BY SPACEFLIGHT NOW

Follow the mission of space shuttle Columbia on the fourth servicing call to the orbiting Hubble Space Telescope. Reload this page for the very latest. A text only version is also available for faster access.

SATURDAY, MARCH 9, 2002

Scientists around the world are standing in line for a chance to use the Hubble Space Telescope's new camera and other instruments. In fact, in recent months the Space Telescope Science Institute has been flooded with eight times as many observing proposals as the telescope can accommodate. Read full story.

1038 GMT (5:38 a.m. EST)

Flying 900 feet above the Hubble Space Telescope, Columbia has just performed a thruster firing to accelerate the separation from the vicinity of the observatory.

Hubble is in the hands of its flight control team to slowly begin returning to science operations over the next few weeks.

For our Spaceflight Now Plus subscribers, here is a clip of today's Hubble deployment:

Video coverage for subscribers only:
   VIDEO: HUBBLE DEPLOYED FROM COLUMBIA QT or RV

1004 GMT (5:04 a.m. EST)

The overhauled Hubble Space Telescope -- sporting new solar arrays, electrical heart, advanced camera and infrared cooling system -- is once again flying on its own. The astronauts released the observatory from the end of shuttle Columbia's robotic arm at 5:04 a.m. EST today after the completely successful fourth servicing of the 12 year old telescope.

The astronauts will be interviewed by reporters later today. Sunday will largely be an off-duty day. Monday will be spent packing up and prepping Columbia for return to Earth. Landing is scheduled for 4:30 a.m. EST Tuesday at Kennedy Space Center, Florida to end the 11-day mission.

0953 GMT (4:53 a.m. EST)

The Space Telescope Operations Control Center has given its "go" to deploy Hubble. The shuttle flight control team then issued its approval for release, calling the astronauts with the news to proceed with an on-time deployment 11 minutes from now.

0940 GMT (4:40 a.m. EST)

The main door on the end of the Hubble Space Telescope is now swinging open, allowing starlight into the observatory once again.

Deployment of Hubble remains targeted for 5:04 a.m. EST, the start of a 19-minute window of opportunity for release.

0930 GMT (4:30 a.m. EST)

Hubble ground controllers are quite busy readying the telescope for its upcoming deployment. The astronauts have positioned Hubble in the release orientation on the end of the robotic arm.

0900 GMT (4:00 a.m. EST)

Hubble, riding on Columbia's arm, has been released from the servicing platform in the rear of the shuttlle's payload bay. The telescope will be maneuvered to the proper position for the upcoming deployment.

0756 GMT (2:56 a.m. EST)

With Hubble's six batteries fully charged, the power stream provided by the shuttle can be disconnected. The umbilical from Columbia to the telescope will be unplugged as activities continue in advance of Hubble's release, just over two hours from now.

0708 GMT (2:08 a.m. EST)

Columbia's robotic arm, operated by astronaut Mike Massimino, has just grappled the Hubble Space Telescope. Later this morning the observatory will be lifted out of the shuttle's payload bay and deployed back into space.

0530 GMT (12:30 a.m. EST)

The Columbia astronauts are gearing up to release the rejuvenated Hubble Space Telescope back into open space early today, wrapping up a surprisingly successful five-spacewalk flight to upgrade the $2 billion observatory's electrical system and scientific instruments. Read full story.

FRIDAY, MARCH 8, 2002

Astronauts John Grunsfeld and Richard Linnehan began repressurizing the shuttle Columbia's airlock at 11:06 a.m. EST today, officially ending a seven-hour 20-minute spacewalk, the crew's fifth and final excursion devoted to servicing the Hubble Space Telescope. Read spacewalk wrap-up story.

1609 GMT (11:09 a.m. EST)

Grunsfeld and Linnehan are back in the airlock and their space walk officially came to an end at 11:06 a.m. EST. Their excursion had a duration of 7 hours and 20 minutes. With the conclusion of this spacewalk, STS-109 has achieved a new record for the most EVA hours in a single shuttle flight: 35 hours and 55 minutes. The previous record of 35 hours and 26 minutes was set on the first Hubble servicing mission in 1993. The total number of EVA hours spent servicing Hubble is 129 hours 10 minutes. (Statistics provided by Bill Harwood.)

1555 GMT (10:55 a.m. EST)

Hubble's twin High Gain Antenna are being deployed.

1540 GMT (10:40 a.m. EST)

After paying tribute to their ground support teams, Grunsfeld and Linnehan returned to the airlock but Linnehan has left the airlock briefly to check a cover on the flight support structure is correctly positioned over an antenna cover.

1442 GMT (9:42 a.m. EST)

The astronauts are now moving on to pack up their tools and equipment as the fifth and final spacewalk of this mission draws to a close.

1441 GMT (9:41 a.m. EST)

Flight controllers have decided the radiator skirt position is adequate and not to work on it any longer.

"Better is the enemy of good enough," said CAPCOM Mario Runco. "We're going to press ahead and call it a day."

1425 GMT (9:25 a.m. EST)

Mission control has asked Grunsfeld to try to reposition the skirt that keeps light from warming the back side of the newly installed NICMOS cooling system radiator.

1416 GMT (9:16 a.m. EST)

The aft shroud doors are verified closed.

1400 GMT (9:00 a.m. EST)

The two spacewalkers are working to close the doors to the aft shroud area where they have been working to install the experimental NICMOS cryo cooler device.

1352 GMT (8:52 a.m. EST)

Linnehan continues to work ensuring the cryo cooler cabling is correctly placed, while Grunsfeld is finishing up work the capillary pump loop evaporator, part of the cooler system.

1332 GMT (8:32 a.m. EST)

Grunsfeld and Linnehan are working to attach the bundle of connectors from the radiator to the cooling box they installed in Hubble's aft shroud earlier in the spacewalk.

1306 GMT (8:06 a.m. EST)

Linnehan is feeding the bundle of connectors through a hole in the aft shroud of the telescope. The attachment of these connectors to the cryo cooler will complete installation of the device.

1254 GMT (7:54 a.m. EST)

Grunsfeld is preparing a bundle of connectors on the cooler radiator that will be snaked through the base of the telescope's aft shroud for attachment to the newly installed cooler device.

1247 GMT (7:47 a.m. EST)

Grunsfeld and Linnehan continue to work routing cables for the NICMOS Cryo Cooler.

1224 GMT (7:24 a.m. EST)

The radiator is now securely in place and the astronauts will move on to the installation of electrical cables for the NICMOS cooler device.

1220 GMT (7:20 a.m. EST)

The radiator has been reinstalled to the aft shroud of Hubble. Although the astronauts say the alignment isn't perfect, Mission Control says it is acceptable.

1206 GMT (7:06 a.m. EST)

The alignment of the radiator panel is off a bit. So the spacewalkers are unlatching it and will try attaching it again.

1156 GMT (6:56 a.m. EST)

The radiator has been placed on the side of the Hubble Space Telescope. The spacewalkers will now engage latches to hold the panel in position.

1142 GMT (6:42 a.m. EST)

Grunsfeld is holding onto the radiator panel while riding on the end of Columbia's robotic arm. The spacewalkers released the panel from its launch carrier in the rear of the shuttle's payload bay. They will soon mount it to the observatory as part of the NICMOS cryocooler system.

The spacewalkers are nearly three hours into this planned 6 1/2-hour EVA. Mission Control reports the crew is virtually right on the timeline.

1120 GMT (6:20 a.m. EST)

Rick Linnehan is getting off the robot arm; John Grunsfeld will get on for the next phase of the cryocooler installation work. Upcoming will be the retrieval of the NICMOS radiator panel from its launch carrier in Columbia's payload bay for attachment to the side of Hubble.

1109 GMT (6:09 a.m. EST)

The spacewalkers have now electrically connected the new cryocooler. For more on the cryocooler, here is the NASA fact sheet:

The Near Infrared Camera and Multi-Object Spectrometer (NICMOS), dormant since January of 1999, will be reactivated by a high tech cooling system, the NICMOS Cryocooler.

Installed on Hubble in February of 1997, NICMOS used infrared vision to probe dark, dusty, never-before-seen regions of space with the optical clarity that only Hubble can provide. Its infrared detectors operated at a very cold temperature (minus 352 degrees Fahrenheit, which is minus 272 degrees Celsius, or 60 degrees Kelvin). To keep the detectors cold, NICMOS was encased in a thermos-like container filled with solid nitrogen ice. Unfortunately, the nitrogen ice was consumed more quickly than planned due to a very small heat leak. In anticipation of this shortened lifespan, NICMOS's subscribed observations were tripled in order to get the most usage of this instrument before it ran out of coolant. In 1999-with its supply of ice exhausted-NICMOS became dormant.

Scientists and engineers at NASA's Goddard Space Flight Center in Greenbelt, MD, devised a way of adding a new, high-tech refrigeration device to NICMOS to re-cool its detectors and other components. The Hubble team developed the NICMOS Cryocooler-a state-of-the-art, mechanical, cryogenic cooler that is expected to return NICMOS to active duty.

Using non-expendable neon gas as a coolant, this closed system delivers high cooling capacity, extremely low vibration and high reliability. It employs a miniature cryogenic circulator to remove heat from NICMOS and transport it to the cryocooler. The system uses a tiny turbine turning at up to 400,000 rpm (over 100 times the maximum speed of a typical car engine). The NICMOS Cryocooler is virtually vibration-free - which is very important for Hubble. Vibrations could affect image quality in much the same way that a shaky camera produces blurred pictures.

The new cryogenic system is expected to re-cool the NICMOS infrared detectors to about minus 334 degrees Fahrenheit (minus 203 degrees Celsius or 70 degrees Kelvin). This is an ideal temperature for the detectors and will make NICMOS more sensitive to incoming light, thereby allowing it to collect more light. Engineers expect it to increase the life span of NICMOS to more than 5 years.

In 1998, the Hubble team successfully demonstrated this new cooler technology aboard the Space Shuttle Discovery on STS-95. This was the first on-orbit test of a high performance, high efficiency, mechanical cryocooler. The test took place less than 18 months after development began-an extremely short time for successfully developing a new space technology.

Retrofitting NICMOS with the new cryocooler will more than double its lifetimeŅensuring a greater scientific return on the original investment. This revolutionary technology paves the way for exciting advances in infrared astronomy on Hubble and beyond.

In the case of NICMOS, the cryocooler is replacing the solid nitrogen cooler that originally encased the instrument. But this advanced type of cryocooler can replace both liquid and solid nitrogen-based cooling systems on Earth as well as in space.

The cyrocooler offers earthly benefits in electronics manufacturing, medical imaging, and magnetic field detection. One particularly important application is in brain imaging. Magnetic encephalograms, which measure brain waves, allow doctors to determine if the various parts of the brain are functioning properly. This new cooler technology could make such brain imaging equipment more "user friendly," compact and affordable.

1048 GMT (5:48 a.m. EST)

The cryocooler has been positioned on the floor of the instrument bay, just in front of NICMOS. The spacewalkers will latch it in place.

1029 GMT (5:29 a.m. EST)

With the cryocooler in hand, Linnehan is riding the robot arm up out of payload bay and back to Hubble for the installation.

1018 GMT (5:18 a.m. EST)

Robot arm operator Scott Altman has maneuvered Linnehan back to Columbia's payload bay to retrieve the NICMOS cryocooler from its launch container.

1010 GMT (5:10 a.m. EST)

Linnehan is now preparing the hole on the bottom of the telescope through which the plumbing from the cryocooler will be fed.

0955 GMT (4:55 a.m. EST)

With the telescope opened, the spacewalkers have several activities to perform before the cryocooler is actually installed. They are currently working on disconnecting a ground strap and the cryo vent line to NICMOS.

0940 GMT (4:40 a.m. EST)

Riding on the end of Columbia's 50-foot robot arm, spacewalker Rick Linnehan is now swinging open the large aft shroud doors nearly an hour into today's planned 6 1/2 hour EVA.

0915 GMT (4:15 a.m. EST)

The spacewalkers are moving through preparatory steps for today's EVA. They will soon open up the aft shroud doors on Hubble for the installation of the NICMOS cryocooler.

0846 GMT (3:46 a.m. EST)

EVA 5 BEGINS. The fifth and final planned spacewalk of shuttle Columbia's mission to rejuvenate the Hubble Space Telescope has officially begun.

Astronauts John Grunsfeld and Rick Linnehan switched their suits from shuttle-provided power to internal batteries at 3:46 a.m. EST, marking the start of this planned 6 1/2-hour EVA to mount an experimental refrigerator to the observatory designed to revive a dormant infrared camera-spectrometer.

We have posted a comprehensive spacewalk preview story. And check out our detailed timeline of today's activities in space.

We'll update this page from time to time as the spacewalk progresses.

0843 GMT (3:43 a.m. EST)

The depress is now complete and Columbia's outer airlock hatch has been opened by the astronauts.

0834 GMT (3:34 a.m. EST)

The depressurization of Columbia's airlock is now underway. The start of today's spacewalk is running a few minutes behind schedule.

0330 GMT (10:30 p.m. EST Thurs.)

Mission Control has announced that the Columbia astronauts will be allowed to sleep in tonight by about a half-hour. So that will push back the day's activities accordingly, putting the target start time of the spacewalk at 3:22 a.m. EST.

0100 GMT (8:00 p.m. EST Thurs.)

Columbia's astronauts are scheduled to be awakened at 10:22 p.m. EST tonight for Flight Day 8 -- the day devoted to the fifth and final spacewalk of the mission. Spacewalk preparations for John Grunsfeld and Rick Linnehan will begin about two hours later, leading to the start of a 6 1/2-hour EVA at 2:52 a.m. EST.

In a pre-flight interview, Grunsfeld described the objectives of this spacewalk to install an experimental cooling system on Hubble to revive the NICMOS science instrument:

"This mission, STS-109, is a little bit different than any of the previous Hubble missions because we're doing a number of things that folks never thought we would do on Hubble. Although they've talked about the power control unit change-out before, I don't think anybody ever thought we'd really do it. It's just too hard.

"On EVA day 5, (we're) putting on the cooling system. And so, we're going to hang on handrails a large 12-foot-by-4-foot radiator on the outside of the telescope. (Nobody ever thought we'd do anything like that.) And, we're going to snake through the bottom of the telescope a bunch of plumbing that contains electronic control lines but also cooling lines. That's kind of like installing an external air conditioner in a house for the first time. And, plumbing it through a hole in the bottom of the telescope that was essentially a vent line previously.

"So Rick and I are first going to open up the big doors on the bottom of the telescope and we'll put in the cryo cooler (that's the refrigerator). And it's a relatively large box that goes on the floor of the telescope and clamps into handrails, again, that nobody ever thought would be used for putting items. And, Rick will get that all plumbed up; and we'll start some of the connections.

"Jim and Mike will have fed through a large cable harness from the Advanced Camera for Surveys side that's hooked up to the electronics for the cryo cooler. And then, we'll hook up the rest of that. At that, while Rick's hooking up all of the components on the inside of the telescope, a very delicate area again (everything inside is a scientific instrument, and he'll have to be very careful there), I'm going to go to the back of the payload bay and start taking the bolts off of the radiator.

"After that, Rick and I are going to switch places. I'll be on the arm; Rick will become the free-floater. And, I'll go back and hold on to the radiator, and Rick will undo the final latch. At which point, Nancy will drive me out over the port wing, holding this large 12-foot-long radiator. And I'll bring it around to the front of the telescope and hang it on the handrails. And Rick and I together will clamp it down.

"After that, Rick is going to climb underneath the telescope and get into a foot restraint so that he's looking straight up through this little hole (it's about that big) in the bottom of the telescope. And, I'll swing the cables around and underneath to him, and then he'll start feeding them up through the hole. I'll go inside the telescope and start pulling it up. And, we'll try and get this very, very long - I think it's ten feet or so of cable - through the bottom of the telescope.

"We've trained this many times in the pool; but nobody's done anything like this on Hubble. Once it's through, we'll clamp down a little holder in the bottom of the telescope that keeps any light from getting into the telescope from the bottom; and so that'll still be dark inside the telescope. (It's good to have no light inside the telescope from other than the place where the mirror is.) And, we'll hook up all the connections and close the doors."

THURSDAY, MARCH 7, 2002

Spacewalkers James Newman and Michael Massimino successfully installed a new $75 million camera inside the Hubble Space Telescope today, accomplishing the primary scientific goal of the fourth Hubble servicing mission. Read full story.

1632 GMT (11:32 a.m. EST)

Today's spacewalk has been officially clocked at 7 hours and 30 minutes in duration. It began at 4 a.m. EST and concluded at 11:30 a.m. EDT.

1628 GMT (11:28 a.m. EST)

Repressurization of the airlock is underway.

1624 GMT (11:24 a.m. EST)

The spacewalkers are back inside the airlock and the outer hatch is now closed.

1616 GMT (11:16 a.m. EST)

The two spacewalkers have completed an inventory of the tools they used during today's spacewalk and are returning to the shuttle's airlock.

1550 GMT (10:50 a.m. EST)

The two spacewalkers continue to work to remove shades and covers installed to protect the telescope while it was shutdown on Wednesday for the Power Control Unit replacement. They are running well over an hour behind schedule.

1530 GMT (10:30 a.m. EST)

Massimino is checking that equipment bays opened during yesterday's replacement of the Power Control Unit are properly latched shut, while Newman is removing a thermal shade placed over a bay to protect its contents during yesterday's telescope shutdown.

1511 GMT (10:11 a.m. EST)

The first functional test of the newly installed electronics support module for the NICMOS Cryo Cooler has gone well according to Hubble ground controllers.

1504 GMT (10:04 a.m. EST)

The spacewalkers have closed the aft shroud doors and are working to latch them closed.

1448 GMT (9:48 a.m. EST)

The electronics support module for the NICMOS Cryo Cooler is now hooked up to Hubble's power supply and Newman and Massimino are making sure the associated cables do not snag on any of the equipment inside the telescope's aft shroud.

1421 GMT (9:21 a.m. EST)

Massimino is now hooking up cables to the new electrical box.

1405 GMT (9:05 a.m. EST)

The spacewalkers are busy hooking up an electrical harness that will route power to the NICMOS Cryo Cooler.

1343 GMT (8:43 a.m. EST)

The spacewalkers are bolting down the electrical box for NICMOS Cryo Cooler inside the aft-shroud of the Hubble Space Telescope. Once the box is in place Newman will unplug four electrical connectors from the COSTAR corrective optics device and connect them to a harness that will power the NICMOS cooler. COSTAR, installed in 1993 to fix Hubble's blurred vision, is no longer needed as all instruments are now fitted with their own corrective optics.

1329 GMT (8:29 a.m. EST)

Riding the shuttle's robot arm, Mike Massimino is carrying the electrical box for the NICMOS Cryo Cooler to the aft shroud of the Hubble Space Telescope.

1306 GMT (8:06 a.m. EST)

The functional test of the Advanced Camera for Surveys is getting underway while the astronauts prepare for their next task, the installation of an electrical box for the NICMOS Cryo Cooler.

1250 GMT (7:50 a.m. EST)

The Faint Object Camera has now latched down in its cargo bay carrier for the return to Earth. The next task for the two spacewalkers is to install an electrical box for the NICMOS Cryo Cooler. The spacewalk officer in mission control reports the astronauts are running about 30 minutes behind schedule.

1246 GMT (7:46 a.m. EST)

Newman and Massimino are working to latch down the Faint Object Camera in its cargo bay carrier.

1233 GMT (7:33 a.m. EST)

The newly installed $75 million Advanced Camera for Surveys has passed an "aliveness" test according to Hubble flight controllers at NASA's Goddard Space Flight Center.

1220 GMT (7:20 a.m. EST)

Spacewalker Jim Newman has lifted the Faint Object Camera off the temporary stowage fixture on the side of the payload bay. He will maneuver it into the carrier that the Advanced Camera for Surveys had been launched in.

1209 GMT (7:09 a.m. EST)

Spacewalker Mike Massimino is now hooking up the ground strap and four electrical cables to the Advanced Cameras for Surveys. Once this is completed, Hubble ground controllers can conduct an "aliveness test" on the new instrument.

1158 GMT (6:58 a.m. EST)

The latches have been tightened. The Advanced Cameras for Surveys is now locked down inside the Hubble Space Telescope following this morning's successful installation by the spacewalking astronauts.

The spacewalkers will now load the old Faint Object Camera into the carrier vacated by ACS for the ride back to Earth.

1143 GMT (6:43 a.m. EST)

The Hubble Space Telescope has a new scientific instrument. The Advanced Camera for Surveys has been installed into the observatory by the spacewalkers. After checking the alignment, the crew will then engage latches to hold the phone booth-sized instrument in place.

1138 GMT (6:38 a.m. EST)

ACS is being loaded into Hubble.

1134 GMT (6:34 a.m. EST)

The spacewalkers are checking alignments before sliding the ACS into the Hubble Space Telescope. Newman is holding the instrument in his hands while riding on the robot arm; Massimino is free-floating to give guidance cues to Newman.

Mission Control reports the astronauts are currently 25 minutes behind the timeline.

1124 GMT (6:24 a.m. EST)

Still riding on the end of Columbia's Canadian-built robotic arm, spacewalker Jim Newman is slowly lifting the phone booth-sized Advanced Camera for Surveys out of its launch carrier.

1112 GMT (6:12 a.m. EST)

The spacewalkers have now moved on to the job of preparing the Advanced Camera for Surveys to be lifted out of the carrier in the middle of Columbia's cargo bay.

1105 GMT (6:05 a.m. EST)

With the Faint Object Camera now removed, Massimino has floated into the aft shroud of the telescope to install a wiring harness that will be used by the NICMOS electronics module, which will be installed later in this spacewalk.

1052 GMT (5:52 a.m. EST)

Newman has parked the Faint Object Camera atop a special fixture on the left side of the payload bay, basically getting the instrument out of the way in preparation for lifting the Advanced Camera for Surveys out of its launch container and installing it into the telescope. The Faint Object Camera ultimately will be stowed into the ACS's container for return to Earth.

1042 GMT (5:42 a.m. EST)

The Faint Object Camera, the last of Hubble's original science instruments, is now being removed from the observatory. Jim Newman is sliding the FOC out. He will then temporarily stow the instrument to a fixture on the side of Columbia's payload bay while the Advanced Camera for Surveys is installed.

0954 GMT (4:54 a.m. EST)

The aft shroud doors are open. Massimino will now unhook connectors and release latches holding the Faint Object Camera inside Hubble. Once that work is completed, Newman will pull the instrument out of the telescope while riding on the end of Columbia's robot arm.

0940 GMT (4:40 a.m. EST)

Hubble ground controllers report the Faint Object Camera has been powered down in preparation for its removal from the telescope by the spacewalkers. Meanwhile, Jim Newman is about to open the aft shroud doors for the FOC removal and subsequent installation of the Advanced Camera for Surveys this morning.

0901 GMT (4:01 a.m. EST)

EVA 4 BEGINS. The fourth of five spacewalks to overhaul the Hubble Space Telescope during this flight of space shuttle Columbia has officially begun.

Astronauts Jim Newman and Mike Massimino switched their suits from shuttle-provided power to internal batteries at 4:00 a.m. EST, marking the start of this planned 6 1/2-hour EVA that will see the no-longer-used Faint Object Camera removed from Hubble and the new Advanced Camera for Surveys installed into the orbiting observatory. The spacewalkers will also install the NICMOS electronics support module.

We have posted a comprehensive spacewalk preview story. And check out our detailed timeline of today's activities in space.

We'll update this page from time to time as the spacewalk progresses.

0851 GMT (3:51 a.m. EST)

Airlock depressuziation is underway for this morning's spacewalk to enhance the scientific reach of the Hubble Space Telescope. The official start time of the spacewalk will be clocked with Newman and Massimino switch their suits to internal battery power.

0841 GMT (3:41 a.m. EST)

Mission Control has given the "go" for airlock depress, which is now expected in a few minutes.

0820 GMT (3:20 a.m. EST)

Astronauts Jim Newman and Mike Massimino are sealed inside Columbia's airlock, preparing for the start of today's spacewalk. Depressurization is expected to start in 15 to 20 minutes.

0525 GMT (12:25 a.m. EST)

Flush with success after upgrading the Hubble Space Telescope's power system, the Columbia astronauts now turn their attention to beefing up the observatory's scientific horsepower with installation of a $75 million camera during the mission's fourth spacewalk today. The 6 1/2-hour EVA begins at around 3:30 a.m. EST. Read full story.

WEDNESDAY, MARCH 6, 2002

NASA managers, elated at the successful replacement of the Hubble Space Telescope's central power controller, will delay the start of the next two servicing spacewalks to give Columbia's astronauts time to catch up on their rest after getting off to a late start today. Read full story.

1517 GMT (10:17 a.m. EST)

Columbia's airlock is now being repressurized. Today's spacewalk lasted 6 hours 48 minutes.

1510 GMT (10:10 a.m. EST)

The functional test of the newly installed PCU device is now underway.

1457 GMT (9:57 a.m. EST)

Grunsfeld and Linnehan are returning to the airlock as this spacewalk draws to a a close.

1442 GMT (9:42 a.m. EST)

Controllers at the Space Telescope Operations Control Center report that the aliveness test of the new Power Control Unit has been successfully completed.

1438 GMT (9:38 a.m. EST)

Grunsfeld is removing thermal shades from the telescope's star trackers.

1424 GMT (9:24 a.m. EST)

Power from Columbia is flowing to the telescope. The full revival of the observatory will begin shortly, starting with the activation of the Wide Field Planetary Camera.

1423 GMT (9:23 a.m. EST)

Hubble's six batteries have now been reconnected.

1421 GMT (9:21 a.m. EST)

The aliveness test of the new PCU continues and is reported to be going well.

1402 GMT (9:02 a.m. EST)

Hubble has a heart beat! Telemetry is once again being received from the telescope's newly installed PCU. The spacewalkers are now working to hook up the telescope's batteries.

1331 GMT (8:31 a.m. EST)

Grunsfeld is now connecting fuse plugs to the four power distribution units. This will allow the new PCU to route power to the various telescope systems.

1318 GMT (8:18 a.m. EST)

All 36 cables are now connected to Hubble's new Power Control Unit.

1300 GMT (8:00 a.m. EST)

28 of the 36 cables are now connected to Hubble's new PCU.

1255 GMT (7:55 a.m. EST)

Grunsfeld has now mated 24 of the 36 electrical connectors for the new PCU.

1242 GMT (7:42 a.m. EST)

Mission commentator Rob Navias reports that 20 out of the 36 PCU connectors have now been reconnected. The telescope has now been without power for about three hours.

1230 GMT (7:30 a.m. EST)

Grunsfeld has now connected one third of the cables to the new PCU box.

1220 GMT (7:20 a.m. EST)

Six connectors on the new PCU now mated. 30 left to go.

1214 GMT (7:14 a.m. EST)

Two more cables are now connected. 32 remain.

1211 GMT (7:11 a.m. EST)

Grunsfeld has connected the first two cables to the PCU. They are located on the bottom of the box. The remaining 34 connectors run down the left side of the box.

1204 GMT (7:04 a.m. EST)

Grunsfeld is about to start work to hook up the 36 electrical connectors to the new PCU. The old box is now secured in the payload bay for the return to earth.

1154 GMT (6:54 a.m. EST)

John Grunsfeld has inserted the new PCU in equipment bay 4 and will now start work to bolt it down.

1143 GMT (6:43 a.m. EST)

Grunsfeld handed the old PCU to Linnehan down in the payload bay and picked up the new unit. He is headed back up to the telescope to begin the process of installing the new PCU.

1134 GMT (6:34 a.m. EST)

Just over three hours into today's spacewalk, John Grunsfeld has pulled the old PCU, the electrical heart of the Hubble Space Telescope, out of the observatory. Riding on the end of the shuttle's robot arm, Grunsfeld will carry the unit down to the payload bay to be stowed for the ride home. He will then pick up the new PCU to be installed into the telescope as the spacewalk continues.

1128 GMT (6:28 a.m. EST)

Linnehan and Grunsfeld have switched places. Grunsfeld has now finished getting the final connectors unhooked and will now unbolt the PCU.

1051 GMT (5:51 a.m. EST)

More than half of the connectors -- 23 of the 36 -- have been demated from the old PCU. Linnehan will do seven more before letting Grunsfeld finish the job. Mission Control reports Linnehan is right on the timeline.

1026 GMT (5:26 a.m. EST)

After some prep work around the PCU, Linnehan has started unhooking the 36 connectors.

0936 GMT (4:36 a.m. EST)

The Hubble Space Telescope has been completely powered off. The observatory is now without a heart beat.

The power down is considered risky -- the observatory has never been turned off in its 12-year life in orbit. Although engineers are confident Hubble, the crown jewel of astronomy, will power back up at the end of today's spacewalk, obviously there is drama.

Hubble was built to be serviced by astronauts in orbit, but removal of the PCU was never planned. As a result, the spacewalkers will have only limited vision into the area where the box is located as they work to disconnect 36 cables and other umbilicals.

The spacewalkers must complete the Power Control Unit replacement and restore power by the end of the day, or Hubble's critical systems could be damaged by the effects of the normal temperature extremes of space.

While NASA managers typically downplay the drama associated with key events like this one, Anne Kinney, director of astronomy and physics at NASA headquarters, said she was "nervous as hell" about the PCU swap out.

The spacewalk preview story has full details on the power down.

Meanwhile, spacewalker Rick Linnehan has gained access to the Power Control Unit in Bay 4. He will remove the first 30 connectors. Then John Grunsfeld will take over to remove the final six connectors and pull out the PCU. This removal work will take a couple of hours.

0930 GMT (4:30 a.m. EST)

As soon as Grunsfeld finishes installing thermal covers over Hubble's fixed head star trackers, Hubble will be powered down. The "go" to turn Hubble off has been given by Mission Control as soon as Grunsfeld completes his work.

0925 GMT (4:25 a.m. EST)

Spacewalker Linnehan has completed disconnecting the three batteries in Bay 2. Hubble is now one command away from being turned off.

0910 GMT (4:10 a.m. EST)

The three batteries in Hubble's Bay 3 have been disconnected. Linnehan, riding on the end of Columbia's robot arm, is now moving to Bay 2 to unhook the remaining three batteries.

0905 GMT (4:05 a.m. EST)

Linnehan is now working to disconnect six batteries in Hubble while Grunsfeld deploys thermal covers on parts of the observatory -- all preparatory steps to the replacement of the PCU.

0900 GMT (4:00 a.m. EST)

We have updated our timeline of today's spacewalk based on the actual start time.

0828 GMT (3:28 a.m. EST)

EVA 3 BEGINS. Running two hours late after a water leak forced astronaut John Grunsfeld to change into a new spacesuit, the spacewalk considered the riskiest and most challenging ever attempted on the Hubble Space Telescope has now started. The planned seven-hour excursion began at 3:28 a.m. EST when Grunsfeld and fellow spacewalker Rick Linnehan switched their suits from shuttle-provided power to internal batteries.

Over the next hour the spacewalkers will move through prep work in advance of replacing Hubble's Power Control Unit, the electrical heart of the observatory. Also upcoming will be the power down of Hubble.

Read a comprehensive spacewalk preview story.

0827 GMT (3:27 a.m. EST)

The airlock is at vacuum and the outer hatch is now being opened.

0811 GMT (3:11 a.m. EST)

Airlock depressurization is now beginning. Meanwhile, steps are underway to power down the Hubble Space Telescope for the first time since it was launched in April 1990. The telescope is being turned off so its Power Control Unit can be replaced by the spacewalkers today.

0755 GMT (2:55 a.m. EST)

Depressurization of Columbia's airlock is expected in about 15 minutes. Grunsfeld is nearing completion of the procedure to breathe pure oxygen to purge his blood stream of nitrogen to prevent "the bends" during the spacewalk. The official start time of the spacewalk is clocked when the astronauts switch their suits to internal battery power, now expected around 3:30 a.m. EST.

0725 GMT (2:25 a.m. EST)

Spacewalk preparations are underway for John Grunsfeld in his new suit. Mission Control now projects the start time of today's spacewalk will be around 3:40 a.m. EST (0840 GMT). The EVA is scheduled to last at least seven hours.

0654 GMT (1:54 a.m. EST)

After discussions between the shuttle flight control team and Hubble project officials, it was decided to keep with the plan to replace the Power Control Unit today, albeit a couple hours later than planned.

0642 GMT (1:42 a.m. EST)

At the moment it appears flight controllers are favoring the plan of pressing ahead with Power Control Unit replacement today. The spacewalk is now estimated to start at around 3:30 a.m. EST, two hours later than planned. The EVA will last about seven hours, making for an incredibly long workday for the crew. They would get to bed late, then sleep in and push back the start of tomorrow's spacewalk to install the Advanced Camera for Surveys.

The spacewalk team in Mission Control suspects that a valve in the suit's cooling system popped open for some reason, causing the water leak.

The astronauts are currently working to re-size another spacesuit onboard to fit Grunsfeld.

0630 GMT (1:30 a.m. EST)

Grunsfeld is making his way out of the old suit and into the new suit. The other astronauts are working to mop up the water in the airlock from the leak, which remains unexplained.

Meanwhile, Hubble remains powered up. Controllers had not yet progressed to the point of turning off the observatory for this morning's intended replacement of the Power Control Unit.

Since it will obviously take some time for Grunsfeld to don the other suit and complete the pre-spacewalk preparatory work, NASA officials are discussing whether to keep with the game plan of replacing the Power Control Unit today or instead jumping to the work scheduled for Thursday's spacewalk. The PCU spacewalk is expected to last seven hours from start to finish, making it a long day for the crew. This suit problem is delaying the start of the spacewalk by at least an hour, making the PCU replacement today an even longer workday than envisioned.

0616 GMT (1:16 a.m. EST)

Given the delay in the start of the spacewalk, Mission Control is now talking about how this impacts the overall timeline for the day and whether the lengthy task of replacing the Power Control Unit can still be accomplished. There is the option, NASA says, of performing the tasks of spacewalk No. 4 of installing the Advanced Camera for Surveys this morning and deferring the spacewalk No. 3 job of the PCU replacement until tomorrow.

0612 GMT (1:12 a.m. EST)

The shuttle crew has just been instructed by Mission Control to get John Grunsfeld out of his current spacewalking spacesuit and into another as a result of the water leak with his cooling garment system. It is not clear what caused the leak. The spacewalkers were in the airlock preparing to start the EVA about a half-hour from now.

NASA estimates this suit switch will delay the start of this morning's spacewalk by approximately an hour -- to 2:30 a.m. EST. But that is just an estimate at this point.

0610 GMT (1:10 a.m. EST)

Flight controllers are discussing options to recover from this problem involving water seeping from John Grunsfeld's suit.

0607 GMT (1:07 a.m. EST)

The astronauts report John Grunsfeld's spacesuit has leaked some water from the cooling system. Mission Control is discussing the situation. It is possible Grunsfeld will have to switch to another suit, which would delay the start of today's EVA by approximately an hour.

0530 GMT (12:30 a.m. EST)

Since it was launched in 1990, the Hubble Space Telescope has undergone eye surgery to correct its flawed vision, an electronic brain transplant and numerous other upgrades and repairs to replace aging or broken components and to install new instruments. On Wednesday, the $2 billion observatory faces its riskiest operation yet, the equivalent of open heart surgery to replace its central power system controller. Read a comprehensive spacewalk preview story.

0200 GMT (9:00 p.m. EST Tues.)

Columbia's seven astronauts have been awakened for the most challenging day of their mission to overhaul the Hubble Space Telescope. Tonight, the observatory will be powered down for the first time since it was launched in April 1990 so spacewalkers John Grunsfeld and Rick Linnehan can replace Hubble's Power Control Unit, the electrical heart of the telescope.

Hubble was built to be serviced in orbit but removal of the PCU was never planned. As a result, the spacewalkers will have limited vision into the area where the box is located as they work to disconnect 36 cables and other umbilicals.

"What makes it difficult is, as you're facing the PCU, those connectors are on the left-hand side, they're not staring right at you, they're on the left face," lead flight director Bryan Austin said. "And that's on the side that that bay door is hinged. For the suited crewman to reach his hand in there, he's pretty much reaching in there blind.

"I kind of equate it to changing out spark plugs on your car. There's always those spark plugs down there where you sort of can't see real well, you've just got to go down and feel and make sure you're oriented such that you're unscrewing it without a lot of offset force."

Once Hubble is shut down for the PCU change out, an imaginary "thermal clock" will start ticking. The astronauts must complete the PCU replacement and restore power by the end of the day, or Hubble's critical systems could be damaged by the effects of the normal temperature extremes of space.

Also making this spacewalk dramatic is the potential of a problem turning Hubble back on after the new Power Control Unit is installed.

"That scares me a lot, it kind of violates a long-standing policy in the space business that if something's working well you turn it off and just hope it comes back on," said Ed Weiler, NASA's associate administrator for space science.

"We're not doing that cavalierly, we fully anticipate that everything will work just fine," he said. "But it is a risk that we've never faced before. So this mission is no cakewalk."

Despite the risk of replacing the PCU, officials say it is necessary job because the current unit cannot provide enough power to run all of Hubble's instruments at the same time and it has suffered an internal problem that could one day cripple the observatory if it gets worse.

The spacewalk begins at about 1:30 a.m. EST. See a timeline.

Grunsfeld previewed the spacewalk in this pre-flight NASA interview:

"Even while Rick and myself are in the airlock on the EVA-3, the activity will have already started. Up in the flight deck, Jim (Newman) and Mike (Massimino) will have started to work their steps on the avionics on Hubble, to start powering it off. And, the folks on the ground are going to kick off a procedure called the "super proc." You know, I imagine that there's some guy at a computer console with a big "S" on the shirt, you know, in a cape and his hands madly clicking on the keys. Of course, it's not really like that. But, they're going to send a large program up to Hubble to tell it to start turning things off.

"Once we egress the airlock, Rick and I are in turbo mode because we have to go out and there's various times that we have to hit (gates, if you will) to get Hubble in position to change out the Power Control Unit. We have to get thermal covers on some of the bays because, once Hubble's unpowered, space is a very cold place; and it's going to start radiating to space, cooling off, and some of the equipment can't get cold. It's just a limit on the mechanical components, on electronic components. It's kind of like if you live in Minnesota, where our pilot Duane Carey comes from, you know, if you leave your car out at a restaurant, in the bitter cold and come out and expect it to turn on, it may or may not turn on. Hubble's the same way. We don't want it to get too cold.

"And so, Rick and I are going to be speedily getting Hubble ready, to change out the Power Control Unit. And that, as I said, includes putting some thermal covers on. Rick is going to start disconnecting batteries. They're the same batteries that I worked on, on STS-103, so we have a little bit of experience in that area. And then, Rick is going to start disconnecting connectors on the Power Control Unit, as soon as he can get there. We're going to try and stay ahead of the power curve, so to speak, because this is an EVA that could go long. There's so many unknowns in it, that it, if any of these EVAs on our flight are going to be long ones, this would be the one to look for.

"We're prepared if necessary to swap out roles if it becomes too tedious. This is the kind of task that Mark Lee said was very difficult, so we're preparing for that. So, while Rick is disconnecting connectors, I'm going to be just by his side relaxing, as if, you know, I'm sort of on deck, in a, you know, just keeping, you know, warm but ready to go. If Rick gets tired, I'll jump in his place and disconnect until we get all the connectors off.

"Then we'll swap the PCU. It's about halfway up the telescope in a little electronics bay. So, I'll take it out. Nancy (Currie) will take me down to meet Rick. In the payload bay, we'll change it out for the new box. I'll put the new box in, and then start connecting. While I'm connecting the connectors, Rick is going to be by my side relaxing. In case I get too tired, he can jump in and take a few connectors.

"And, that's the plan; but we're ready for anything."

"And then, we'll continue back undoing all the things that we did earlier by putting the batteries back on line, taking thermal covers off. And once we have the batteries back on line, you know, then the man with the big S and the fast fingers is going to send commands up to start Hubble systems back on."

TUESDAY, MARCH 5, 2002

Astronauts James Newman and Michael Massimino began repressurizing the shuttle Columbia's airlock at 8:56 a.m. this morning, officially ending a seven-hour 16-minute spacewalk. The astronauts installed a second solar array on the Hubble Space Telescope and a new reaction wheel to help it move from target to target. Initial tests show both components are healthy and operating normally. Read full story, which includes a preview of tonight's third spacewalk.

1400 GMT (9:00 a.m. EST)

Today's spacewalk ended at about 8:56 a.m. and had a duration of 7 hours and 16 minutes.

1355 GMT (8:55 a.m. EST)

Newman and Massimino are back in the airlock as their spacewalk comes to a close.

1311 GMT (8:11 a.m. EST)

Mission control has informed the Columbia crew that the functional test of the new Reaction Wheel Assembly was successful.

1257 GMT (7:57 a.m. EST)

One of the Hubble Space Telescope's aft shroud latches has checked out fine. The second latch will require replacement. This should be a fairly swift task, according to mission commentator Rob Navias.

1237 GMT (7:37 a.m. EST)

Newman has successfully installed a new installation panel over the telescope's equipment bay 6 -- an unplanned activity added to today's outing after the spacewalker got ahead of schedule. The astronauts are now finishing up tests on two of the telescope's aft shroud latches.

1212 GMT (7:12 a.m. EST)

A functional test of the new Reaction Wheel Assembly is now underway.

1204 GMT (7:04 a.m. EST)

With the spacewalkers running ahead of schedule, Flight Director Bryan Austin has instructed the astronauts to conduct at least two extra tasks: the installation of a thermal blanket panel on equipment bay 6 and a drive test on two bolts on the aft shroud doors behind which are located the NICMOS and STIS instruments. The test is designed to check if a new latching mechanism will be required for the door.

Meanwhile, Hubble flight controllers report a successful aliveness test of the newly installed Reaction Wheel Assembly.

1158 GMT (6:58 a.m. EST)

Massimino has completed the installation of the new Reaction Wheel Assembly and closed the door to the equipment bay where it is housed. Hubble flight controllers will now conduct an "aliveness test" to ensure it is working properly.

1140 GMT (6:40 a.m. EST)

Now five hours into today's spacewalk. Massimino is now installing the new Reaction Wheel Assembly.

The spacewalkers are running about 20 minutes ahead of schedule. So Mission Control is considering adding some low-priority tasks to this EVA.

1133 GMT (6:33 a.m. EST)

Handoff of the Reaction Wheel Assemblies has occurred. Massimino, riding on the end of the shuttle's robot arm, took the old wheel down to the payload bay carrier where Newman had unbolted the new unit. They traded wheels and Massimino is headed back to up to Hubble to install the new RWA. Newman will now stow the old wheel for return to Earth.

1125 GMT (6:25 a.m. EST)

The spacewalkers have removed the suspect Reaction Wheel Assembly on the Hubble Space Telescope in preparation for installation of a fresh unit. This job is actually the highest priority item on NASA's list of things to be accomplished on this Hubble servicing mission.

The Reaction Wheel Assembly in question -- RWA-1 -- is one of four gyroscopic devices used in moving, or "slewing", the observatory from one astronomical target to the next.

Last November, gyro speed telemetry from RWA-1 briefly dropped out, the result of an internal electrical problem. Although the device has worked properly ever since, NASA officials became concerned it could fail. Hubble can operate with just three RWAs, but another problem would leave the telescope unable to slew and thus, unable to accomplish any scientific observations. As a result, the space agency decided to add the RWA replacement to Columbia's mission, albeit at the last minute.

1116 GMT (6:16 a.m. EST)

Spacewalker Massimino is working to remove the old Reaction Wheel Assembly from Hubble, while Newman is unbolting the new unit from its launch carrier in Columbia's payload bay.

1105 GMT (6:05 a.m. EST)

Hubble ground controllers report the "aliveness test" of the newly installed port solar array was successfully completed. And the spacewalkers have been given a "go" to disconnect the old Reaction Wheel Assembly for replacement.

1050 GMT (5:50 a.m. EST)

The spacewalkers have completed their work to deploy the Hubble Space Telescope's new port-side power-generating solar array. The observatory now has two new, more powerful arrays following the installation of the starboard one yesterday. Ground controllers will run a series of tests this morning confirm the port array's health.

The next major task upcoming for the spacewalkers is replacement of a Reaction Wheel Assembly on Hubble.

1042 GMT (5:42 a.m. EST)

The new port solar array has been unfolded. The spacewalkers will now tighten some locking bolts on the array.

1032 GMT (5:32 a.m. EST)

The spacewalkers are beginning to deploy the new port-side solar array, opening it up like a book.

1025 GMT (5:25 a.m. EST)

Just like yesterday's spacewalk, there was a bit of trouble getting the old array fully locked down on the payload carrier. But after some extra effort, Massimino has successfully secured the array for its trip back to Earth. Massimino, still on the end of the arm, is now headed back up to the new array for deployment.

1000 GMT (5:00 a.m. EST)

While Jim Newman continues working with electrical connectors between Hubble and its new port solar array, Mike Massimino is back in the cargo bay to fully secure the old array to the carrier for return to Earth. Once both complete their current jobs, they will then open up the new array.

0948 GMT (4:48 a.m. EST)

The spacewalkers have attached the new solar array to the Hubble Space Telescope. Newman will now bolt the array into place to firmly secure it to the observatory.

0916 GMT (4:16 a.m. EST)

The new solar array has been lifted from its launch carrier. Massimino is holding on to the array as he rides from the payload bay up to Hubble. Newman will now climb back up to the telescope to bolt the array into place when it arrives shortly.

0901 GMT (4:01 a.m. EST)

With the new diode box installed, Newman joined Massimino in the cargo bay to assist is releasing the new solar array from the carrier structure. Massimino, riding on the end of the robot arm, has the new array in hand now and is beginning to lift it out of the carrier. He will ferry it up to the telescope for installation.

0840 GMT (3:40 a.m. EST)

Now two hours into today's spacewalk. Newman is working to hook up all the connectors between the new diode box and the telescope. Meanwhile, Massimino has stowed the old box in the payload bay and is now preparing release latches holding the new array in its launch carrier aboard Columbia.

Mission Control says the spacewalkers are about 25 minutes ahead of the timeline.

0828 GMT (3:28 a.m. EST)

Jim Newman has unbolted the old diode box from the Hubble Space Telescope and handed it to Mike Massimino for transport to the shuttle's payload bay for return to Earth. Massimino had the new box in his hand and gave it to Newman for installation on the telescope. The new unit is suited to handle the additional power the new solar array will generate.

0803 GMT (3:03 a.m. EST)

The spacewalkers have bolted the old array to a carrier structure in Columbia's payload bay. Massimino will later engage some latches to firmly hold the array in place for its ride home. Now the spacewalkers will turn their attention to replacing the diode box assembly on Hubble's port side to support the new, more powerful array.

0751 GMT (2:51 a.m. EST)

Hubble's port solar array has been detached from the observatory by the spacewalkers. Jim Newman unbolted the array from the telescope and Mike Massimino, riding on the end of the shuttle's robot arm, has the free array in his hands. The array will be stowed back in Columbia's payload bay for the return to Earth.

So the two second-generation solar arrays delivered to Hubble during the first servicing mission in December 1993 have been removed during the first two spacewalks of this fourth servicing mission. Spacewalkers installed one of the smaller but more powerful third-generation arrays yesterday to the starboard side of the observatory. The new port array will be installed later this morning.

0735 GMT (2:35 a.m. EST)

While Jim Newman works to disconnect cabling with the diode box assembly for the old solar array, Mike Massimino is loosing a series of bolts on three access doors on the side of Hubble as a get-ahead task for tomorrow's spacewalk to replace the observatory's Power Control Unit.

0725 GMT (2:25 a.m. EST)

Now 45 minutes into today's spacewalk. The port-side solar array, which had been sticking straight out from the body of the telescope, has been folded upright against Hubble in preparation for removal. Mission Control reports the spacewalkers are running about a half-hour ahead of the timeline.

0640 GMT (1:40 a.m. EST)

EVA 2 BEGINS. For the second straight day astronauts from space shuttle Columbia have embarked on a spacewalk to give the Hubble Space Telescope an overhaul.

Astronauts Jim Newman and Mike Massimino switched their suits from shuttle-provided power to internal batteries at 1:40 a.m. EST, marking the start of this planned 6 1/2-hour EVA.

The spacewalkers plan to remove Hubble's port-side solar array and install of a new array that will allow the telescope to generate more power to run its new generation set of science instruments. They will then replace one of the telescope's four Reaction Wheel Assemblies used for pointing during science observations.

After initial setup work, the array replacement is expected to take about four hours, followed by the hour-long job of switching out the reaction wheel, some other quick tasks and then cleanup of the payload bay.

The mission's first spacewalk, successfully completed early Monday by John Grunsfeld and Rick Linnehan, replaced Hubble's starboard array. This morning's EVA will complete the solar array replacement work by installing the new port-side array.

"Mike and I have a similar day on the second spacewalk, but we don't have as much initial configuration to do," Newman said in a NASA pre-flight interview. "Since John and Rick are the first ones out the door, they have to do a little bit of initial configuration in order to set up the payload bay for the rest of the spacewalks. And they'll do some final de-configuration on the very last spacewalk.

"When Mike and I go outside, I'll immediately head back and get to work and Mike will take a couple of minutes, just to get his space legs. He will have an opportunity to translate a little bit around in the payload bay in order to become familiar with what it's like to be a spacewalker, and then we're going to put him right to work as well."

This is the fifth spacewalk for Newman, who is wearing the suit with horizontal broken red stripes, and first for Massimino who has the suit with diagonally broken red stripes.

We'll update this page periodically during the spacewalk.

0637 GMT (1:37 a.m. EST)

The airlock has been depressurized and the astronauts have just opened the outer hatch.

0624 GMT (1:24 a.m. EST)

Airlock depressurization has now started.

0615 GMT (1:15 a.m. EST)

Mission Control has given the Columbia crew a "go" for airlock depressuziation for this morning's spacewalk. The official start time of the spacewalk will be clocked with Newman and Massimino switch their suits to internal battery power.

0330 GMT (10:30 p.m. EST Mon.)

The shuttle crew was awakened for Flight Day 5 at 8:53 p.m. EST by the children's song "Floating in the Bathtub," by Tonya Evetts Weimer.

Astronauts Jim Newman and Mike Massimino will take their turn as the spacewalking duo tonight, heading into Columbia's payload bay at about 1:30 a.m. EST for a 6 1/2-hour EVA to replace Hubble's other power-generating solar array and swap out a suspect gyroscopic device, called a Reaction Wheel Assembly, that is used to point the observatory.

The work to remove the old port-side solar array and install a new, more powerful one will be quite similar to the job performed early Monday by the mission's other spacewalking team of John Grunsfeld and Rick Linnehan.

Tonight will see Newman as the "free floating" astronaut and Massimino as the crewman riding on the end of the shuttle's robotic arm. Newman will work to disconnect the old array and later bolt the new one in place and hook up cabling. Massimino will transport the old structure to the payload bay to be stowed for the return to Earth and hand-carry the new array to the telescope. Mission specialist Nancy Currie will be the robot arm operator.

After the array replacement is completed, the spacewalkers will turn their attention to changing out the Reaction Wheel Assembly in the telescope's Bay 6. Massimino will ride the arm to Bay 6, remove the old wheel and then carry it to the payload bay where Newman will be waiting with the new component. They will exchange wheels and Massimino will take the new device back to Bay 6 for installation, while Newman stows the old wheel for the ride home.

MONDAY, MARCH 4, 2002

Shuttle Columbia astronauts John Grunsfeld and Rick Linnehan removed the Hubble Space Telescope's starboard solar array this morning and installed a new, more powerful array during a successful seven-hour spacewalk. It was the first of five consecutive days of spacewalks scheduled for Columbia's mission to rejuvenate the observatory. Read our full story.

1348 GMT (8:48 a.m. EST)

Today's spacewalk came to an official end at 8:38 a.m. EST (1338 GMT) and had a duration of seven hours and one minute.

1340 GMT (8:40 a.m. EST)

Repressurization of the airlock is underway. Controllers are about to move the newly installed solar array as part of its functional test.

1330 GMT (8:30 a.m. EST)

The airlock outer hatch is closed.

1326 GMT (8:26 a.m. EST)

The two spacewalkers have returned to Columbia's airlock as they wrap up their spacewalk to install Hubble's first new solar array.

1322 GMT (8:22 a.m. EST)

Mission control reports the aliveness test of the new solar array was successful. A functional test to check the array can turn to track the sun will follow shortly.

1304 GMT (8:04 a.m. EST)

The two spacewalkers have completed all their major tasks for this spacewalk. Linnehan has successfully installed thermal covers on two of the telescope's equipment bays to ensure crucial components don't get too cold when the observatory is switched off on Wednesday for the replacement of the power control unit. They are now stowing and checking their tools before returning to the airlock.

1245 GMT (7:45 a.m. EST)

The final major cable has been connected by Grunsfeld to route power from the new solar array to Hubble. An "aliveness test" can now be performed to verify the health of the new array. Meanwhile, Linnehan continues the installation of thermal blankets on the telescope.

1237 GMT (7:37 a.m. EST)

Now six hours into today's spacewalk.

1208 GMT (7:08 a.m. EST)

The two spacewalkers are swapping places. Grunsfeld will take up position on the robot arm, while Linnehan works free-floating. Mission control's EVA officer reports the spacewalkers are running about 30 minutes behind schedule.

1149 GMT (6:49 a.m. EST)

The locking bolts have been tightened, completing most of the work to install the first new solar array.

Linnehan will now move on to install an insulation cover over the telescope's equipment bay 10. This is to keep warm the scientific instrument command and data handling computer while the observatory is switched off during the replacement of the power control unit, scheduled for Wednesday.

Meanwhile, Grunsfeld will connect a cable to connect the new array to route power to Hubble's batteries.

1143 GMT (6:43 a.m. EST)

The EVA officer in mission control reports the spacewalkers are running about 20 minutes behind schedule, but they have plenty of consumables to finish all their planned tasks.

1141 GMT (6:41 a.m. EST)

The new array is now completely unfolded and Linnehan will start work tightening the bolts to lock the array open.

1136 GMT (6:36 a.m. EST)

Linnehan is now carefully unfolding the brand new solar array on the starboard side of the Hubble Space Telescope.

1125 GMT (6:25 a.m. EST)

After some extra effort, Linnehan has finally gotten all four latches secured to hold down the old array. And Mission Control has given the spacewalkers a "go" to deploy, or open up, the new array.

1100 GMT (6:00 a.m. EST)

Cables are being connected with the new starboard solar array by spacewalker Grunsfeld. Meanwhile, spacewalker Linnehan is having some difficultly locking a fourth and final clamp that will hold the old array to the carrier aboard Columbia for return to Earth. All four clamps are required to be secured.

1030 GMT (5:30 a.m. EST)

Hubble has received the first of two new, more powerful solar arrays. The spacewalkers have physically attached the starboard array and work to connect cabling is underway before it is opened up.

The new arrays are the third set built for the observatory. Hubble's first two pairs were flexible and rolled up like window shades. The newest ones are flat and rigid and fold up like a book rather than roll up.

Here is the NASA fact sheet on the new arrays:

Though one third less solar cell area, these third-generation arrays will produce 20 percent more power than the current set. The new arrays collect the extra electricity needed to power a new generation of science instruments. This added power enables all the science instruments to be powered on and ready to operate simultaneously -- allowing for more discoveries in less time.

The high efficiency solar panels have supporting frames made of aluminum-lithium, which is stronger and lighter than the type of aluminum commonly used in spacecraft construction. These supports are much less sensitive to the extreme temperature changes of Hubble's harsh environment.

During each 97-minute orbit, Hubble spends about two-thirds of its time in searing sunlight and the other third in the frigid darkness of Earth's shadow. These brutal, rapidly cycling conditions cause the temperature of the solar panels to fluctuate between minus 94 degrees Fahrenheit (minus 70 degrees Celsius) and 187 degrees Fahrenheit (86 degrees Celsius). The solar arrays reach their hottest temperature just ten minutes after leaving the chill of Earth's shadow.

Such dramatic, repeated temperature changes may cause tiny vibrations and movements within a spacecraft's solar array structure. If these movements are large enough, they cause motion of the main body of the telescope, and may affect the sensitivity of Hubble's pointing control instruments and interfere with long-term science observations.

This excessive movement was observed with Hubble's original solar arrays, which were replaced in 1993 with a much more stable pair. Since then, advances in solar cell technology and spacecraft design have led to the development of even more stable and efficient solar arrays.

These smaller, stiffer arrays are easier for the astronauts to work around during servicing missions -- easier to fold up and move out of their way. Their smaller size decreases on-orbit drag and slows the rate at which Hubble's orbit decays. Over time, all low Earth orbiting satellites feel the effects of atmospheric drag and lose altitude. These new arrays will slow that rate of altitude loss.

The Hubble program bought these solar panels from the production line of a commercial system of communications satellites. At NASA's Goddard Space Flight Center in Greenbelt, Md., four of these panels were attached to an aluminum-lithium support wing structure to create each of the complete structures called "wings." A total of 8 panels were used in the construction of these two wings. Hubble team members at Goddard fabricated the support wing structures, the composite mast assembly, and the electrical assembly for these wings. By using these off-the-shelf panels and fabricating the support systems at Goddard the Hubble program saved considerable time and expense.

Hubble's new solar arrays are just the latest chapter in a longstanding, international partnership between NASA and the European Space Agency (ESA). ESA built Hubble's first two sets of solar arrays. For the newest pair, ESA designed, developed and tested the Solar Array Drive Mechanisms, which maneuver the arrays to keep them constantly pointed at the Sun.

ESA also provided the ability to test the new arrays in a unique, never-before-done way. ESA's world-class test facility in The Netherlands features a huge test chamber that can realistically simulate the extreme temperature cycles of Hubble's orbit -- including sunrise and sunset. This chamber, combined with the size of the new array and ESA's vast Hubble experience, made this facility the only place in the world capable of performing this test.

In October of 2000, one of the new arrays was shipped to the ESA test site, located at the European Space Research and Technology Center (ESTEC) in Noordwijk, The Netherlands. Here the combined ESA/NASA team conducted the special thermal test to measure the amount of movement produced within the solar array due to the harsh extremes of Hubble's environment. After extensive evaluation, the team verified that Hubble's new arrays would stay steady throughout the extreme temperature cycles of each orbit.

1025 GMT (5:25 a.m. EST)

The spacewalkers have soft-mated the new solar array to the Hubble Space Telescope. A clamp band will now be tightened to firmly hold the array in place. Then some cabling will be connected between the array and observatory. The astronauts will open the array later in this EVA.

0951 GMT (4:51 a.m. EST)

The new array is being carried from the payload bay to Hubble in the hands of spacewalker Linnehan, who is riding on the end of Columbia's robot arm.

0930 GMT (4:30 a.m. EST)

With the new diode box installed on Hubble, the two spacewalkers are working to remove the new array from the carrier aboard the shuttle.

0910 GMT (4:10 a.m. EST)

Continuing to ride on the end of the shuttle's Canadian-built robot arm, Rick Linnehan is down in the payload bay to release the new solar array from its launch carrier.

0903 GMT (4:03 a.m. EST)

The old diode box has been removed. It will be stowed on the array carrier in the payload bay to be returned to Earth.

0847 GMT (3:47 a.m. EST)

John Grunsfeld is currently disconnecting the old solar array diode box from Hubble. Rick Linnehan is preparing the new box for installation to go along with the new solar array.

0837 GMT (3:37 a.m. EST)

Now two hours into the spacewalk. The old array has been clamped down to the carrier in Columbia's payload bay for return to Earth.

0822 GMT (3:22 a.m. EST)

The starboard solar array has been removed from the Hubble Space Telescope. It is now in the hands of spacewalker Rick Linnehan, who will transport the structure to a carrier in the payload bay where it will be stowed for the trip back to Earth.

This array and its twin on the other side of the observatory were installed during the first Hubble servicing mission in 1993. They weigh 339 pounds each and measure 40 feet long by 10.8 feet wide, delivering about 4,600 watts of power from silicon solar cells.

Due to the wear and tear of temperature extremes and normal space radiation, these flexible panels now provide just 63 percent of their original power. In addition, they suffer from structural problems and some shorted circuitry in the wiring connecting all the solar cells.

Hubble's new arrays are heavier -- 640 pounds per wing -- and more powerful, generating some 5,270 watts. But they are smaller than Hubble's flexible panels, measuring just 23 feet long and 8.5 feet wide.

The additional power generated by the new gallium arsenide solar cells will enable astronomers for the first time to operate all of Hubble's instruments simultaneously for multi-disciplinary observations. In addition, their smaller size will reduce the atmospheric drag that constantly acts to reduce Hubble's altitude.

The old array on the port side of Hubble will be replaced tomorrow.

0818 GMT (3:18 a.m. EST)

The spacewalkers have folded up the old solar array boom, moving it from its perpendicular configuration to an orientation parallel to the telescope's body. Grunsfeld has also disconnected a series of cables in preparation for the actual removal of the array from Hubble.

0737 GMT (2:37 a.m. EST)

Now one hour into today's spacewalk. Grunsfeld and Linnehan are running about 10 minutes ahead of the spacewalk timeline. Since the EVA started about 10 minutes late, everything is balancing out.

The spacewalkers have moved through the early chores of this EVA, including the gathering of tools and equipment. The main task of this spacewalk -- removal and replacement of starboard solar array -- will be starting shortly.

0637 GMT (1:37 a.m. EST)

EVA 1 BEGINS. The first of five challenging spacewalks to give the 12-year old Hubble Space Telescope a makeover during this flight of shuttle Columbia has officially begun.

Astronauts John Grunsfeld and Rick Linnehan switched their suits from shuttle-provided power to internal batteries at 1:37 a.m. EST, marking the start of this planned 6 1/2-hour EVA that will see one of Hubble's solar arrays removed and replaced with one that will allow the telescope to generate more power to run its new generation set of science instruments.

Grunsfeld will disconnect the old array and Linnehan will temporarily mount it on a cargo carrier in the payload bay. Grunsfeld then will install a diode box needed to ensure power from the arrays flows to Hubble's batteries and not vice versa while Linnehan pulls the new array, folded in half, from its carrier.

Grunsfeld will attach the new solar wing, crank it open and wire it to the diode box. Another cable, known as P601, will be connected to route power to a diode box controller.

The spacewalkers also will do a bit of preparatory work needed before Hubble can be powered down for replacement of the power control unit during the third spacewalk. They will install a light shield over Hubble's star trackers and thermal covers over the Wide Field-Planetary Camera-2 and equipment bays five and 10.

This is the third spacewalk for Grunsfeld, which is wearing the suit with red stripes, and first for Linnehan who has the all-white suit.

See our update below, from 0200 GMT, for a preview of the spacewalk timeline by Grunsfeld.

We'll update this page from time to time as the spacewalk progresses.

0632 GMT (1:32 a.m. EST)

The hatch from the airlock to the payload bay has been opened.

0621 GMT (1:21 a.m. EST)

Airlock depressuziation is underway for this morning's spacewalk to service the Hubble Space Telescope. The official start time of the spacewalk will be clocked with Grunsfeld and Linnehan switch their suits to internal battery power.

0614 GMT (1:14 a.m. EST)

The hatch from the shuttle's middeck to the airlock is being closed in preparation for airlock depressurization.

0445 GMT (11:45 p.m. EST Sun.)

Mission specialists John Grunsfeld and Rick Linnehan are donning their spacesuits in preparation for the spacewalk to replace one of the power-generating solar arrays on the Hubble Space Telescope. This will be the first of five consecutive days of spacewalks to rejuvenate the observatory. Mission Control reports the astronauts are just about on the scheduled timeline, with the 6 1/2-hour spacewalk now expected to start at around 1:20 a.m. EST.

0200 GMT (9:00 p.m. EST Sun.)

The astronauts were awakened to the sounds of "Twinkle, Twinkle Little Star" a few minutes ago as the crew begins Flight Day 4 -- a day devoted to the first of five spacewalks for Columbia's mission to service the Hubble Space Telescope.

The EVA is scheduled to begin at about 1:30 a.m. EST, but could start as much as an hour early for spacewalkers John Grunsfeld and Rick Linnehan. The excursion's main goal is the removal of Hubble's starboard solar array and installation of a new, more powerful one.

In a pre-flight interview, Grunsfeld previewed this spacewalk:

"The first EVA day I think will set the stage for all five of our spacewalks. It's in the beginning of the EVA day, first of all I'll come out of the airlock. And then, Rick Linnehan will come out of the airlock. And for me that's very exciting; he's a classmate of mine. This is his third flight but his first spacewalk. And so, I'll get to see my friend and my spacewalking buddy come out of the airlock for the first time on his first spacewalk. But, we won't have much time to enjoy the view because this is a very busy day.

"This is the day where we have to set up the payload bay. We've gotten to orbit; we've grappled Hubble; put it on the servicing structure; and now we have to go and get the payload bay and Hubble ready for servicing. And, that involves a number of activities with putting a special support post under the telescope to rigidize it (the BAPS post). I'm going to put an antenna cover over a small, delicate antenna at the bottom of the telescope so that we don't inadvertently hit it. Rick is going to be setting up the shuttle robotic arm, the robotic manipulator system, with a special foot-plate that we can stand on and that holds our tools. So we'll both be very busy right at, right from the start. That'll take about an hour or so.

"Now from there, we move straight into the solar array change-out. If all goes well, the solar arrays will be all rolled up; and we'll go up on the telescope about halfway up; and we'll take off those flexible arrays that are now rolled up, we'll take them off and put them into the payload bay on the shuttle. And then, we'll take out the new solar arrays. And, they're quite a bit different than the old ones. Instead of being rolled up, they're actually rigid arrays; and they open like a book.

"So, we're going to take these roughly 9-foot-by-12-foot arrays out; and Rick is going to hold on to the array; and Nancy Currie will lift Rick up out of the payload bay, using the robotic arm, with a 640-pound solar array in front of him. Rick is then going to steer it around towards the telescope, and then together Rick and I will insert it into the fitting onto Hubble.

"And then Rick is going to open up the solar array, like a book, exposing it to sunlight. And, we'll cinch that down, clean up a little bit of the payload bay, and come back in.

"There are a few other little things that we're going to do. We're going to wrap some cables in preparation for the next EVA day where we'll put the second solar array on."

Watch this page for periodic updates throughout the spacewalk.

SUNDAY, MARCH 3, 2002
1815 GMT (1:15 p.m. EST)

NASA officials are Mission Control say this morning's retrieval of the Hubble Space Telescope and retraction of the observatory's twin solar arrays all went as planned. Read our full story.

1505 GMT (10:05 a.m. EST)

Hubble has been moved into position on its payload bay craddle for the first of five planned spacewalks to service the orbiting observatory.

1455 GMT (9:55 a.m. EST)

Flight controllers earlier today asked the crew to isolate one of the shuttle's water storage tanks because of a potential problem with one of the electricity-generating power plants. Controllers believe fuel cell No.3 might be seeping hydrogenated water and controllers want to preserve prestine water supplies needed for the space suits.

"We would like to isolate tank C until we understand the problem exactly," CAPCOM Steve MacLean told mission commander Scott Altman. "No impact right now. We are just being conservative."

The shuttle's fuel cells mix liquid oxygen and liquid hydrogen to generate electricity and water. The fuel cells are critical components and any problem with them is worth following closely.

1446 GMT (9:46 a.m. EST)

Hubble's port solar array appears to have successfully retracted, clearing the way for the first spacewalk of the mission and the installation of new more powerful, electricity-generating panels. Once again, one of two microswitches does not indicate a complete retraction and controllers are working to tighten the array.

1440 GMT (9:40 a.m. EST)

The port solar array has begun to retract.

1439 GMT (9:39 a.m. EST)

Once again a microswitch failure has stalled the retraction. The switch is being reset.

1438 GMT (9:38 a.m. EST)

The Space Telescope Operations Center has sent commands to retract the observatory's port solar array.

1437 GMT (9:37 a.m. EST)

Columbia has orbited into daylight and has been given a "go" for free-drift prior to the retraction of the port solar array.

1419 GMT (9:19 a.m. EST)

Columbia should sail into sunlight in about 15 minutes. Controllers will allow about three more minutes to allow the array to warm in the sun before retraction begins.

1415 GMT (9:15 a.m. EST)

Flight controllers are waiting for Columbia to orbit into daylight before starting the retraction of the Hubble Space Telescope's port solar array.

1349 GMT (8:49 a.m. EST)

Hubble is being rotated to bring the port solar array into view.

1342 GMT (8:42 a.m. EST)

Both microswitches are now giving a "stowed" indication. Next the telescope will be rotated 180 degrees for the port solar array retraction.

1340 GMT (8:40 a.m. EST)

Flight controllers have not received a "stowed" indication from one of two microswitches. The Space Telescope Operations Center will attempt to drive the array once more to get that second microswitch to give a "stowed" signal. This does not appear to be a significant problem as mission control's EVA officer reports that the array is sufficiently retracted for spacewalk activities.

1328 GMT (8:28 a.m. EST)

The starboard solar array blankets appear to have successfully retracted.

1323 GMT (8:23 a.m. EST)

The solar array appears to be retracting now.

1322 GMT (8:22 a.m. EST)

Mission control believes a failed microswitch might have prevented the retraction of the array. That microswitch will be reset and commands will be sent again.

1320 GMT (8:20 a.m. EST)

Commander Scott Altman reports no sign of motion in the solar array despite the fact commands were sent to retract the array.

1317 GMT (8:17 a.m. EST)

The shuttle is now in "free drift" so its maneuvering jets don't distrub the retraction of the arrays. Space telescope controllers are about to send the retraction command.

1315 GMT (8:15 a.m. EST)

The crew has been given a "go" by mission control for the retraction of the starboard array.

1314 GMT (8:14 a.m. EST)

We are standing by for the retraction of the first solar array. The crew has positioned payload bay TV cameras to observe the operation and is waiting for any motion in the arrays to dampen out before proceeding.

1307 GMT (8:07 a.m. EST)

The telescope is now in position for the retraction of the starboard solar array.

1257 GMT (7:57 a.m. EST)

The crew has been given a "go" to turn the Hubble Space Telescope into position for the starboard solar array retraction. This will allow the crew to observe the array retraction through the aft cockpit windows.

1243 GMT (7:43 a.m. EST)

The solar array slew is now complete. The crew has been given a "go" to pivot the Hubble Space Telescope on its craddle to the 75 degree position in readiness for the solar array retraction. It will take about four minutes to reach this position.

1227 GMT (7:27 a.m. EST)

The Hubble Space Telescope's solar arrays are being turned to the correct position for their retraction later today. The move should take about 14 minutes. The arrays will be parallel to Columbia's payload bay once they reach their intended position.

1051 GMT (5:51 a.m. EST)

The motorized power umbilical has been plugged into the base of Hubble from Columbia. Also, the robot arm has ungrappled the telescope, now that is berthed on the servicing platform in the shuttle's payload bay. The arm, which is fitted with several video cameras, now will be used to conduct a survey of Hubble's exterior, giving ground controllers their first close-up look at the observatory in over two years.

1032 GMT (5:32 a.m. EST)

The Hubble Space Telescope is now firmly locked down on the Flight Support System servicing platform in the rear of shuttle Columbia's payload bay.

Basically the workbench for Hubble, the platform features a Lazy Susan-like ring that the telescope actually sits on, allowing the observatory to be rotated and pivoted as needed to provide the best available access to various worksites for spacewalkers and the upcoming retraction of the solar arrays.

The craft's arrays are to be rolled up starting in about three hours.

But before the retraction occurs, the shuttle will be maneuvered to an attitude where the arrays can recharge Hubble's onboard batteries. The arrays were positioned for the retrieval in such a way that they weren't able to collect enough sunlight to properly recharge the batteries. An umbilical will also be attached to Hubble to supply power from the shuttle.

1017 GMT (5:17 a.m. EST)

Hubble now 15 inches above the servicing platform.

1014 GMT (5:14 a.m. EST)

Mis