ROSAT

Spacecraft n°:

Germany spacecraft n°: 17

Launch data:

Designation 20638 / 90049A Launch date 01 Jun 1990 Launch site CC, LC-17A Launch vehicle Delta-6920-10 (#195) Operator DLR(German aerospace research establishment) Mission Scientific: X-ray astronomy Earth orbit: Perigee/Apogee 565 / 584 km Inclination 52,99° Period 96,10 min

A joint West German/UK/US observatory that will study the sky in the X-ray and Extreme Ultraviolet 5XUV) wavelengths. The spacecraft's XUV Wide Field Camera was supplied by a UK consortium led by Leicaster University. From August 1990 to January 1991 ROSAT will make a full sky survey. About 100,000 new X-ray sources are expected to be found. It will be the first time an all sky survey in the XUV wavelength has been concluded.

Description:

• Germany's ROSAT satellite (Rongtensatellit) was the third X-ray mission to image the extrasolar X-ray sky, following Einstein and Exosat. It made the first imaging all-sky survey; its telescope observed at lower energy (`softer', longer wavelengths) than Chandra and XMM and so it was particularly sensitive to the (relatively) lower temperature nearby interstellar gas. It discovered X-rays from comets interacting with the solar wind, cataloged high redshift X-ray galaxy clusters and measured their dark matter, and identified many new quasars.
• The ROSAT X-ray telescope (XRT) and its main cameras, the two PSPC (Position Sensitive Proportional Counter), PSPC-B and PSPC-C, were developed under the leadership of the Max-Planck-Institut fur extraterrestriche Physik (MPE) in Garching bei Munchen. The XRT could also image onto the HRI microchannel-plate camera developed at Smithsonian Astrophysical Observatory (SAO) in Cambridge, Massachusetts, while Leicester University's EUV Wide Field Camera was a separate telescope bolted on the side. The spacecraft was controlled from GSOC (Oberpfaffenhofen/Weilheim) while US participation included the GSFC guest observer facility and the SAO science data center.
• Another detector, the HRI (High Resolution Imager) has higher spatial resolution and can be rotated into the focus of the telescope. ROSAT also carries a piggyback British telescope, the Wide Field Camera which will observe the sky in the extreme ultraviolet.

Mission details:

• The ROSAT (Rontgensatellit) x-ray astronomy satellite was launched on a Delta 6920 on Jun 1, 1990.
  Launched to a 564 x 584 km x 53.0 deg orbit on 1990 Jun 1, the satellite is similar to the Einstein Observatory (1978-81) but with more sensitive detectors. ROSAT was in a 244 x 250 km orbit as of 2011 Oct 10. The PSPC-C carried out the X-ray all-sky survey between launch and an accident on 1991 Jan 25, when PSPC-C was destroyed by accidentally observing the Sun during a system failure. The PSPC-B took over for the pointed-target phase of science observations, together with the HRI. PSPC-B was retired in 1994 when its gas supply was near empty and the HRI was the sole instrument between 1994 and 1998. It had higher spatial resolution than PSPC, but didn't have the energy resolution that enabled PSPC to distinguish different X-ray spectra.
• ROSAT was damaged after an attitude control problem on 1998 Sep 20. When performing a slew (change of pointing direction), the reaction wheels that manage the satellite's angular momentum were unable to keep up and the satellite's aperture followed the wrong track across the sky, crossing the Sun and resulting in destruction of the ultraviolet filter on the HRI. This makes it the only astronomy satellite to have attempted suicide-by-solar-observing on two separate occasions.
• The science program was declared abandoned on 1998 Oct 28; however, the last dribble of PSPC-B detector gas was used for test observations between 1998 Dec 6 and 18. The spacecraft was abandoned on 1999 Feb 12.
• The 2.5 tonne ROSAT astronomy satellite will reenter later in October 2011. As much of 1 tonne of the dense X-ray Telescope mirror assembly may survive reentry. On Oct 10, 2011 ROSAT was in a 244 x 250 km x 53.0 deg orbit.
• ROSAT re-entered between 0143 and 0157 UTC on Oct 23, 2011 according to data from USSTRATCOM. Including the final orbital data released later on Oct 23, the uncertainty range covers the Indian Ocean, the Andaman Sea, Myanmar, Laos and China.

Externe Links: