Session
Technical Session II: New Mission Concepts I
Abstract
The SAC-A is a Low Cost - Short Schedule - Small Bus dedicated to test equipment and new technologies which may be used in operational or scientific missions with more immunity to failures. The opportunity to fly in a low orbit for a reasonable period of time, allows the characterization of the behavior of this new instrumentation in real world applications and also to compute performance. The 68 kg satellite will have an almost octagonal configuration to be fitted within the Hitchhiker Motorized Door Canister with Hitchhiker Ejection System (HES) envelope. This volume is approximately a cylinder of 19" diameter by 20.5 maximum height. The orbit will be circular @ 162 nm (300 km) altitude with an inclination of 28.5 deg. Using a solar factor activity, F10.7 factor, equal to 76 and a ballistic coefficient of 0.0088 km2/kg the expected lifetime is 3.5 months. The stabilization method consists of spinning the satellite around the maximum moment of inertia placed normal to the orbital plane, from 4 rpm to 15 rpm. Air core magnetic coils will be able to change the rotation velocity. An electrical motor with an additional mass to increase the inertia is added to the system for three reasons: a clean ejection, maintain the attitude of the satellite after separation and before the system is turned on, and finally to spin the satellite. This "momentum wheel" will be ON 10 minutes in total, just 4 minutes before separation and 6 minutes after ejection. The proposed mission has as its main objective to investigate the performance of new algorithms which process GPS data in spinning satellite applications. New software, and new tools for analyzing data could be validated and be operative for applications on CoNAE's next generation satellites. The satellite has a triaxial magnetometer to be used for attitude determination and as another piece of information to check the performance of the DGPS. The expected accuracy obtained with the magnetometer along a complete orbit is approximately of 1 deg. (higher than the 2 deg. expected with the DGPS). The technological experiments are a CCD Camera and a small solar panel with Argentinean Solar Silicon Cells. The Camera will take digital space photography using a commercial unit with off the shelf optics. The objective is to apply this device, with minor modifications, as a operational assembly Camera + Optics for Earth Resources and/or Star Imager in satellites of low and medium resolution/accuracy. The Silicon solar panel will be measured in space to characterize the performance and degration of the cells and also the quality of the assembly (performed in Brazil). In the near future, these cells could be used in the CoNAE's small satellite for on board power generation. The satellite also uses the magnetometer for scalar measurements of the Earth Magnetic Field. A main concern in past missions was the determination of a precise orbit which may have a good correlation between time and inertial position. It was not possible to improve the limit of 50 meters as the lower bound for the orbit determination using a terrestrial network.
SAC-A Satellite
The SAC-A is a Low Cost - Short Schedule - Small Bus dedicated to test equipment and new technologies which may be used in operational or scientific missions with more immunity to failures. The opportunity to fly in a low orbit for a reasonable period of time, allows the characterization of the behavior of this new instrumentation in real world applications and also to compute performance. The 68 kg satellite will have an almost octagonal configuration to be fitted within the Hitchhiker Motorized Door Canister with Hitchhiker Ejection System (HES) envelope. This volume is approximately a cylinder of 19" diameter by 20.5 maximum height. The orbit will be circular @ 162 nm (300 km) altitude with an inclination of 28.5 deg. Using a solar factor activity, F10.7 factor, equal to 76 and a ballistic coefficient of 0.0088 km2/kg the expected lifetime is 3.5 months. The stabilization method consists of spinning the satellite around the maximum moment of inertia placed normal to the orbital plane, from 4 rpm to 15 rpm. Air core magnetic coils will be able to change the rotation velocity. An electrical motor with an additional mass to increase the inertia is added to the system for three reasons: a clean ejection, maintain the attitude of the satellite after separation and before the system is turned on, and finally to spin the satellite. This "momentum wheel" will be ON 10 minutes in total, just 4 minutes before separation and 6 minutes after ejection. The proposed mission has as its main objective to investigate the performance of new algorithms which process GPS data in spinning satellite applications. New software, and new tools for analyzing data could be validated and be operative for applications on CoNAE's next generation satellites. The satellite has a triaxial magnetometer to be used for attitude determination and as another piece of information to check the performance of the DGPS. The expected accuracy obtained with the magnetometer along a complete orbit is approximately of 1 deg. (higher than the 2 deg. expected with the DGPS). The technological experiments are a CCD Camera and a small solar panel with Argentinean Solar Silicon Cells. The Camera will take digital space photography using a commercial unit with off the shelf optics. The objective is to apply this device, with minor modifications, as a operational assembly Camera + Optics for Earth Resources and/or Star Imager in satellites of low and medium resolution/accuracy. The Silicon solar panel will be measured in space to characterize the performance and degration of the cells and also the quality of the assembly (performed in Brazil). In the near future, these cells could be used in the CoNAE's small satellite for on board power generation. The satellite also uses the magnetometer for scalar measurements of the Earth Magnetic Field. A main concern in past missions was the determination of a precise orbit which may have a good correlation between time and inertial position. It was not possible to improve the limit of 50 meters as the lower bound for the orbit determination using a terrestrial network.
