Visible radiation, or light that we see, is the most common type of electromagnetic radiation but many other types of radiation exist depending on wavelength size. Each space telescope uses only a small portion of the electromagnetic spectrum. Hubble, for instance, observes mostly with visible radiation (wavelengths from about 360 to 780 nanometer, or one billionth of a meter), but also uses some ultraviolet (UV) radiation that is slightly shorter in wavelength, and infrared (IR) radiation that is slightly longer.
The types of EM radiation are: radio, microwave, infrared, visible, x ray, and gamma ray. Radio wave radiation has the longest wavelength, with a range from a few millimeters (where one millimeter equals one millionth of a meter) to about 50,000 kilometers (where one kilometer equals one thousand meters). Gamma-ray radiation occurs at wavelengths of 0.01 nanometers or less--the shortest wavelength of all radiation. Of all the many different space telescopes in operation today, each one operates in a specific range within the electromagnetic spectrum.
For example, the Wilkinson Microwave Anisotropy Probe (WMAP) is a NASA satellite that uses microwave radiation to measure the temperature of heat from the Big Bang explosion, the theory of the universe's origin. Microwaves range from 30 centimeters (where one centimeter equals one hundredth of a meter) to about one millimeter in wavelength. In 2003, NASA announced that WMAP had photographed the early universe with first-generation stars that had formed only 200 million years after the Big Bang. WMAP also pinpointed the age of the universe at about 13.7 billion years old.
The Spitzer Space Telescope (SST) is an infrared (IR) radiation observatory that was launched by NASA in August 2003 into a orbit about the Sun. The wavelength of IR radiation ranges from 750 nanometers to one millimeter. In 2005, SST observed radiation from an extrasolar planet, the first direct observation from a planet orbiting a star other than the Sun.
The Galaxy Evolution Explorer (GALEX), launched by NASA in April 2003, makes observations with ultraviolet (UV) radiation (about 400 nanometers to one nanometer in wavelength) to measure star and galaxy formation in the early universe, galactic distances, and star formation rates. In all, GALEX is developing a history of star formation for the first ten billion years of the universe.
X-ray radiation occurs in a wavelength range of ten to 0.01 nanometers. Two telescopes that use x rays include the X-ray Multi-Mirror Newton (XMM-Newton), which was launched by the European Space Agency in December 1999 and is expected to operate until 2010, and the Chandra X-ray Observatory (Chandra), which was launched by NASA in July 1999 and is still functioning nominally.
The Space Shuttle Discovery will fly to Hubble on one of its last missions (sometime after May 2008) to service the ailing telescope. If successful, the Hubble's useful life will be extended to at least 2013. In that year, the James Webb Space Telescope (JWST) is scheduled to be launched as the replacement for Hubble. However, the JWST will observe only in the infrared region of the EM spectrum, not in the visible and ultraviolet parts, like Hubble.
As you can see, Hubble only operates in one small region within the electromagnetic spectrum. Many other telescopes are currently operating at other radiation regions so that many different types of celestial bodies of being observed. Even though Hubble will eventually be decommissioned, many other telescopes are now in use, or will soon be launched into space, to continue scanning the universe--looking with eyes that are specifically sensitive to a particular type of radiation. Hubble has been very important to the advancement of science, but it is just one of many space telescopes. Like people, Hubble will live a useful life but eventually will be replaced by a new generation of space telescopes.