stations, and the deployment period to achieve the final constellation. The six ROCSAT-3 satellites will be delivered by a single Minotaur launch into the same orbit plane initially. The dispersion of the satellites into the target constellation utilizes the principle that satellites at different altitudes will precess into different orbits over the time. By adjusting the altitude profiles, the six ROCSAT-3 microsatellites would be placed into six orbit planes. Considering ionospheric research, the fuel constraint, and the launcher lifting capability, the mission orbit of 800 km is selected. The inclination angle of 72 degrees is selected as the results of the trade studies involving the location of receiving stations and the precession rate of the orbit. The dominant factor in the selection of the separation angle among orbit planes is the requirement of distribution of the sounding data uniformly. With the constraint of the deployment period, the separation angle is currently defined as 24 degrees. Furthermore, in order to minimize the downlink confliction among satellite passes at the ground stations, a true anomaly separation of 52.5 degrees between satellites in adjacent orbit planes is selected. The mission life of ROCSAT-3 is 2 years. The constellation will be achieved 13 months after launch. An early phase mission plan has also been developed for the deployment period when the satellites are at lower altitudes. At altitude below 500 km, a pitch-biased attitude control can be used to point either the forward or aft occultation antenna at the desired angle for conducting the experiment.
