Mission Accomplished: Leaving Hubble Better Than Ever

Why is Hubble important?

NASA's Hubble Space Telescope is fulfilling the hopes astronomers long held for a large, optically superb telescope orbiting above Earth's distorting atmosphere and providing uniquely clear and deep views of the cosmos.

After months of training and a seven-month postponement, the STS-125 crew's mission got under way with an on-time launch into a brilliant-blue Florida sky. The May 11, 2009, liftoff of space shuttle Atlantis took place at 2:01 p.m. EDT from Launch Pad 39A at NASA's Kennedy Space Center. As if to say, "Come on up!" the 19-year-old Hubble was passing directly over Kennedy at the time of the launch. The mission ended later than planned at the backup landing site, Edwards Air Force Base in California. Lingering tropical rain in Florida produced three consecutive days of wave-offs at Kennedy before Atlantis made an 11:39 a.m. EDT touchdown at Edwards on May 24.

Veteran astronaut Scott Altman commanded this final space shuttle mission to Hubble, with Gregory C. Johnson as pilot. Mission specialists included veteran spacewalkers John Grunsfeld and Mike Massimino, and first-time space fliers Andrew Feustel, Michael Good and Megan McArthur, who served as flight engineer.

The mission's major upgrades to Hubble and what they provide:

• Wide Field Camera 3 - Hubble's new panchromatic camera will allow astronomers to better observe galaxy evolution, dark matter and dark energy.
• Cosmic Origins Spectrograph - The most sensitive spectrograph ever flown on Hubble, the new instrument will peer further into the universe than ever before in the near and far ultraviolet ranges.
• Advanced Camera for Surveys - Now repaired, it's one of Hubble's primary cameras, which stopped working in 2007. It's responsible for some of the most famous images from Hubble.
• Space Telescope Imaging Spectrograph - Inoperable since 2004, the repaired instrument reveals information about planets, comets, stars and galaxies.
• Science Instrument Command and Data Handling System - Replacement of the unit that failed in September 2008, returns full function for sending information and receiving commands.
• Fine Guidance Sensor 2 - Replaced, it is one of three sensors that help point and lock the telescope on targets.
• Rate Sensor Units - The six new gyroscopes in these units work with the Fine Guidance Sensors to help precisely point the telescope.
• Battery Module Units - Replaced, they power Hubble when the solar arrays are out of the sun's reach.

The tasks ahead of the crew were monumental: conduct spacewalks on five consecutive days that would leave the telescope upgraded and sending back even more spectacular images well into the next decade.

To mitigate the risk to the crew should Atlantis sustain damage on ascent or during the mission, space shuttle Endeavour was stationed at Kennedy's Launch Pad 39B as a standby rescue vehicle. A unique risk was the orbit in which Hubble resides. It contains a higher level of debris that potentially could have struck Atlantis during the mission. Another factor was the lack of "safe haven" normally provided by the International Space Station on other missions.

Both before and after the capture and servicing of Hubble, the astronauts conducted careful inspections of Atlantis' exterior using the shuttle's 50-foot-long orbiter boom sensor system attached to its 49-foot-long robotic arm. No significant damage from either launch or the days in space was found. Once mission managers gave Atlantis a clean bill of health, Endeavour was released from its standby duties.

The heart of the servicing mission -- the capture of Hubble, five spacewalks and release of the refurbished telescope -- spanned flight days three through nine. By the end of the last spacewalk, all the mission objectives to improve Hubble's view of the universe and extend its life had been accomplished.

Two days after launch, Atlantis caught up to Hubble 350 miles above Earth. It was up to Altman and Johnson to bring the shuttle close enough to the telescope so that McArthur could use the robotic arm to capture it and gently place it on a rotating work stand in the payload bay. From there, the pairs of spacewalkers would conduct their work.

Both Grunsfeld and Massimino had been to Hubble before, and each was paired with a first-time spacewalker. Grunsfeld teamed with Feustel on the first, third and fifth spacewalks and Massimino worked with Good during the other two.

Each spacewalk was planned to last about 6 1/2 hours, but most lasted between seven and eight hours.

Here's the breakdown of the marathon spacewalks:

• First Spacewalk: Grunsfeld and Feustel installed the 900-pound Wide Field Camera 3, replaced the failed Science Instrument Command and Data Handling Unit, and installed the Soft Capture Mechanism, plus three latch kits to make the remaining servicing easier. Spacewalk time: seven hours and 20 minutes.
• Second Spacewalk: Massimino and Good replaced all three Rate Sensor Units, each containing two gyroscopes, and also replaced a 460-pound Battery Module Unit. Spacewalk time: seven hours and 56 minutes.
• Third Spacewalk: Grunsfeld and Feustel installed the new Cosmic Origins Spectrograph and repaired the Advanced Camera for Surveys. Spacewalk time: six hours and 36 minutes.
• Forth Spacewalk: Massimino and Good replaced a power supply board in the Space Telescope Imaging Spectrograph using special tools developed for this mission. Spacewalk time: eight hours and two minutes.
• Fifth Spacewalk: Grunsfeld and Feustel replaced another of Hubble's 460-pound Battery Module Units, removed and replaced Fine Guidance Sensor 2, and installed New Outer Blanket Layers on the exterior of three bays of the telescope. Spacewalk time: seven hours and two minutes.

While not without some troublesome moments, the spacewalkers overcame any difficulties to accomplish all the repairs and upgrades of the challenging mission. An onboard IMAX camera captured their work for a Hubble 3-D movie due to debut in 2010.

The days before landing provided an opportunity for the crew to have some needed off-duty time, as well as a chance to speak to U.S. President Barack Obama, the crew orbiting on the International Space Station, reporters back on Earth, and to testify before a U.S. Senate committee -- a first-time event from space.

At the completion of the final spacewalk, the moment came when human hands had touched Hubble for the last time. The STS-125 crew left the telescope ready to dazzle the world for years to come, with more scientific discoveries and stunning images now possible because of its improved view that stretches from our solar system to the far reaches of the universe.