Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!ucsd!pacbell.com!ames!trident.arc.nasa.gov!yee From: yee@trident.arc.nasa.gov (Peter E. Yee) Newsgroups: sci.space.shuttle Subject: STS-35 Press Kit [Part 2 of 3] (Forwarded) Message-ID: <1990Nov30.074835.29975@news.arc.nasa.gov> Date: 30 Nov 90 07:48:35 GMT Sender: usenet@news.arc.nasa.gov (USENET Administration) Reply-To: yee@trident.arc.nasa.gov (Peter E. Yee) Organization: NASA Ames Research Center, Moffett Field, CA Lines: 700 o Hopkins Ultraviolet Telescope (HUT) uses a spectrograph to examine faint astronomical objects such as quasars, active galactic nuclei and normal galaxies in the far ultraviolet. o Ultraviolet Imaging Telescope (UIT) will take wide-field-of-view photographs of objects such as hot stars and galaxies in broad ultraviolet wavelength bands. o Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) will study the ultraviolet polarization of hot stars, galactic nuclei and quasars. These instruments working together will make 200 to 300 observations during the STS-35 mission. The Astro ultraviolet telescopes are mounted on a common pointing system in the cargo bay of the Space Shuttle. The grouped telescopes will be pointed in the same direction at the same time, so simultaneous photographs, spectra and polarization studies will be available for each object observed. The telescopes will be operated by Columbia's crew. A fourth Astro instrument, the Broad Band X-Ray Telescope (BBXRT), will view high-energy objects such as active galaxies, quasars and supernovas. This telescope is mounted on a separate pointing system secured by a support structure in the cargo bay. For joint observations, BBXRT can be aligned with the ultraviolet telescopes to see the same objects, but it also can be pointed independently to view other X-ray sources. BBXRT will be operated remotely by ground controllers. Since the ultraviolet telescopes and the X-ray telescope are mounted on different support structures, they can be reflown together or separately. The Hopkins Ultraviolet Telescope The Hopkins Ultraviolet Telescope is the first major telescope capable of studying far ultraviolet (FUV) and extreme ultraviolet (EUV) radiation from a wide variety of objects in space. HUT's observations will provide new information on the evolution of galaxies and quasars, the physical properties of extremely hot stars and the characteristics of accretion disks (hot, swirling matter transferred from one star to another) around white dwarfs, neutron stars and black holes. HUT will make the first observations of a wide variety of astronomical objects in the far ultraviolet region below 1,200 Angstroms (A) and will pioneer the detailed study of stars in the extreme ultraviolet band. Ultraviolet radiation at wavelengths shorter than 912 A is absorbed by hydrogen, the most abundant element in the universe. HUT will allow astronomers, in some instances along unobserved lines of sight, to see beyond this cutoff, called the Lyman limit, because the radiation from the most distant and rapidly receding objects, such as very bright quasars, is shifted toward longer wavelengths. HUT was designed and built by the Center for Astrophysical Sciences and the Applied Physics Laboratory of The Johns Hopkins University in Baltimore, Md. Its 36-inch mirror is coated with the rare element iridium, a member of the platinum family, capable of reflecting far and extreme ultraviolet light. The mirror, located at the aft end of the telescope, focuses incoming light from a celestial source back to a spectrograph mounted behind the telescope. A grating within the spectrograph separates the light, like a rainbow, into its component wavelengths. The strengths of those wavelengths tell scientists how much of certain elements are present. The ratio of the spectral lines reveal a source's temperature and density. The shape of the spectrum shows the physical processes occurring in a source. The spectrograph is equipped with a variety of light-admitting slits or apertures. The science team will use different apertures to accomplish different goals in their observation. The longest slit has a field of view of 2 arc minutes, about 1/15th the apparent diameter of the moon. HUT is fitted with an electronic detector system. Its data recordings are processed by an onboard computer system and relayed to the ground for later analysis. Johns Hopkins scientists conceived HUT to take ultraviolet astronomy beyond the brief studies previously conducted with rocket- borne telescopes. A typical rocket flight might gather 300 seconds of data on a single object. HUT will collect more than 300,000 seconds of data on nearly 200 objects during the Astro-1 mission, ranging from objects in the solar system to quasars billions of light-years distant. HUT Vital Statistics Sponsoring Institution: The Johns Hopkins University, Baltimore, Md. Principal Investigator: Dr. Arthur F. Davidsen Telescope Optics: 36 in. aperture, f/2 focal ratio, iridium- coated paraboloid mirror Instrument: Prime Focus Rowland Circle Spectrograph with microchannel plate intensifier and electronic diode array detector Field of View of Guide TV: 10 arc minutes Spectral Resolution: 3.0 A Wavelength Range: 850 A to 1,850 A (First Order) 425 A to 925 A (Second Order) Weight: 1,736 lb Size: 44 inches in diameter 12.4 ft. in length Wisconsin Ultraviolet Photo-Polarimeter Experiment Any star, except for our sun, is so distant that it appears as only a point of light and surface details cannot be seen. If the light from objects is polarized, it can tell scientists something about the source's geometry, the physical conditions at the source and the reflecting properties of tiny particles in the interstellar medium along the radiation's path. The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE), developed by the Space Astronomy Lab at the University of Wisconsin- Madison, is designed to measure polarization and intensity of ultraviolet radiation from celestial objects. WUPPE is a 20-inch telescope with a 5.5-arc-minute field of view. WUPPE is fitted with a spectropolarimeter, an instrument that records both the spectrum and the polarization of the ultraviolet light gathered by the telescope. Light will pass through sophisticated filters, akin to Polaroid sunglasses, before reaching the detector. Measurements then will be transmitted electronically to the ground. Photometry is the measurement of the intensity (brightness) of the light, while polarization is the measurement of the orientation (direction) of the oscillating light wave. Usually waves of light move randomly -- up, down, back, forward and diagonally. When light is polarized, all the waves oscillate in a single plane. Light that is scattered, like sunlight reflecting off water, is often polarized. Astro-1 astronomers expect to learn about ultraviolet light that is scattered by dust strewn among stars and galaxies. They also can learn about the geometry of stars and other objects by studying their polarization. To date, virtually no observations of polarization of astronomical sources in the ultraviolet have been carried out. WUPPE measures the polarization by splitting a beam of radiation into two perpendicular planes of polarization, passing the beams through a spectrometer and focusing the beams on two separate array detectors. In the ultraviolet spectrum, both photometry and polarization are extremely difficult measurements to achieve with the high degree of precision required for astronomical studies. To develop an instrument that could make these delicate measurements required an unusually innovative and advanced technical effort. Thus, the WUPPE investigation is a pioneering foray with a new technique. The targets of WUPPE investigations are primarily in the Milky Way galaxy and beyond, for which comparative data exist in other wavelengths. Like the Hopkins Ultraviolet Telescope, WUPPE also makes spectroscopic observations of hot stars, galactic nuclei and quasars. Operating at ultraviolet wavelengths that are mostly longer than those observed by HUT (but with some useful overlap), WUPPE provides chemical composition and physical information on celestial targets that that give off a significant amount of radiation in the 1,400 to 3,200 A range. WUPPE Vital Statistics Sponsoring Institution: University of Wisconsin, Madison Principal Investigator: Dr. Arthur D. Code Telescope Optics: Cassegrain (two-mirror) system, f/10 focal ratio Instrument: Spectropolarimeter with dual electronic diode array detectors Primary Mirror Size: 20 in. diameter 279 sq.* in. area Field of View: 3.3 x 4.4 arc minutes Spectral Resolution: 6 Angstroms Wavelength Range: 1,400 to 3,200 Angstroms Magnitude Limit: 16 Weight: 981 lb Size: 28 inches in diameter 12.4 ft. in length * This and subsequent changes were made to avoid confusion since the computer will not create exponents for cm2 or the circle over the A for Angstrom. The Ultraviolet ImagingTelescope In the 20 years that astronomical observations have been made from space, no high-resolution ultraviolet photographs of objects other than the sun have been made. Nonetheless, the brief glimpses of the ultraviolet sky have led to important discoveries in spiral galaxies, globular clusters, white dwarf stars and other areas. Deep, wide-field imaging is a primary means by which fundamentally new phenomena or important examples of known classes of astrophysical objects will be recognized in the ultraviolet. The Ultraviolet Imaging Telescope (UIT), developed at NASA's Goddard Space Flight Center in Greenbelt, Md., is the key instrument for these investigations. UIT is a powerful combination of telescope, image intensifier and camera. It is a 15.2-inch Ritchey Chretien telescope with two selectable cameras mounted behind the primary mirror. Each camera has a six- position filter wheel, a two-stage magnetically focused image tube and a 70-mm film transport, fiber optically coupled to each image tube. One camera is designed to operate in the 1200 - 1700 Angstrom region and the other in the 1250-3200 Angstrom region. Unlike data from the other Astro instruments, which will be electronically transmitted to the ground, UIT images will be recorded directly onto a very sensitive astronomical film for later development after Columbia lands. UIT has enough film to make 2,000 exposures. A series of 11 different filters allows specific regions of the ultraviolet spectrum to be isolated for energy-distribution studies. After development, each image frame will be electronically digitized to form 2,048 x 2,048 picture elements, or pixels, then analyzed further with computers. UIT has a 15-inch diameter mirror with a 40-arc-minute field of view -- about 25 percent wider than the apparent diameter of the full moon. UIT has the largest field of view of any sensitive UV imaging instrument planned for flight in the 1990s. It will photograph nearby galaxies, large clusters of stars and distant clusters of galaxies. A 30-minute exposure (the length of one orbital night) will record a blue star of 25th magnitude, a star about 100 million times fainter than the faintest star visible to the naked eye on a dark, clear night. Since UIT makes longer exposures than previous instruments, fainter objects will be visible in the images. The instrument favors the detection of hot objects which emit most of their energy in the ultraviolet. Common examples span the evolutionary history of stars -- massive stars and stars in the final stages of stellar evolution (white dwarfs). Images of numerous relatively cool stars that do not radiate much in the ultraviolet are suppressed, and UV sources stand out clearly. The UIT's field of view is wide enough to encompass entire galaxies, star clusters and distant clusters of galaxies. This deep survey mode will reveal many new, exciting objects to be studied further by NASA's Hubble Space Telescope. Although the Hubble Space Telescope will have a much higher magnification and record much fainter stars, the UIT will photograph much larger regions all at once. In addition, the UIT will suffer much less interference from visible light, since it is provided with "solar blind" detectors. For certain classes of targets, such as diffuse, ultraviolet-emitting or ultraviolet-scattering nebulae, UIT may be a more sensitive imager. A wide selection of astronomical objects will be studied in this first deep survey of cosmic phenomena in the ultraviolet. The UIT is expected to target hot stars in globular clusters to help explain how stars evolve. Another experiment may help astronomers learn whether properties and distribution of interstellar dust are the same in all galaxies. High-priority objects are Supernova 1987A and vicinity, star clusters, planetary nebulae and supernova remnants, spiral and "normal" galaxies, the interstellar medium of other galaxies and clusters of galaxies. UIT Vital Statistics Sponsoring Institution: NASA Goddard Space Flight Center (GSFC), Greenbelt, Md. Principal Investigator: Theodore P. Stecher (NASA GSFC) Telescope Optics: Ritchey-Chretien (variation of Cassegrain two-mirror system with correction over wide field of view) Aperture: 15 in. Focal Ratio: f/9 Field of View: 40 arc minutes Angular Resolution: 2 arc seconds Wavelength Range: 1,200 A to 3,200 A Magnitude Limit: 25 Filters: 2 filter wheels, 6 filters each Detectors: Two image intensifiers with 70-mm film, 1,000 frames each; IIaO astronomical film Exposure Time: Up to 30 minutes Weight: 1,043 lb Size: 32 inches in diameter 12.4 ft. in length THE BROAD BAND X-RAY TELESCOPE The Broad Band X-Ray Telescope (BBXRT) will provide astronomers with the first high-quality spectra of many of the X-ray sources discovered with the High Energy Astronomy Observatory 2, better known as the Einstein Observatory, launched in the late 1970s. BBXRT, developed at NASA's Goddard Space Flight Center in Greenbelt, Md., uses mirrors and advanced solid-state detectors as spectrometers to measure the energy of individual X-ray photons. These energies produce a spectrum that reveals the chemistry, structure and dynamics of a source. BBXRT is actually two 8-inch telescopes each with a 17 arc-minute field of view (more than half the angular width of the moon). The two identical telescopes are used to focus X-rays onto solid-state spectrometers which measure photon energy in electron volts in the "soft" X-ray region, from 380 to 12,000 eV. The use of two telescopes doubles the number of photons that are detected and also provides redundancy in case of a failure. X-ray telescopes are difficult to construct because X-ray photons are so energetic that they penetrate mirrors and are absorbed. A mirror surface reflects X-rays only if it is very smooth and the photons strike it at a very shallow angle. Because such small grazing angles are needed, the reflectors must be very long to intercept many of the incident X-rays. Since even shallower angles are required to detect higher-energy X-rays, telescopes effective at high energies need very large reflecting surfaces. Traditionally, X-ray telescopes have used massive, finely polished reflectors that were expensive to construct and did not efficiently use the available aperture. The mirror technology developed for BBXRT consists of very thin pieces of gold-coated aluminum foil that require no polishing and can be nested very closely together to reflect a large fraction of the X-rays entering the telescope. Because its reflecting surfaces can be made so easily, BBXRT can afford to have mirrors using the very shallow grazing angles necessary to reflect high-energy photons. In fact, BBXRT is one of the first telescopes to observe astronomical targets that emit X-rays above approximately 4,000 electron volts. The telescope will provide information on the chemistry, temperature and structure of some of the most unusual and interesting objects in the universe. BBXRT can see fainter and more energetic objects than any yet studied. It will look for signs of heavy elements such as iron, oxygen, silicon and calcium. These elements usually are formed in exploding stars and during mysterious events occurring at the core of galaxies and other exotic objects. BBXRT will be used to study a variety of sources, but a major goal is to increase our understanding of active galactic nuclei and quasars. Many astronomers believe that the two are very similar objects that contain an extremely luminous source at the nucleus of an otherwise relatively normal galaxy. The central source in quasars is so luminous that the host galaxy is difficult to detect. X-rays are expected to be emitted near the central engine of these objects, and astronomers will examine X-ray spectra and their variations to understand the phenomena at the heart of quasars. Investigators are interested in clusters of galaxies, congregations of tens or thousands of galaxies grouped together within a few million light- years of each other. When viewed in visible light, emissions from individual galaxies are dominant, but X-rays are emitted primarily from hot gas between the galaxies. In fact, theories and observations indicate that there should be about as much matter in the hot gas as in the galaxies, but all this material has not been seen yet. BBXRT observations will enable scientists to calculate the total mass of a cluster and deduce the amount of "dark" matter. A star's death, a supernova, heats the region of the galaxy near the explosion so that it glows in X-rays. Scientists believe that heavy elements such as iron are manufactured and dispersed into the interstellar medium by supernovas. The blast or shock wave may produce energetic cosmic ray particles that travel on endless journeys throughout the universe and instigate the formation of new stars. BBXRT detects young supernova remnants (less than 10,000 years old) which are still relatively hot. Elements will be identified, and the shock wave's movement and structure will be examined. BBXRT was not part of the originally selected ASTRO payload. It was added to the mission after the appearance of Supernova 1987A in February 1987, to obtain vital scientific information about the supernova. In addition, data gathered by BBXRT on other objects will enhance studies that would otherwise be limited to data gathered with the three ultraviolet telescopes. BBXRT Vital Statistics Sponsoring Institution: NASA Goddard Space Flight Center, Greenbelt, Md. Principal Investigator: Dr. Peter J. Serlemitsos Telescope Optics: Two co-aligned X-ray telescopes with cooled segmented lithium- drifted silicon solid-state detectors in the focal planes Focal Length: 12.5 ft. each, detection area 0.16 in. diameter pixel Focal Plane Scale: 0.9 arc minutes per mm Field of View: 4.5 arc minutes (central element); 17 arc minutes (overall) Energy Band: 0.3 to 12 keV Effective Area: 765 cm2 at 1.5 keV, 300 cm2 at 7 keV Energy Resolution: 0.09 keV at 1 keV, 0.15 keV at 6 keV Weight: 1,500 lb (680.4 kg) Size: 40 inches in diameter 166 inches in length ASTRO CARRIER SYSTEMS The Astro observatory is made up of three co-aligned ultraviolet telescopes carried by Spacelab and one X-ray telescope mounted on the Two-Axis Pointing System (TAPS) and a special structure. Each telescope was independently designed, but all work together as elements of a single observatory. The carriers provide stable platforms and pointing systems that allow the ultraviolet and X-ray telescopes to observe the same target. However, having two separate pointing systems gives investigators the flexibility to point the ultraviolet telescopes at one target while the X-ray telescope is aimed at another. Spacelab The three ultraviolet telescopes are supported by Spacelab hardware. Spacelab is a set of modular components developed by the European Space Agency and managed by the NASA Marshall Space Flight Center, Hunstville, Ala. For each Spacelab payload, specific standardized parts are combined to create a unique design. Elements are anchored within the cargo bay, transforming it into a short-term laboratory in space. Spacelab elements used to support the Astro observatory include two pallets, a pressurized igloo to house subsystem equipment and the Instrument Pointing System. The pressurized Spacelab laboratory module will not be used for Astro. Rather, astronauts and payload specialists will operate the payload from the aft flight deck of the orbiter Columbia. Pallets The ultraviolet telescopes and the Instrument Pointing System are mounted on two Spacelab pallets -- large, uncovered, unpressurized platforms designed to support scientific instruments that require direct exposure to space. Each individual pallet is 10 feet long and 13 feet wide. The basic pallet structure is made up of five parallel U-shaped frames. Twenty-four inner and 24 outer panels, made of aluminum alloy honeycomb, cover the frame. The inner panels are equipped with threaded inserts so that payload and subsystem equipment can be attached. Twenty-four standard hard points, made of chromium-plated titanium casting, are provided for payloads which exceed acceptable loading of the inner pallets. Pallets are more than a platform for mounting instrumentation. With an igloo attached, they also can cool equipment, provide electrical power and furnish connections for commanding and acquiring data from experiments. Cable ducts and cable support trays can be bolted to the forward and aft frame of each pallet to support and route electrical cables to and from the experiments and the subsystem equipment mounted on the pallet. The ducts are made of aluminum alloy sheet metal. In addition to basic utilities, some special accommodations are available for pallet-mounted experiments. For Astro-1, two pallets are connected together to form a single rigid structure called a pallet train. Twelve joints are used to connect the two pallets. Igloo Normally Spacelab subsystem equipment is housed in the core segment of the pressurized laboratory module. However, in "pallet only" configurations such as Astro, the subsystems are located in a supply module called the igloo. It provides a pressurized compartment in which Spacelab subsystem equipment can be mounted in a dry-air environment at normal Earth atmospheric pressure, as required by their design. The subsystems provide such services as cooling, electrical power and connections for commanding and acquiring data from the instruments. The igloo is attached vertically to the forward end frame of the first pallet. Its outer dimensions are approximately 7.9 feet in height and 3.6 feet in diameter. The igloo is a closed cylindrical shell made of aluminum alloy and covered with multi-layer insulation. A removable cover allows full access to the interior. The igloo consists of two parts. The primary structure -- an exterior cannister -- is a cylindrical, locally stiffened shell made of forged aluminum alloy rings and closed at one end. The other end has a mounting flange for the cover. A seal is inserted when the two structures are joined together mechanically to form a pressure-tight assembly. There are external fittings on the cannister for fastening it to the pallet, handling and transportation on the ground, and thermal control insulation. Two feed-through plates accommodate utility lines and a pressure relief valve. Facilities on the inside of the cannister are provided for mounting subsystem equipment and the interior igloo structure. The cover is also a cylindrical shell, made of welded aluminum alloy and closed at one end. The igloo has about 77.7 cubic feet of interior space for subsystems. Subsystem equipment is mounted on an interior or secondary structure which also acts as a guide for the removal or replacement of the cover. The secondary structure is hinge-fastened to the primary structure, allowing access to the bottom of the secondary structure and to equipment mounted within the primary structure. Instrument Pointing System Telescopes such as those aboard Astro-1 must be pointed with very high accuracy and stability at the objects which they are to view. The Spacelab Instrument Pointing System provides precision pointing for a wide range of payloads, including large single instruments or clusters of instruments. The pointing mechanism can accommodate instruments weighing up to 15,432 pounds and can point them to within 2 arc seconds and hold them on target to within 1.2 arc seconds. The combined weight of the ultraviolet telescopes and the structure which holds them together is 9,131 pounds. The Instrument Pointing System consists of a three-axis gimbal system mounted on a gimbal support structure connected to the pallet at one end and the aft end of the payload at the other, a payload clamping system for support of the mounted experiment during launch and landing and a control system based on the inertial reference of a three-axis gyro package and operated by a gimbal-mounted microcomputer. Three bearing-drive units on the gimbal system allow the payload to be pointed on three axes: elevation (back and forth), cross-elevation (side to side) and azimuth (roll), allowing it to point in a 22-degree circle around a its straight-up position. The pointing system may be maneuvered at a rate of up to one degree per second, which is five times as fast as the Shuttle orbiter's maneuvering rate. The operating modes of the different scientific investigations vary considerably. Some require manual control capability, others slow scan mapping, still others high angular rates and accelerations. Performance in all these modes requires flexibility achieved with computer software. The Instrument Pointing System is controlled through the Spacelab subsystem computer and a data-display unit and keyboard. It can be operated either automatically or by the Spacelab crew from the module (when used) and also from the payload station in the orbiter aft flight deck. In addition to the drive units, Instrument Pointing System structural hardware includes a payload/gimbal separation mechanism, replaceable extension column, emergency jettisoning device, support structure and rails and a thermal control system. The gimbal structure itself is minimal, consisting only of a yoke and inner and outer gimbals to which the payload is attached by the payload-mounted integration ring. An optical sensor package is used for attitude correction and also for configuring the instrument for solar, stellar or Earth viewing. The Astro-1 mission marks the first time the Instrument Pointing System has been used for stellar astronomy. Three star trackers locate guide stars. The boresite tracker is in the middle, and two other trackers are angled 12 degrees from each side of the boresite. By keeping stars of known locations centered in each tracker, a stable position can be maintained. The three ultraviolet telescopes are mounted and precisely co- aligned on a common structure, called the cruciform, that is attached to the pointing system. Image Motion Compensation System An image motion compensation system was developed by the Marshall Space Flight Center to provide additional pointing stability for two of the ultraviolet instruments. When the Shuttle thrusters fire to control orbiter attitude, there is a noticeable disturbance of the pointing system. The telescopes are also affected by crew motion in the orbiter. A gyro stabilizer senses the motion of the cruciform which could disrupt UIT and WUPPE pointing stability. It sends information to the image motion compensation electronics system where pointing commands are computed and sent to the telescopes' secondary mirrors which make automatic adjustments to improve stability to less than 1 arc second. The Astro-1's star tracker, designed by the NASA Jet Propulsion Laboratory, Pasadena, Calif., fixes on bright stars with well-known and sends this information to the electronics system which corrects errors caused by gyro drift and sends new commands to the telescopes' mirrors. The mirrors automatically adjust to keep pointed at the target. Broad Band X-ray Telescope and the Two-Axis Pointing System (TAPS) Developed at the NASA Goddard Space Flight Center, these pointing systems were designed to be flown together on multiple missions. This payload will be anchored in a support structure placed just behind the ultraviolet telescopes in the Shuttle payload bay. BBXRT is attached directly to the TAPS inner gimbal frame. The TAPS will move BBXRT in a forward/aft direction (pitch) relative to the cargo bay or from side to side (roll) relative to the cargo bay. A star tracker uses bright stars as a reference to position the TAPS for an observation, and gyros keep the TAPS on a target. As the gyros drift, the star tracker periodically recalculates and resets the TAPS position. ASTRO OPERATIONS Operation of the Astro-1 telescopes will be a cooperative effort between the science crew in orbit and their colleagues in a control facility at the Marshall Space Flight Center and a support control center at Goddard Space Flight Center. Though the crew and the instrument science teams will be separated by many miles, they will interact with one another to evaluate observations and solve problems in much the same way as they would when working side by side. On-Orbit Science Crew Activities The Astro science crew will operate the ultraviolet telescopes and Instrument Pointing System from the Shuttle orbiter's aft flight deck, located to the rear of the cockpit. Windows overlooking the cargo bay allow the payload specialist and mission specialist to keep an eye on the instruments as they command them into precise position. The aft flight deck is equipped with two Spacelab keyboard and display units, one for controlling the pointing system and the other for operating the scientific instruments. To aid in target identification, this work area also includes two closed-circuit television monitors. With the monitors, crew members will be able to see the star fields being viewed by HUT and WUPPE and monitor the data being transmitted from the instruments. The Astro-1 crew will work around the clock to allow the maximum number of observations to be made during their mission. The STS-35 commander will have a flexible schedule, while two teams of crew members will work in 12-hour shifts. Each team consists of the pilot or flight mission specialist, a science mission specialist and a payload specialist. The crew and the ground controllers will follow an observation schedule detailed in a carefully planned timeline. In a typical Astro-1 ultraviolet observation, the flight crew member on duty maneuvers the Shuttle to point the cargo bay in the general direction of the astronomical object to be observed. The mission specialist commands the pointing system to aim the telescopes toward the target. He also locks on to guide stars to help the pointing system remain stable despite orbiter thruster firings. The payload specialist sets up each instrument for the upcoming observation, identifies the celestial target on the guide television and provides any necessary pointing corrections for placing the object precisely in the telescope's field of view. He then starts the instrument observation sequences and monitors the data being recorded. Because the many observations planned create a heavy workload, the payload and mission specialists work together to perform these complicated operations and evaluate the quality of observations. Each observation will take between 10 minutes to a little over an hour. The X-ray telescope requires little attention from the crew. A crew member will turn on the BBXRT and the TAPS at the beginning of operations and then turn them off when the operations conclude. The telescope is controlled from the ground. After the telescope is activated, researchers at Goddard can "talk" to the telescope via computer. Before science operations begin, stored commands are loaded into the BBXRT computer system. Then, when the astronauts position the Shuttle in the general direction of the source, the TAPS automatically points the BBXRT at the object. Since the Shuttle can be oriented in only one direction at a time, X-ray observations must be coordinated carefully with ultraviolet observations. GROUND CONTROL Astro-1 science operations will be directed from a new Spacelab Mission Operations Control facility at the Marshall Space Flight Center. BBXRT will be controlled by commands from a supporting payload operations control facility at Goddard. Spacelab Mission Operations Control Beginning with the Astro-1 flight, all Spacelab science activities will be controlled from Marshall's Spacelab Mission Operations Control Center. It will replace the payload operations control center at the Johnson Space Center from which previous Spacelab missions have been operated. The Spacelab Mission Operations Control team is under the overall direction of the mission manager. The Spacelab Mission Operations Control team will support the science crew in much the same way that Houston Mission Control supports the flight crew. Teams of controllers and researchers at the Marshall facility will direct all NASA science operations, send commands directly to the spacecraft, receive and analyze data from experiments aboard the vehicle, adjust mission schedules to take advantage of unexpected science opportunities or unexpected results, and work with crew members to resolve problems with their experiments. Brought to you by Super Global Mega Corp .com