The Diffuse X-ray Spectrometer

photo of DXS in the shuttle bay

* Mission Overview

The Diffuse X-Ray Spectrometer (DXS) consisted of 2 large area Bragg crystal spectrometers that covered the energy range 0.15 - 0.28 keV. DXS was flown as an attached payload of the Space Shuttle (STS-54) and the two spectrometers were mounted on opposite sides of the shuttle cargo bay as part of the GSFC Shuttle Payload of Opportunity Carrier system, part of the Hitchhiker shuttle series.
The experiment was designed primarily to detect the diffuse X-ray background. During the 80 orbit nights of DXS data collection time during the shuttle mission, the orbiter was oriented such that the DXS detectors repeatedly scanned the same arc on the sky - within 10° of the galactic plane from longitudes 150°-300°. The sky covered was divided into 5 distinct regions Auriga, MonoGemPuppis Vela and Crux.

* Instrumentation

DXS consisted of 2 large area Bragg crystal spectrometers. Each DXS detector contained a curved panel of Bragg crystals mounted above a position-sensitive proportional counter. A spectrum would be dispersed across the counter, with all portions of the spectrum being measured simultaneously. This eliminated the problem in conventional Bragg spectrometers of false features being introduced by a time-varying background. Yet while all wavelengths were measured at the same time, the various wavelengths came from different directions in the sky. Thus, the spectrometers were rocked back and forth about an axis perpendicular to the dispersed direction to obtain complete spectral coverage along an arc of the sky.

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