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| Advanced CCD Imaging Spectrometer | |
|---|---|
| Name | Advanced CCD Imaging Spectrometer |
| Operator | National Aeronautics and Space Administration (NASA) |
| Mission | Chandra X-ray Observatory |
| Type | X-ray imaging spectrometer |
| Launched | July 23, 1999 |
| Manufacturer | Lockheed Martin, Massachusetts Institute of Technology (MIT) |
Advanced CCD Imaging Spectrometer
The Advanced CCD Imaging Spectrometer is a focal-plane instrument flown on the Chandra X-ray Observatory designed for imaging and spectroscopic observations of X-ray sources. It provides high angular resolution imaging comparable to instruments used by Hubble Space Telescope observers, and complements dispersive devices like the High-Energy Transmission Grating and Low-Energy Transmission Grating. The instrument has enabled studies of objects from the Sun and Moon to distant quasars and galaxy clusters.
The instrument was developed through collaborations among NASA, the Smithsonian Astrophysical Observatory, MIT, and contractors including Lockheed Martin and Ball Aerospace. It consists of arrays of charge-coupled device detectors derived from designs used at institutions such as Lawrence Livermore National Laboratory and Brookhaven National Laboratory. Key scientific programs have involved observers from Harvard University, Caltech, University of Cambridge, University of California, Berkeley, and CXC (the Chandra X-ray Center). Missions and proposals using the instrument have been reviewed by panels including members from Jet Propulsion Laboratory, European Space Agency, Space Telescope Science Institute, and national academies such as the National Academy of Sciences.
The detector assembly comprises two arrays: the imaging array and the spectroscopic array, populated with frame-transfer CCDs similar to devices developed at MIT Lincoln Laboratory and commercial suppliers like Teledyne Technologies. Mechanical support, thermal control, and electronics were provided by teams at Lockheed Martin, Raytheon, and TRW Inc. Electronics include clocking circuits, bias supplies, analog-to-digital converters, and event-processing firmware developed with contributions from SAO and MIT Kavli Institute for Astrophysics and Space Research. The instrument includes cooling systems using radiators similar in heritage to those on Voyager and Cassini–Huygens, and shielding informed by designs from ROSAT and ASCA. Optical blocking filters mitigate contamination from visible light, an approach used by XMM-Newton and Suzaku. Mounting and alignment interfaces adhere to standards practiced by Boeing and Northrop Grumman for space payload integration.
Operational modes include timed exposure, continuous clocking, and subarray readouts, enabling trade-offs among time resolution, spectral resolution, and pile-up mitigation similar to strategies employed for XMM-Newton EPIC and Suzaku XIS. The instrument achieves arcsecond-level imaging consistent with the Chandra mirrors built by Raytheon Optical Systems and tested at facilities like Marshall Space Flight Center and Goddard Space Flight Center. Performance metrics such as energy resolution, quantum efficiency, and point-spread function have been monitored against pre-launch expectations established with inputs from Lawrence Berkeley National Laboratory and Los Alamos National Laboratory. Flight software updates were coordinated with teams at Chandra X-ray Center, NASA Ames Research Center, and university partners including Columbia University.
Calibration programs used celestial standards such as Cassiopeia A, Crab Nebula, Vela Pulsar, Perseus Cluster, and Cygnus X-1 alongside on-board calibration sources designed with vendors like Ebara and laboratories including Brookhaven National Laboratory. The Chandra calibration database (CALDB) maintained by Chandra X-ray Center aggregates response matrices and gain maps analogous to databases for XMM-Newton and Suzaku. Data processing pipelines run at the Chandra X-ray Center and science centers at Harvard-Smithsonian Center for Astrophysics, Caltech, and STScI produce level 1 and level 2 products following conventions similar to the FITS standards promoted by the International Astronomical Union and NASA HEASARC. Analysis tools such as CIAO have been developed with contributions from MIT, SAO, and international collaborators including ESA scientists.
The instrument has delivered key observations of supernova remnants including Cassiopeia A and Tycho's Supernova, detailed imaging of galaxy clusters like Perseus Cluster and Coma Cluster, and studies of compact objects such as Cygnus X-1, Vela Pulsar, and numerous magnetars. It enabled mapping of hot gas in systems studied by teams at University of Chicago, Princeton University, Yale University, and University of Michigan, contributing to cosmological constraints that complement results from Planck and WMAP. Observations impacted research on black holes in M87, NGC 1275, and distant quasars observed in surveys coordinated with Sloan Digital Sky Survey and follow-ups by Keck Observatory and Very Large Telescope. The instrument supported time-domain studies with observatories such as Swift, Fermi Gamma-ray Space Telescope, and ground arrays like VERITAS and H.E.S.S..
Deployed on STS-93 during the Columbia (STS-93) mission, the observatory and instrument entered routine operations under management by NASA Marshall Space Flight Center and Chandra X-ray Center. Ground operations have involved scheduling coordination with agencies such as ESA and facilities including Deep Space Network and mission planning teams at Goddard Space Flight Center. The instrument's lifetime and observing programs have been shaped by proposals reviewed by panels with members from National Science Foundation, European Southern Observatory, and academic institutions including University of Oxford and University of Tokyo.
Over its operational life, the instrument has experienced issues such as radiation-induced charge transfer inefficiency and contamination layers on optical blocking filters, phenomena also encountered by instruments on XMM-Newton and Suzaku. Mitigation strategies included operating temperature adjustments, charge-injection techniques tested at Brookhaven National Laboratory, and software calibration updates distributed through CALDB. Occasional anomalies prompted reviews by teams at Chandra X-ray Center, NASA Headquarters, and external review boards with participation from Los Alamos National Laboratory and Lawrence Livermore National Laboratory.
Category:Space telescopes Category:X-ray astronomy instruments