VLBA Shared Risk Observing

 

The VLBA Shared Risk Observing (SRO) program allows observers access to capabilities that are essentially commissioned, but are not well tested. Note that if a shared risk project fails, it may not be re-observed. In semester 2025A  shared risk observing on the VLBA includes:

  1. Recording wide-band VLA visibilities in parallel with phased VLA (Y27) VLBI, and
  2. Copying baseband data to user-provided disk packs (baseband copy).

If proposers are in doubt as to whether their proposed setups are Shared Risk or Resident Shared Risk are encouraged to get in touch with NRAO staff (e.g. by using the NRAO helpdesk) well before the proposal deadline.  We emphasize the "shared risk" nature of the SRO program. Since observers will be attempting to use capabilities that are not well-tested, NRAO can make no guarantee of the success of any observations made under this program, and no additional commitment is made beyond granting the hours actually assigned by the peer review process.

For more information on General Observing (GO), Shared Risk Observing (SRO), and Resident Shared Risk Observing (RSRO), please see the VLBA Observational Status Summary Offered Capabilities section.

Recording wide-band VLA visibilities in parallel with Y27 VLBI

In addition to recording VLA phased array (Y27) data on the Mark 6 unit for VLBI purposes, this mode will deliver wider bandwidth data through WIDAR for the VLA itself. This would be useful to optimize the sensitivity of the VLA observations as a secondary (VLA only) science product. Currently, this only supports standard VLA 8-bit continuum modes with a 2-GHz bandwidth. To request VLA wide-band data for a project, specify your needs in the final box of the Technical Justification ("Note any other technical considerations..."). 

Baseband data copy

The raw data recorded on the station recorders can be copied to user-supplied media for correlation at a different location that has the capability of  reading VLBA baseband data (in VDIF format).   For a successful proposal requesting this VLBA Shared Risk capability, the following items should be addressed in the proposal:

  • If correlation is needed to be performed elsewhere; e.g. a higher time resolution than can be provided by the VLBA DiFX correlator
  • The use of baseband copy should be fully justified in the proposal, either in the technical justification, or the science justification of the proposal
  • The acceptance and consideration of the request of baseband copy is subject to VLBA resources available
  • Proposers are expected to provide their own media storage, which is compatible with the copy mechanism

The use of baseband copying may be requested by selecting the "Baseband Copy" checkbox under "Special Features" in the VLBA Resource in the PST.

Questions or request for clarifications on baseband copy to other media should be sent to the NRAO helpdesk.

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