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High Resolution Imager (HRI)

NSSDCA ID: 1990-049A-01

Mission Name: ROSAT
Principal Investigator:Dr. Frank R. Harnden, Jr.


The high resolution imager (HRI) was essentially a copy of the HRI provided for the HEAO 2 mission, modified to comply with the electrical and mechanical interfaces of ROSAT. Incoming X-ray photons were converted to electrons at a photocathode. The electrons were multiplied in a pair of cascaded microchannel plates (MCP) with a gain of about 100 million. A crossed grid at the exit of the MCP collected the electron cloud, thereby yielding a measurement of the location of the incoming photon with an positional accuracy of about 25 micrometers. A radioactive calibration source was attached to the retractable vacuum door in front of the HRI. For in-flight calibration, a UV source was integrated into the HRI.

Alternate Names

  • HRI

Facts in Brief

Mass: 30.5 kg
Power (avg): 10.3 W

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Astronomy: X-Ray

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Dr. John GerdesExperiment ManagerSmithsonian Astrophysical Observatory
Dr. Stephen S. HoltExperiment ScientistNASA Goddard Space Flight
Dr. Frank R. Harnden, Jr.Principal InvestigatorSmithsonian Astrophysical

Selected References

  • ROSAT mission description, ROSAT Scientific Data Center and Max-Plank-Institut fur Extraterrestriche Physik, NRA 91-OSSA-3, Appendix F, Jan. 1991.
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