March 25, 2004

"First Fringes" Obtained Using EVLA Test Antenna

A major milestone for the Expanded VLA (EVLA) Project was achieved on March 24, when the EVLA Test Antenna, equipped with the new electronics designed for the Expanded VLA, successfully worked with another, unmodified, VLA antenna as an interferometer system. The pair of antennas was aimed at Cygnus A, a galaxy some 600 million light-years away in the constellation Cygnus. The telltale signature that the antenna pair was working together, called interferometer fringes, was first seen at 2:41 p.m., MST, (2141 UTC) on March 24.

The observation was made at a wavelength of 3.6 centimeters. When Cygnus A began to go below the horizon, the test continued with observations of the galaxy 3C84.

The EVLA test antenna has been undergoing modifications since April of 2003. It now incorporates the complete suite of backend and data-transmission equipment that will be used for all EVLA antennas when the first phase of the VLA Expansion project is completed in 2012. With this new equipment, radio signals collected from astronomical objects are amplified and digitized, then transmitted via a high-bandwidth fiber-optic system to the VLA Control Building. In the original VLA, signals are transmitted in analog form via microwave waveguide. The new EVLA system can carry approximately 100 times more information than the old analog system. Such an increase will make the VLA much more sensitive to faint radio-emitting objects, providing scientists with a dramatically more powerful tool for studying the Universe. In the March 24 test, signals received by the EVLA test antenna were transmitted via the optical fiber to the VLA Control Building, then, after processing to make them compatible for the VLA's central computer, called the correlator, combined with signals transmitted from another antenna via the old waveguide system. The success of this test confirmed that the new EVLA electronics and software systems are functioning. The test also demonstrates that observing at the VLA can continue as antennas are converted to the EVLA configuration over the coming years.

EVLA First Fringes: From left, Barry Clark, Ken Sowinski, Jim Jackson and Mike Revnell smile after successfully getting the first interferometer fringes using the EVLA Test Antenna, March 24, 2004. CREDIT: NRAO/AUI/NSF, Craig Walker

CREDIT: NRAO/AUI/NSF

The VLA Test Antenna (Antenna 13), which has been undergoing conversion into the EVLA configuration since April of 2003. CREDIT: NRAO/AUI/NSF

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Copyright © 2009 Associated Universities, Inc.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.