NASA shut its Hubble 20 years ago today. Know reason here!

The Servicing Mission 3B was actually the fourth visit to Hubble. NASA divided the original Servicing Mission 3 into two parts and conducted 3A in December of 1999 and 3B in 2002 

During SM3B a new science instrument was installed: the Advanced Camera for Surveys (ACS). Several other activities were accomplished as well over a 12-day mission with 5 spacewalks.

(Image credit: NASA)

The PCU controls and distributes electricity from the solar arrays and batteries to other parts of the Hubble telescope. NASA replace the original PCU after 11 years of Hubble's launch that required it to be completely powered down for the first time since its launch in 1990. (Image credit: NASA)

20 years ago NASA replaced Hubble's camera with its Advanced Camera for Surveys (ACS) that provides a wide field of view, superb image quality, and exquisite sensitivity and also has 10 times more discovery power than the camera it replaced. (Image credit: NASA)

Four astronauts trained for five scheduled spacewalks to upgrade and service the Hubble Space Telescope during the STS-109 mission in early 2002. (Image credit: NASA)

Four astronauts trained for five scheduled spacewalks to upgrade and service the Hubble Space Telescope during the STS-109 mission in early 2002.  (Image credit: NASA)