Designed to last at least 15 years, Hubble is providing intriguing new data about black holes, the birth of galaxies, planetary systems around other stars, and, of course, the expansion of the universe.
Astronomers can also get an idea of how the universe evolved. The farther away an object is, the earlier it formed after the Big Bang. That's because the light we see now had to travel the enormous distance between the object and the Earth, and light can only travel 300,000 kilometers per second. As a result, the HST's observations give us snapshots of the universe at different periods in its history. For example, in 1995 Hubble took a series of pictures now known as the Hubble Deep Field. The telescope looked at the same patch of sky for 10 days straight and took long exposures. Scientists discovered a bewildering assortment of at least 1,500 galaxies at various distances and different stages of evolution. It allowed them to test theories about how those galaxies formed.
Like any other mechanical device, though, Hubble needs periodic tune-ups. As a result, the observatory is maintained by a team of hundreds of scientists, engineers, and computer programmers at the Space Telescope Science Institute the Goddard Space Flight Center. The HST also has regular planned servicing missions. NASA sends astronauts up on the Space Shuttle for maintenance every three years, or sooner if required.
The first major servicing mission came just after launch. Hubble's primary mirror was incorrectly shaped during manufacture, so the telescope could not focus all the light from an object to a single sharp point. Instead, it saw a fuzzy halo around objects it observed, and the images it sent to Earth were pretty much useless. Astronauts were sent up on the space shuttle @Endeavour to catch the telescope, haul it into the shuttle's cargo bay, and install two new devices -- similar in function to ordinary eyeglasses -- to correct the problem. The new lens system was called @COSTAR (Corrective Optics Space Telescope Axial Replacement), and it consisted of several small mirrors that would intercept the beam from the flawed mirror, correct for the defect, and relay the corrected beam to the scientific instruments at the focus of the mirror.
