Revisiting Hubble

More than 18 years after transforming the way humans peer into the cosmos, the Hubble Space Telescope will receive a fifth and final visit from Space Shuttle astronauts on a challenging mission geared at enhancing the telescope’s capabilities and extending the life of the orbiting observatory.

The STS-125 mission, or Servicing Mission 4, is scheduled to launch in October 2008 and will bring Atlantis and a crew of seven to Hubble on an 11-day flight to replace equipment, upgrade software and install two new cutting-edge science instruments.

Launched in 1990 and last serviced in 2002, the 43.5-foot long, 12-ton telescope sees space-based objects 10 times more clearly than typical Earth-based equipment. One of NASA’s longest and most successful science missions, Hubble is capable of imaging objects up to 14 billion light years away and has precisely measured the age of the universe, provided the first concrete evidence of black holes, allowed views of Martian weather and enabled insight into the evolution of galaxies, the births of stars and the composition of planets within Earth’s own solar system.

“Hubble is one of the most important things we’re doing in manned spaceflight,” said Frank Richmond, USA STS-125 Flight Manager. “It has been a phenomenon ever since it started sending good data back from space.”

STS-125 also will create a unique processing challenge at the Kennedy Space Center, as Space Shuttles will be required to be on launch pads 39-A and 39-B at the same time. Due to the nature of the Hubble mission, the Shuttle will not be in the same orbital plane as the International Space Station and would not be able to take refuge there in the event of an emergency. If required, a contingency mission – designated STS-400 – must be ready to launch within seven days after the launch of STS-125.

To protect for such a contingency, Atlantis will be rolled out to launch pad 39-A and prepared for the HST flight while Endeavour will stand on pad 39-B, ready to launch on STS-400 if necessary. Once Atlantis returns to Earth, Endeavour’s middeck will be reconfigured for flight and then rolled to launch pad 39-A and processed for the STS-126 mission to follow in November 2008.

“The biggest challenge with the launch on need requirement is that we’ll have to share resources between the two vehicles,” Richmond said. “It also will be near the end of hurricane season, so we’ll have to be poised to roll two vehicles back in case of inclement weather. Our team will need to be prepared for everything.”

Shortly after arriving in orbit, Atlantis will fire its thrusters to adjust its flight path toward the telescope, and once about 30 feet away from Hubble, the Shuttle’s robotic arm will grapple the telescope and berth it to a platform in the rear of the Shuttle’s payload bay where it can be easily accessed by spacewalkers.

Crewmembers will be split into teams of two to accommodate the mission’s five spacewalks to be conducted on consecutive days, currently scheduled for flight days four through eight.

The spacewalks will enable astronauts to replace all of Hubble’s six gyroscopes, install fresh batteries and exchange a Fine Guidance Sensor with a new one. Spacewalkers will also replace thermal insulation on critical component bays of the telescope and attach a mechanism that will aid in Hubble’s final deorbiting.

“Some of the tasks we’re going to do on these spacewalks have never been performed on orbit before,” said Christy Hansen, STS-125 EVA Task Lead. “The challenges of that have made training for this mission’s spacewalks significantly different than Station missions.”

Along with maintenance, the spacewalks will advance Hubble’s scientific capabilities with the installation of the Cosmic Origin Spectrograph (COS) and Wide-Field Camera 3 (WFC3). Once installed, the COS will be the most sensitive ultraviolet spectrograph ever flown on Hubble and is expected to improve the telescope’s sensitivity at least 10 times. The WFC3, capable of seeing infrared and ultraviolet light, will be used for probing distant galaxies, dark energy and planets within Earth’s solar system. Working in conjunction with the Hubble’s Advanced Camera for Surveys, the instruments are expected to yield unrivaled data and images from space.

While the Hubble mission is anticipated to excite public interest, it has a special legacy at USA as three current employees played crucial roles in the early success of the orbiting telescope.

Launched aboard STS-31 in 1990, Loren Shriver, USA’s Vice President of Engineering and Integration, commanded the mission that was responsible for initially deploying Hubble. During the almost six-day flight, Shriver and his crew worked to leave the Hubble at an altitude of 330 nautical miles above Earth, and the telescope soon transmitted its first image back to scientists on the ground on May 20, 1990.

“This mission holds some of my fondest memories of space flight,” Shriver said. “It’s easy to get caught up in the technicalities of your job while in space and miss the significance of the work you’re doing. After we landed, I think it hit all of us.”

Bill Reeves, USA Functional Director and Associate Program Manager for Program Integration, oversaw the Hubble deployment mission as NASA lead flight director.

“After the landing of STS-31, I conveyed to my team the significance of what they accomplished,” Reeves said. “I told them that they just put an instrument in orbit that would require astronomy books to be rewritten.”

Despite the success of deployment, problems for Hubble soon began as it was realized that its primary mirror was incorrectly shaped and prohibited the telescope from delivering clear, sharp images. The crew of STS-61 that included Dick Covey as Mission Commander was tasked with repairing the instrument. The mission focused on tuning up the spacecraft and installing two tools that compensated for the primary mirror’s incorrect shape. After five days of work and subsequent checkout, the mission was declared a success as Hubble’s vision was drastically improved.

“At the time, this was the most complex Shuttle mission ever flown,” Covey said. “Success was accomplished through extraordinary planning and preparation, flawless execution by the flight and ground team and a great deal of plain good luck. Bringing the Hubble to its full capabilities and enabling its fantastic scientific discoveries remains one of the most noble and rewarding missions a Space Shuttle crew has flown.”

Since these missions, Hubble has continuously transmitted about 120 gigabytes of science data every week, enough to equal about 3,600 feet of books on a shelf. This data has inspired more than 7,000 scientific articles and continues to help scientists explore deep space. Following the completion of STS-125 and this final servicing mission, the upgrades made to the telescope are expected to keep Hubble operating nominally through 2013.

“It is easy to be awestruck looking at the views we have today from Hubble,” Richmond said. “But it’s even more amazing to think of the sights we’ll see after this servicing mission.”

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