The Hubble Space Telescope is getting one final repair before it's mission will be ended.
"Periodic maintenance visits by astronauts have been the lifeblood of the Hubble telescope ever since it was launched in 1990 from the shuttle. Floating above the murky atmosphere, the telescope was designed to see the stars with peerless precision. It was hailed as the greatest advance in astronomy since Galileo, until astronomers discovered shortly after its launching that it couldn’t be focused because its mirror had been exquisitely polished to the wrong shape."
Ever since 1993 when astronauts refitted the Hubble Space Telescope with a new lens that allowed man's clearest vision into the depths of space there have been three more missions that have retrofitted Hubble with updated parts to ensure the improvement of the space telescope's capabilities.
"On the Atlantis mission that began Monday, astronauts for the first time will be opening instruments and replacing circuit boards in space. The last maintenance mission was in March 2002.
"Virtually every important part of the telescope, except the warped mirror itself, has been replaced over the last 19 years. The result, astronomers say, is that the telescope today is 100 times as powerful as the one they thought they were putting in orbit back in 1990.
"In 2003, astronomers used Hubble to record the deepest optical and infrared images ever made, showing galaxies forming in the primordial mist only 800 million years after the Big Bang. Before it conked out due to electrical problems in 2007, Hubble’s Advanced Camera for Surveys took one of the first ever images of a planet around another star, a dot orbiting Fomalhaut, and it had become the foremost instrument on or near the Earth for investigating dark energy, the strange effect that is accelerating the expansion of the universe.
"Another instrument, the Space Telescope Imaging Spectrograph, or STIS, made the first identification of ingredients in the atmosphere of a planet around another star.
"If all goes well, in five spacewalks starting Thursday morning, the crew members will revamp and refresh the telescope, which has dazzled the public and the science community with its iconic cosmic postcards. Then they will say goodbye on behalf of humanity forever. Sometime in the middle of the next decade, the Hubble will run out of juice, and it will eventually be crashed into the ocean.
The mission to repair the Hubble took on a new meaning "last fall, when a router that controls all the telescope’s instruments and data failed, shutting Hubble down. Engineers on the ground resuscitated the router by activating a backup electrical channel on the telescope, but rather than send astronauts all the way to space in order to leave the telescope with no further backup should the other side of the router fail, NASA postponed the already long-delayed mission until a replacement router could be readied."
"The problematic router is scheduled to be replaced during the first spacewalk along with the Wide-Field Planetary Camera 2, which has been on the telescope since 1993 and is currently the only operating instrument on Hubble. In its place will be the new Wide-Field Camera 3.
"On the second day the astronauts will install the new Cosmic Origins Spectrograph in place of Hubble’s original corrective lenses, which are no longer needed. The spectrograph is designed to investigate an invisible “cosmic web” of dark matter and primordial gas that is thought to stretch like tendrils through space connecting galaxies and in which most of the atoms in the universe are thought to reside.
"More dicey and uncertain are the plans on the third and fourth days to attempt to repair the advanced camera and the imaging spectrograph, partly because these instruments were not designed to be opened in space and partly because the engineers, especially in the case of the camera, have had to do instrument forensics from 350 miles away and don’t know for sure what went wrong inside of them.
The payoff from successfully repairing the Hubble would be that the space telescope "would return as much data in the next six months as it did in the first eight years of its life."
The flight comes as NASA is once again at a crossroads. The agency lacks a permanent administrator; Christopher Scolese has been acting administrator since Michael D. Griffin stepped down in January, and the White House is said to have been having trouble finding a candidate who can pass various forms of muster.
"The agency has begun laying off workers as part of the decision to retire the shuttles next year. Last week, President Obama ordered a review of the agency’s long-heralded plan to return humans to the Moon and of the Constellation spacecraft that are to succeed the shuttle.
"So if it is the beginning of the last act for the Hubble, the flight Monday also marks the beginning of the end for the space shuttle, whose greatest legacy might very well be the role it played in the repair and maintenance of the Hubble, what Commander Altman recently called “an incredible example of how humans and machines can work together.”
Dr. Grunsfeld, who has earned the sobriquet of “Hubble repairman” for his previous exploits in space with the telescope, said: “The only reason Hubble works is because we have a space shuttle. And of all things we do, I think Hubble is probably the best thing we use it for.”
"If all goes completely to plan on Hubble Servicing Mission 4, the orbiting observatory will be reborn as the most productive telescope in history, with even greater powers to probe the Universe's deep history and help cosmologists make sense of one of their biggest problems - "dark energy".
"Hubble was also at the forefront of unveiling the existence of dark energy: the name coined for a mysterious and pervasive force which appears to be inflating the Universe at an ever increasing speed.
"Cosmologists had assumed that for most of the 14-odd billion years since the Big Bang, the Universe's expansion had been slowing down.
"In the mid-1990s Hubble - along with the ground-based Keck telescope in Hawaii - made the key measurements on distant exploding stars, supernovae, which showed otherwise.
"It was the most shocking cosmological revelation since the 1920s when astronomer Edwin Hubble discovered that the Universe was expanding.
"The mystery of dark energy may be a little clearer, if not solved, with the new camera the astronauts are going to install.
"This is the Wide Field Camera 3 - an instrument with the dimensions of a street telephone box.
"Like Hubble's existing, but currently dead, Advanced Camera for Surveys, the WFC-3 has a sensitive detector which can form images of very distant galaxies in the same wavelengths of light our eyes perceive.
"These objects are so faraway, their starlight started its journey across the cosmos just under 13 billion years ago. The camera catches them as they were at that early time - though only just. They are very faint.
"But the new Wide Field Camera will make its great advance by virtue of a second detector chip, sensitive to wavelengths of light in the infrared part of the spectrum.
"This will let astronomers use Hubble to see deeper with more detail. This is because visible light from stars that has travelled from very far away in the cosmos has been "stretched" en route as the Universe itself has expanded.
"Its wavelengths are widened - or "red-shifted" - in proportion to the distance it has crossed. So if a galaxy or supernova is well beyond 13 billion years away, all of its light reaches us as infra-red radiation.
"According to Steven Beckwith - professor of astronomy at University of California, Berkeley, and former director of the Space Telescope Science Institute - the new Wide Field Camera should help to characterise the nature of dark energy.
"Thanks to its infrared vision, it will be able to pick up large numbers of supernovae too distant and red-shifted for other instruments.
"Studies of the light from each exploding star will allow astronomers to get a better idea of how fast or slowly the Universe was expanding at different times in its early history. Plotting this is vital in the challenge of figuring out what dark energy is.
"Theorists have come up with many possibilities but none fit with our current understanding of physics.
Steven Beckwith said: "I think the new instrument will let us zero on those few ideas that could be right and get rid a lot of bad ideas. But I don't think it will tell us the answer."
"The problem of dark energy aside, the new Wide Field Camera will give us a deeper view into the early Universe in general: the epoch when the first galaxies and stars came into being.
"To date Hubble has seen back to 900 million years after the Big Bang. Steven Beckwith says that with WFC-3, the telescope's view will extend to 400 million years after creation.
"It is almost anyone's guess what astronomers will see, although theory would suggest the earliest mini-galaxies of stars should have formed by then.
"They would be untidy ill-formed blobs lacking the size and regular shapes of "modern day" galaxies like our own Milky Way.
"They would be populated by stars much more massive and burning more fiercely than our Sun.
"This is how astronomers picture the first galaxies and stars that formed out of dark gaseous debris created in the Big Bang.
"Exactly when that happened and starlight began to flood across the Universe is unknown. Steven Beckwith speculates that Hubble's new camera might pin-point the "Cosmic Dawn", if it broke more than half a billion years after the Big Bang.
The Hubble Space Telescope's imagery of a deep space field full of stars' galaxies and nebula.
"The other new instrument for Hubble is the Cosmic Origins Spectrograph (COS). COS is also the size of a phone booth.
"It does not make spectacular images but its kind of work is just as important for astronomers. Spectrographs make measurements of the motions, temperatures and chemical make-up of galaxies, stars and planets.
"What distinguishes COS is its great sensitivity to very faint objects and that it works at the ultraviolet end of the spectrum - a "flavour" of light radiation largely screened out by the Earth's atmosphere.
"COS team member Mike Shull at the University of Colorado, Boulder, describes the instrument as "a very fancy prism which takes the light from Hubble's mirror and spreads it out into its component colours."
"Every element whether it is helium, oxygen or carbon has a unique set of fingerprints that get imprinted on the light."
"The imprinting of particular wavelengths at tell-tale intensities reveals which chemical elements are present in distant planets, stars, galaxies or even the great expanses of space between galaxies.
"In the past 20 years, astronomers have found that galaxies are not uniformly distributed across the sky.
"Galaxies are concentrated along a filamentary network called the Cosmic Web. Between these vast films and fingers of galaxies are even more immense voids of very nearly empty darkness. But there is something in them - a vanishingly tenuous amount of gas."
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