The VLBA RSRO Program
The VLBA Resident Shared Risk Observing (RSRO) program provides users with early access to new capabilities in exchange for a period of residency in Socorro to help commission those capabilities. Proposals for any area of user interest are welcome; several desirable developments are listed below. Details of participation in the VLBA RSRO program are provided in a following section.
Suggested RSRO Studies
Mixed Y27 VLBI recording and VLA observing modes. Currently, the VLA phased-array mode can only do VLBI recording in the same mode as is being observed on the VLA. Users who want to observe with the full VLA bandwidth and only record the 2 Gbps for VLBI, or record a different polarization configuration than that observed, could contribute by assisting development of decoupled observing configurations.
"Y1" VLBI observing on the VLA. The phased-VLA capability is currently limited to a single subarray. Thus, any VLBI observation either uses, or idles, each of the VLA's 27 antennas, which can only be justified when a large number are required for scientific success. RSRO participants could contribute to extending the VLBI mode to a subarrayed configuration, to re-establish the "Y1" mode, with a single VLA antenna joining the VLBA. That capability was valued in the pre-EVLA era for studies of intermediate-scale sources requiring baselines between the VLA's A configuration and the VLBA's shortest spacings.
DDC-4 capability at Arecibo. All required hardware and most software required to use a DDC-4 observing mode is already available at Arecibo. An RSRO participant with experience in using the Field System control software could assist in commissioning of the DDC-4 mode, and have early access to that capability. In this case the residency would be at Arecibo, but remote assistance from VLBA personnel in Socorro would be available.
Rapid response capability. Dynamically scheduling the VLBA in response to a trigger should allow observing to begin within 5 to 10 minutes, in opportune situations. Establishing a general rapid-response capability that would cover all conceivable cases is not considered feasible, so this RSRO program would allow the definition of triggers and responses suitable to a specific case of interest to the proposing user group. The work required would include setting up software infrastructure and operations procedures for automated preemption of ongoing array activity, subject to prioritization constraints.
3mm VLBI with the LMT. New VLBI equipment has been installed at the Large Millimeter Telescope in Mexico, provided through a collaboration with MIT Haystack Observatory and the Smithsonian Astrophysical Observatory, enabling VLBI using their Redshift Search Receiver at 3mm. Further commissioning will be needed to make this capability fully operational with the rest of the High Sensitivity Array. RSRO participants are invited to assist with this effort.
Participation in the VLBA RSRO Program
The primary requirement of the RSRO program is that there be at least one expert from each participating group will to reside in Socorro and to contribute to commissioning, while incurring as little overhead from VLBA staff as possible. Limited support for accommodation in the
RSRO proposals should be submitted using the NRAO Proposal Submission Tool in response to a regular proposal call. The proposal should include a scientific justification, as for normal proposals, which will be peer reviewed as part of NRAO's time allocation process. Selecting "VLBA RSRO" from the "Observing Mode" menu on the Resources page makes an "RSRO Comments" text-entry facility available for describing the technical resources required. A description of the personnel who will be involved in the residency along with their expertise and proposed dates of residency should also be included in the technical justification section.
Acceptance of RSRO proposals will be based on both the outcome of the time allocation process and a review by NRAO staff to assess how the proposed capability and associated commissioning activities fit with VLBA priorities.
In general, one week of resident commissioning effort is expected for every 20 hours of VLBA time awarded to an RSRO project, subject to negotiation. Ideally, residency should be at least 2 months, which is the minimum time useful to become familiar with technical aspects of the VLBA and to contribute effectively to commissioning. The period(s) of residency should in general occur in advance of the observing time awarded in order to commission the requested capabilities.
It is possible for a member of the NRAO scientific staff to satisfy the residency requirement on an RSRO proposal. NRAO staff considering providing the residency requirement for an RSRO proposal should consult with their supervisor for further information. Graduate students will, in general, not satisfy the residency requirement, although there may be exceptional cases. Graduate students will be allowed to accompany their advisors as long as the advisor takes primary responsibility for managing the student's efforts. Resident personnel will work under NRAO management in order to optimize the overall commissioning effort. A set of deliverables will be agreed upon in advance of the start of the residency.
The types of proposals considered under the RSRO program may include large (>200 hours) as well as normal projects. Qualified large projects proposed by consortia will be considered as long as the residency requirements are met. A single individual may satisfy the residency requirement for several small projects.
We emphasize the "shared risk" nature of the RSRO program. Since observers will be attempting to use capabilities under development and in the process of being commissioned, 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.