Performance and Preliminary Calibration of the Hopkins Ultraviolet Telescope on the Astro-2 Mission
Jeffrey W. Kruk, Samuel T. Durrance, Gerard A. Kriss,
Arthur F. Davidsen, William P. Blair, Brian R. Espey
Department of Physics & Astronomy, Johns Hopkins University,
Baltimore, MD 21218
and
David Finley
Eureka Scientific, Berkeley, CA 94602
Abstract:
An improved version of the Hopkins Ultraviolet Telescope (HUT) made its
second flight aboard the space shuttle Endeavour on the Astro-2 mission
from 1995 March 2-18.
The longer mission duration and greatly improved pointing stability
relative to Astro-1 made possible 385 observations of 265 celestial targets
in the far-ultraviolet (820-1840 Å), more than four times that observed
on the first flight.
Our selection of objects includes quasars (and intervening material),
active, starburst, and normal galaxies, cataclysmic variables, supernova
remnants, white dwarfs, Wolf-Rayet stars, O-B stars, reflection nebulae,
and solar system targets.
We give a preliminary assessment of the in-flight performance and
calibration of HUT.
The spectrograph had a resolution of 2-4 Å over the first order
wavelength range of 820-1840 Å.
Our photometric calibration is derived from comparison of model stellar
atmospheres to observations of the white dwarf HZ 43, and
we estimate this to be accurate to 
5%.
The peak effective area is 
at 1160 Å where the
instrument sensitivity is 
.
Our effective area exceeds the peak of 
achieved on
the Astro-1 mission from 912-1606 Å, largely due to the silicon carbide
coatings used on the primary mirror and the spectrograph grating.
As on Astro-1, the instrumental dark count outside the South Atlantic
Anomaly was less than 
counts s
Å
.
Subject headings: artificial satellites, space probes --- instrumentation: spectrographs
--- instrumentation: detectors --- telescopes --- ultraviolet: general
kruk@pha.jhu.edu