Advanced Camera for Surveys (ACS)

The Advanced Camera for Surveys (ACS) is a third-generation Hubble Space Telescope (HST) instrument installed in March 2002 during HST Servicing Mission 3B. The ACS CCD Electronics Box and Low Voltage Power Supply incrementally failed in June 2006 and January 2007, causing the loss of the ACS Wide Field Channel (WFC) and High Resolution Channel (HRC). 

The replacement components (CEB-R and LVPS-R) installed on 16 May 2009 during HST Servicing Mission 4 (SM4), successfully restored the function of the WFC but not that of the HRC. Consequently, only the WFC and the Solar Blind Channel (SBC) are available to observers. 

Credit: https://www.stsci.edu/hst/instrumentation/acs