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May 12, 1997
HST Update:
HST UPGRADES SHOW BIRTH AND DEATH OF STARS

 NICMOS PEERS INTO HEART OF DYING STAR

NICMOS PEERS INTO HEART OF DYING STAR

 

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New data released by NASA today include direct evidence of a supermassive black hole and remarkable new details on the explosive life cycle of stars. NASA also reported that all new Hubble instruments and upgrades are generally performing well.

"We're extremely excited about the quality and precision of the images from Hubble," said Wes Huntress, NASA Associate Administrator for Space Science. "Following check-out of the instruments, Hubble will return to full science operations, and we can expect a continuing flow of new and exciting discoveries."

These initial results clearly demonstrate the ability of the new instruments to fulfill their science goals with the Hubble Telescope, say project astronomers. Project officials are pleased to report that other instruments and electronics installed during the second servicing mission are performing well.

Among Hubble's recent observations:

 NICMOS PEERS INTO HEART OF DYING STAR

Jets and Gaseous Disk Around the Egg Nebula -- A new infrared instrument peered deep into the dust-obscured central region around a dying star embedded in the Egg nebula. A nebula is a cloud of dust and gas 3,000 light years from Earth. The new images provide a clear view of a twin pair of narrow bullet-shaped "jets" of gas and dust blasted into space. The instrument, called the Near Infrared Camera and Multi-Object Spectrometer, also revealed an unusual scalloped edge along a doughnut-shaped molecular hydrogen cloud in the nebula.

"Because we can now see these 'missing pieces' in infrared and visible light, we have a more complete view of the dynamic and complicated structure of the star," said Rodger Thompson of the University of Arizona, Tucson, the principal investigator for the infrared instrument. "It also allows us to see a 'fossil record' of the star's late evolutionary stages."

NICMOS CAPTURES THE HEART OF OMC-1

Unveiling Violent Starbirth in the Orion Nebula - The new infrared instrument penetrated the shroud of dust along the back wall of the Orion nebula, located in the "sword" of the constellation Orion. Data revealed what can happen to a stellar neighborhood when massive young stars begin to violently eject material into the surrounding molecular cloud. Although ground-based infrared cameras have previously observed this hidden region known as OMC-1, the Hubble's new instrument provides the most detailed look yet at the heart of this giant molecular cloud. Hubble reveals a surprising array of complex structures, including clumps, bubbles, and knots of material.

Most remarkable are "bullets" composed of molecular hydrogen -- the fastest of which travels at more than one million mph (500 km/s). These bullets are colliding with slower-moving material, creating bow shocks, like a speedboat racing across water.

 STIS RECORDS A BLACK HOLE'S SIGNATURE

Monster Black Hole in Galaxy M84 - In a single exposure, a new powerful instrument called the Space Telescope Imaging Spectrograph discovered a black hole at least 300 million times the mass of the Sun. The spectrograph made a precise observation along a narrow slit across the center of galaxy M84, located 50 million light-years away. This allowed the instrument to measure the increasing velocity of a disk of gas orbiting the black hole. To scientists, this represents the signature of a black hole, among the most direct evidence obtained to date. Due to their nature, it's impossible to directly photograph black holes. Scientists must instead look for clues to show the effects of black holes on surrounding dust, gas and stars.

"Hubble proved the existence of supermassive black holes three years ago," said Bruce Woodgate of the Goddard Space Flight Center, Greenbelt, MD, and principal investigator for the new spectrograph. "With this new instrument, we can do it 40 times faster than we used to."

STIS CHEMICALLY ANALYZES THE RING AROUND
                                                                        SUPERNOVA 1987A

Composition and Structure of the Ring Around Supernova 1987A - The new spectrograph also provides an unprecedented look at a unique and complex structure in the universe -- a light-year-wide ring of glowing gas around Supernova 1987A, the closest supernova explosion in 400 years. The spectrograph dissects the ring's light to tell scientists which elements are in the ring and helps paint a picture of the physics and stellar processes which created the ring. This gives astronomers better insight into how stars evolve and become a supernova, and into the origin of the chemical elements created in these massive explosions.

VIEW OF NICMOS' DEWAR DURING INSTALLATION

Hubble Status -- NASA project officials are encouraged that a problem detected earlier with one of the cameras on the infrared instrument has shown some improvement. The problem stems from the unexpected movement of the dewar -- an insulated vessel containing solid nitrogen at extremely cold temperatures. After launch, the nitrogen expanded more than expected as it warmed, moving the dewar into contact with another surface in the mechanism and pushing one of the cameras out of its range of focus. The camera has moved back about one-third of the distance required to be within reach of the instrument's internal focusing mechanism. This is because the dewar is "relaxing" toward its normal state, as pressure caused by the expansion of the nitrogen is reduced. The ice keeps the sensitive infrared detector cooled. Project officials also are considering how to deal with unexpected, excessive coolant loss.

"We are anticipating a shorter lifetime for the instrument, but we don't know how much shorter," said Goddard Hubble Project Scientist David Leckrone. "We are taking steps to work around the problem, and will increase the percentage of time this instrument will be used."

NASA officials also report that other upgrades to Hubble are performing well, including the newly installed solid state recorder, fine guidance sensor and solar array drive electronics. The solid state recorder has significantly improved data storage and playback, and the new fine guidance sensor is by far the best of the three on Hubble.

Images and text reproduced for educational use with permission from The Space Telescope Science Institute. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), for NASA, under contract with the Goddard Space Flight Center. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA).


April 28, 1997
HST Update:
Recommisioning Status Report

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READY FOR THE HUNT

Before the Space Telescope Imaging Spectrograph (STIS) can begin sniffing out black holes, the instrument must be tested to make sure it's ready for the challenge.

This testing program doesn't last a day, a week, or even a month. It is a two-month program consisting of an exhaustive series of tests. That's because scientists can't lift the telescope's hood and tinker with the instrument. Not when it's in an Earth-circling observatory that is 380 miles above our planet's surface. Instead, scientists must rely on special computers that perform a series of diagnostic tests on STIS. If adjustments must be made, scientists send detailed instructions to Hubble's electronic brain - its computers - on how to do it.

The long testing program also is important to ensure that STIS can perform its job accurately and efficiently. The instrument's job is to collect information from celestial objects, many of them very dim and distant ones. Based on this information, scientists will make assumptions about an object, such as its temperature or composition. So, STIS must be very precise in order to collect accurate information.

AN INSTRUMENT WITH MANY PARTS

STIS is one complex instrument. It has 65 apertures or light openings - a point-and-shoot camera has one - and 14 defraction gratings, which divide light into a spectrum of colors. The apertures vary in size. For example, a car license plate would fill the instrument's smallest aperture. STIS also has three separate detectors: a Charge-Coupled Device (CCD) and two Multi-Anode Microchannel Plate Arrays (MAMAs). Each detector records light from a different part of the spectrum. STIS's spectral range is from visible to far ultraviolet light.

HIGH VOLTAGE DETECTORS

The instrument's detectors are very sensitive. The two MAMA detectors cannot be turned on for several months because scientists must wait for the pressure to decrease inside STIS's closet-sized compartment. Too much pressure could short-circuit the MAMA detectors' high voltage power supply.

TOO MUCH LIGHT

Scientists also must wait to open STIS's eyes to bright light. Too much bright too soon could damage the instrument's optical equipment, including its four main mirrors. That's why Hubble doesn't look at the bright Earth for the first two weeks after the servicing mission.

FRAME A PICTURE

Once STIS opens its eyes, it will begin collecting light from celestial objects, such as stars and galaxies. An object's light is its resume, telling scientists something about the object. STIS will gather light and divide it into its wavelengths or colors. The colors provide information about an object's composition, temperature, density, and velocity.

But STIS can't make observations if the target object moves out of its field of view. It is not as simple as pointing a 35mm camera at a subject, glancing through the eyepiece to make sure it's in the frame, and clicking the picture. Hubble is moving at 17,500 mph, and many target objects are very dim and difficult to see. That's why Hubble has two Fine Guidance Sensors that lock onto stars - called guide stars - near the target object to keep the telescope steady during an observation. The Fine Guidance Sensors are good enough for the telescope's Wide Field and Planetary Camera II (WFPC2), which has a large aperture. But STIS has many small apertures, and scientists don't know the positions of guide stars accurately enough. If a guide star's position is slightly off, STIS's target object might be out of the field of view because of the small aperture.

So, scientists have thrown in a safety step for STIS. After the Fine Guidance Sensors have locked onto guide stars, the STIS's CCD detector takes a picture of the target object. The image tells instrument's computers whether the object is in view. If the object is not in the picture, STIS will tell the telescope where to move to find it. All of these decisions are made by STIS's sophisticated computer software. Scientists must check the software to make sure it is doing its job. Scientists can't have STIS telling the telescope to move to the right when the object is to the left.

HOW BRIGHT IS IT?

Once a target object is found, STIS must calculate its brightness. Knowing an object's brightness determines how long STIS must look at it to collect necessary information. In other words, an object's brightness determines how many orbits Hubble needs to make an observation. The telescope orbits the Earth every 97 minutes, completing about 15 passes around our planet a day. For example, it took about 150 orbits for the telescope to observe the Hubble Deep Field, which represents a pinhole view of the early universe. So, scientists must check STIS to make sure they know how sensitive the instrument is to light.

COSMIC SHOWER

Light is radiation, and it's STIS's job to collect it. But there's another form of radiation that STIS isn't crazy about. Through testing, scientists discovered that the instrument is more sensitive than expected to a large radiation field over South America. But scientists have solved the problem by juggling some STIS observing schedules.

Called the South Atlantic Anomaly, this well-known region is where the Van Allen radiation belts dip lower in altitude than elsewhere. The Van Allen belts are two doughnut-shaped regions - between 200 and 500 miles high - of magnetically trapped charged particles that encircle Earth. Hubble and all spacecraft are affected by the belts when they pass through them. Hubble's Wide Field and Planetary Camera 2 (WFPC2) does not make observations when the telescope passes through the region, sometimes as often as nine times a day. Before entering the region, Hubble's computers send digital images from WFPC2 so that the data won't be corrupted. The Van Allen belts act as a thin, protective skin for Earth, trapping charged particles before they bombard our planet and harm us.


March 25, 1997
STS-82 Update:
New Camera on Hubble Space Telescope Unfocused

NICMOS Dewar Container

NICMOS Dewar Container

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March 25, 1997
CAPE CANAVERAL, Fla. (AP) -- An infrared camera installed by spacewalking astronauts on the Hubble Space Telescope last month is partly out of focus and will not last as long as planned, NASA said today.

``We are going to lose some lifetime, there's no question about that,'' said Ed Weiler, NASA's chief Hubble scientist.

Provided the $105 million Near-Infrared Camera and Multi-Object Spectrometer does not deteriorate further, scientists should be able to work around the problem and still collect all the desired data on black holes and remote stars and galaxies, Weiler said.

``We tend to be very conservative considering our history,'' he said, referring to Hubble's originally flawed mirror. ``Until we're absolutely sure things are going to go the way we think they will, we always want to look at the worst case.''

One of three cameras in the Near-Infrared Camera and Multi-Object Spectrometer, called Nicmos, is too far out of focus to be corrected by on-board systems, Weiler said. The two others are working fine, he said.

Scientists believe the focusing problem with camera No. 3 resulted from the expansion of nitrogen ice, needed to keep the infrared detectors operating at minus-355 degrees Fahrenheit. The expanding ice apparently pushed on some of the camera mechanisms more than expected. Astronomers noticed this movement two weeks ago.

``The Nicmos probably will rewrite the physics books on solid nitrogen,'' Weiler said. ``The models that it was built upon were not totally correct.''

Because of additional heat entering the nitrogen container, the nitrogen will last at least a few months less than the full 4 1/2 years, provided the problem corrects itself, Weiler said. In that case, the focus of camera No. 3 would be restored naturally, perhaps in six months to one year.

The lifetime of Nicmos will be cut in half, however -- to 2 1/4 years -- if the nitrogen continues to be lost at the current rate. Scientists already are scrambling to push up the star-gazing schedule for Nicmos if this should happen.

Scientists plan to conduct another focus test on Thursday night to further assess the situation.

Nicmos, about the size of a telephone booth, was designed and built by the University of Arizona. It represents one-fourth of the entire Hubble science program, and its out-of-focus camera No. 3 represents one-fourth of the Nicmos science program.

NASA launched Hubble in 1990 with a flawed primary mirror that left the telescope nearsighted. Spacewalking astronauts installed corrective optics in 1993. The February mission to install Nicmos, another state-of-the-art science instrument and other equipment, was the second servicing mission for the $2 billion Hubble.


 

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