October: Last Visit to the Hubble Space Telescope

October 2008

Last Visit to the Hubble Space Telescope

By Calvin L. Chrisman

8x10.aiPeople all over the world have been thrilled by the magnificent images of our solar system and the universe sent back by the Hubble Space Telescope since its launch in 1990. If all goes as planned, October will mark the fourth and final servicing mission to Hubble. It will be made by astronauts flying the space shuttle Atlantis. This mission was long planned, but was canceled after the tragic loss of the shuttle Columbia and its crew in 2003. After much public outcry, the mission was reinstated in 2006 and will be flown with shuttle Endeavour ready as back-up should problems develop. (The astronauts cannot use the International Space Station as a refuge because of their differing orbits).

Most are aware of the initial problems with the HST’s primary mirror, which was ground (very) slightly out of tolerance, making it difficult to take scientifically accurate measurements with the instrument. The first servicing mission took out one camera on the HST and used that space to add something called COSTAR, which effectively added “spectacles” to correct the telescope’s vision. The surprising thing today is that no cameras or other instruments on Hubble rely on COSTAR. As new instruments have been added in subsequent servicing missions, they have been designed with the slightly flawed mirror in mind. The current repair mission will remove COSTAR and replace it with a spectrograph which will study the formation of galaxies and large scale structure in the universe. The five day mission will add other upgraded cameras and sensors; will replace all batteries and gyroscopes; and will upgrade other electronics on the satellite. When Atlantis departs, the Hubble Space Telescope will be in better shape than it has ever been leading to more exciting science and more breathtaking pictures. It should be able to function in orbit for at least another five years and perhaps can go for as long as ten.

Last month, we talked about watching the International Space Station pass over Black Mountain. If skies are clear, you should have the same opportunity to view the space shuttle and the HST. The ISS is usually quite bright while the Hubble is dimmer at third or fourth magnitude. With Atlantis docked to it, the combined spacecraft will be brighter and more easily visible. To find out when you can view a pass, go to the Heavens Above website (http://www.heavens-above.com). Just type in your zip code and click on the HST link. As of this writing, the launch of the mission is scheduled for the evening of October 14th. This can change, but you can track the launch by going to the NASA website, Spaceflight Now (http://www.spaceflightnow.com). Give it a try and be sure to wave at the astronauts as they fly overhead.

Clear Skies!

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