Appendix A: Program Description
Contents
- Description of the Cooperative Program
- Strengths of the ROSAT Program
- Mission Description
- Data Processing and Analysis
Description of the Cooperative Program
This solicitation invites proposals for participation in the National Aeronautics and Space Administration (NASA) program to conduct astronomical observations and analyze data using the Roentgensatellit (ROSAT). ROSAT is a cooperative program in X-ray astronomy between the Federal Republic of Germany and the United States. Under the agreement between NASA and the German Federal Ministry for Research and Technology (DARA), the Federal Republic of Germany provided a spacecraft with an 0.8 meter diameter X-ray telescope and two identical position sensitive proportional counters (PSPC) mounted in the focal plane of the telescope. NASA provided a high resolution imager (HRI) mounted in the focal plane of the telescope, and launched the ROSAT. Announcements for the ROSAT observing program similar to this one are being issued in the Federal Republic of Germany by the DARA and in the United Kingdom by the British Science and Engineering Research Council (SERC).
Strengths of the ROSAT Program
Proposers should note the HRI's unique strengths and merits in X-ray astronomy are for high spatial resolution, low-background, soft X-ray imaging, and for the study of the structure of diffuse or low surface brightness features. The large amount of time available exclusively for wide-field, high resolution X-ray imaging studies in this "HRI-only" mission phase makes this opportunity unique. We therefore encourage observers to consider proposing large programs, such as a very deep observation, mapping modest sized structures, or a series of medium depth observations of a sample of objects. While no fraction of the observing time has been specifically earmarked for large projects, and proposals for large programs will be subject to the same rules and restrictions as all others, it is our expectation that it will be possible to select one or more such programs.
Mission Description
The ROSAT X-ray telescope consists of four concentric Wolter type-I grazing incidence mirror pairs. The outer mirror has an aperture of 84 cm and a focal length of 240 cm. The unobscured collecting area is 1141 cm**2. The energy response extends from 0.1 to 2 keV, and the on-axis angular resolution is better than 5 arc seconds. The focal plane assembly consists of a carousel carrying 3 imaging X-ray detectors; only one instrument can occupy the focal point at any one time. The HRI is a copy of the high resolution imager flown on the second High Energy Astronomy Observatory (HEAO-2; "Einstein") spacecraft, but with increased quantum efficiency. It is a two-dimensional microchannel plate-based instrument that has a spatial resolution of better than 5 arc seconds, a temporal resolution of 62 micro-seconds, and a field of view of 36 arc minutes. The HRI has an energy response extending from 0.2 keV to beyond the cutoff in the mirror response at about 2.0 keV. The effective area of the HRI is 45 cm**2 near 0.28 keV and 95 cm**2 near 1 keV. It has essentially no energy resolution. All ROSAT observations will be pre-planned. No real-time operations will be available. A detailed description of the ROSAT spacecraft, the scientific instruments and their sensitivities, and spacecraft operations are contained in Appendix F, which can be obtained from the anonymous FTP account heasarc.gsfc.nasa.gov, in the directory rosat/nra_info. (A printed version can be mailed, if necessary.)The ROSAT also carries an independent wide-field extreme ultraviolet camera (WFC), provided by the British Science and Engineering Research Council (SERC). Observations with the WFC are not included in the agreement between the DARA and NASA. Therefore, proposals to make observations with the WFC are not solicited under this announcement.
ROSAT was launched from the NASA Kennedy Space Center on June 1, 1990, into an orbit of 53 degree inclination and 580 km altitude. After a 2-month check-out phase, 6 months were devoted to an all-sky survey. The initial episode of pointed observations of specific X-ray targets began on February 7, 1991. This announcement solicits proposals for pointed observations during the next 1-year episode of pointed observations, beginning about September 1994.
During the pointed phase, NASA receives 50 percent of the telescope time, now using the HRI in the focal plane. The entire U.S. share of the observing time will be made available competitively to guest observers. That is, there are no principal investigator rights to the U.S. ROSAT data. A joint NASA/DARA/SERC ROSAT International Users' Committee (IUC) has been established to coordinate the observing program and to eliminate unwarranted duplication of observations.
Data Processing and Analysis
Data from ROSAT are recorded on board the spacecraft and transmitted to the German Space Operations Center (GSOC) ground station near Weilheim, Federal Republic of Germany. Initial processing of the data is performed at the GSOC, Oberpfaffenhofen, Federal Republic of Germany, and at the German ROSAT Science Data Center located at the Max Planck Institute for Extraterrestrial Physics (MPE), Garching, Federal Republic of Germany (referred to as Level 0 processing.). Following initial processing, the data are shipped to the U.S. ROSAT Science Data Center located at the NASA Goddard Space Flight Center (GSFC), Greenbelt, Maryland, for further reduction (Level 1) and distribution of U.S. data to investigators selected as a part of the U.S. ROSAT program. German- and British-owned data are processed and distributed through ROSAT data centers in their respective countries.The processing of the U.S. data at GSFC is carried out with the assistance of the Smithsonian Astrophysical Observatory (SAO), Cambridge, Massachusetts. The SAO/GSFC team has developed interactive analysis routines (Level 2) that are portable and that will be available to interested astronomers. These routines are being developed under the Image Reduction and Analysis Facility (IRAF) executive and the BSD 4.2 UNIX environment. The SAO/GSFC system is referred to as PROS.
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