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About TUES


 The AIT/LSW (Tübingen) Ultraviolet Echelle  Spectrometer (TUES), flew on the Orbiting and  Retrievable Far and Extreme Ultraviolet  Spectrograph (ORFEUS)-SPAS for several  days in  September 1993 and again for nearly 2-1/2 weeks in November 1996. The MAST archive includes data only from the 1996 mission.

The picture shows the ORFEUS-SPAS during checkout on the shuttle arm prior to deployment during the first flight. The TUES is visible as the shrouded pyramid-shaped structure emerging to the left from the telescope. The Berkeley spectrometer (BEFS) is at the prime focus (just inside). The small telescope in the foreground is the Astro-SPAS star tracker, while the long, shiny tube on the far side of the platform is Princeton's IMAPS experiment.

The ORFEUS telescope is 1 meter in diameter and 4 meters long. The echelle spectrometer sits at the Newtonian focus of the telescope and is dispersed by a 316 l/mm grating and cross dispersed by a second grating which also serves as a camera mirror. The detector is a microchannel plate registering individual photons at the echelle array surface and was built at the University of Tübingen. This detector has a maximum count rate of 32,000 cts/sec and an active surface of 40 x 40 mm (with 45 pixels per mm). The echelle includes nearly continuous coverage over the wavelength range 910 - 1410 Å (orders 40 - 61). The sensitivity has a broad maximum at about 1100 Å, giving an overall effective area of about 1.3 cm2. The spectral resolution is about 13,000 and thus is similar to the coverage of both FUSE and the short wavelength half of the Short Wavelength Prime (SWP) camera range of the IUE. The bright limit of TUES was about 3 magnitudes brighter than FUSE, so objects in the range 2X10-9 - 10-12 ergs/cm2/s/Å at 1150 Å were observed. A few objects had not been previously observed by the IUE. Almost all objects observed were stars.

Most of the observations were conducted by Drs. Ron Polidan, Richard Miller, and Peter Vedder.