The Cosmic Background Imager


The Cosmic Background Imager (CBI) consisted of 13 radio telescopes working together to form an interferometer, and was designed to image and measure the small variations in temperature in the cosmic microwave background (CMB). The CBI was able to measure both the temperature and polarization properties of the CMB on angular scales from 5 arc minutes to one degree (spherical harmonic scales from l = 3000 down to l = 300).

CBI operated in the frequency range 26-36 GHz and is sited at 5080m (~16700 feet) on the Llano de Chajnantor in the Andes of northern Chile. The telescope was a collaborative project being led by Caltech - for much more information about the CBI and the results that it has produced, have a look at the Official CBI Webpage.

Research highlights with CBI:

Measurement of the CMB power spectrum on angular scales from 5 arc minutes to one degree (spherical harmonic scales from l = 3000 down to l = 300).
Detection of excess power in the CMB power spectrum at high l-values.
Detection and measurement of the E-mode polarization of the CMB.
Investigation of diffuse foregrounds.
Physics of clusters of galaxies via the Sunyaev-Zel'dovich effect.

CBI2 Upgrade

In 2006, the CBI was upgraded to CBI2. This work was led by the University of Oxford. The original 0.9m dishes were upgraded to 1.4m dishes each with a new foam cone supporting the new secondaries. The array was re-configured to maximise the number of long baselines. Between 2006 and 2009, CBI2 made observations of CMB fields, SZ clusters and galactic foregrounds. Much of this data has now been published, but some analysis continues to be done.

Have a look at the pictures in the links below to see the upgrade...
CBI2 Pics (1) - Oxford and first week in San Pedro
CBI2 Pics (2) - Assembling the antennas in San Pedro
CBI2 Pics (3) - Installation of the antennas on the mountain