Chapter 1: Introduction

The Advanced Camera for Surveys (ACS), a third-generation instrument, was installed in the Hubble Space Telescope (HST) during Servicing Mission 3B, on March 7, 2002. Its primary purpose was to increase HST imaging discovery efficiency by a factor of 10, with a combination of detector area and quantum efficiency that surpassed previous instruments.

ACS has three independent channels that have provided wide field, high resolution, and ultraviolet imaging capabilities respectively, using a broad assortment of filters designed to address a large range of scientific goals. In addition, coronagraphic, grism spectroscopy, and polarimetric (imaging and grism spectroscopic) capabilities have made the ACS a versatile and powerful instrument.

In May 2009, Servicing Mission 4 (SM4) successfully restored the ACS Wide Field Channel (WFC) to regular service after its failure in January 2007. Unfortunately, the ACS High Resolution Channel (HRC) was not restored to operation during SM4, so it cannot be proposed for new observations. Nevertheless, this handbook retains descriptions of the HRC to support analysis of archived observations. The ACS Solar Blind Channel (SBC) was unaffected by the January 2007 failure of WFC and HRC. The SBC has remained in steady operation, and was not serviced during SM4. It remains available for new observations.

In Cycle 33, ACS/WFC will be offered as shared-risk and may receive minimal calibration and support. Users are encouraged to consult the Late Breaking News section of the Cycle 33 Call for Proposals, the Operations Paradigm Change Review webpage, and the ACS website for the latest news regarding ACS operation and support.

The ACS Instrument Handbook, which is maintained by the ACS Team at STScI, describes the instrument properties, performance, operations, and calibration. It is the basic technical reference manual for the instrument, and should be used with other documents (listed in Table 1.1) for writing Phase I proposals, detailed Phase II programs, and for data analysis. (See Figure 1.1). This handbook is revised before the Call for Proposals for each new HST Cycle is released, and all interim updates are recorded in the Change Log.

Table 1.1: Useful documents