Providing invaluable discoveries to space exploration, the Hubble Space Telescope is a remarkable orbiting observatory composed of four instruments. The Wide Field Planetary Camera 2, Space Telescope Image Spectrograph, Near Infrared Camera Multi-Object Spectrograph, and the Faint Object Camera which gather measurements and capture images of astronomical objects from distant parts of the universe.
Introduction
Imagine standing on top of the Space Needle and being able to read the date on a penny in Tokyo. Although it would seem to be impossible, this is just what the Hubble Space Telescope is capable of. While the popular media has made widely known the problems encountered by the Hubble Space Telescope, few are aware of the invaluable discoveries the telescope and its various instrumentation have made.
The Hubble Telescope is a reflecting telescope. As seen in Figure 1, the incoming light is reflected off the primary mirror onto a secondary mirror. The light from the secondary mirror is then focused onto four instruments at the focal plane. These four instruments, the Wide Field Planetary Camera 2 (WFPC2), Space Telescope Image Spectrograph (STIS), Near Infrared Camera Multi-Object Spectrograph (NICMOS), and the Faint Object Camera (FOC) gather measurement and capture images of astronomical objects. All of these instruments are smaller than 30 centimeters in diameter, thus are relatively easy to replace if they become outdated or break.
The primary mirror is nearly 2.5 meters in diameter and weighs 830 kilograms on Earth. The primary mirror is an engineering marvel: it is the largest object in history to be built with such precision. The glass used on the mirror is designed not to warp and is covered by a thin layer of aluminum about 76 nanometers thick. The mirror was built on a computer-run machine that was specifically designed for the purpose of constructing the primary mirror (Hubble Space Telescope: Design and Development). Soon after Hubble's launch, astronomers saw that the pictures taken by Hubble were blurry and distorted.
The secondary mirror is similarly constructed with the same non-warping glass. This mirror possesses the same aluminum coating along with a special, additional coating 25 nanometers thick. This supplementary coating enables the mirror to reflect ultraviolet light: light with wavelengths shorter than those of visible light (Hubble Space Telescope: Design and Development). There is a necessity to reflect ultraviolet light because certain galaxies are only visible in the ultraviolet spectrum.
The Wide Field Planetary Camera 2, WFPC2, was developed by the Jet Propulsion Laboratory and is capable of photographing images though a selection of 48 color filters. The WFPC2 consists of an L-shaped trio of wide-field sensors and a single smaller higher resolution planetary camera.
