Long duration hard X-ray transatlantic payload

This note describes the HXR80M large area hard X-Ray Astronomy experiment. The payload is scheduled for a flight on board of a transatlantic balloon to be launched the next July from the Milo Base (Sicily), in the framework of the CNR experimental transatlantic campaign.The detectors are two Multiwire Spectroscopic Proportional Chambers (MWSPC) having 2,700 cm² sensitive area each.The two detectors are filled with an extremely pure Xenon-Isobutane mixture (impurity less than 1ppm) at high pressure (3–6 Atm) in order to obtain good spectral resolution and high efficiency. The field of view of the MWSPC's is limited by an array of three collimators each, having respectively 8°×8° and 5°×5° FWHM.The on board data handling is performed by microprocessor controlled electronics. In particular a micro Multichannel Analyzer (μMCA) is employed to obtain the spectrum of the detected photons. The scientific and housekeeping data are send to ground through a 1.2 Kbit PCM HF Telemetry link.The scientific aim of the experiment is the survey of the sky belt around the 38th parallel and in particular the observation of faint galactic objects and galactic binary systems in the range 15–200 keV.