April 24 – Look! Up In The Sky!

Today’s Factismal: The Hubble Space Telescope has made over 1,000,000 observations in the 25 years it has been in orbit.

It is rare to have a failure turn into a success. And it is even rarer to have that success become a beloved part of the scientific community. And yet, that is exactly what happened with the Hubble Space Telescope, or HST for short.

The Hubble Space Telescope in orbit (Image courtesy NASA)

The Hubble Space Telescope in orbit
(Image courtesy NASA)

The HST wasn’t the first telescope in space (that honor belongs to an unnamed telescope flown on a sounding rocket), nor was it the first telescope into orbit (that would be the Explorer 11 satellite, launched in 1962). What it was was the first orbiting space telescope that had a large enough mirror to do a better job than ground-based telescopes and that could be upgraded. Another thing that it was, though this wasn’t widely known at the time, was a prototype for a new series of spy satellites.

An image of galaxies in a small portion of the dark sky. IThe HSAT stared at one spot for nearly five days to make this image. (Image courtesy NASA)

An image of galaxies in a small portion of the dark sky. The HST stared at one spot for nearly five days to make this image.
(Image courtesy NASA)

Astronomers wanted a telescope in space because it would allow them to overcome the jitter and optical distortion caused by the Earth’s atmosphere and because it would allow them to do things that literally cannot be done on Earth, such as looking in one spot for a five days at a time. And NASA wanted to give them one. So together and with a little help from the NRO, they convinced Congress to fund the HST – though Congress denied NASA the funds to test the mirrors (a decision that they would regret).

Even with funding, it took time to build the HST. And by the time that the HST was ready to launch, the Space Shuttle had suffered a major setback and was on hold. What with one thing and another, the telescope that had been proposed in 1974, built in 1979, and ready for launch in 1986, didn’t actually make it into orbit until 1990, some sixteen years after the program began.

An early image from teh HST showing hte

An early image from the HST showing the “astigmatism” problem
(Image courtesy NASA)

But the worst was yet to come. Though the HST was producing good images, they weren’t great. A check of the calibration equipment showed that the mirror had been mis-ground, introducing a type of astigmatism that kept it from giving the best images it could. Instead of showing up as sharp points, the stars were blurry disks. America’s great space telescope was a flop and NASA was the laughing stock of the world.

So NASA sent another mission to the telescope, a mere three years after it had been launched. The astronauts fitted the Hubble with a corrective lens that removed the astigmatism. And the images started flowing out. Hubble brought us close-ups of new stars being born and of the wonders hidden in the “dark” sky. Over the next fifteen years, Hubble met every mission objective and then some.

A barred galaxy as seen by the HST (Image courtesy NASA)

A barred galaxy as seen by the HST
(Image courtesy NASA)

But the world of Earth-bound astronomy had forged ahead in the meantime. We now had telescopes with adaptive optics that could do almost everything that the HST could only with larger mirrors and lower costs. By 2009, the HST had become obsolete and NASA planned to scrap it. However, a letter-writing campaign showed that there was enough public support for one last mission to upgrade the HST and keep it flying for another five years. And so NASA made one last set of adjustments to the turkey that became a star.

Today, the HST is orbiting somewhere overhead, taking pictures of the cosmos and sending them down for us to see, enjoy, and use. If you’d like to help in that last part, then why not join the astronomers at Galaxy Zoo as they classify galaxies using images from the HST?

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