Repair of the Advanced Camera for Surveys
The Advanced Camera for Surveys (ACS) was installed on Hubble during Servicing Mission 3B in 2002, replacing the Faint Object Camera (FOC).
ACS includes three sub-instruments, or channels: the Wide Field Channel (WFC), the High Resolution Channel (HRC), and the Solar Blind Channel (SBC).
In July 2006, an electronics failure in its Low Voltage Power Supply (LVPS) effectively placed the WFC and HRC offline.
The repair of ACS during Servicing Mission 4 restored the WFC by replacing four boards within the existing electronics bay with a single new power supply attached to the outside of the instrument. The new supply effectively bypasses the broken circuit elements. The High Resolution Channel (HRC) was not able to be fixed.
One of the highest priorities of Servicing Mission 4 was the installation of a powerful new instrument, the Wide Field Camera 3 (WFC3), a camera covering wavelengths from the near-ultraviolet to the near-infrared. WFC3 has enormous scientific potential, providing high sensitivity over a wide field of view and with a wide range of wavelength coverage. The capabilities of ACS and WFC3 overlap in some areas; however, each offers some key abilities not provided by the other, and together are wonderfully complementary.ACS has several unique capabilities that are unmatched by WFC3. This includes full-field slitless spectroscopy using a very sensitive red grism, and a coronagraph in the high-resolution channel of the ACS. The latter of these is critical for studying planet formation and evolution around nearby stars
Fact Sheet (PDF)