Posted April 24, 2015

Hubble: 25 years of world class engineering

When we celebrate 25 years of Hubble Space Telescope, of course we marvel at thousands of pretty pictures and the solutions they gave us to many astronomical riddles, such as the age of the Universe. But we also have to pay respect to the engineers who made this possible. The Hubble Space telescope was launched exactly 25 years ago on the date of this posting, April 24th. Its history is a long chain of engineering feats without which the thing wouldn't have worked, or even existed.

Take its mirror, 2.4 meter in diameter and polished so finely, if you could blow the thing up to the size of the Atlantic there would be no irregularities on it higher than 10 cm. Unfortunately said mirror was polished with extreme precision in slightly the wrong shape and this was a major engineering fail (the cause of which turned out to be the use of a faulty testing device).

But then again this problem was corrected by another big engineering success: designing, manufacturing and installing corrective optics in the next three years. This gave Hubble its originally specified sharpness - ten times better than the faulty version, which was already better than any ground-based telescope. The story of this repair mission is told in this video from NASA's Jet Propulsion Laboratory. It also reviews Hubble's many astronomical successes:

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Another exciting story is about changing Hubble's power control unit (PCU). When this unit needed to be replaced in 2002, changing it required switching off the telescope entirely. This had never been done before. The next video is about this operation and a very mundane unexpected thing that went wrong after months of painstaking preparations.

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After 25 years, the Hubble telescope is the longest living instrument in orbit. As this article in The Guardian points out, it probably won't be living very much longer. A limiting factor is the lifetime of the on board gyroscopes, which are needed to keep the telescope neatly pointed at its target of the day. The Hubble has six 'gyros.' They have been replaced multiple times as the average life span of a gyroscope is about five years. But now the space shuttles are no longer flying so there will be no more servicing missions.

Engineers have found ways to use not six, but three, two, or even one gyro and still have a working telescope. This means some working gyros can be kept as backups, to be used only when others fail. This way the telescope can be used longer than it otherwise would have been. Quite possibly it can stay afloat until its successor, the James Webb Space Telescope, is launched in 2018. That would be exceeding expectations just once more.

Finally, for those of you who like a party, you can witness one in the video below, live on 24th of A pril itself and presumably on demand thereafter. NASA and ESA celebrate the anniversary with a program full of science and entertainment. In that order.

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Oh yeah, that's right: The pretty pictures and the science they made possible. Look here, for instance.


About Herbert Blankesteijn

Herbert Blankesteijn is a technology journalist from the Netherlands who has written for many prominent Dutch newspapers. He presented and directed television and radio programmes and has 10 books to his name. Herbert is interested in nascent fields such as 3D printing, drones, robotics and the private space business.