The Celescope Experiment

The primary purpose of this Special Report is to inform interested scientists of the capabilities and limitations of the Celescope experiment. Testing of the Celescope experiment as an independent subsystem has been completed; the experiment has now been installed in Orbiting Astronomical Observatory (OAO) Spacecraft No. A-2, in preparation for launch late in 1968. This report can therefore be considered as final regarding all aspects of the Celescope experiment before launch. This report supersedes Special Report No. 110, published December 1962. Since this new report is addressed to a different group of readers than was No. 110, it does not provide so much detail as did the earlier one. Detailed information can be obtained from the various Project Celescope reports listed in Appendix A. The Celescope experiment is addressed primarily to the study of the atmospheres of the hotter stars by means of photometric measurements in those regions of the ultraviolet that are accessible only from above the earth's atmosphere. Named for its pioneering as a truly celestial telescope, the Celescope concept originated from a series of meetings in February 1958 involving the scientific staffs of Harvard College Observatory and Smithsonian Astrophysical Observatory. Project Celescope has been supported by the National Aeronautics and Space Administration as part of their Orbiting Astronomical Observatory program. The second OAO satellite will contain SAO's Celescope experiment and the University of Wisconsin's ultraviolet photometry experiment. The manner chosen for accomplishing the primary mission of the Celescope project is to conduct a sky survey, with reasonable photometric accuracy, in four ultraviolet bands centered at 2600, 2300, 1600, and 1500Å. The 1500 Å band includes the hydrogen Lyman-alpha resonance line at 1216 Å, whereas the other bands are insensitive to that wavelength. One of the most important aspects of this survey is the generation of a catalog containing ultraviolet photometric data for all stars observed. The Celescope is a set of four 12-inch f/2 telescopes, each equipped with a television camera. The field of view of each is approximately 2° square. The instrument is designed to operate primarily as a television stellar photometer.