CSO: The Caltech Submillimeter Observatory

Link to CSO Web site

I. General project/facility description

1. Overview of the facility/project
   The CSO consists of a 10.4m diameter Leighton dish, in an astrodome, sited on Mauna Kea, Hawaii, at about 14,000 feet elevation. The observatory is fully equipped with receivers and bolometer cameras to service the complete spectral range, between about 190 GHz (1.8 mm) and 950 GHz (0.34 mm). At sea level, in Hilo, there is a 7,000 square foot office and laboratory building. The CSO also owns 6 bedrooms at the mid-level dormitory.

2. Managing institution and organization
   The CSO is owned and managed by Caltech. There is a lease agreement with the University of Hawaii (UH) which provides for 10% of observing time to UH. Also the University of Texas (UT) is a minor partner. The CSO is operated by a director with a staff of about 20, split between Pasadena and Hawaii. There is an external Time Allocation Committee (TAC) which also functions as an advisory board to the director.

3. Funding source(s)
   The primary funding source for the CSO is the NSF. Currently the funding is about 90% NSF, 5% Caltech (JPL) and 5% UT (private).

4. Construction history and cost
   The total cost of construction of the CSO (1984-1987) in 2003 dollars was about $14M (~$11M from NSF), using an inflation factor of 1.6 (CPI). This includes the cost of the telescope, dome, buy-in to the site, the initial set of receivers, the 6 dormitory rooms at the mid-level facility and the Hilo building ($1.5M - private).

5. Operational history and cost
   Operation cost largely has been borne by the NSF from about 1987 to the present and, taking inflation into account, has remained fairly constant at about $2.5M/yr (2003 dollars).
   When the LSAT becomes operational as a world class facility (~2010), it will replace the CSO as a world-leading facility and it is anticipated that NSF anticipated that NSF would not support both telescopes. However, the CSO might very well still occupy a critical niche and would remain open, funded by other sources. Options might include:
   • The CSO might become part of the SMA to provide the short spacing data. At 10.4m, it is about the right size for the SMA 6m antennas.
   • The CSO might provide a long baseline, high sensitivity component to the SMA.
   • A consortium of universities, possibly including Caltech and UH, might wish to operate the CSO independently.
   • The CSO might be devoted to specific programs such as large area, Bolocam maps for ALMA, providing test-bed capability for Sofia and other space missions. Spitzer follow-up is proving successful and may still be needed in 2010. Herschel and Planck follow-up will certainly be active, then. NASA might want a first rate facility to support Space missions.

II. Technical details

1. Specifics of telescope/instrument
   The telescope has a diameter of 10.4 m and achieves a surface accuracy of about 17 µ (RMS) when operated with the surface real-time correction scheme (DSOS). This scheme adjusts the surface as a function of elevation, the errors being corrected out by heating/cooling of the panel support rods, resulting in control of the panel positions. The error maps at each elevation are pre-determined by the CSO point source mapping, holography device.
   Facility continuum bolometer instruments include BOLOCAM, 144 pixels operative over 26 sq arcmin in the 1-2 mm range, and SHARC II, 384 pixels covering 2.3 sq arcmin in the 350-450 µ (700-890 GHz) range. Five low noise heterodyne receivers offer capabilities across the 350 µ to 1.6 mm (180-900 GHz) band. Several non-facility instruments are also used; HERTZ (U. of Chicago); SuZie (Stanford S-Z bolometers) and FIBRE (Goddard F-P spectrometer).
   The CSO also participates in short-baseline interferometry with the James Clerk Maxwell Telescope (JCMT), located approximately 180 meters from the CSO and the SMA.

2. New capabilities anticipated/planned in next 5-10 years
   
   • Kinetic Inductance Camera with > 1000 pixels.
   • Polarization Camera (modification to SHARC II)
   • Upgrade all heterodyne systems to 4 GHz IF bandwidth and balanced input
   • New high sensitivity, correlating, broadband receivers dual polarization, on/off pixels for 180-280 and 280-380 GHz bands.
   • Grating (Z-Spec) bolometer camera, moderate resolution (~100 MHz), very high sensitivity, full atmospheric window bandpass.
   • Very high IF bandpass (~30 GHz) 280-300 GHz, correlating Rx (student)

III. User profile

1. % of "open skies" time
   About 50% "open skies" time (see below).

2. Institutional affiliations of users
   The CSO provides 50% of the observing time to the National/International community through a 6 monthly call for proposals and a nationally constituted TAC. The remaining time is allocated to U. Texas (7.5%), U. Hawaii (10%) and Caltech (32.5%). Usually, annually, there is one month shut-down for major engineering and four nights/month for receiver engineering or telescope optimization.
   In 2003, there were 186 users, of which 50 were from Caltech. 44 institutions in the US and worldwide were represented by users.

3. Student access, involvement, usage
   In 2003, 57 (roughly 1/3) of the users were students and 6 students were directly involved in building detectors/receivers.

IV. Science Overview

1. Current forefront scientific programs
   
   • Bolocam mapping of deep survey fields for distant, dusty galaxies.
   • CMB Fluctuation on arcminute scales with Bolocam.
   • Bolocam/SHARC II SEDs for Spitzer survey fields.
   • Bolocam/SHARC II SEDs of distant, intermediate and nearby galaxies.
   • Bolocam S-Z studies of galaxy clusters to give estimate of H_o and peculiar velocities.
   • Spectroscopy of intermediate and nearby galaxies as templates for distant galaxies.
   • Chemical evolution in the ISM -- high levels of deuteration (e.g. ND₃, H₂D⁺, D₂H⁺) in cold regions.
   • ISM magnetic field studies using ion-molecule linewidth ratios.
   • ISM dust polarization studies.

2. Major discoveries (through 1999)
   
   • Detection of HDO in comets and the comparison of the deuterium content of comets and the ISM.
   • Submillimeter H₂O masers.
   • Detection of lines of H₃O⁺.
   • Detection of NH₂.
   • Detection of PH₃ in Jupiter.
   • Turbulence and Intermittency in the ISM
   • High velocity outflow phase of PPNs.
   • Development of superconducting tunnel junction receivers for mm/submm astronomy.
   • Development of the quasi-optical dual slot antenna.
   • Development of kinetic induction detectors.

3. Science highlights of last 5 years
   
   • Detection of the high frequency increment effect in S-Z clusters.
   • Measurements of H_o from S-Z clusters with Bolocam.
   • The dust temperature in high z objects, from the SEDs.
   • Detection of triply deuterated ammonia (ND₃) in cold dense regions of the ISM.
   • Detection of D₂S in cold dense regions of the ISM.
   • Detection of D₂H⁺ in cold dense regions of the ISM.
   • A new probe of the ISM magnetic field: Ion -- Molecule linewidth ratios.
   • CI (1-0) and (2-1) studies Detection and mapping in galaxies

     -- comparison of cooling with high J CO lines

     -- template for distant galaxies.

   • Detection in carbon stars

4. Main future science questions to be addressed
   
   • Bolocam projects
     • Blind surveys to find new S-Z clusters
     • Large scale mapping of galactic plane, for complete inventory of protostars.
   • SHARC II projects
     • Many (>100 already) Luminous IR galaxies are being discovered by Spitzer. SHARC II can trace the SEDs across the peaks to give the luminosity.
     • As a Nyquist sampling, filled array, SHARC II provides unprecedented high fidelity images of continuum objects in the galaxy and of nearby galaxies.
   • Z-Spec projects
     • About 40% of newly discovered high redshift galaxies cannot be detected in the radio, or be searched for optical redshifts. z-spec will have appropriate spectral resolution and sufficient sensitivity to detect lines in these extreme objects, without requiring prior knowledge of the redshift
   • New Broadband, high sensitivity receivers
     • The broadband correlating receivers are sensitive enough to study lines in high Z galaxies, but require knowledge of the approximate frequency. Thus, they will be used on the lines detected by Z-Spec, to reveal the dynamics.

   • Synergies with other major forefront facilities
     
     • Wide area mapping for ALMA.
     • 1mm - 350 µ SED points for Spitzer field objects.
     • Long baseline, large aperture addition to SMA.
     • z measurements (Z-Spec) for distant source counts (Spitzer etc..).
     • KIDS -- large submm continuum camera (newest technology) -- test bed for LSAT.
     • Calibration and supporting spectra for Herschel/HIFI.

   • Unique contributions
     
     • Hands-on facility for observer students.
     • Development of new technology (e.g. high frequency SIS receivers, largest submillimeter cameras -- Bolocam, SHARC II, future KIDS).
     • Test bed for novel submm instrumentation.
     • Trains future receiver and camera builders.

V. Education/Outreach activities

1. Visitor facility
   As one of the Mauna Kea Obseravatories, the CSO is affiliated with the Onizuka Center for International Astronomy and makes regular financial, content, and planning contributions to the Onizuka Visitors' Information Station which hosts over 100,000 Mauna Kea visitors annually. Members of the CSO staff regularly participate in events at the Visitor Information Station and elsewhere in Hawaii. In 2004, activities included career talks at schools, mentoring science fair participants, supervising local student employees and the production of display materials, PPT presentations and videos.

2. Student programs
   In addition to the students who use the CSO for their research or work on instrument/receiver development, members of the CSO staff in Hawaii supervise undergraduate students on site.

VI. Documentation/website URLs

1. URL of facility website:
   http://www.cso.caltech.edu
2. URL of EPO website
   http://www.cso.caltech.edu/outreach/log/CSOoutreach.htm
3. URL(s) of any brief overviews of project/facility
   http://www.submm.caltech.edu/introduction
4. URL(s) of miscellaneous documentation
   http://www.submm.caltech.edu/cso/recent_results/recent_results.html