| Observing frequency: | 26-36 GHz (wavelength ~ 1 cm) |
| Number of channels: | 10 channels, each 1 GHz wide |
| Number of antennas: | 13 |
| Number of baselines: | 78 |
| Receivers: | HEMT amplifiers, cooled to 6 K |
| Correlator: | 780 analog complex correlators |
| Antenna: | Cassegrain, 0.90 m diameter |
| Primary beam: | Gaussian FWHM 44 arcmin |
| Minimum baseline: | 1.00 m (l ~ 630), or 0.58 m with smaller antennas |
| Maximum baseline: | 5.51 m (l ~ 3500) |
| Synthesized beamwidth: | FWHM 4.5 - 8.0
arcmin, depending on configuration |
| System temperature: | 20 K |
| Noise in visibility measurements: | 3.3 Jy s-1/2 rms in each 1-GHz channel |
| Noise in image from a single pointing: | 4 mJy/beam rms in 900 s, 10 channels, at center of primary beam |
| Noise in mosaic image (multiple 900-s pointings separated by 20 arcmin): | 2.4 mJy/beam rms, ~ uniform across image |
| Brightness sensitivity in mosaic image: | 13 - 41 ľK rms, depending on configuration |
| Polarization: | Circular (RCP), giving images of Stokes I. Images of Q and U can be made (more slowly) by
switching some antennas to LCP and cross-correlating L and R |
The CBI is an array of 13 antennas, each 90 cm in diameter, mounted on
a single altaz platform, giving interferometer baselines that can be
adjusted in length from 1 to 5.5 m. An interferometer of baseline
d is sensitive to cosmic microwave background radiation
structure with multipole l = 2
d/
, where
is the wavelength (about 1 cm). The orientation of the baselines can
be changed by rotating the platform. The CBI measures 10 channels for
each of 78 baselines simultaneously. The instantaneous field of view
is set by the primary beam of the antennas. Larger fields can be
imaged by assembling data from multiple pointings (called
``mosaicing''). From a mosaic observation of a 2° × 2° field of 9 h
duration (36 × 15 min) we can use standard synthesis imaging
techniques to make an image with rms noise over the whole field of 2.4
mJy/beam.
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