ORFEUS-SPAS 1, 2

ORFEUS-SPAS [NASA]

ORFEUS-SPAS (Orbiting & Retrievable Far & Extreme UV Spectrometer - Shuttle Palette Satellite) is a joint NASA - DARA (the German space agency) project. The ORFEUS-SPAS 1 payload carried three ultraviolet instruments mounted on the free-flying Astro-SPAS module. The reusable Astro-SPAS platform is designed to be deployed from the Space Shuttle cargo bay for up to 2 weeks of free-flying science observations. The ORFEUS-SPAS I mission was flown in September 1993. The mission acquired astronomical data on numerous targets during 5 days of observations. A second, 14 day flight (ORFEUS SPAS II) took place on STS-80 in November 1996.

The three ORFEUS-SPAS 1 instruments performed astronomical ultraviolet spectroscopy over the wavelength range 400 - 1250 Å. These instruments were:

• Far Ultraviolet (FUV) Spectrometer
  An off-axis paraboloidal mirror can be driven into the light path from the primary mirror of the 1 meter ORFEUS telescope, collimating the beam and directing it into the FUV spectrometer. This is an Echelle spectrometer provided by AIT and the Landessternwarte Heidelberg (LSW). This instrument is designed to provide of point sources over the range 900 - 1350 Å with a resolving power of R = 10,000. Unfortunately, this instrument failed to produce scientifically useful data during the ASTRO-SPAS I flight.
• Extreme Ultraviolet (EUV) Spectrometer
  The Berkeley EUV spectrometer is positioned at the prime focus of the 1 m ORFEUS Telescope. It is designed to provide high-resolution(lambda/5000) spectroscopy of point sources between 390 and 1200 Å, with an effective area of ~ 4-6 cm. Due to various problems, its effective resolution during the ASTRO-SPAS I mission was ~ lambda/3300.
• Interstellar Medium Absorption Profile Spectrograph (IMAPS)
  IMAPS was mounted parallel to the ORFEUS optical axis. It consists of an objective grating and an echelle spectrograph that can record very high resolution (~ 1.25 km/s) ultraviolet spectra of stars over the wavelength interval 950-1150 Å.