STS-67 Day 14 Highlights

Back to STS-67 Flight Day 13 Highlights:

On Thursday, March 16, 1995 at 6 a.m. CST, STS-67 Payload Status Report # 29 reports: (14/5:22 MET) All three ultraviolet telescopes were pointed at Jupiter and one of its 16 moons, Io, as the second Astro Observatory (Astro-2) mission continued aboard the Space Shuttle Endeavour last night.

The science team for the Hopkins Ultraviolet Telescope (HUT) recorded spectrographic data about ultraviolet emissions around Io. HUT scientists are especially interested in how Jupiter's magnetosphere and torus, a donut-shaped field of ionized particles that follows Io's path around Jupiter, are affected by the reddish particles erupting from Io's volcanoes.

Astronomers with the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) team observed Jupiter to learn more about the polarization properties of its atmosphere. The Ultraviolet Imaging Telescope (UIT) scientists used one of their two wide-field cameras to produce ultraviolet images of Jupiter to determine the planet's reflectiveness and cloud structure and provide ultraviolet images of the entire Jovian system.

HUT continued the search for helium in the intergalactic regions of space last night, using a quasar (Q 1542+54) as background lighting. HUT scientists are looking for evidence of helium left over from the primordial fireball that many believe marked the birth of the universe. Helium reveals itself as a telltale absorption line at a certain extreme ultraviolet wavelength. Principal Investigator Arthur Davidsen will use HUT's spectrograph to search for the characteristic signature created when helium atoms absorb light from this quasar.

HUT was also used to observe Markarian 66, a starburst galaxy, for Guest Investigator Dr. Claus Leitherer of the Space Telescope Science Institute in Baltimore, Md. Leitherer is using HUT's capacity to detect short ultraviolet wavelengths to study the ionized radiation that escapes from bright, relatively nearby starburst galaxies. HUT observations of the far ultraviolet radiation from these galaxies will be used to determine whether they could play an important role in ionizing the intergalactic medium.

UIT imaged NGC 6318, a relatively old cluster of stars. This cluster of stars has a low metal content, indicating it was formed early in the life of the Milky Way galaxy. Since most hot stars emit radiation in the ultraviolet and cooler stars emit in the lower ultraviolet range, the UIT instrument is especially suited for making images of these types of stars. Astronomers will analyze these Astro-2 images, looking for hot accreting binaries, hot white dwarfs, planetary nebula, and objects associated with X-ray sources.

As UIT made images of a faint dwarf galaxy known as IC 2574, HUT made spectrographic recordings and WUPPE observed the orientation of the ultraviolet energy being emitted from the galaxy. Because this type of galaxy emits such a faint trace of ultraviolet radiation, very little is known about the formation of young stars there. Astro-2 scientists are using their sensitive telescopes to explore this little-known region of the universe.

UIT was also pointed at the Baades Window, an unusually clear line of sight towards the center of our Milky Way galaxy. Because of the relative lack of obscuring dust in this field of view, the UIT can image stars and star clusters in the central bulge of the galaxy, where stars are thought to be both ancient and rich in metals.

WUPPE and HUT observed a reflection nebula near the star Eta Carinae. Reflection nebulae are colorful objects. Starlight is scattered by dust grains, producing brilliant illumination in the cloud. WUPPE scientists will analyze their data to learn more about the chemical composition, size, distribution and shape of the dust grains. HUT astronomers observed the nucleus and surrounding region of this nebula, searching for effects of the shock wave that was created when the nova exploded.

WUPPE and HUT also jointly observed AO Cassiopeia, a close binary star system (two stars so close that they not only orbit each other but actually influence each other's evolution). Astronomers have observed that the more evolved a star is (in a close binary system), the less massive the star becomes because it donates material to the younger star. WUPPE scientists are studying the effects of the dust-scattering processes in the distorted atmospheres of close binaries. These data will provide new information about the evolution of these stars and help astronomers learn more about the mass transfer of material between close binaries.

The WUPPE telescope also gathered data about the orientation of dust grains between the stars last night. To help scientists study this polarization of interstellar medium, WUPPE was pointed at three stars, which served as background lights to illuminate the interstellar dust. As astronomers learn more about the polarization of interstellar medium, they can make allowances for this intervening matter when studying other celestial objects.

During the next 12 hours, the Astro-2 ultraviolet telescopes will be pointed at the moon, two Seyfert galaxies, and single and multiple star systems to study electron scattering. These astronomical instruments will also observe interstellar medium and young star populations in a galaxy.

On Thursday, March 16, 1995 at 8 a.m. CST, STS-67 MCC Status Report # 28 reports: Astronomical observations using the ASTRO-2 payload will continue throughout Friday morning aboard Endeavour prior to the transition from payload operations to the landing timeline, four hours before the deorbit ignition of the Shuttle's orbital maneuvering system engines.

On Thursday, March 16, 1995 at 5 p.m. CST, STS-67 MCC Status Report # 29 reports: Commander Steve Oswald spoke with U.S. Astronaut Norm Thagard aboard the Mir Space Station in a radio hookup between the two spacecraft. Former shuttle crewmates, Oswald and Thagard exchanged congratulations on their respective flights and discussed the symbolic importance of Thagard's venture as the first American to visit the Russian space outpost. Thagard and his Russian crewmates arrived at Mir early this morning to begin three months of scientific and medical research.

The Red team astronauts -- Oswald, Pilot Bill Gregory, Mission Specialist John Grunsfeld and Payload Specialist Ron Parise -- conducted final data takes with the ASTRO telescopes and reviewed entry messages prepared by the flight controllers who will guide Endeavour to its scheduled landing tomorrow afternoon at the Kennedy Space Center. Tonight, at 6:33 PM CST, Endeavour will eclipse the existing endurance record for a Shuttle, breaking the mark of 14 days, 17 hours and 55 minutes in orbit. That record was set by Columbia last year, on the STS-65 mission.

On Thursday, March 16, 1995 at 6 a.m. CST, STS-67 Payload Status Report # 30 reports: (14/17:22 MET) The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) team wrapped up two studies about how stars put material back into the interstellar medium, which in turn can build new stars. They viewed the star Xi Persei to complete their study of Oe/Be stars. These rapidly spinning, hot massive stars are found primarily in the arms of spiral galaxies. The WUPPE observations should help determine the shapes of the gas shells spun off or otherwise ejected by the stars.

WUPPE also observed Vela X-1, in the instrument's final polarization measurement of an X-ray binary star. It is believed that such systems are made up of a neutron star, which may be a pulsar, in an eccentric orbit around a more normal primary star. At the closest approach, the neutron star gravitationally strips material off the primary star. The material then flows along the neutron star's magnetic field and crashes onto the surface to produce a sudden burst of X-rays. However, much of the stripped material forms a disk around the neutron star instead of settling onto star's surface. The WUPPE measurements will help define the geometry and the extent of this circumstellar disk, as well as details about the densities and temperatures within the shells.

Observations of the stars HD 147888 and Omicron Scorpii were for WUPPE's study of the dust between stars in our galaxy. The WUPPE team will use their findings about variations in the distribution, shapes and composition of this dust to understand more about this raw material for star formation. A better knowledge of how the dust polarizes light also will allow astronomers to subtract the interference of intervening dust from star observations.

The Hopkins Ultraviolet Telescope (HUT) team selected two white dwarf stars for today's observation block. Today's study of the white dwarf RE 1738 completed Guest Investigator Dr. David Finley's data set for his calibration of temperature scales for these small but massive remains of dying stars. The mission's fourth observation of 1424+535 added more information about a transitory evolutionary stage of white dwarf stars with powerful magnetic fields. These pulsating white dwarfs undergo periodic changes in brightness, but the causes of the pulsations and the chemical composition of the stars' visible surfaces is not well understood.

Guest Investigator Dr. Brian Espey got one last look at a symbiotic star system with a joint HUT and WUPPE observation of AG Draconis. The study essentially aims to "take the temperature" of the hot, sub-dwarf component of this two-star group, whose co-orbiting members vary widely in temperature. Espey also hopes to determine the size and density of the cool material that lies in the atmosphere of the red giant component.

The HUT team made their last quasar observation when they viewed PG 1351, one that is relatively closer than those HUT is using in its search for intergalactic helium. HUT is examining "nearby" quasars to understand better the processes taking place within these extremely energetic objects. Team members will also search their data to test the widely accepted theory that quasars are powered by supermassive black holes.

The majority of targets chosen by the Ultraviolet Imaging Telescope (UIT) team today were galaxies. They selected two active galaxies thought to have black holes at their centers. NGC 1566 is a faint, nearby Seyfert I type galaxy, the type which radiates most strongly in ultraviolet and X-ray wavelengths and has high gas velocities and spectra resembling a quasar. NGC 3226-7 is a Seyfert II galaxy, with a lower gas velocity than the Type 1 Seyferts. UIT astronomers are studying both types to learn more about how energy is transferred between the galaxies' centers and surrounding regions.

UIT photographed two final spiral galaxies, NGC 5236 and M 63, for the atlas of these stunning celestial objects being assembled during this mission -- most of which had never before been photographed in the ultraviolet. Astronomers can use the shapes of nearby spiral galaxies revealed in ultraviolet light to classify more distant galaxies photographed in visible light by the Hubble Space Telescope. The radiation from those far-away galaxies was actually emitted in ultraviolet wavelengths, then stretched by the expansion of the universe into the visible band by the time it reached Earth's vicinity.

UIT concluded its Astro-2 album of galaxies by imaging a section of one of our nearest neighboring galaxies, the Small Magellanic Cloud. The UIT team led the Astro observatory in viewing NGC 362, the last globular cluster observation of the flight. The camera's ultraviolet images pick out hot stars from the clutter of cooler objects. UIT also imaged the Thumbprint Nebula in the mission's only look at that particular dark cloud of gas and dust in interstellar space.

This morning's planned observation of Earth's moon was unsuccessful, due to problems with the tricky maneuver of tracking such a nearby object with a system designed for stellar pointing. However, the Astro-2 instruments successfully viewed the moon twice before in the mission.

On Thursday, March 16, 1995 at 11 p.m. CST, STS-67 Payload Status Report # 31 reports: (14/22:22 MET) 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. 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."

sts-67-patch Return to STS-67 Mission Summary