ORFEUS-SPAS II

Description

The ORFEUS-SPAS II mission followed the ORFEUS-SPAS I mission flown in 1993, motivated by improvements in instrument performance and the critical need for additional observation time. The purpose of the ORFEUS-SPAS II mission was to conduct investigations of celestial sources in the far and extreme ultraviolet spectral range, and to increase understanding of the evolution of stars, the structure of galaxies, and the nature of the interstellar medium. ORFEUS-SPAS II was one of a series of planned joint DARA (German Space Agency) /NASA missions. The name arises from the reusable Astro-Shuttle Pallet Satellite (Astro-SPAS), and the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometers (ORFEUS) Telescope carried on Astro-SPAS.

ORFEUS-SPAS was a free-flying platform designed to be deployed and retrieved from the space shuttle. The Astro-SPAS carrier was powered by batteries, and data from the instruments were stored on tape. Absolute pointing was accurate to within a few arc seconds. ORFEUS-SPAS is 4.5m in length and has a 2.5m width base. Operation of ORFEUS-SPAS was approximately 40km from the shuttle.

ORFEUS-SPAS II carried the same three spectrometers, operating over the wavelength range 400 - 1250 Angstroms, as was carried on ORFEUS-SPAS I. The Tubingen Ultraviolet Echelle Spectrometer (TUES) and the Berkeley Extreme and Far-UV Spectrometer (BEFS) were housed on the primary instrument - the ORFEUS 1-m telescope. The Interstellar Medium Absorption Profile Spectrograph (IMAPS) was operated independently from ORFEUS.

The ORFEUS-SPAS II mission was flown in November-December 1996. The mission acquired spectra of numerous celestial objects during 14 days of observations. Efficiency of 62.5% for all instruments was achieved.