Space Shuttle Cleared for Landing

Discovery in orbit. Image credit: NASA Click to enlarge
Space Shuttle mission managers today completed their assessment of Discovery’s fitness to handle the rigors of re-entry into the atmosphere.

“We have cleared Discovery to re-enter,” said Wayne Hale, chairman of the Mission Management Team (MMT), during a news conference at NASA’s Johnson Space Center, Houston.

The MMT determined the Orbiter’s heat shield and other systems are in good shape. They also decided a spacewalk is unnecessary to repair damage to a thermal blanket on Discovery’s outer skin.

Earlier this week, Discovery (STS-114) mission managers determined two components of the Shuttle’s Thermal Protection System, tile and Reinforced Carbon-Carbon, were fit for re-entry and landing. Today, the MMT cleared the final element: thermal blankets. One blanket is slightly torn and billowing in orbit.

The MMT considered the results of overnight testing at NASA’s Ames Research Center, Moffett Field, Calif. Engineers ran samples of torn thermal blankets through wind tunnels at velocities many times faster than the speed of sound. Tests showed it was highly unlikely the blanket would tear off or strike the Orbiter. Other analyses showed the blankets would still protect Discovery from re-entry heat.

Based on the analysis of the blankets and considering the risks of a fourth spacewalk, mission managers decided the torn blanket did not need repair. “We’ve assessed this risk to the very best of our knowledge, and we believe the risk is small,” Hale said.

New imaging capabilities developed after the Space Shuttle Columbia accident allowed mission managers to see and analyze the torn thermal blanket. Data from the images were used to re-create blanket samples for the wind tunnel tests. “I think it’s remarkable we have capability to look at these small things in flight,” Hale said.

Discovery is set to land Monday, Aug. 8 at NASA’s Kennedy Space Center, Fla. The first opportunity for Commander Eileen Collins to land the Space Shuttle is at 4:46 a.m. EDT.

For information about STS-114 on the Web, visit:
http://www.nasa.gov/returntoflight

Original Source: NASA News Release

Massive Asteroids Transformed the Earth’s Surface

Asteroid. Image credit: NEAR Click to enlarge
A cluster of at least three asteroids between 20 and 50 kilometres across colliding with Earth over 3.2 billion years ago caused a massive change in the structure and composition of the earth?s surface, according to new research by ANU earth scientists.

According to Dr Andrew Glikson and Mr John Vickers from the Department of Earth and Marine Sciences at ANU, the impact of these asteroids triggered major earthquakes, faulting, volcanic eruption and deep-seated magmatic activity and interrupted the evolution of parts of the Earth?s crust.

The research extends the original discovery of extraterrestrial impact deposits, discovered in South Africa by two US scientists, D.R. Lowe and G.R. Byerly, identifying their effects in the Pilbara region in Western Australia.

?Our findings are further evidence that the seismic aftershocks of these massive impacts resulted in the abrupt termination of an over 300 million years-long evolutionary stage dominated by basaltic volcanic activity and protracted accretion of granitic plutons,? Dr Glikson said.

The identification of impact ejecta ? materials ejected by the hitting asteroid ? is based on unique minerals and chemical and isotopic compositions indicative of extraterrestrial origin, including iridium anomalies.

The impact ejecta from the Barberton region in the eastern Transvaal indicate the formation of impact craters several hundred kilometres in diameter in oceanic regions of the earth, analogous to the lunar maria basins (large dark impressions on the surface of the moon). The seismic effects of the impacts included vertical block movements, exposure of deep-seated granites and onset of continental conditions on parts of the earth surface.

In the Pilbara, the formation of fault escarpments and fault troughs is represented by collapse of blocks up to 250-metres wide and 150-metres high, buried canyons and a major volcanic episode 3240 million years ago.

?The precise coincidence of the faulting and igneous activity with the impact deposits, coupled with the sharp break between basaltic crust and continental formations, throws a new light on the role of asteroid impacts in terrestrial evolution,? Dr Glikson said.

Preliminary indications suggest that at about the same time the Moon was also affected by asteroid impacts and by resurgent volcanic activity.

Dr Glikson and Mr Vickers will continue to investigate the extent and effects of large asteroid impacts by studying early terrains in other parts of the world, including India and Canada.

Original Source: ANU News Release

Book Review: Cold Dark Matter

Brett’s main character is Morgan O’Brien. She’s a principal investigator based in Ottawa, Ontario and who works for the fictitious National Council of Science and Technology. The plot revolves about a death at the Canadian telescope in Hawaii coupled with a loss of important record books. O’Brien is implored by a friend to investigate, for personal reasons. The story begins in Hawaii with much of the action centring about the telescope and its ancillary buildings as well as the related personnel. After many hooks and twists in the plot, O’Brien returns to Ottawa, timed naturally to amplify the contrasts in weather. There she chases down more leads and journeys through downtown streets and the cottage country in the north of the Gatineaus. The action extends up the government chain to another fictitious unit, a civilian security force attached to the Prime Minister’s Office. From there, and after dancing through some risque steps, O’Brien pounces upon the very unexpected but plausible resolution.

It is not often that I have the pleasure of reading a book partly based in my own city of Ottawa. Because of this, I had a pleasantly warm feeling while reading the passages based on regions I frequent. More important though, I could also easily evaluate the authenticity of its contents. Given this, Alex Brett’s done great work in describing the national capital region, its weather, geography and some of its more colourful elements. Because of this, I expect similar accuracy for the surroundings in Hawaii and the FrancoCanadian telescope though I have been to neither. The sprinkles of astronomical facts and events appear equally reasonable hence lending credence to the assertion that Brett has done her homework.

Apart from the facts, the real substance of a work of fiction are the characters and the plot. Brett points out that all characters are imaginary. Its hard not to believe otherwise as, aside from the investigator, most characters have only a superficial development. We get to know of their jobs and work conditions, what their homes look life from the outside and in, but there is very little about who they are. This is particularly challenging with the guilty party, as they seem to have quite a minor role and presence, yet they wind up being the cause for all the trials and tribulations. The personality of the investigator on the other hand does come through clearly. As is perhaps typical of the genre, she imbibes an amazing amount of caffeine, pushes her body through unbelievable physical challenges and appears to be able to survive with nearly no sleep. Actually, aside from being female, there is not too much differentiating this P.I. from others of the same genre. In many ways, I preferred reading the description of her assistant, a much more complex and intriguing individual with a checkered background and a very likely challenging future.

In addition to the characters, the plot is the driver for mystery aficionados. It must be readily believable yet not entirely obvious. Here, Brett delivers. Connections and twists keep the reader guessing but not frustrated. And like any good mystery, the ending is quite unexpected though not unreasonable given the clues in the story and the setting within the book. I particularly liked seeing a focal point for the crime being technical information rather than the commonly prescribed hard currency.

For a pleasant distraction via a light murder mystery, this book is fine. The plot and main character are constantly moving. The scenes are quite busy and realistic. There’s enough suspense and distractions to keep one guessing right up to the end. One ready improvement would be to reduce the simple diction of present person, past tense. Too often sentences begin with, ‘I felt, I started, I smiled, I read…’. Because of this, the reading feels prescriptive rather than emotive. This prevented me from being fully absorbed as I felt I was reading a newspaper review rather than being a participant in the action.

A good mystery brings together believable characters in a plausible but dastardly scenario. The desire to answer whodunit should be continually fed without giving away too much. Alex Brett’s murder mystery Cold Dark Matter keeps the reader guessing while having great fun playing through observatories in Hawaii and alternate bar scenes in Ottawa. It’s just the thing to have at hand while waiting for the sun to set and the evening’s observing to begin.

Read more reviews, or purchase a copy online from Amazon.com.

Review by Mark Mortimer.

Hubble Sees a Field of Galaxies

Group of galaxies captured by Hubble. Image credit: Hubble Click to enlarge
Gazing deep into the universe, NASA’s Hubble Space Telescope has spied a menagerie of galaxies. Located within the same tiny region of space, these numerous galaxies display an assortment of unique characteristics. Some are big; some are small. A few are relatively nearby, but most are far away. Hundreds of these faint galaxies have never been seen before until their light was captured by Hubble.

This image represents a typical view of our distant universe. In taking this picture, Hubble is looking down a long corridor of galaxies stretching billions of light-years distant in space, corresponding to looking billions of years back in time. The field shown in this picture covers a relatively small patch of sky, a fraction of the area of the full moon, yet it is richly populated with a variety of galaxy types.

A handful of large fully formed galaxies are scattered throughout the image. These galaxies are easy to see because they are relatively close to us. Several of the galaxies are spirals with flat disks that are oriented edge-on or face-on to our line of sight, or somewhere in between. Elliptical galaxies and more exotic galaxies with bars or tidal tails are also visible.

Many galaxies that appear small in this image are simply farther away. These visibly smaller galaxies are so distant that their light has taken billions of years to reach us. We are seeing these galaxies, therefore, when they were much younger than the larger, nearby galaxies in the image. One red galaxy to the lower left of the bright central star is acting as a lens to a large galaxy directly behind it. Light from the farther galaxy is bent around the nearby galaxy’s nucleus to form a distorted arc.

Sprinkled among the thousands of galaxies in this image are at least a dozen foreground stars that reside in our Milky Way Galaxy. The brightest of these foreground stars is the red object in the center of the image. The stars are easily discernable from galaxies because of their diffraction spikes, long cross-hair-like features that look like they are emanating from the centers of the stars. Diffraction spikes are an image artifact caused by starlight traveling through the telescope’s optical system.

This image is a composite of multiple exposures of a single field taken by the Advanced Camera for Surveys. The image, taken in September 2003, was a bonus picture, taken when one of the other Hubble cameras was snapping photos for a science program. This image took nearly 40 hours to complete and is one of the longest exposures ever taken by Hubble.

Original Source: Hubble News Release

Cassini’s Zips Past the Death Star

The great eye of Mimas. Image credit: NASA/JPL/SSI Click to enlarge
The great eye of Saturn’s moon Mimas (MY-muss), a 130-kilometer-wide (80-mile) impact crater called Herschel, stares out from the battered moon in this raw image taken by the Cassini spacecraft during a flyby on Aug. 2.

The Herschel crater is the moon’s most prominent feature, and the impact that formed it probably nearly destroyed Mimas. Cassini flew by Mimas at 62,700 kilometers (38,800 miles) above the moons surface, bringing it closer to the little moon than ever before.

Original Source: NASA/JPL/SSI News Release

Astronaut Successfully Plucks Out Filler From Shuttle’s Belly

The Expedition 11 and STS-114 crewmembers. Image credit: NASA Click to enlarge
Despite days of anticipation and intense planning, space-walking astronaut Steve Robinson made it look easy as he gently pulled two protruding gap fillers from between thermal protection tiles on Discovery’s underside Wednesday morning.

“It looks like this big patient is cured,” Robinson told delighted flight controllers.

Fellow spacewalker Soichi Noguchi of the Japan Aerospace Exploration Agency helped Robinson with preparations, and from a perch near the end of a Space Station truss acted as observer and communication relay station between Robinson and astronaut Andy Thomas aboard Discovery. Thomas was the onboard coach and monitor for Robinson and Noguchi throughout the 6-hour 1-minute spacewalk. Discovery Pilot Jim Kelly and Mission Specialist Wendy Lawrence operated the Station’s Canadarm2, which moved Robinson to and from the worksite. Today’s spacewalk, the third of the mission, began at 3:48 a.m. CDT and concluded at 9:49 a.m.

Deputy Space Shuttle Program Manager Wayne Hale, in Wednesday?s afternoon briefing, said ?The crew demonstrated consummate professionalism and coolness beyond belief. They [the gap fillers] came out just as we thought they would. It looked easy but was not, which is a tribute to the crew and the team on the ground that planned it, so we?re proud of that.?

Gap fillers like those Robinson removed today are thin, coated Nextel fabric. The protruding gap fillers were identified in photos taken by Station crewmembers using telephoto lenses as Discovery did a slow back flip about 600 feet below before docking.

During the spacewalk Noguchi and Robinson, helped by the Station’s robotic arm, installed an external stowage platform outside the station that will be used to house spare parts. Noguchi also installed another Materials International Space Station Experiment (MISSE). Like its predecessors, MISSE 5 exposes samples of various materials to the harsh space environment for several months.

In other activities, Kelly worked with Mission Specialist Charlie Camarda on an inspection of the repair demonstration tiles in Discovery’s cargo bay. Using the Orbiter Boom Sensor System, they looked at tiles brought up for an experimental repair by Robinson and Noguchi on the mission’s first spacewalk Saturday.

Station crewmembers, Commander Sergei Krikalev and NASA Science Officer John Phillips, continued to stow equipment and supplies on the Station and Shuttle. Discovery Commander Eileen Collins operated shuttle systems and supervised activities.

Hale also said the only part of Discovery?s heat shield not yet cleared for entry is a bulging thermal blanket below the Shuttle commander?s window. Managers will meet Thursday morning to review tests to help determine whether the blanket might pose a concern for entry.

The next STS-114 mission status report will be issued Thursday morning, or earlier, if events warrant.

Original Source: NASA News Release

Spitzer Sees Hidden Black Holes

A distant galaxy (yellow) that houses a quasar. Image credit: NASA Click to enlarge
Most of the biggest black holes in the universe have been eating cosmic meals behind closed doors ? until now.

With its sharp infrared eyes, NASA’s Spitzer Space Telescope peered through walls of galactic dust to uncover what may be the long-sought missing population of hungry black holes known as quasars.

“From past studies using X-rays, we expected there were a lot of hidden quasars, but we couldn’t find them,” said Alejo Martinez-Sansigre of the University of Oxford, England. He is lead author of a paper about the research in this week’s Nature. “We had to wait for Spitzer to find an entire population of these dust-obscured objects.”

Quasars are super-massive black holes that are circled by a giant ring of gas and dust. They live at the heart of distant galaxies and can consume up to the equivalent mass of one thousand stars in a single year. As their black holes suck in material from their dusty rings, the material lights up brilliantly, making quasars the brightest objects in the universe. This bright light comes in many forms, including X-rays, visible and infrared light.

Astronomers have puzzled for years over the question of how many of these cosmic behemoths are out there. One standard method for estimating the number is to measure the cosmic X-ray background. Quasars outshine everything else in the universe in X-rays. By counting the background buzz of X-rays, it is possible to predict the approximate total number of quasars.

But this estimate has not matched previous X-ray and visible-light observations of actual quasars, which number far fewer than expected. Astronomers thought this might be because most quasars are blocked from our view by gas and dust. They proposed that some quasars are positioned in such a way that their dusty rings hide their light, while others are buried in dust-drenched galaxies.

Spitzer appears to have found both types of missing quasars by looking in infrared light. Unlike X-rays and visible light, infrared light can travel through gas and dust.

Researchers found 21 examples of these quasars in a small patch of sky. All the objects were confirmed as quasars by the National Radio Astronomy Observatory’s Very Large Array radio telescope in New Mexico and by the Particle Physics and Astronomy Research Council’s William Herschel Telescope in Spain.

“If you extrapolate our 21 quasars out to the rest of the sky, you get a whole lot of quasars,” said Dr. Mark Lacy of the Spitzer Science Center, California Institute of Technology, Pasadena, Calif., a co-author of the Nature paper. “This means that, as suspected, most super-massive black hole growth is hidden by dust.”

The discovery will allow astronomers to put together a more complete picture of how and where quasars form in our universe. Of the 21 quasars uncovered by Spitzer, 10 are believed to be inside fairly mature, giant, elliptical galaxies. The rest are thought to be encased in thick, dusty galaxies that are still forming stars.

A team of researchers based at the University of Arizona, Tucson, found similar quasars using Spitzer. Their research is described at http://uanews.org/science.

Other authors of the Nature paper include Drs. Steve Rawlings and Matt Jarvis, University of Oxford; Drs. Dario Fadda and Francine Marleau, Spitzer Science Center; Dr. Chris Simpson, University of Durham, England; and Dr. Chris Willott, National Research Council Canada, Victoria.

The Jet Propulsion Laboratory, Pasadena, Calif., a division of Caltech, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Spitzer’s multiband imaging photometer, which observed the quasars, was built by Ball Aerospace Corporation, Boulder, Colo.; the University of Arizona; and Boeing North America, Canoga Park, Calif. Spitzer’s infrared array camera, which also observed the quasars, was built by NASA Goddard Space Flight Center, Greenbelt, Md.

A Spitzer false-colored picture of one of the newfound quasars is available at http://www.spitzer.caltech.edu/Media/index.shtml.

For information about NASA and agency programs visit http://www.nasa.gov/home/.

Original Source: NASA News Release

Podcast: Planetary Disk That Refuses to Grow Up

With new instruments, astronomers are filling in all the pieces that help to explain how planets form out of extended disks of gas and dust around newborn stars. This process seems to happen quickly, often just a few million years is all it takes to go from dust to planets. But astronomers have found one proto-planetary disk that refuses to grow up. It’s 25 million years old, and still hasn’t made the transition to form planets. Lee Hartmann is with the Harvard-Smithsonian Center for Astrophysics, and the lead author on the paper announcing the find.
Continue reading “Podcast: Planetary Disk That Refuses to Grow Up”

Audio: Planetary Disk That Refuses to Grow Up

Artist’s conception of the 25-million-year-old protoplanetary disk. Credit: David A, Aguilar (CfA). Click to enlarge
Listen to the interview: Planetary Disk That Refuses to Grow Up (6 MB)

Or subscribe to the Podcast: universetoday.com/audio.xml

Fraser Cain: You’ve found the oldest planetary disk. Can you give me a sense of how unusual this is?

Lee Hartmann: This is about the oldest planetary or protoplanetary disk. The oldest one we’ve found before was something like 10 million years old, so this is about 2 to 2.5 times as old as anything we’ve found before.

Fraser: Was that a big surprise to find something that old?

Hartmann: Yeah, it seems like half or more of stars have some kind of extended dusty disk with something that would make planets. At an age of about a million years or so. And then by 10 million years or so, you’re down to like 10% of all stars or maybe even less than that. So to find this thing at twice the age was really pretty remarkable. We thought that by 20 million years we’d really be down to zero for anything that still had dust around it that was very much like a planetary disk.

Fraser: What could keep the disk stable for so long?

Hartmann: It’s not really clear. The central system in this case is actually a close binary star and so it’s possible – unlike a single star in our solar system – there are two, almost equal mass stars that are orbiting around in a very close orbit and although something the size of somewhere between Mercury’s orbit and Venus’ orbit; something that size. That could be kind of churning things up because each star has its own gravity, and as they move around they could be churning up the disk and agitating the particles. What we think happens to make planets is that the dust, the little dust bunnies, kind of stick electrostatically into small little lumps and then it grows bigger and bigger. And it makes rocks, and then it makes things that are more like asteroids, and finally planets. And the planet forming stage is what really clears out all this dust. And so that process is thought to be very delicate and things kind of settle down over timescales of thousands to millions of years. It’s possible that if you’re churning it up a little bit, keeping the particle suspended then they don’t really stick together that well and don’t go through the rest of the planetary formation process like most other stars do.

Fraser: How common would something like this be? Since this is the oldest one that’s been found, do you think that there are others nearby, or is this just a total fluke?

Hartmann: It’s hard to imagine that there’s only one of these things in the galaxy, let alone the entire Universe. But, this must be a very rare occurrence as far as we can tell. We can see large clusters of stars that are 30 million years old, 50 million years old, 100 million years old, and they haven’t found anything like this in several hundreds or even thousands of stars in total. It’s probably 1 in 1000, maybe, or something like that. That’s sort of what I would guess, but it’s hard to know. We haven’t looked carefully enough at these things. We haven’t been able to until very recently. The Spitzer space telescope has just so much more sensitivity than anything else we were able to do before. It’s just made factors of hundreds of thousands of times our ability to detect faint sources like this thing is. We’re just taking the first baby steps to explore what’s out there and in our own neighbourhood. With the Spitzer telescope, they start looking at some of these other clusters, they’re confirming that twice the age of this system, less than 1 in 1000 is like that. It’s really a fairly unique system. We must have caught it in some special circumstances.

Fraser: Do you think that it could go on for millions and millions of years more. Is this still an early age for it?

Hartmann: This is something that we don’t understand very well. And one of the reasons to study these kinds of systems is that we really need a lot of help in understanding the physics of this. The physics of how planets form out of basically dust bunnies to start with. It’s just such a complicated process, and there are all kinds of things that we don’t quite understand that we really need to have more surveys of these things. I don’t really know what’s going to happen with this system. My own opinion is that it’s probably not going to go on and coagulate into planets if it hasn’t done it already. The theory suggests that there’s kind of a threshold that you have to meet. You have to have just enough stuff to make it happen, to really get over the hump of making larger bodies which can then sweep up all the smaller dust and clear out the disk. If you don’t ever get to that threshold, you might not ever make any planets. My guess is that it might just peter out, and some of the dust grains will either get blown out or spiral in slowly into the star and that’s the end of it, but we don’t really understand.

Fraser: Have planet forming disks been seen around binary systems before?

Hartmann: Yes, if I can just qualify to say that we’re assuming these disks make planets. We haven’t really had the complete smoking gun to say that these dusty disks actually make planets. I think it’s a very strong likelihood because we see all this distributed dust around very young stars and then it’s all gone. We know that we have to coagulate all the dust and get the small stuff and put it into big things to make planets. So that’s the assumption we’re making, but I just wanted to say that we haven’t actually connected the dots on that issue.

Fraser: Right, so have disks been seen around binary systems like this?

Hartmann: Yes, they have. This issue is that basically, you can’t have the disk at the same size orbit as the binary orbit. The other star will just swallow up all the dust, or evaporate it, or blow it away. On the other hand, if you have a very wide binary, if you have something where the other star is very far way, you can have a disk well inside that binary and it doesn’t know there’s another star orbiting around. We orbit around the Sun, and Jupiter is out there at several astronomical units, and that only makes small perturbations on the orbit of the Earth. Similarly, you could have a system in which the two stars are relatively close together and the disk is well outside the outlying area. And so, to that disk, it almost looks like there’s a single star. It’s not exactly like that because the two stars are orbiting around so the gravity is churning it up a little. But it’s not that far away from just having a single object. So as long as the disk is either a lot bigger than the binary, or smaller than the binary, you’re okay. If the disk is a lot bigger than the binary, though, it can be so tenuous, and so spread out that it never really coagulates effectively into planets. That’s something we would kind of predict, but that’s not something that we’re able to demonstrate observationally yet.

Fraser: Do you have some follow on observations planned for this?

Hartmann: What I think we would like to try and do is to get longer wavelength observations to see where the disk ends, because in this set of observations, we’re basically saying that there is a disk, but we don’t know how big it is. The question is, is there anything outside this system that could be perturbing the disk as well. It might even be a triple system for all we know, with a very much wider companion that is low mass and we haven’t seen. And that could really be churning it up and preventing the disk from letting planets coagulate, at least. And then the other thing that we’re trying to do, is that we’re trying to identify other systems like this which are also 20 million years old, 30 million years old. If we can find any more of these things, just to see how common they are, and whether they’re all binaries, or what’s special about them that enables them to last so long. Basically, what we’re trying to do is see the process how a disk turns into planets, but of course that takes millions of years, so you can’t follow that through – at least, I can’t follow it through. It’s like taking a snapshot of a population. You’ve got old people and young people and babies and so on. And you try and infer how the evolution goes from putting the various pieces together. And then some people are largish, or better nourished, and they have a different culture or whatever, and you try to see what different effects have on the population from that snapshot. To try and find other systems that are like this is a way of doing the experiment to see what happens if you have a much wider binary, or what happens if it’s a different mass star in the middle. We can’t really do the experiment, but if we find enough different kinds of objects like this, then nature has done the experiment in different places, and we just need to go out and look at it.

This discovery was originally announced on Universe Today on July 19, 2005.

Astronauts Prepare for Spacewalk to Remove Gap Filler

Photographed from ISS while docked with Discovery. Image credit: NASA Click to enlarge
The Space Shuttle Discovery crew begins their ninth day in space with preparations for the third spacewalk of the mission. This extravehicular activity (EVA) was a preplanned activity for the mission, but now includes a new task — repair of two protruding gap fillers between tiles on the bottom the Shuttle.

The crew began the day waking up at 10:09 p.m. CDT to “Where My Heart Will Take Me,” the theme song from Star Trek: Enterprise. The song, composed by Dennis McCarthy, was selected for the crew as a surprise dedication from the Deputy Shuttle Program Manager Wayne Hale. The International Space Station Expedition 11 crew of Sergei Krikalev and John Phillips woke 30 minutes later.

Mission Specialists Steve Robinson and Soichi Noguchi are scheduled to begin their third spacewalk at 3:14 a.m. CDT as they exit out of the Space Shuttle airlock. The two will be assisted by Andy Thomas, serving as the intravehicular officer overseeing the spacewalk from inside, as well as Pilot Jim Kelly and Mission Specialists Wendy Lawrence and Charlie Camarda who will be supporting various robotic arm activities throughout the day.

The spacewalk is scheduled to last about 7 hours. The first task entails Kelly and Lawrence maneuvering the External Stowage Platform-2 (ESP-2), via the Station’s robotic arm, which they pulled from Discovery’s payload bay earlier today, onto the Station. As the ESP-2 reaches its final position, Robinson and Noguchi will guide the structure and secure it into place. With that task complete, Lawrence and Kelly will conduct a “walk off” maneuver of the Station robotic arm, by attaching the “free” end to the Mobile Base System and releasing the other end from the Destiny Laboratory module to where it will be needed as a platform for Robinson later in the EVA.

The two spacewalkers will move on to individual tasks, with Noguchi installing the Materials International Space Station Experiment-5 (MISSE-5), a materials experiment that will study the degradation of solar cell samples in the space environment. He’ll then remove the Rotary Joint Motor Controller from the Space Station truss before proceeding to a support position to assist Robinson in his final tasks.

Meanwhile, Kelly will work with Camarda, using the Orbiter Boom Sensor System to inspect repair demonstration tiles inside the Shuttle’s payload bay. Later, Camarda will also work with Krikalev and Phillips to continue stowing supplies and equipment inside Discovery and the Station. Discovery Commander Eileen Collins will monitor and supervise all the activities.

Robinson, now attached to the Station robotic arm, will attempt to repair two tile gap filler protrusions located on the underside of Discovery. He will first try to gently pull out the protruding material, and if need be, remove by trimming with a hacksaw.

Gap fillers are used in areas to restrict the flow of hot gas into the gaps between Thermal Protection System components. They consist of a layer of coated Nextel fabric and are normally about 0.020-inch thick. These protrusions were identified from photos taken during the rendezvous pitch maneuver conducted on flight day three, as Discovery approached the orbiting Space Station.

The crews are scheduled to go to sleep about 2:09 p.m. CDT.

Original Source: NASA News Release