Advanced Camera for Surveys

Advanced Camera for Surveys
Name	Advanced Camera for Surveys
Organization	Space Telescope Science Institute / NASA
Launch date	March 1, 2002
Telescope	Hubble Space Telescope
Instruments	Wide Field Channel; High Resolution Channel; Solar Blind Channel
Wavelength	Ultraviolet, visible, near-infrared

Advanced Camera for Surveys The Advanced Camera for Surveys (ACS) is a third-generation imaging instrument installed on the Hubble Space Telescope during STS-109 by the Space Shuttle Columbia crew led by Scott D. Altman and Kenneth D. Bowersox. It was developed by a collaboration including Ball Aerospace, the Goddard Space Flight Center, and the Space Telescope Science Institute with funding from NASA and contributions from ESA. ACS expanded Hubble's capabilities in ultraviolet, visible, and near-infrared imaging, enabling surveys such as the Great Observatories Origins Deep Survey and the Hubble Ultra Deep Field that informed studies tied to Comet Shoemaker–Levy 9 research and cosmological programs influenced by results from the Wilkinson Microwave Anisotropy Probe.

Overview and mission

ACS was designed to provide wide-field and high-resolution imaging to support programs associated with the Hubble Space Telescope mission planning, the Hubble Deep Field, and large Treasury programs such as the COSMOS survey and the GOODS project. The instrument's mission objectives linked to studies of Type Ia supernovae in campaigns related to the Supernova Cosmology Project and the High-Z Supernova Search Team, investigations of galaxy evolution in the context of Lambda-CDM cosmology and comparisons to results from the Sloan Digital Sky Survey. Operational goals were coordinated by the Space Telescope Science Institute and grounded in programmatic directives from NASA and international partners such as the European Space Agency.

Instrument design and components

ACS comprised three principal channels: the Wide Field Channel (WFC), the High Resolution Channel (HRC), and the Solar Blind Channel (SBC). The WFC architecture used a mosaic of charge-coupled devices supplied by contractors linked to Ball Aerospace and readout electronics designed with heritage from Wide Field and Planetary Camera 2 and Near Infrared Camera and Multi-Object Spectrometer. The HRC provided fine-sampled imaging for targets comparable to observations by WFPC2 and complementary to spectroscopic follow-up from Space Telescope Imaging Spectrograph and instruments on Keck Observatory. The SBC, a far-ultraviolet detector, enabled observations relevant to programs linked to Galaxy Evolution Explorer and ultraviolet insights connected to International Ultraviolet Explorer legacy work. Optical elements included filter wheels with bandpasses used in programs referencing calibration standards such as observations of BD+17°4708 and comparison stars from catalogs maintained by the European Southern Observatory and the United States Naval Observatory.

Science objectives and key discoveries

ACS enabled deep, wide-field surveys instrumental to measurements of galaxy morphology, large-scale structure, and gravitational lensing studies connected to analyses from the Sloan Digital Sky Survey and simulations by groups associated with Millennium Simulation. Key ACS results included contributions to the discovery and characterization of high-redshift galaxies in the Hubble Ultra Deep Field, constraints on dark energy parameters when combined with Type Ia supernova samples from the Supernova Cosmology Project and High-Z Supernova Search Team, and maps of dark matter via weak lensing that complemented observations from the Canada–France–Hawaii Telescope Legacy Survey. ACS imaging also provided datasets for stellar population studies in systems such as Andromeda Galaxy fields and globular cluster analyses related to Messier 31 and Omega Centauri, and supported exoplanet transit follow-ups later compared with data from Kepler and Spitzer Space Telescope.

Calibration, operations, and data processing

Calibration of ACS used contemporaneous observations of spectrophotometric standards from lists employed by STScI and cross-calibration with instruments like WFPC2, NICMOS, and the Space Telescope Imaging Spectrograph. Operational planning was integrated into Hubble scheduling tools maintained by the Space Telescope Science Institute and involved anomaly response procedures consistent with protocols used during servicing missions such as STS-103 and STS-125. Data processing pipelines used by the Space Telescope Science Institute converted raw exposures into calibrated data products, applying corrections for charge transfer inefficiency examined relative to radiation effects characterized in studies involving the Van Allen radiation belt environment and charging phenomena modeled in work associated with Goddard Space Flight Center.

Performance and limitations

ACS delivered exceptional sensitivity, field of view, and resolution for many programs, outperforming predecessors like WFPC2 in throughput and survey efficiency, yet it faced limitations from radiation-induced degradation including charge transfer inefficiency that affected faint-source photometry and astrometry, a degradation phenomenon also monitored for GALEX detectors. The HRC experienced an electronics failure that curtailed its operations, analogous to instrument downtime encountered by STIS and NICMOS, while the WFC continued with mitigations informed by calibration programs led by STScI and analysis groups at institutions such as Johns Hopkins University and University of California, Santa Cruz.

Upgrades, replacements, and legacy

ACS was a focal point during servicing missions and its longevity influenced the planning of replacement and complementary instruments like the Wide Field Camera 3 installed in STS-125. The ACS archive remains a cornerstone resource within the Hubble Legacy Archive and supports legacy science exploited by teams at Space Telescope Science Institute, European Southern Observatory, and research programs drawing on synergies with James Webb Space Telescope and ground facilities including Atacama Large Millimeter Array. Its datasets continue to underpin studies in extragalactic astronomy, stellar populations, and cosmology by researchers affiliated with institutions such as Harvard–Smithsonian Center for Astrophysics and Max Planck Institute for Astronomy.

Category:Space telescopes