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ESA Information Note - "ESA switches its infrared space telescope off and will clean its orbit"

> Nr 17-98 - Paris,  18 May 1998
> ----------------------------------------------------------------------
> ESA switches its infrared space telescope off and will clean its orbit
> ----------------------------------------------------------------------
> The European Space Agency's Infrared Space Observatory (ISO) was
> switched off on May 16 at 14:00 h (CEST), thereby bringing to a close
> the highly-successful in-orbit operations of the ISO mission. Prior to
> that, ISO's orbit was changed to force the satellite to burn up in the
> atmosphere in some 20-30 years from now, thus contributing to
> preserving
> the environment in space.
> Controllers at the ESA ground station at Villafranca (Madrid, Spain)
> witnessed the definitive end for the telescope but they didn't have to
> press any 'red button' or the like. The instructions for the switch
> off
> had already been introduced into ISO's computers earlier.
> ISO's last month of life was used to gather as much technical data as
> possible. Various software and hardware systems that, due to the
> superb
> performance of the spacecraft, did not have to be used during the
> operational phase were subjected to detailed tests. Results from these
> tests will benefit future ESA missions, such as XMM and Integral,
> which
> use some of the same components, such as the Star Trackers guiding the
> spacecraft.
> Also, ISO's farewell included a further last gift for the astronomers.
> A
> few of the detectors in the Short Wavelength Spectrometer (SWS), one
> of
> the four instruments on-board the satellite, could still be used after
> exhaustion of the liquid helium. In anticipation of this opportunity,
> a
> special scientific programme had been prepared and was interleaved
> with
> the technology tests. Some 150 extra hours were used to measure nearly
> 300 stars at wavelengths between 2.4 and 4 microns enabling
> astronomers
> to make a detailed spectral classification.
> In fact, ISO continued to give scientific surprises to the very end.
> ISO's 'last light' observation --taken with the SWS instrument just
> before midnight on May 10-- was of emission lines from  hydrogen in a
> hot supergiant star (eta Canis Majoris). The preliminary results show
> that this star, supposed to be ordinary, is probably surrounded by a
> disk of matter.
> Commenting on the satellite switch off, ESA's Director of Science,
> Roger
> Bonnet, said "ISO has allowed us to gain the first clear view of the
> universe at infrared wavelengths. A great amount of work still awaits
> us
> to interpret all ISO's exciting discoveries. We will miss ISO, of
> course
> -- new answers always bring new questions and the wish for yet more
> knowledge; that is why ESA is already working on one of ISO's
> successors, the Far Infrared and Submillimetre Space Telescope,
> ESA's ISO has revolutionised infrared astronomy; its discoveries  have
> already unveiled a totally new face of the universe. Many more results
> are still to come in the months and years after ISO's switch off as
> astronomers continue mining its treasure trove of unique data.
> ISO was put into orbit in November 1995, by an Ariane 44P launcher at
> Europe's Spaceport at Kourou in French Guiana. As an unprecedented
> observatory for infrared astronomy, able to examine cool and hidden
> places in the Universe, ISO has successfully made more than 26,000
> observations. A supply of liquid helium, used to cool the telescope
> and
> instruments close to the absolute zero of temperature, lasted more
> than
> 30 longer than expected, but ran out on 8 April 1998 (see ESA Press
> Information Note No. 11-98 of 9 April).
> Further information is available from:
> ESA Public Relations Division: Tel: +33(0)        Fax:
> +33(0)
> ESA ISO Project Scientist: Dr Martin Kessler at +34.(9)1.813.12.53 or
> mkessler@iso.vilspa.esa.es
> ESA ISO Spacecraft Operations Manager: Juergen Faelker at
> +34.(9)1.813.12.25 or jfaelker@notes.vilspa.esa.es
> ISO on the Internet
> For more details about ISO, results and a picture gallery, visit the
> website:
> http://isowww.estec.esa.nl