NSSDCA ID: 1989-062B-02
Mission Name: HipparcosThe two star mappers, one of which is normally switched off, provide real-time satellite attitude data and allow a posteriori attitude reconstruction. Each star mapper consists of a star mapper grid located at the side of the primary modulating grid, and two photomultipliers measuring the light transmitted by the whole star mapper grid in two different spectral bands, roughly by the Johnson B and V bands. The spectral separation is performed by means of a dichroic beam splitter. Each star mapper consists of four slits, each set at different inclinations with respect to the scanning direction, so that the satellite attitude can be derived from the photomultiplier signals as the star image moves across the grid. The modulated light signal is converted into photon counts by two photomultiplier tubes, which are sampled at a frequency of 600 Hz. Data from the Hipparchos Star Mapper will allow the determination of position and photometric magnitude of about a million stars to a limit of B=12 mag by the end of the mission. The primary purpose of the star mapper is to observe the transit time of bright reference stars of known position when they cross the slits. Initially the positions will be known with an accurary of 1 arc-sec, but toward the end of the mission a better solution for the attitude of the satellite will result in an 0.03 arc-sec astrometric accuracy at B=10.5 mag for the resulting Tycho Output Catalog. The photometric accuracy of the Tycho catalog will be 0.03 mag at B=10.5 mag. The standard errors will roughly increase a factor of two per magnitude for faint magnitudes. Double stars with separations larger than 2 arc-sec will be resolved.
Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office
Name | Role | Original Affiliation | |
---|---|---|---|
Dr. Jean Kovalevsky | Co-Investigator | CNRS Centre d'Etudes Spatiale des Rayonments | kovalevsky@mfg.cnes.fr |
Dr. Pier Luigi Bernacca | Co-Investigator | Osservatorio Astrofisico di Asiago, Italy | bernacca@pd.astro.it |
Dr. Erik Hog | Co-Investigator | Copenhagen University Observatory | |
Dr. Michael Grewing | Co-Investigator | Universitat Tubingen | |
Dr. Michel Grenon | Co-Investigator | Observatoire de Geneve | |
Dr. Michael A.C. Perryman | Principal Investigator | ESA-European Space Research and Technology Centre | astro@esta2.estec.esa.nl |