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High Resolution Imager (HRI)

NSSDC 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 or 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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