High-Resolution Ultraviolet Imaging for
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Joel Wm. Parker
David C. Slater
Inclusive Dates: 04/08/99 - 08/08/99
Background - The Southwest Ultraviolet Imaging
System (SWUIS) has already proven its versatile capabilities as a wide-field observatory
on space shuttle flights STS-85 and STS-93. However, to take maximum advantage of the
capabilities of SWUIS and expand its data return for subsequent flights, a high-resolution
imaging mode (H-RIM) was needed to complement the wide-field capabilities.
Approach - The primary goals of this
quick-look research study were to:
- Design the necessary modification to the SWUIS instrument
- Make initial lab tests on the design
- Fabricate parts in the SwRI machine shop
- Prove the improved visible and UV imaging capabilities in the
- Propose to external sources the application of these new
capabilities to untapped research niches in astrophysics and planetary science.
The development of the H-RIM will provide SwRI with unique
capabilities in observational astrophysics and planetary science. This project was
designed to address the explicit need to provide proof-of-concept demonstration of the
instrument's new and improved features. Attaining this new high-resolution capability
involved constructing an extension tube capable of holding an ultraviolet
(UV)-transmissive lens between the existing Telescope Optical Coupler Assembly (TOCA) at
the output of the SWUIS telescope and the focal plane camera. This lens magnifies the
primary image plane at the output of the TOCA onto the focal plane camera that attaches to
the end of the H-RIM extension tube. To minimize the TOCA/H-RIM extension tube length, the
extension tube was built as a right-angle elbow utilizing a flat relay mirror built into
the tube housing to bend the light passing through the extension tube 908 to the
Xybion-intensified CCD (ICCD) focal plane camera.
Laboratory tests verified the H-RIM extension tube design
before the tube was built. Candidate lenses were procured and tested to measure the
instruments new effective focal length (EFL). These testing results verified the
optical design of the H-RIM tube, which allowed the team to begin assembly of a flight
version of this tube.
Accomplishments - Following fabrication of the
H-RIM extension tube, extensive laboratory testing was conducted to measure the
magnification and spatial resolution performance of SWUIS in H-RIM mode. Modulation
transfer function (MTF) measurements were made using an Air Force test target and an
eight-inch f/10 Schmidt-Cassegrain telescope acting as a collimator for SWUIS in TSM.
Initial results of these MTF tests indicate that SWUIS in H-RIM can achieve a maximum
spatial resolution of approximately 0.8 arcseconds. Without the H-RIM, the maximum spatial
resolution is 2.5 arcseconds (limited by the microchannel plate pore spacing in the
intensifier section of the Xybion ICCD camera). Thus the team has achieved a factor of
approximately 3.1 improvement in spatial resolution with H-RIM.
As a result of the design, fabrication, and testing work
performed under this project, SwRI proposed to NASA for funding to apply SWUIS and to
leverage the new H-RIM mode to areas of astrophysics and planetary science that can not be
studied with other instruments. SwRI proposed to the NASA Astrophysics Suborbital Research
program to use H-RIM to obtain a valuable set of astrophysical observations when SWUIS
flies on the space shuttle in 2000-2001 for its third mission (SWUIS-03). SwRI proposed to
make new and unique UV observations of astrophysical targets including massive stars in
field regions and open clusters, hot stars in globular clusters, emission-line stars, and
transient events. These data will be used to study star-formation processes, to compare
and constrain stellar evolution models, to examine the second-parameter problem in
globular clusters, and to probe galactic evolution. The H-RIM is also an essential part of
an SwRI proposal to the NASA Planetary Suborbital Research program to explore comets deep
within a distance of 1 AU of the sun (at elongation angles too small for other existing UV
instruments to observe) and to study the far-UV reflectance spectra of Mercury and the
Such observations will return a varied and essential data set
with lasting value to several research communities. No other instrument can return this
amount of high-quality UV astrophysical data at such a low cost.
H-RIM extension tube is connected to the TOCA and the
Xybion ICCD camera.
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