Hubble Space Telescope
The Hubble space telescope is a telescope located at the outer edges of Earth's atmosphere, about 600 kilometers above the ground, orbiting the Earth every 100 minutes. It was employed in April 1990 as a joint project of NASA and ESA and has since lead to several discoveries in astronomy.
Working outside the atmosphere has advantages because the atmosphere obscures images and filters out electromagnetic radiation at certain wavelengths, mainly in the infrared.
The unit weighs about 11,000 kilograms, is 13.2 meters long, has a maximal diameter of 4.2 meters and cost $ 2 billion (2 × 109 dollars).
The telescope is a reflector with two mirrors; the main mirror has a diameter of about 2.4 meters. It has various spectrometers and three cameras: one for faint objects in a small field, one wide field camera for planetary pictures, and one infrared camera.
It uses two solar panels to generate electricity, which is mainly needed to power the cameras and the four large flywheels used to orient and stabilize the telescope. The telescope's infrared camera and multi object spectrometer need to be cooled down to minus 180 degrees Celcius for operation.
The telescope was launched by space shuttle, and has been revisited several times in order to correct malfunctions and install new equipment. Because of atmospheric drag, the telescope slowly loses height (and gains speed) over time, and the space shuttle pulls it back to a higher orbit every time it visits.