The main Hubble components are:
Mirrors:
Hubble's two mirrors were ground so that they do not deviate from a perfect curve by more than 1/800,000th of an inch. If Hubble's primary mirror were scaled up to the diameter of the Earth, the biggest bump would be only six inches tall.
Primary Mirror Diameter: 94.5 in (2.4 m)
Primary Mirror Weight: 1,825 lb (828 kg)
Secondary Mirror Diameter: 12 in (0.3 m)
Secondary Mirror Weight: 27.4 lb (12.3 kg)
Solar arrays.
Flanking the telescope's tube are two thin, blue solar arrays. Each wing-like array has a solar cell "blanket" that converts the Sun's energy into 2,800 watts of electricity. The solar arrays convert sunlight directly into electricity to run the telescope's scientific instruments, computers and radio transmitters.
The solar arrays are designed for replacement by visiting astronauts. They can be folded for shuttle trips to and from Hubble.
Exterior body.
Designers of the Hubble Space Telescope had to take into account the conditions in which it was to operate. Hubble would be subject to the rigors of zero gravity and temperature extremes — fluctuations of more than 100 degrees Fahrenheit during each trip around Earth.
Hubble's optical system is held together by a truss (supporting "skeleton") measuring 210 in (5.3 m) in length and 115 in (2.9 m) in diameter. The 252 lb (114 kg) truss is made of graphite epoxy — the same material used in many golf clubs, tennis racquets and bicycles. Graphite epoxy is a stiff, strong, and lightweight material that resists expanding and contracting in extremes of temperature.
Pointing instruments.
Gyroscopes.
Hubble's pointing assistants, always face the same direction, like the needle of a compass. They sense the telescope's angular motion and provide a short-term reference point to help Hubble zero in on its target.
Reaction wheels.
These are Hubble's "steering" system. The reaction wheels spin one way, and Hubble spins the other. Flight software commands the reaction wheels to spin, accelerating or decelerating as needed to rotate the telescope toward a new target.
Fine guidance system.
These are Hubble's targeting devices. They aim the telescope by locking onto "guide stars" and measuring the position of the telescope relative to the target. The sensors provide the precise reference point from which the telescope can begin repositioning.
Science instruments.
Wide field & planetary camera.
The Wide Field/Planetary Camera (WFPC) (pronounced as wiffpick) was a camera installed on the Hubble Space Telescope until December 1993. This first WFPC consisted of two separate cameras, each comprising 4 800x800 pixel Texas Instruments CCDs arranged to cover a contiguous field of view. The Wide Field camera had a 0.1 arcsecond pixel scale and was intended for the panoramic observations of faint sources at the cost of angular resolution. The Planetary Camera had a 0.043 arcsecond pixel scale and was intended for high-resolution observations. Selection between the two cameras was done with a four-facetted pyramid that rotated by 45 degrees.
As part of the corrective service mission (STS-61 in December 1993) the WFPC was swapped out for a replacement version. The Wide Field and Planetary Camera 2 improved on its predecessor and incorporated corrective optics needed to overcome the main mirror defect. To avoid potential confusion, the WFPC is now most commonly referred to as WFPC1.
On its return to Earth, the WFPC was disassembled and parts of it were used in Wide Field Camera 3, which was installed in Hubble on May 14, 2009 as part of Servicing Mission 4, replacing WFPC2.
Cosmic Spectograph.
The Goddard High Resolution Spectrograph (GHRS or HRS) was a spectrograph installed on the Hubble Space Telescope. It was replaced by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) in 1997.
High speed photometer.
The High Speed Photometer (HSP) was a scientific instrument installed on the Hubble Space Telescope. The HSP was designed to measure the brightness and polarity of rapidly varying celestial objects. It could observe in ultraviolet, visible light, and near infrared at a rate of one measurement per 10 microseconds. The design was novel in that despite being able to view through a variety of filters and apertures, it had no moving parts.
The HSP was one of the instruments on Hubble at launch. Its primary mission was compromised by the optical problems with the telescope, although some projects were still successful. During the first servicing mission, in December 1993, it was replaced by the Corrective Optics Space Telescope Axial Replacement (COSTAR), which corrected the optical problem for the remaining instruments.
Faint object camera.
The Faint Object Camera (FOC) was a camera installed on the Hubble Space Telescope from launch in 1990 until 2002. It was replaced by the Advanced Camera for Surveys.
The camera was built by Dornier GmbH and was funded by the European Space Agency. The unit actually consists of two complete and independent camera systems designed to provide extremely high resolution, exceeding 0.05 arcseconds. It is designed to view very faint UV light from 115 to 650 nanometers in wavelength.
The camera was designed to operate at low, medium, or high resolution.
Advanced camera for surveys.
The Advanced Camera for Surveys (ACS) is a third generation axial instrument aboard the Hubble Space Telescope (HST). ACS is a highly versatile instrument that became the primary imaging instrument aboard HST. It offered several important advantages over other HST instruments: three independent, high-resolution channels covering the ultraviolet to the near-infrared regions of the spectrum, a large detector area and quantum efficiency, resulting in an increase in HST's discovery efficiency by a factor of ten, a rich complement of filters, and coronagraphic, polarimetric, and grism capabilities. The observations undertaken with ACS provided astronomers with a view of the Universe with uniquely high sensitivity, as exemplified by the Hubble Ultra Deep Field, and encompass a wide range of astronomical phenomena, from comets and planets in our Solar System to the most distant quasars known.
Faint object spectograph.
The Faint Object Spectrograph (FOS) was a spectrograph installed on the Hubble Space Telescope. It was replaced by the Space Telescope Imaging Spectrograph in 1997, and is now on display in the National Air and Space Museum in Washington DC.
Space telescope imaging spectograph.
The Space Telescope Imaging Spectrograph (STIS) is a spectrograph, also with a camera mode, installed on the Hubble Space Telescope. It operated continuously from 1997 until a power supply failure in 2004. After repairs, it began operating again in 2009. The spectrograph has made many important observations, including the first spectrum of the atmosphere of an extrasolar planet, HD 209458b.
The STIS was installed on Hubble in 1997 during its second servicing mission (STS-82) by Mark Lee and Steven Smith, replacing the High Resolution Spectrograph and the Faint Object Spectrograph. It was designed to operate for five years. On August 3, 2004 an electronic failure rendered STIS inoperable, ending its use 2 years beyond its predicted lifespan. In order to bring it back to operational status, the instrument was repaired by space shuttle astronauts during STS-125, Servicing Mission 4, launched on May 11, 2009. The STIS has three 1024×1024 detector arrays. The first is a charge-coupled device with a 52×52 arc-second field of view, covering the visible and near-infrared spectrum from 200 nm to 1030 nm. The other two detectors are Multi-Anode Multichannel Arrays, each with a 25×25 arc-second field of view. One is Cs2Te, and covers the near-UV between 160 nm and 310 nm. The other is CsI and covers the far-UV between 115 nm and 170 nm.
Fine guidance systems.
Two of the sensors point the telescope at an astronomical target and then hold that target in a scientific instrument's field of view. The third sensor is available to perform scientific observations.
The sensors aim the telescope by locking onto "guide stars" and measure the position of the telescope relative to the object being viewed. Adjustments based on these constant, minute measurements keep Hubble pointed precisely in the right direction.
Corrective optics (COSTAR).
The Corrective Optics Space Telescope Axial Replacement (COSTAR), removed from Hubble during Servicing Mission 4 in 2009, was an ingenious device created to solve a famous Hubble Space Telescope problem. By placing small and carefully designed mirrors in front of the original Hubble instruments, COSTAR --installed during the 1993 First Servicing Mission -- successfully improved their vision to their original design goals.
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