1 Introduction

The German spacecraft ORFEUS-SPAS was the primary payload aboard the Space Shuttle Columbia during mission STS-80, flown from 19 November to 7 December, 1996. The ORFEUS telescope was the main instrument aboard the astronomy platform Shuttle Pallet Satellite (ASTRO-SPAS).

The ASTRO-SPAS is a free flying platform that is designed to operate autonomously in the vicinity (up to 60km) of the Space Shuttle for a limited period of up to 14 days. It was designed by the Daimler-Benz Aerospace AG (DASA) in Ottobrunn, Germany.

With a mission duration of 17.7 days STS-80 was the longest shuttle flight to date, the free flying time of ORFEUS-SPAS was 14 days. ORFEUS-SPAS was released a few hours after launch on 20 November, 1996. It was the third flight of the reusable ASTRO-SPAS platform and the second flight of the ORFEUS-SPAS configuration.

The ORFEUS telescope (Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer) (Krämer et al. 1988, 1990; Grewing et al. 1991, 1992) consists of a 1m normal incidence mirror with a focal length of 2.4m and two spectrometers as focal plane instrumentation: the Berkeley spectrograph and the Echelle spectrograph. The Berkeley spectrograph was developed by the Space Sciences Laboratory of the University of California at Berkeley (Hurwitz & Bowyer 1986, 1996; Hurwitz et al. 1998) and the Echelle spectrograph was developed by the University of Tübingen and the Landessternwarte Heidelberg (Appenzeller et al. 1988). As a third independent instrument, the Interstellar Matter Absorption Profile Spectrometer (IMAPS) was attached to the ASTRO-SPAS (Jenkins et al. 1996).

The ORFEUS telescope and the Echelle spectrometer were designed and built by Kayser-Threde GmbH in Munich, Germany. The Echelle detector as well as the Echelle electronics and the Echelle onboard processor were designed and built by the Institute for Astronomy and Astrophysics, Department Astronomy, of the University of Tübingen.

The ORFEUS-SPAS total instrument operation time was 263$.\!\!^{\rm h}$0, while the net integration time was 164$.\!\!^{\rm h}$9, resulting in an efficiency of 62.5% for all instruments. This is an extremely high value as compared to other satellite missions.

50% of the total integration time were reserved for Guest Investigators selected by peer review. The other 50% were used by the Principal Investigator teams who had provided the instruments. 65 distinct objects were observed with the Echelle spectrometer.

In this paper we present the performance figures for the Echelle spectrometer and a short description of the principles of the data extraction procedure.