NEW YORK: April 24 marks the 25th anniversary of the launch of the Hubble Space Telescope (HST) aboard a space-shuttle.
Dollar for dollar (NZ$1.6 billion), the HST has delivered more science than any other astronomical instrument.
It is a prime example of our overwhelming desire to find out more about who we are and where we live. The magnificent pictures of near and deep space objects captured by the HST over the last 25 years have awed the public and scientists alike.
The advantages of a telescope in space have long been realised; removed from the atmospheric barrier that disrupts telescope optics, pristine clear images can be captured. Also because the atmosphere strongly absorbs infra-red and ultra-violet light radiation, information from starlight can be gleaned which is unattainable from an Earth based telescope.
In the 1970s construction began on the telescope, a Cassegrain reflector comprising two hyperbolic mirrors. The main mirror was specified to be polished to an accuracy of 10 nanometres, that is, no bumps greater than 0.000001mm high were allowed.
The mirror contract was awarded to Perkins-Elmer Optics who began the challenging task of its fabrication in 1979.
The work was interrupted by several cost disputes which meant NASA had to delay the launch from the originally planned date of 1983 to September 1986. However in January 1986, the Challenger space-shuttle exploded shortly after lift off and all shuttle operations were cancelled until the cause of the accident was established.
The cost of storing the telescope, which involved keeping it powered up in a spotlessly clean room purged with nitrogen gas, was $6 million per month. Shuttle flights resumed in 1988 and the HST mission was rescheduled for a lift off in April 1990.
NASA planned several servicing missions for the telescope. To facilitate access and the logistics involved in these missions, the HST was put into a low-Earth-orbit, about 400 kilometres above the surface.
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