| The Primary Mirror
Final Preparations
Shortly after this image was taken, the Hubble telescope was shipped to Kennedy Space Center and
loaded into the cargo bay of the shuttle Discovery. The telescope measures 13.1 m (43.5 ft) in
length, 4.27 m (14.0 ft) in diameter, and weighs 11,000 kg (25,500 lb). Note the size of the workers
standing near the base of the telescope. Also note the orange cylinder attached to the telescope; this
is one of the two solar arrays that provide power to Hubble's batteries. Once unrolled in orbit, each
array will be over 12 m (40 ft) long and provide 1200 watts of power.
Launch
The Hubble Space Telescope was first scheduled for launch in 1986. But due the tragic loss of the
shuttle Challenger in late January of that year, the launch was delayed four years. In April 1990, the
Hubble telescope was lifted into orbit aboard the shuttle Discovery.
Deployment
Crew members aboard the shuttle Discovery shot this photograph April 25, 1990. It shows the
deployment of the Hubble Space Telescope from the payload bay, guided by the shuttle's robotic
arm. The giant spaceborne telescope was put into orbit to collect information about a large variety of
astronomical objects, from neighboring planets and stars to the most distant galaxies and quasars. |
The primary mirror of the Hubble telescope measures 2.4 m (8 ft) in diameter and weighs about 826
kg (1820 lbs). It is constructed of ultra-low expansion silica glass and coated with a thinlayer of pure
aluminum to reflect visible light. A thinner layer of magnesium fluoride is layered over the aluminum to
prevent oxidation and to reflect ultraviolet light.
Pointing the HST
This artist's concept is a view from near the Hubble telescope, looking back at the shuttle Discovery
shortly after deployment. The telescope's tracking system is very accurate. The pointing system
comprises reaction wheels that actually move the telescope, gyros that report its position, star
trackers that provide reference points, and the onboard computer that controls the pointing process.
Relaying Data
The path by which Hubble data arrive on Earth is outlined here. Images received by the telescope are
converted into digital code and radioed to Earth using high-gain antennas at a rate of one million bits
per second. Once the digital code is received by ground stations, it is converted into photographs or
spectrograph readings for use by scientists.