CARMA 2011 VLBI Calibration

R.L. Plambeck 
University of California, Berkeley

ABSTRACT

In March/April 2011 CARMA participated in a 1mm VLBI experiment organized
under the auspices of the Event Horizon Telescope. Other stations
participating were the Arizona Radio Observatory Submillimeter Telescope on
Mt Graham, Arizona; and the Submillimeter Array, the James Clerk Maxwell
Telescope, and the Caltech Submillimeter Observatory, all on Mauna Kea,
Hawaii.

Left circularly polarized signals in two 480 MHz wide bands, centered at
229.089 and 229.601 GHz, were recorded at all sites. During this experiment
CARMA was treated as a `double' VLBI station -- signals were recorded on
separate VLBI recorders for 2 separate CARMA telescopes, which then were
treated as independent VLBI stations.  In this way, the flux densities
measured on the CARMA-CARMA VLBI baseline could be compared with flux
densities measured with the local CARMA correlator. For some of the
observations, the signals from 7 CARMA telescopes were phased together in a
beamformer and sent to one of the VLBI recorders.

This document describes the calibration of the CARMA data for this
experiment, including the absolute flux calibrations, computation of the
system equivalent flux densities for single telescopes and the subarray of
phased telescopes, and estimates of the phasing efficiency.