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| COSMOSOMAS | |
|---|---|
| Name | COSMOSOMAS |
| Caption | COSMOSOMAS experiment antenna array |
| Type | Radio microwave survey instrument |
| Site | Teide Observatory, Tenerife |
| Operator | Instituto de Astrofísica de Canarias, Consejo Superior de Investigaciones Científicas |
| Wavelength | Centimetre (10–20 GHz) |
| Built | 1998 |
| Status | Completed |
COSMOSOMAS COSMOSOMAS was a ground-based microwave survey instrument designed to map diffuse sky emission at centimetre wavelengths. Located at the Teide Observatory on Tenerife and operated by teams from the Instituto de Astrofísica de Canarias and the Consejo Superior de Investigaciones Científicas, COSMOSOMAS produced large-area maps that probed the Cosmic Microwave Background, Galactic foregrounds, and anomalous microwave emission. The experiment's results interfaced with contemporaneous projects such as COBE, WMAP, and Planck while involving collaborations with institutions like University of Cambridge, Instituto de Astrofísica de Canarias, and University of Manchester.
Developed in the late 1990s and deployed at Teide Observatory on Tenerife, the instrument targeted angular scales complementary to satellite missions including COBE and WMAP. COSMOSOMAS focused on the 10–20 GHz band to bridge frequency coverage between radio facilities like Effelsberg 100-m Radio Telescope and millimetre observatories such as IRAM 30m Telescope. Scientific drivers included characterization of the Cosmic Microwave Background anisotropies, separation of Galactic emission components manifested in surveys like Haslam 408 MHz survey and the Reich survey, and investigation of the so-called anomalous microwave emission linked to spinning dust models proposed by researchers following work on Draine and Lazarian mechanisms. Principal institutions involved included Instituto de Astrofísica de Canarias, Consejo Superior de Investigaciones Científicas, and several European university groups.
The COSMOSOMAS concept employed a pair of circular scanning radiometers mounted on a precision azimuth-elevation platform inspired by mechanical designs used at facilities such as Jodrell Bank Observatory and Parkes Observatory. Each radiometer used cooled HEMT amplifiers analogous to receivers developed for projects like WMAP and early designs for Planck's Low Frequency Instrument. The optical train incorporated off-axis reflectors and a rotating mirror assembly comparable in principle to scanning mechanisms used by BOOMERanG and ARCADE experiments. Frequency bands centered near 11 GHz and 15 GHz were selected to optimize sensitivity to a mix of free-free, synchrotron, and spinning dust emission, while feedhorns and polarization probes were designed drawing on heritage from VLA and ATCA instrumentation. Cryogenic cooling, gain stabilization, and radiometric chain design followed best practices from laboratories such as CERN and NIST for low-noise microwave electronics.
COSMOSOMAS used continuous circular scanning at constant elevation, producing declination stripes that, after Earth rotation synthesis, produced wide-area maps over seasons of observing similar to mapping strategies adopted by WMAP and ground experiments like QUaD. Raw timestreams were processed to remove atmospheric fluctuations, ground pickup, and instrumental drifts using filtering techniques akin to those employed in analyses for BOOMERanG and MAXIMA. Data processing pipelines incorporated destriping algorithms informed by methods used by Planck Collaboration teams and map-making approaches developed within the HEALPix community. Calibration traces referenced celestial calibrators such as Jupiter, Cas A, and Tau A and cross-comparisons were performed against external surveys including the Haslam 408 MHz map and WMAP foreground products. Quality control involved flagging influenced by weather records from Teide Observatory and telemetry archived by participating institutes.
COSMOSOMAS produced diffuse emission maps that constrained the spectrum and morphology of low-frequency Galactic foregrounds, providing evidence for a rising component compatible with models of spinning dust emission previously hypothesized by Draine and Lazarian. Cross-correlation studies contrasted COSMOSOMAS maps with templates derived from the IRAS far-infrared survey, the Hα surveys by Finkbeiner, and radio maps such as the Reich and Reich survey, supporting associations between microwave excess emission and interstellar dust traced by CO and HI surveys from facilities like NRAO and Arecibo Observatory. The experiment offered independent checks on CMB anisotropy measurements by WMAP and later informed component separation procedures used by the Planck Collaboration. Results were discussed in contexts involving theoretical work by groups at Princeton University, University of Oxford, and Cambridge University regarding foreground modeling and cosmological parameter estimation.
Calibration of COSMOSOMAS relied on primary planetary calibrators such as Jupiter and compact supernova remnant sources like Cassiopeia A and Crab Nebula (Tau A), with transfer standards cross-checked against measurements from Effelsberg and VLA. Systematic error budgets addressed 1/f noise, atmospheric opacity variations at Teide Observatory, and ground spillover influenced by terrain features near the site cataloged by Instituto de Astrofísica de Canarias. Beam characterization used raster scans of bright point sources including Tau A and 3C 273 to quantify sidelobe response, while bandpass measurements referenced laboratory standards from NIST. End-to-end simulations, informed by methodologies from Planck and WMAP teams, estimated residual contamination levels and uncertainty contributions to map-domain power spectra.
COSMOSOMAS left a legacy of low-frequency microwave maps that filled a niche between classic radio surveys and satellite millimetre experiments, influencing subsequent studies of anomalous microwave emission pursued by groups at Imperial College London, University of British Columbia, and Harvard-Smithsonian Center for Astrophysics. Its datasets were incorporated into multi-frequency analyses and motivated instrument concepts in projects such as QUIJOTE and small-aperture experiments targeting polarized low-frequency foregrounds used by collaborations including SPT and ACT. Methodological contributions to scanning strategies and destriping techniques informed pipeline development at the Planck Collaboration and at observatories like IRAM.
The project was a collaborative effort primarily between the Instituto de Astrofísica de Canarias, the Consejo Superior de Investigaciones Científicas, and university partners across Europe and North America including University of Cambridge, University of Manchester, and University of Oxford. Operations integrated logistical support from the Teide Observatory staff and technical development drawing on expertise from instrumentation groups at CERN, NIST, and several radio astronomy laboratories. Data analyses engaged theorists and observers affiliated with institutions such as Princeton University, Imperial College London, and Harvard-Smithsonian Center for Astrophysics, resulting in publications that bridged observational cosmology and interstellar medium studies.
Category:Radio telescopes Category:Microwave astronomy instruments