Quick Look

High-Resolution Ultraviolet Imaging for Astrophysics, 15-9138

Principal Investigators
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 lab
• 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 instrument’s 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 moon.

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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