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Hopkins Ultraviolet Telescope Technical Summary

HUT Technical Summary

Principal Investigator: Dr. Arthur F. Davidsen
Developing Institution: The Johns Hopkins University
Telescope Optics: 90-centimeter (36-inch) aperture, f/2 focal ratio,
silicon carbide-coated, parabolic mirror
Spectrograph: Prime-focus, Rowland-circle design using a
600 line/mm grating coated with silicon carbide
Spectral Resolution: 3.0 angstroms
Wavelength Range: 825 to 1850 angstroms (first order)
420 to 925 angstroms (second order)
Detector: photon-counting
microchannel-plate intensifier
cesium iodide photocathode
1024 element photo-diode array detector
Time Resolution: 1 ms in high time mode
2 s in histogram mode
Dark Count Rate: 0.001 counts/Angstrom/s
Peak Effective Area: 35 sq. cm at 1200 angstroms
Sensitivity: S/N of 10 per Angstrom in 1800 s
for Flambda=3.3e-14 ergs/cm2/s/A
Weight: 789 kilograms (1736 pounds)
Dimensions: 1.1 meter (4 feet) diameter
3.7 meters (12 feet) length
Field of View of Guide TV: 10 arc-minutes

The Hopkins Ultraviolet Telescope (HUT) was designed and built by members of the Center for Astrophysical Sciences and the Applied Physics Laboratory of The Johns Hopkins University in Baltimore, Maryland. HUT consists of a 90-centimeter (36-inch) f/2 mirror that focuses light from celestial sources onto a prime focus spectrograph.

Covering the 825-1850-angstrom region with about 3-angstrom resolution, HUT opened the astrophysically important 912 to 1200-angstrom window to detailed scrutiny for the first time. In typical 1800 s integrations, HUT observed faint astronomical objects with visual magnitudes of about 16.

Originally designed to explore the far- and extreme-ultraviolet ranges on Astro-1, HUT was modified for Astro-2 to concentrate on the far-ultraviolet. The changes made to HUT for Astro-2 included a new detector system and new silicon carbide coatings on the mirror and grating which replaced the original iridium and osmium. These improvements provided a factor of 2.3 increase in sensitivity in the primary operating range of 825 to 1850 angstroms, especially in the 912- to 1200-angstrom region unique to HUT.

What is HUT? provides a less technical description of HUT for the general reader.