The Expanded Very Large Array (EVLA) project
The Expanded VLA (EVLA) project is a program to modernize the electronics of the Very Large Array (VLA) that was built in the 1970s and 1980s in order to improve several key observational parameters by an order of magnitude or more. Some of the details of the EVLA Project may be found on the web, at http://www.aoc.nrao.edu/evla/. The EVLA project is funded jointly by the US National Science Foundation (NSF), the Canadian National Research Council, and the CONACyT funding agency in Mexico. Total funding was approximately $94 million in Year 2006 dollars, including $59 million in new NSF funding, $16 million in redistributed effort from the NRAO Operations budget, $17 million for the correlator from Canada, and $2 million from Mexico.
The EVLA project was completed on time and on budget at the end of 2012, 11 years after it began. Its key observational goals were (1) complete frequency coverage from 1 to 50 GHz; (2) continuum sensitivity improvement by up to an order of magnitude (nearly two orders of magnitude in speed) by increasing the bandwidth from the VLA's 100 MHz per polarization to 8 GHz per polarization; and (3) implementation of a new correlator that can process the large bandwidth with a minimum of 16,384 spectral channels per baseline. All goals were met. A comparison of some of the EVLA performance parameters with those of the original VLA is provided in Table 1.
Parameter | VLA | EVLA | Factor |
---|---|---|---|
Continuum Sensitivity (1-σ, 9 hr) | 10 µJy | 1 µJy | 10 |
Maximum BW in each polarization | 0.1 GHz | 8 GHz | 80 |
Number of frequency channels at max. BW | 16 | 16,384 | 1024 |
Maximum number of freq. channels | 512 | 4,194,304 | 8192 |
Coarsest frequency resolution | 50 MHz | 2 MHz | 25 |
Finest frequency resolution | 381 Hz | 0.12 Hz | 3180 |
Number of full-polarization sub-correlators | 2 | 64 | 32 |
Log (Frequency Coverage over 1-50 GHz) | 22% | 100% | 5 |
- Note: The "Factor" gives the factor by which the EVLA parameter will be an improvement over the equivalent VLA parameter.