Astro-2 Public Affairs Status Report #31 11:00 p.m. CST (14/22:22 MET), March 16, 1995 Spacelab Mission Operations Control Marshall Space Flight Center Huntsville, Ala. "This has been an outstanding mission," said Astro-2 Mission Scientist Dr. Charles Meegan as the 16-day astronomy mission drew to a close. "We had planned to explore 23 different science programs and we 'nailed' them all." Science activities for the second Astro observatory (Astro-2) ended shortly after 11 p.m. CST, with all three telescopes taking ultraviolet observations of the full moon. "From my point of view, this mission has been nothing short of absolutely spectacular," said Hopkins Ultraviolet Telescope (HUT) Principal Investigator Dr. Arthur Davidsen. "It's been 17 years since we began thinking about doing far ultraviolet spectroscopy with HUT as a complement to what we can do with the Hubble Space Telescope and this is a dream come true. " The telescope, developed at The Johns Hopkins University in Baltimore, Md., conducted spectroscopy in far ultraviolet wavelengths to reveal what elements are present in an object, as well as identify physical processes taking place there. More than 200 separate successful observations were made of over 100 celestial objects selected by HUT investigators. All of these observations made up 21 separate investigations, 14 carried out by permanent members of the HUT team and 7 by guest investigators who joined the HUT team for Astro-2. One of Davidsen's primary objectives for HUT during Astro-2 was to use two high redshift quasars as background lighting to search for helium in the space between galaxies. Detecting helium in intergalactic space and determining how much of it is there could provide answers to the questions about the "Big Bang" that is believed to have marked the beginning of our universe. "I can tell you that we succeeded in getting data needed to answer these questions. It's too early to say what the answer might be, but it will be very exciting to see these data," explained Davidsen. In other Astro-2 observations, HUT made simultaneous ultraviolet measurements with the Hubble Space Telescope of Jupiter's aurora, or northern lights, and its effect on the planet. HUT scientists also studied the atmosphere of Jupiter's moon Io and the torus (donut-shaped cloud) of ionized gas it produces around Jupiter. HUT astronomers say observations such as this will lead to a greater understanding of the processes taking place on that planet. Ultraviolet emissions from the atmospheres of Venus and Mars were also targets of observations for HUT during this mission. Detailed analysis may reveal the presence of several interesting elements, including argon, neon and helium. HUT also observed less distant quasars and Seyfert galaxies to study details of their ultraviolet radiation. The studies could help confirm the theory that these objects contain supermassive black holes, which swallow matter from their surroundings. The observations could shed light on the dynamics of the gas clouds in the nuclei, or cores, of such active galaxies. HUT observed other celestial objects during the course of this mission. The telescope was used to study extragalactic objects, numerous cataclysmic variable stars, symbiotic star systems, hot white dwarf stars and several starburst galaxies to help astronomers learn more about the life of stars, from "birth" to the violent explosion marking the "death" of a star. Another of Astro-2's instruments, the Ultraviolet Imaging Telescope (UIT), which was developed at NASA's Goddard Space Flight Center, Greenbelt, Md., took wide-field, electronically intensified images of objects in ultraviolet light on film. UIT astronomer Dr. Steve Maran explained, "Our data say we got good exposures on all the science programs and high-priority targets. Now, we'll just have to wait until we get our film developed." Maran was referring to the many images UIT made, including about 2 dozen large spiral galaxies to be used in an ultraviolet atlas of such objects. The atlas will be a fundamental resource for astronomers for many years to come. UIT made for the first time ultraviolet images of the entire moon. These images will be studied to investigate the ultraviolet reflectivity of the moon, and to correlate changes in reflectivity with known changes in lunar surface features. This information can then be used to compare with the reflectivity of other planetary satellites in our solar system to understand more about their surfaces and the physical processes that have been responsible for their evolution. Scientists for UIT will spend the next several years analyzing their data from Astro-2. Some of these data include a census of rare, hot stars (with temperatures over 15,000 degrees Kelvin) in about a dozen star clusters. These hot stars, very much more evolved than the sun, have shed their outer layers so that scientists can see almost down to their nuclear-burning cores. UIT imaged more than 20 elliptical galaxies during this mission. The photographs will allow astronomers to map the still-mysterious "ultraviolet excess" - an excessive amount of ultraviolet radiation coming from galaxies containing large quantities of old stars, which normally have low ultraviolet emissions. This astronomical oddity was first noticed by WUPPE Principal Investigator Dr. Arthur Code over 25 years ago. In order to better understand this excess emission, UIT scientists will combine their images of clusters and galaxies with spectra from HUT and data from the Hubble Space Telescope. Observations of some of the faintest galaxies in the universe were photographed by UIT during Astro-2. Astronomers took advantage of the very dark sky background, using UIT to photograph very low surface brightness galaxies. "This could be the UIT observation with most potential for surprises," said UIT team member Dr. Steve Maran. "Ground-based observations show an unexpected blue glow. Our ultraviolet images may tell us where it's coming from." UIT also made images during over 140 co-observations of objects selected by HUT and WUPPE. In one series of co-observations, UIT got about 13,000 seconds of ultraviolet imaging of the quasar field 1700+64. UIT scientists will examine these images, searching for unusual ultraviolet-emitting objects over a vast range of distances in the universe. "We obtained a treasure chest of data for all our major programs, "said Dr. Arthur Code, principal investigator for WUPPE. Polarization measurements reveal the orientation of light as it is influenced by astronomical media. "Until this mission, the only set of ultraviolet spectropolarimetry in existence was that obtained during Astro-1 and a few objects obtained by the Hubble Space Telescope. Astro-2 observations greatly expand the data base and present a number of tantalizing results," Code said. He summarized the theme of WUPPE observations as "making stars" - how material is put back into the interstellar medium and builds new stars. WUPPE sampled some 20 different views for its study of the interstellar medium, using hot stars located behind interstellar dust clouds to measure the properties of the grains. In addition to examining the dust clouds in the Milky Way, WUPPE studied the interstellar medium in a nearby galaxy, the Large Magellanic Cloud. The instrument also got excellent observations of four Wolf- Rayet stars, an evolutionary stage of massive stars in which strong stellar winds eject shells of material into the interstellar medium. WUPPE's study of rapidly rotating "Be" stars, which yield matter back into space in the form of an equatorial disk and polar wind, covered a large range of spectral temperatures and rotation rates within the Be class. Results will be used to test the validity of new theories about the nature of these stars, developed after surprising results from Astro-1. The Wisconsin instrument gathered more information on interstellar dust with their observation of a reflection nebula, binaries, massive supergiant stars, and active galaxies. The WUPPE team benefited from "unexpected serendipity," Code said, when observations of three recently exploding novae gave the team a unique opportunity to follow the early history of these stellar explosions. "The results imply that the shell of gas ejected from the nova is asymmetrical from very near the beginning of the outburst," Code reported. A major factor in the mission's success was the smooth operation of the Instrument Pointing System (IPS), which pointed the three telescopes at their targets, and the Image Motion Compensation System (IMCS), which sensed small disturbances and compensated for them in two of the telescopes. "The IPS and IMCS for the first time achieved operational capacity," Astro-2 Mission Manager Robert Jayroe said. "In my estimation, the IMCS and IPS teams have done everything but make the hardware stand up and do a tap dance." Users of more than 200,000 computers from 59 countries logged on to the Astro-2 "home page," tracking the mission's progress and leaving messages for the STS-67 crew members. Astro-2 was the first Space Shuttle mission to have it's own home page on the Internet World Wide Web. More than 2.4 million requests for information were recorded over the last 15 days, to the delight of the home page administrators at NASA's Marshall Space Flight Center in Huntsville, Ala. To follow the mission in progress, visit Astro-2's home page on the Internet World Wide Web: URL "http://astro-2.msfc.nasa.gov"