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Description
The EXOSAT Medium Energy experiment (ME) was an array of eight proportional counters with a total geometric area of 1600 cm^2. The field of view was square and 0.75 degrees x 0.75 degrees FWHM on each side. Each proportional counter consisted of an argon chamber on top of a xenon chamber separated by a 1.5 mm beryllium window. The fractional energy resolution, dE/E, was 21(E/6 keV)^-0.5 percent FWHM for the argon chambers. The output from each chamber was pulse height analyzed into 128 channels with the argon chambers sensitive from 1-20 keV and the xenon from 5-50 keV. To optimize the background subtraction, each half of the detector array was alternately offset to a source-free region of sky to monitor the particle background. Only results from the argon detectors are included in the EXOSAT ME database. The high count rates given by the ME required OBC (on board computer) programs to compress the data prior to their being telemetered. Depending on the objective of the observation the OBC programs traded time resolution against spectral information. Depending on the telemetry load, and the OBC programs running for the other two experiments, two or three ME programs could be run simultaneously. The spectral orientated programs gave spectra plus intensity profiles. The timing programs gave purely intensity profile data with in some cases selectable channels. The highest time resolution possible for a single selectable energy band was 0.2 ms. The products available within this database has been created using the data sampled by the spectral orientated OBC programs. This is a service provided by NASA HEASARC .
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