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Smithsonian Astrophysical Observatory (SAO)

Charles Alcock, Director

The Smithsonian Astrophysical Observatory (SAO) was established in 1890 as a research unit of the Smithsonian Institution concentrating on studies of solar radiance. Sixty-five years later, SAO assumed responsibility for establishing an optical network for tracking the first artificial satellites. From this pioneering effort, the size and scope of SAO grew with the international space program to include major research in virtually all branches of astrophysics, as well as in areas of earth and planetary sciences.

Since 1955, when its headquarters moved to Cambridge, Massachusetts, SAO has pursued such research in close collaboration with the Harvard College Observatory (HCO) and the Harvard University Department of Astronomy.  On July 1, 1973, the Smithsonian Institution and Harvard University formalized their collaboration as the Harvard-Smithsonian Center for Astrophysics (CfA) to coordinate the related research activities of the two observatories under a single director. Today the observatories retain their separate identities, each responsible to its parent organization; however, the joint venture draws on the coordinated strengths of the two organizations and the combined staffs in six research divisions: Atomic and Molecular Physics; High Energy Astrophysics; Optical and Infrared Astronomy; Radio and Geoastronomy; Solar, Stellar, and Planetary Sciences; and Theoretical Astrophysics. In addition, the CfA has a Science Education Department.


Observational facilities include the multipurpose Fred Lawrence Whipple Observatory (FLWO) on Mt. Hopkins in Arizona and the Submillimeter Array Telescope (SMA) on Mauna Kea, Hawaii, the latter a collaboration with the Academia Sinica’s Institute of Astronomy and Astrophysics of Taiwan. The major instrument on Mt. Hopkins is the 6.5-m-diameter optical telescope of the MMT Observatory, a facility operated jointly with the University of Arizona.  SAO scientists have developed and deployed a suite of advanced wide-field imagers and spectrographs for the MMT including the Hectospec/Hectochelle fiber-fed optical spectrographs, the Megacam imager, and MMIRS, an infrared spectrograph and imager.  VERITAS, the Very Energetic Radiation Imaging Telescope Array System, is a major ground-based gamma-ray observatory at FLWO with an array of four 12-m optical reflectors for gamma-ray astronomy in the GeV – TeV energy range. Also located at the FLWO are: the MINiature Exoplanet Radial Velocity Array (MINERVA), the MEarth planet hunter,  a 1.2-m imaging optical/infrared telescope, and the 1.5-m Tillinghast spectroscopic telescope. FLWO is also home to HAT, the Hungarian Automated Telescope, a completely automated set of small aperture telescopes that search for transiting extra-solar planets; four HAT-Net telescopes are at FLWO, and two are at the SMA site in Hawaii.

In addition to these SAO-operated facilities, the Center for Astrophysics has a 20% share of the twin 6.5-m Magellan telescopes in Chile, operated by a five-institution consortium headed by the Observatories of the Carnegie Institution of Washington.   A set of f/5 wide-field optics, identical to those at the MMT, have been installed at the Magellan Clay Telescope.  These new Magellan optics allow the operation of Megacam and MMIRS in the Southern Hemisphere.  Not least, SAO/CfA is involved in the development of both the 25-m Giant Magellan Telescope, with its partners in the Magellan consortium and others, and the Large Synoptic Survey Telescope.

Special laboratories are maintained for the development of telescope instrumentation and for the spectroscopy of atoms and moleculesA 1.2-m radio telescope on the roof of the Observatory in Cambridge is used for the study of molecular clouds and the structure of the Milky Way through the spectral lines of CO and other molecules.

SAO instrumentation is also operating in space. The Chandra X-ray Observatory, the third of the National Aeronautics and Space Administration’s (NASA) Great Observatories, carries the SAO-designed High Resolution Mirror Assembly X-ray telescope and the SAO-designed and -built High Resolution Camera (HRC). Chandra, which SAO operates for NASA, is used to study X rays from high-energy regions of the Universe. The Spitzer Space Telescope uses SAO’s Infrared Array Camera (IRAC) as its 3-to-10 micron camera for the study of both the very deep, early universe and the formation of stars and planets locally.  NASA’s Solar Dynamics Observatory (SDO) provides better-than-high-definition views of the Sun using SAO’s Atmospheric Imaging Assembly telescope. SAO’s Ultraviolet Coronograph Spectrometer (UVCS) is one of a suite of instruments onboard the International Solar and Heliospheric Observatory (SOHO) spacecraft.  The SAO-designed and -built X-Ray Telescope (XRT) is a high-resolution grazing-incidence telescope on board the Japanese Hinode satellite, which is designed to observe the generation, transport, and emergence of solar magnetic fields in the sun.  SAO instruments are also onboard NASA’s Transition Region and Coronal Explorer (TRACE) spacecraft to study the sun.

Numerous facilities serving the general scientific community are located at the CfA in Cambridge. The Institute for Theoretical Atomic, Molecular and Optical Physics, established in 1988 to attract and encourage talented graduate students to enter this field, emphasizes theoretical study of fundamental questions in atomic and molecular physics, hosts many visitors, both long- and short-term, and conducts conferences and workshops. The Center for X-ray Technology, established in 2003 as a collaborative effort with other institutions, promotes the development of detectors and optics leading to space telescope applications, including X-ray interferometers. The Institute for Theory and Computation (ITC), also hosted by the CfA, is dedicated to research in high-end astrophysical computing.  The ITC consists of members of the Harvard Department of Astronomy, Smithsonian astrophysicists, postdoctoral researchers, graduate students, and associates at other institutions.

Other services at SAO include the Minor Planet Center, which disseminates information on asteroid and comet discoveries worldwide. The United States’ gateway for SIMBAD, an international astronomical computer database, is also located at the Cambridge site, as is Harvard’s extensive collection of astronomical photographic plates, the largest in the world. In addition, SAO conceived, developed, and now operates the Astrophysics Data System (ADS), funded by NASA. This service includes on-line access to more than 11 million abstracts of articles in the fields of astronomy, astrophysics, space instrumentation, and space physics. Full-text on-line journals are also available.  The HITRAN database of molecular parameters for transmission through and emission from planetary atmospheres is maintained at SAO for more than 5000 users worldwide.  SAO participates in the National Virtual Observatory (NVO) and the International Virtual Observatory (IVOA) collaborations, whose aims are to implement improved connectivity between the various astronomical data archives in the world.

SAO, on behalf of NASA, serves as the site of both the Chandra X-ray Observatory Science Center (CXC) and the Chandra Operations and Control Center, the latter of which conducts Chandra flight operations on an around-the-clock basis. The CXC develops and oversees the General Observer program for this mission, as well as calibrates, manages, and distributes data received from Chandra.

The CfA’s library, which includes the SAO collection as well as that of HCO, is available to the staff and to visitors. Located near the center of a community of universities, government agencies, and corporate scientific enterprises, SAO investigators enjoy access to a variety of facilities and counsel, and they may avail themselves of opportunities to pursue academic interests within the community. Smithsonian staff and their Harvard colleagues at the CfA publish more than 500 papers each year in internationally known journals.

Office of the Director


ALCOCK, Charles Roger, Director, Harvard-Smithsonian Center for Astrophysics; Professor of Astronomy, Harvard University. B.Sc. (1972) Auckland University, New Zealand; Ph.D. (1977) California Institute of Technology. Research specialties: Large astronomical surveys; outer solar system; cosmic dark matter; astronomical data mining; virtual observatory technologies.

BRICKHOUSE, Nancy Susan, Astrophysicist; Senior Science Advisor, Harvard-Smithsonian Center for Astrophysics. B.S. (1977) University of North Carolina; Ph.D. (1984) University of Wisconsin. Research specialties: Plasma physics; solar and stellar coronae; plasma emission line spectroscopy; ultraviolet and X-ray spectroscopy of astrophysical sources; laboratory astrophysics.


The scientific objectives of the CfA are intentionally flexible so that response to new research opportunities can be prompt and effective. By design, the research programs reflect the strongest areas of the two observatories and concentrate in fields where the contribution to national goals and scientific excellence can best be realized.  These broad objectives are pursued by the six major divisions as follows:   

Atomic and Molecular Physics

High Energy Astrophysics

Optical and Infrared Astronomy

Radio and Geoastronomy

Solar, Stellar, and Planetary Sciences

Theoretical Astrophysics

Science Education Department


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