Instrument Overview

3-D, labeled drawing of ACS (122kb JPEG)

The Advanced Camera for Surveys (ACS) is a third-generation instrument to be installed on the Hubble Space Telescope (HST) during the Third Servicing Mission (SM 3B), currently scheduled for launch in February 2002. By design the ACS will advance HST's capability for surveys and discovery by about a factor of ten (defined as the quantum efficiency (QE) × the field of view (FOV) at 8000 Å). It will make deep imaging surveys of clusters of galaxies and study the environments of galactic nuclei and the formation of planetary systems. The ACS features three cameras to provide imaging coverage from 120 to 1000 nanometers.

Wide Field Camera

The Wide Field Camera (WFC) will be a high throughput, wide field, optical and near-infrared (I band) camera.

This channel will be optimized for surveys in the near-infrared to search for galaxies and clusters of galaxies in the early universe.

350 - 1050 nanometer spectral response
202" × 202" field of view
0.049" pixel size
2 butted 2048 × 4096, 15 µm/pixel CCD detectors
45% throughput at 700 nanometers (including the HST optical telescope assembly (OTA) )
half critically sampled at 500 nanometers
three mirror optical design (overcoated silver)

High Resolution Channel

The High Resolution Camera (HRC) is designed for high angular resolution imaging and coronography. The HRC optical path will include a coronagraph which will improve the HST contrast near bright objects by about a factor of ten.

This channel will be used for diffraction-limited studies of the light in the centers of galaxies with massive black holes, as well as ordinary galaxies, star clusters, and gaseous nebulae. HRC/SBC optical path

200 - 1050 nanometer spectral response
29.1" × 26.1" field of view
0.028" × 0.025" pixel size
1024 × 1024, 21 µm/pixel, near UV-enhanced CCD detector
25% throughput at 600 nanometers
critically sampled at 500 nanometers
three mirror optical design (MgF₂ on Aluminum)

Solar Blind Camera

The third camera is a far-ultraviolet, Solar-Blind Camera (SBC) that has a relatively high throughput and intended primarily for faint object and extended object imaging.

This channel will be used to find hot stars, quasars, and to study aurora on Jupiter.

115 - 180 nanometer spectral response
34.59" × 30.8" field of view
0.033" × 0.030" pixel size
1024 × 1024, Csl 25 µm/pixel MAMA detector (STIS spare)
6% throughput at 121.6 nanometers
two mirror optical design (MgF₂ on Aluminum)

Filter Set

"The primary objective of the ACS filter set is to provide a comprehensive set of broadband filters appropriate for photometric and survey imaging programs, narrowband imaging over a wide range of redshifts, and a low dispersion spectroscopic survey capability. The WFC and HRC filter complement comprises seventeen bandpass filters (thirteen of which are spectrally compatible with both HRC and WFC), five linear ramp filters, a grism, a near-UV prism and two sets of polarizers - one optimized for the visible and the other for the near-UV. The SBC filter complement comprises six bandpass filters and two dispersing elements." ₁

Sloan Digital Sky Survey g,r,i,z filters included

Coronagraph

The coronagraph will have two high-contrast options. These options will be used for the observation of quasar host galaxies, circum-nuclear regions in active galactic nuclei, stellar disks and outflows, protostellar disks and jets, and some planetary observations such as the Io torus. They can also be used in searches for substellar companions to nearby stars.

For use with the High Resolution Channel (HRC)
1.8 and 3.0 arcsec diameter occulting spots

References

Clampin, M., Boffi, F., Cox, C., Hartig, G. Jedrzejewski, R., Mutchler, M., and Stiavelli, M. 1998, Advanced Camera for Surveys Instrument Mini-Handbook
Ford, H.C. and the ACS Science Team 1998, The HST Advanced Camera for Surveys, in Space Telescopes and Instruments V, eds. P.Y. Bely and J.B. Breckinridge, Proc. SPIE, Vol. 3356, 234. Abstract (html), 15-page paper (PDF, .3 MiB)