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The Planetary Society BlogBy Emily LakdawallaHubble Astronauts Boldly Go Where No One has Gone Before!May. 21, 2009 | 10:33 PDT | 17:33 UTC
by Ken Kremer
By Monday afternoon (May 18) the four spacewalking astronauts had finished the last of 5 back to back, grueling and dramatic spacewalks which completely overhauled the Hubble Space Telescope on this fifth and final space shuttle servicing call. Overcoming numerous difficulties and obstacles in real time, they accomplished all objectives by working in pairs of two on alternating days. The key was several years of endless training and back up planning. Hubble is now ready to continue its exploration of the cosmos with a full complement of science instruments. Expect the first "new" images to be released in September. The astronauts have installed two new and powerful state of the art science instruments Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS), six gyroscopes essential for stabilizing the massive 24,000 pound structure, six batteries to power and prolong the telescopes lifetime, replaced a fine guidance sensor (FGS), replaced three thermal blankets which protect the electronics and swapped out the science data computer (SIC & DH) with a refurbished ground spare on which every single operation of the telescope depends. No SIC &DH, No Data, No Science, No Nothing, No Point. The Hubble Space Telescope is the perfect demonstration of why we need both humans and robots working together side by side to explore and exploit space for the scientific, economic and cultural benefit of all mankind. All too often, the public debate on space is framed as man vs. machine when it really should be man & machine, how can we best work together to maximize the bounty. Human hands have touched the Hubble Space Telescope for the last time. Astronauts Andrew Feustel and John Grunsfeld are almost certainly the last human ‘Hubble Huggers' after spending seven hours and two minutes putting the finishing touches on the telescope in the final Hubble spacewalk conducted from a space shuttle airlock.
Along with fellow spacewalkers Mike Massimino and Michael Good, the crew's five spacewalks lasted 36 hours and 56 minutes all together. There have been 23 spacewalks devoted to Hubble, totaling 166 hours and six minutes. Hubble science operations will restart after about four months of check out and calibration activities. During their final spacewalk on Monday May 18, Feustel and Grunsfeld first removed the old nickel hydrogen battery module from Bay 3 on the telescope and then installed a fresh module. Each battery module weighs 460 pounds and contains three batteries each weighing about 125 pounds. Ed Weiler, NASA Associate Administrator for the Science Mission Directorate, told me in an interview that "The batteries on Hubble are all original equipment. They have functioned well but we felt it wise to replace them on this last mission". They were only designed to operate for five years. They also replaced the Fine Guidance Sensor (FGS) 2 with a refurbished and upgraded unit. Hubble has three FGS units which provide pointing information for the spacecraft and also serve as a scientific instrument for determining the precise position and motion of stars, known as astrometry. The FGS system serves as the telescope's pointing control system and has a precision comparable to being able to hold a laser beam focused on a dime 200 miles away, the distance from Washington D.C. to New York City. On Sunday May 17, the 4thEVA of the mission, Astronauts Mike Massimino and Michael Good conducted the sixth longest spacewalk in history for the delicate and intricate task of removing and capturing 111 screws to be able to revive the Hubble Space Telescope's two-dimensional spectroscopy capability. In the 8 hour, 2 minute spacewalk, Massimino and Good repaired the Space Telescope Imaging Spectrograph (STIS) by replacing a power supply board. STIS, installed on the Hubble Space Telescope in 1997, stopped working in August 2004 due to a power supply failure and was in a "safe mode."
Custom designed tools, which I'll detail in an upcoming report, were utilized to remove the screws with a Fastener Capture Place (FCP) in an operation expected to be quite difficult and with no guarantee of success. When a handrail obstructing the path could not be removed due to a stripped screw, Astronaut Mike Massinimo had to apply brute force to carefully rip the handrail off using techniques developed on the fly in real time at the NASA Goddard Spaceflight Center while not damaging the instrument or tearing apart his spacesuit with potentially lethal consequences. This dramatic illustration of human ingenuity occurred three hours into the grueling spacewalk. The astronauts then removed the screws and delicately replaced the dead power supply card. An "aliveness test" conducted shortly thereafter confirmed that the STIS had been restored to life. Further functional tests are ongoing. STIS separates light into its component colors to reveal information about the chemical content, temperature and motion of planets, comets, stars, interstellar gas and galaxies. The information it can provide will help scientists better understand the physical properties of the material universe – putting the physics in astrophysics. During EVA 3 on Sunday, May 17, astronauts Grunsfeld and Feustel ambitious objective was the removal of the Corrective Optics Space Telescope Axial Replacement (COSTAR) , the installation of the new Cosmic Origins Spectrograph COS) and the repair of the Advanced Camera for Surveys (ACS). The swap out of COSTAR for COS proceeded flawlessly in the bay next to ACS. COS is a fourth generation Hubble instrument designed to perform extremely sensitive spectroscopy to probe the large scale structure of the universe and determine how elements needed for life first formed. ACS was installed during the last servicing mission (SM-3B) in 2002 by a crew including Altman, Grunsfeld and Massimino. The camera was Hubble's most popular and widely used until an electrical short caused its three science data observing channels (wide field, high resolution and solar blind) to fail in 2007. The solar blind channel was subsequently restored to operation.
ACS was not designed to be repaired in space. So, the astronaut's difficult task was to restore the remaining two channels by delicately extracting and replacing four blown circuit cards. In a reversal of Murphy's law, the seemingly impossible was accomplished with relative ease using custom designed tools. They succeeded in restoring the wide field camera (WFC) science data channel which was the prime objective of the ACS repair. There had been some pre-launch hope that the repairs might also bring the High Resolution channel (HRC) back to life through a process called "back-powering." However, HRC did not return to operability and was always considered a possible "extra", not the main objective which was WFC. In the upcoming Hubble observing cycle already planned out, WFC claimed 83% of ACS's observing time. The ACS repair effort is considered to be fully successful with the restoration of the WFC. Functional test analysis following the spacewalk repairs confirmed the work to be successful. ACS doubles Hubble's field of view (FOV) and is responsible for many of its most impressive images of deep space. ACS can see in wavelengths from the far ultraviolet to visible light, making it capable of studying some of the earliest events in the universe. This week I presented lectures at two astronomy clubs in central Florida covering the STS-125 mission and the broad reach of NASA's current exploration of the solar system. I was honored to meet the parents of space walking astronaut Andrew Feustel on Tuesday evening and share with them and the large attentive crowd the benefits and excitement of science and space exploration.
I'll report soon on my visits this week to the Atlas V and Delta 4 launch pads used to blast many science payloads into space, including the upcoming lunar LRO/LCROSS mission discussed in my feature here from Monday May 18. Planetary Society volunteer Ken Kremer is reporting for us from the Kennedy Space Center, where he witnessed the launch of Space Shuttle Atlantis to the Hubble Space Telescope on May 11. Kremer is a research scientist and freelance journalist who spends his spare time giving public outreach presentations on behalf of The Planetary Society as a volunteer and NASA's Jet Propulsion Laboratory as a Solar System Ambassador. He also enjoys creating Mars mosaics. Thanks Ken! |
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