SCINTILLATOR-BASED LOW ENERGY PARTICLE IMAGING SPECTROMETER FOR NANOSATELLITES

Physical Sciences Inc. (PSI), in cooperation with the Boston University Center for Space Physics, and under the sponsorship of the Air Force Research Laboratory Space Vehicle Directorate, has developed and tested a lightweight, multi-configuration sensor to monitor the space weather environment. The scintillator-based Low Energy Particle Imaging Spectrometer (LEPIS) is ideally suited to monitoring the lower energy (20 to 1000 keV) charged particle environment. The LEPIS design is also compatible with the weight, volume, and power requirements of nanosatellites (<0.5 kg, <0.5 W). The LEPIS design does not rely upon a magnetic sector to discriminate between particle types; rather it takes advantage of particle cross-section characteristics and scintillator properties to discriminate. We have already proven the feasibility of our approach; i.e., using thin films of materials to create particle-specific detectors, fiber-optically coupled to a position-sensitive photomultiplier tube. The result is a tremendous savings in sensor weight and volume. Background Space Weather The need to monitor space weather is becoming essential because of the potential for satellite loss or service interruption during periods of high geomagnetic activity or severe radiation conditions. Space weather is the manifestation of the intimate connection between the earth and the sun. The space surrounding the earth is a highly dynamic environment that responds to changes in the sun. The sun is constantly bombarding the earth with highenergy particles and radiation. The dynamic interaction between this solar wind, the earth's magnetic field and the sun’s magnetic field determines the space weather. Since the space environment responds dramatically and sensitively to changes in the electromagnetic fields, particles and magnetic fields arriving from the sun, it is important to have early warning of such events. This response occurs with time delays of hours to days, and is at the core of space weather. Satellites in earth orbit interact continuously over many years with this highly dynamic space environment. Rapid changes in the space environment cause increased radiation damage, single event upsets, spacecraft charging and damage to materials. All of these effects degrade satellite performance. Most often satellite systems degrade gradually in time; however, there are striking examples of sudden, unpredicted spacecraft failures caused by correlated with geomagnetic activity. The LEPIS, as part of a constellation of space weather monitoring nanosatellites, would provide a crucial early warning of enhanced geomagnetic activity. A warning of days or even hours of an impending geomagnetic event would allow satellite operators to take action to minimize damage or service interruptions caused by the accompanying increased radiation. To protect against damage and service outages, spacecraft operators might