Mission Overview

Spacelab 2 was flown aboard the Space Shuttle Challenger (STS-51F) from 29 July-6 August 1985. One of the scientific experiments aboard the pallet was an X-ray telescope (XRT). While the Shuttle failed to get to the intended orbit because of a premature main engine shutdown, this did not seem to affect the XRT performance.

Launch Information

Launch Date: 1985-07-29 at 21:00:00 UTC
Launch Vehicle: Shuttle
Launch Site: Cape Canaveral, United States
Decay Date: 1985-08-06

Trajectory Description
Type: Orbiter
Central Body: Earth
Epoch start: 1985-07-29 21:00:00 UTC

Orbital Parameters
Periapsis 312.0 km
Apoapsis 321.0 km
Period 90.9000015258789 minutes
Inclination 49.5°
Eccentricity 6.719999946653843E-4


XRT was the first orbiting instrument able to make images directly at high energies. The Spacelab XRT, developed by the University of Birmingham, used a coded mask technique to make images at energies 2.5-25 keV. The instrument consisted of 2 co-aligned telescopes mounted together on an alt- azimuth system carried in the Space Shuttle payload bay. The main elements of each telescope were a gold coated coded mask in which the opaque elements occupied ~ 50% of the mask area, supported about 3 m from a position sensitive proportional counter. The 2 masks had different sized holes, producing different angular resolutions (3 arcmin and 12 arcmin, FWHM) of the sky. The higher resolution telescope was used to make detailed studies of the brighter sources and the other telescope was used to look at fainter regions of diffuse emission. Each telescope had a field of view of about 6 deg x 6 deg.


Over 75 hours of data were obtained including observations of 8 galactic clusters, the galactic center region, and the Vela SNR.