Observations of the soft X-ray background with the XQC microcalorimeter sounding rocket

On March 28, 1999 the X-ray Quantum Calorimeter (XQC) sounding rocket instr ument completed its third flight to observe the soft X-ray background in th e 0.02-1.0 keV energy band. The detector system is a 36-pixel ion implanted microcalorimeter array with 0.5 x 2.0 mm HgTe absorbers that is operated a t 60 mK with a single-stage adiabatic demagnetization refrigerator. The det ector array, mounting system, thin film filters and dewar infrastructure ha ve all undergone substantial improvements since the last Eight. The result is a scientifically successful observation of the diffuse soft X-ray backgr ound that reveals several emission lines from highly ionized elements in th e interstellar medium. Preliminary results show strong emission from both O VII and O VIII. In this paper, we discuss problems and their solutions for this mature Low-Temperature Detector (LTD) instrument and recent astrophys ical results. (C) 2000 Elsevier Science B.V. All rights reserved.