Session
Technical Session IX: Instrumentation and Sensors
Abstract
Physical Sciences Ins. (PSI) has developed compact, lightweight, low power instrumentation for in-situ monitoring of the orbital environment of spacecraft/payload systems and the effects of this environment on long-term degradation of specific materials and solar photovoltaic arrays. This instrumentation, which will be flown on STEP-3 mission in October 1994, is especially suited for applications on small satellites. It is being developed under a BMDO-sponsored program called space-Active Modular Materials ExperimentS (SAMMES). SAMMES consists of four sensor modules, called Test Modules (TMs), and a controller, called the System Control Module (SCM). The TMs are 15x16x14 cm high, weigh 2.6-3.2 kg, and their electronics consume 4-8 watts power in operational mods. The SCM is 15x20x20 cm high, weighs 5.2 kg, and consumes 9 watts in operational mods. The SCM and TMs are equipped with power-conserving quiescent modes; 1.3-5.3 watts for TMs and 2.7 watts for the SCM. The four Test Modules are called Low Earth Orbit (LEO TM), CALorimeter (CAL TM), Temperature-controlled Quartz Crystal Microbalance/Actinometer (TQCM/ACT TM) and Solar PhotoVoltaic (SPV TM). The LEO module contains sensors for measuring space environment parameters such as atomic oxygen flux, and contaminant accretion, cumulative dose of ionizing radiation, solar irradiance, and local solar angle. The calorimeter module contains sensors (calorimeters) coated with materials whose long duration degradation in the space environment is to be evaluated on the STEP-3 mission, e.g. thermal control paints and films, charge control coatings and optical coatings. The TQCM/ACT TM contains actinometers and TQCMs coated with test materials to accurately measure their erosion due to the atomic oxygen and charge particle environment. The SPV TM continuously monitors the current vs. voltage characteristics of solar cell samples to evaluate their degradation due to the radiation and contamination environment. The TMs are equipped with heaters for each test material sample to maintain its temperature at a fixed value or to vary it linearly. These heaters consume typically about 0.5 watt each. The SCM communicates with the TMs via a MIL-SID-1553 bus and with the spacecraft on 1553, RS232/422 interfaces. The SCM controls the experiments by selecting TMs, sensors, setting test material temperatures, etc. It periodically polls the TMs for sensor data, puts them in the quiescent mode, and then goes into the quiescent mode itself. SAMMES is fully autonomous and can be run with minimal ground intervention. The SCM has several megabytes of RAM and EEPROM for data storage. It has the capability of performing onboard data reduction using preprogrammed or uploaded algorithms.
Spacecraft Environment and Systems Monitoring Instrumentation for Small Satellites
Physical Sciences Ins. (PSI) has developed compact, lightweight, low power instrumentation for in-situ monitoring of the orbital environment of spacecraft/payload systems and the effects of this environment on long-term degradation of specific materials and solar photovoltaic arrays. This instrumentation, which will be flown on STEP-3 mission in October 1994, is especially suited for applications on small satellites. It is being developed under a BMDO-sponsored program called space-Active Modular Materials ExperimentS (SAMMES). SAMMES consists of four sensor modules, called Test Modules (TMs), and a controller, called the System Control Module (SCM). The TMs are 15x16x14 cm high, weigh 2.6-3.2 kg, and their electronics consume 4-8 watts power in operational mods. The SCM is 15x20x20 cm high, weighs 5.2 kg, and consumes 9 watts in operational mods. The SCM and TMs are equipped with power-conserving quiescent modes; 1.3-5.3 watts for TMs and 2.7 watts for the SCM. The four Test Modules are called Low Earth Orbit (LEO TM), CALorimeter (CAL TM), Temperature-controlled Quartz Crystal Microbalance/Actinometer (TQCM/ACT TM) and Solar PhotoVoltaic (SPV TM). The LEO module contains sensors for measuring space environment parameters such as atomic oxygen flux, and contaminant accretion, cumulative dose of ionizing radiation, solar irradiance, and local solar angle. The calorimeter module contains sensors (calorimeters) coated with materials whose long duration degradation in the space environment is to be evaluated on the STEP-3 mission, e.g. thermal control paints and films, charge control coatings and optical coatings. The TQCM/ACT TM contains actinometers and TQCMs coated with test materials to accurately measure their erosion due to the atomic oxygen and charge particle environment. The SPV TM continuously monitors the current vs. voltage characteristics of solar cell samples to evaluate their degradation due to the radiation and contamination environment. The TMs are equipped with heaters for each test material sample to maintain its temperature at a fixed value or to vary it linearly. These heaters consume typically about 0.5 watt each. The SCM communicates with the TMs via a MIL-SID-1553 bus and with the spacecraft on 1553, RS232/422 interfaces. The SCM controls the experiments by selecting TMs, sensors, setting test material temperatures, etc. It periodically polls the TMs for sensor data, puts them in the quiescent mode, and then goes into the quiescent mode itself. SAMMES is fully autonomous and can be run with minimal ground intervention. The SCM has several megabytes of RAM and EEPROM for data storage. It has the capability of performing onboard data reduction using preprogrammed or uploaded algorithms.
