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Research Objectives:
This is a NASA-funded experiment that studies the origins of cosmic rays. The instrument is configured with state-of-the art particle detectors to measure cosmic ray composition from protons to iron nuclei over the energy range 1-10³ TeV in a series of balloon flights. The goal is to observe cosmic ray spectral features and/or abundance changes that might signify a limit to supernova acceleration. Particle charge (Z) measurements will be made with a timing-based detector and a pixelated silicon matrix to minimize the effect of backscatter from the calorimeter. Particle energy measurements will be made with a transition radiation detector for Z > 3 and a sampling tungsten/scintillator calorimeter for Z > 1. In-flight cross calibration of the two detectors allows better determination of the particle energy. Measurements of relative abundances of secondary comic rays (e.g., B/C) as well as primary spectra will allow determination of cosmic ray source spectra at this high energy, where measurements are currently not available. The instrument has been tested and calibrated with a series of beam tests at CERN.
The science instrument will be integrated with a flight command data module (CDM) support system developed for by the NASA Wallops Flight Facility. The CDM is attached to the bottom of the payload and will provide the CREAM instrument with power and communications. The power system consists of ten solar panels and four batteries that will provide 28V power to the instrument. The power system will also provide support system instrumentation with 5, 12, and 28V (regulated and unregulated) power. The communication interface between the science instrument and the CDM is through flight computers with an Ethernet connection. All commands are received by the CDM flight computer and are forwarded to the instrument flight computer or to the CDM components. The Tracking and Data Relay Satellite System (TDRSS) antenna is the prime over-the-horizon communications system with a 100 Kb/s down-link capability. Real-time science and housekeeping data will be down-linked continuously. All data will also be recorded on two hard drives onboard the CDM. If data is not down-linked during real time during a TDRSS zone of exclusion, that data can be retrieved from the hard drive and down-linked at 50 Kb/s. Other communication platforms that serve as backups to TDRSS include line-of-site, Iridium, and Argo µGPSI.
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