SPAS (Shuttle Pallet Satellite) was a reusable free-flying vehicle built by Messerschmitt-Bolkow-Blohm which could be deployed and retrieved by the Space Shuttle's Remote Manipulator System (RMS). The original SPAS, with materials processing and SDI ("Star Wars")-related sensor payloads, was carried on three missions but not deployed on the second of these because of an electrical problem with the RMS.

 

ORFEUS (Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer), was a German astronomical payload that flew twice aboard SPAS. The main instrument was a 1-m telescope with extreme ultraviolet and far ultraviolet spectrometers of high spectral resolution. Also carried was the Princeton Interstellar Medium Absorption Profile Spectrograph which studied the fine structure of UV absorption lines in stellar spectra caused by interstellar gas, and several non-astronomy payloads.

 

CRISTA, equipped for observation of the Earth's atmosphere, also flew on two SPAS missions.

 

spacecraft	shuttle deployment	retrieval	mission	orbit	mass
SPAS-I	Jun 18, 1983		STS-7	228 × 947 km
SPAS-1A	Feb 3, 1984		STS-11	not deployed
SPAS-II	Apr 28, 1991		STS-39	248 × 263 km × 57.0°
ORFEUS-SPAS I	Sep 13, 1993	Sep 18, 1993	STS-51	301 × 331 km × 28.5°	3,202 kg
CRISTA-SPAS I	Nov 4, 1994	Nov 12, 1994	STS-66
ORFEUS-SPAS II	Nov 19, 1996	Dec 4, 1996	STS-80
CRISTA -SPAS II	Aug 7, 1997	Aug 16, 1994		282 × 296 km × 57.0°