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The Orbiting Retrievable Far and Extreme Ultraviolet Spectrometers (ORFEUS)-SPAS
payloads were joint DARA (German Space Agency)/NASA missions flown on two
shuttle flights. The first flight was September 12-22, 1993 aboard the shuttle Discovery. The second flight, aboard Columbia, was from November 19,
through December 7, 1996.
The free-flying ORFEUS-SPAS platform was designed to be deployed and and retreived
from the shuttle.
The three instruments on the ORFEUS were designed to provide astronomical
ultraviolet spectroscopic observations over the wavelength range
from 40 to 140 nanometers. The three instruments were:
Tübingen Ultraviolet Echelle Spectrometer (TUES); (PI) Prof. Michael Grewing;
University of Tübingen
Berkeley Extreme and Far-UV Spectrometer (BEFS);
(PI) Dr. Mark Hurwitz;
University of California, Berkeley.
This instrument was called the Extreme Ultraviolet (EUV) Spectrometer
in the ORFEUS-SPAS II Mission Research Announcement. It was later renamed.
Interstellar Medium Absorption Profile Spectrograph (IMAPS);
(PI) Dr. Edward Jenkins;
The largest science instrument onboard was a 1-meter telescope. The telescope
primary was coated with iridium to improve its light gathering power in the
ultraviolet. Incoming light was focused to a movable mirror which deflected
the light rays into the FUV Spectrometer (i.e., TUES), which operated in
the 90-140 nanometer range. When the pick-off mirror was moved out
of the beam, light fell instead onto the BEFS Spectrometer, which
covered wavelengths between 39 and 120 nanometers.
A second, separate instrument, the IMAPS Spectrograph, recorded extremely high resolution spectral data in the 95-115 nanometer range.