NRAO, with the assistance of astronomers and engineers from the Naval Research Laboratory, has installed a 74 MHz receiver and a removable dipole on the Pie Town VLBA antenna (PT). Recent brief tests of this system show the VLA-PT link appears to work as expected at a frequency of 74 MHz. We will therefore entertain proposals for the use of the VLA-PT link at 74 MHz for the upcoming A configuration (25 January 2002 to 06 May 2002). The proposal deadline is October 1, 2001.
We emphasize that the 74 MHz system on the VLA-PT link is an experimental system, so observers should be aware that successful science observations are not guaranteed. We therefore require that users who are allocated time to use the VLA-PT link at 74 MHz send a member of their observing team to the VLA during the observations and schedule a visit to the AOC afterwards. This will provide first-hand experience in the behavior of the link, up-to-date information on the latest recommended calibration techniques, and direct NRAO user support. We also note that simultaneous operation of the VLA-PT link at 74 and 327 MHz ("4P" mode) is not expected to be available for the upcoming A configuration.
The major importance of the link for scientific observations is the factor of two improvement in angular resolution for sources with declinations north of about +40 degrees (12 arcseconds at 74 MHz), while maintaining the full sensitivity of the VLA (about 50 mJy/beam for a full track at 74 MHz). At lower declinations, the angular resolution is improved over the A configuration, but the full factor of two improvement in all directions is generally not realized. Of course, single snapshots will achieve enhanced resolution in only one dimension.
Since the Pie Town antenna is an important resource that must be shared with the VLBA, users proposing to use the VLA-PT link must make a strong scientific justification for the inclusion of PT. Item 11 of the VLA proposal cover sheet has been modified to contain a box that must be checked to request the PT link. Proposers should obtain the most recent VLA proposal cover sheet.
Users and other interested parties can be kept up-to-date on the status of the VLA-PT link through this page.
Questions and comments about observing with the VLA-PT link, proposal preparation, capabilities, should be directed to Mark Claussen or Jim Ulvestad.
M. J. Claussen and N. E. Kassim
[an error occurred while processing this directive] Modified on Wednesday, 05-Jan-2005 16:12:06 EST [an error occurred while processing this directive]