The other instruments in the HST are a Faint Object Camera, a High Resolution Spectrograph, a Faint Object Spectrograph and a High Speed Photometer. To improve the images in these instruments NASA arranged to fit one corrective optical system common to them all, known as COSTAR. As COSTAR required some space the astronauts had to take out the least used of the instruments, the High Speed Photometer and replace it with COSTAR, which is in the form of a box about the size of a small refrigerator. In that box have been fitted ten mirrors, twelve DC motors, four movable arms and many sensors. As well as installing W17PC and COSTAR, astronauts in the Space Shuttle Endeavour replaced the solar cell arrays which have been troubled by jitter, and also three gyroscopes which are essential for measuring the telescope motions about its three axes of rotation. The telescope was equipped with three pairs of gyros, but one gyro in each pair had already failed – if one more gyro had failed the telescope would have become inoperable. According to Sky and Telescope, even if there had been no problems with HST’s optics or solar cells, NASA would have sent up a repair team just to replace the gyros.
In 1994 HST sent back images of the Orion Nebula. The images released by NASA depicted the births of planets near newborn stars.
In November 1995 NASA released images of the Eagle Nebula, which confirmed the birth of stars.
In 1996 “Deep Field” images were sent back by the telescope, providing an insight into the history of the universe, dating back more than 10 billion years.
During the second servicing mission in February 1997, scientists updated some of Hubble’s instruments and in October, NASA extended Hubble’s operations from 2005 to 2010.
In 1999 HST shut down when a fourth gyroscope on board the telescope failed. Servicing Mission 3A (STS-103) was launched in December.
In 2002 Servicing Mission 3B was launched for the installation of the NICMOS Cooling System (NCS).
In 2003 HST viewed the core of one of the nearest globular star clusters, called NGC 6397.
The next servicing mission was cancelled after the Shuttle Columbia accident and the NASA Administrator decided to cancel all further HST on-orbit servicing, including Servicing Mission 4, a decision based on the risks to the Shuttle astronauts associated with future HST servicing missions.
The depressed astronaut