Design and performance details are given for the Cosmic Background Imager (CBI), an interferometer array that is measuring the power spectrum of fluctuations in the cosmic microwave background radiation (CMBR) for multipoles in the range 400 < l < 3500. The CBI is located at an altitude of 5000 m in the Atacama Desert in northern Chile. It is a planar synthesis array with 13 0.9-m diameter antennas on a 6-m diameter tracking platform. Each antenna has a cooled, low-noise receiver operating in the 26-36 GHz band. Signals are cross-correlated in an analog filterbank correlator with ten 1 GHz bands. This allows spectral index measurements which can be used to distinguish CMBR signals from diffuse galactic foregrounds. A 1.2 kHz 180-deg phase switching scheme is used to reject cross-talk and low-frequency pick-up in the signal processing system. The CBI has a 3-axis mount which allows the tracking platform to be rotated about the optical axis, providing improved (u,v) coverage and a powerful discriminant against false signals generated in the receiving electronics. Rotating the tracking platform also permits polarization measurements when some of the antennas are configured for the orthogonal polarization.Comment: 14 pages. Accepted for publication in PASP. See also http://www.astro.caltech.edu/~tjp/CBI

We describe the instrumentation, experiment design and data reduction for the first season of observations with the Degree Angular Scale Interferometer (DASI), a compact microwave interferometer designed to measure anisotropy of the Cosmic Microwave Background (CMB) on degree and sub-degree scales (l ≃ 100-900). The telescope was deployed at the Amundsen-Scott South Pole research station during the 1999-2000 austral summer and conducted observations of the CMB throughout the following austral winter. In its first season of observations, DASI has mapped CMB fluctuations in 32 fields, each 3. • 4 across, with high sensitivity.

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This paper presents a methodology that employs the electrostatic field variations caused by thundercloud formation or displacement to generate lightning warnings over a region of interest in Southeastern Brazil. These warnings can be used to prevent accidents during hazardous operations, such as the manufacturing, loading, and test of motor-rockets. In these cases, certain equipment may be moved into covered facilities and personnel are required to take shelter. It is also possible to avoid the threat of natural and triggered lightning to launches. The atmospheric electric field database, including the summer seasons of 2007/2008 and 2008/2009 (from November to February), and, for the same period and region, the cloud-to-ground lightning data provided by the Brazilian lightning detection network-BrasilDAT-were used in order to perform a comparative analysis between the lightning warnings and the cloud-toground lightning strikes that effectively occurred inside the area of concern. The analysis was done for three areas surrounding the sensor installation defined as circles with 5, 10 and 15 km of radius to determine the most effective detection range.

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