24. Photographic Astrometry (Astrometrie Photographioue)

Extract

Despite some much publicized disappointments, the highlights of Astrometry during the past three year period are dominated by the successful launches of the ES A Hipparcos astrometric satellite and the NASA Hubble Space Telescope. For the past 15 to 20 years the research activities of many Commission members have been monopolized by the design and development of the associated instrumentation and the preparation of catalogues of objects to be observed. Unfortunately, the successful launch of Hipparcos was followed by a failure of the apogee boost motor to ignite and place the satellite into its proper geostationary orbit. After considerable replanning, the perigee was raised to a safe level and access to additional ground stations was arranged so that observations could still be made from the 10.6 hour period elliptical orbit. Even though Hipparcos passes through the Earth’s particle radiation belts twice a day, little degradation in the solar panel output has been observed subsequent to the initial decrease in the output and a lifetime of approximately three years is predicted for the satellite.