Advanced Camera For Surveys

The Advanced Camera for Surveys (ACS) is a third generation axial instrument aboard the Hubble Space Telescope (HST). The initial design and scientific capabilities of ACS were defined by a team based at Johns Hopkins University. ACS was assembled and tested extensively at Ball Aerospace & Technologies Corp. and the Goddard Space Flight Center and underwent a final flight-ready verification at the Kennedy Space Center before integration in the cargo bay of the Columbia orbiter. It was launched on March 1, 2002 as part of Servicing Mission 3B (STS-109) and installed in HST on March 7, replacing the Faint Object Camera (FOC), the last original instrument.

ACS is a highly versatile instrument that became the primary imaging instrument aboard HST. It offered several important advantages over other HST instruments: three independent, high-resolution channels covering the ultraviolet to the near-infrared regions of the spectrum, a large detector area and quantum efficiency, resulting in an increase in HST's discovery efficiency by a factor of ten, a rich complement of filters, and coronagraphic, polarimetric, and grism capabilities. The observations undertaken with ACS provided astronomers with a view of the Universe with uniquely high sensitivity, as exemplified by the Hubble Ultra Deep Field, and encompass a wide range of astronomical phenomena, from comets and planets in our Solar System to the most distant quasars known.

On 25 June 2006 ACS went out of action due to electronic failure. It was powered up successfully after switching to its redundant (Side-2) set of electronics. The instrument sub-systems, including the CCD detectors, all seemed to be working well and after some engineering tests, ACS resumed science operations on July 4, 2006. On 23 September 2006, the ACS again failed, though by 9 October the problem had been diagnosed and resolved. On January 27, 2007 the ACS failed due to a short circuit in its backup power supply. The instrument's Solar Blind Channel (SBC) was returned to operation on 19 February 2007 using the side-1 electronics. The Wide Field Channel (WFC) was returned to service by STS-125 in May 2009. The High Resolution Channel (HRC), however, remains offline.