Preparation and Execution of Observations
1. Observation Preparation
If a proposal’s Disposition Letter indicates that time is allocated at a scheduling priority of A, B, C, or D then Observatory staff will convert the proposal to a project which is eligible to compete for time in the dynamic queue. All observations on Observatory facilities are executed using the concept of Scheduling Blocks (SBs), although the blocks may not be specifically called Scheduling Blocks. An accepted proposal might require tens or hundreds of Scheduling Blocks to gather the data necessary for exploring that project’s objectives.
It is the responsibility of the proposing team to prepare for observations. Proposers should review the technical and science comments that result from the review process when preparing their project for observation. Failing to create Scheduling Blocks will result in the awarded time to be forfeited. At any point in the project preparation process, a project may be withdrawn, and a NRAO Science Helpdesk ticket should be submitted in such an event.
Each facility may have unique requirements for preparing a project for observation. It is the responsibility of the proposing team to familiarize themselves with the requirements and resources that are relevant to their project. Users should submit a ticket to the NRAO Science Helpdesk if they have questions. The links below to should also be reviewed by users.
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GBT |
For specific policies concerning observer responsibilities, remote observing, observer assistance, student observing, and non-standard instrumentation and software, see https://greenbankobservatory.org/science/gbt-observers/observing/observing-policies/ and https://greenbankobservatory.org/science/gbt-observers/observing/ for observing preparation. |
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VLA |
The proposing team is responsible for creating SBs ahead of the observing configuration. The Observation Preparation Tool (OPT) is the required online tool to prepare VLA observations. Observers should consult the references online when preparing for VLA projects: https://science.nrao.edu/facilities/vla/observing. |
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VLBA |
All VLBA observations begin with the program SCHED. When a satisfactory SCHED input file has been achieved, observers should email that input file to vlbiobs@nrao.edu. Further resources are available online:
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2. General and Shared Risk Observing
VLA, VLBA, and GBT observing are classified into two categories: General Observing (GO) and Shared Risk Observing (SRO). The GO category includes the standard capabilities of VLA, VLBA, or GBT whereas the SRO program accommodates those who seek to utilize the facilities beyond their regular capacities. The Call for Proposals provides a detailed outline of what constitutes these categories for each facility.
The Observatory expects that most SRO programs will have no or only minor problems that can be corrected quickly. If an SRO program fails, however, and it becomes clear that detailed testing with additional expertise is needed, then the project must make an experienced member from their team available to help troubleshoot the problem. In some cases, this may require the presence of that experienced member. If adequate support from the project is not given, then the time on the telescope still will be forfeited. The additional effort is to be determined based on discussions with the Observatory staff and management and the project team.
VLA or VLBA SRO proposals will not be carried over if they cannot be scheduled for reasons associated with the shared risk component(s) of the observations, even if awarded priority A. VLA or VLBA RSRO proposals will not be awarded priority A, but would be subject to the same conditions on carry-over as SRO proposals. Those projects in the VLA or VLBA Shared Risk and Resident Shared Risk categories may not be re-observed if they fail due to problems with the shared risk/resident shared risk component(s) of the observation. If observers believe that an observation should be failed after inspecting their data they should submit a ticket to the NRAO Science Helpdesk as soon as possible and in all cases prior to the expiry of the period of eligibility for scheduling.
For GBT SRO, the proposing team may be asked to provide a "backup" receiver if the original one is not available. In such cases, the observation may proceed with the backup receiver, as long as the observation is not considered a duplicate observation, as defined in Section 7.3.
3. Observation Scheduling, Project Completion, and Carry-over
Science observations will be scheduled taking into account many factors, including, for example, the weather and proposal grade. The individual SBs of approved projects will remain in the observing queue until one of the following two criteria are met:
- The allocated time of a project has been executed.
- The potential scheduling period has ended.
For semester proposals, Section 4.3 defines the relevant scheduling periods for Regular, Triggered, and Large proposals. VLA DDT proposals remain in the observing queue for the configuration they request or until the end of the observing semester, whichever occurs first. VLBA and GBT DDT proposals remain in the observing queue until the end of the observing semester. If a project is not completed within these time frames, the project is considered terminated and the proposers should consider submitting a new proposal in the appropriate Call for Proposals.
For both semester and DDT proposals that are dynamically scheduled observations, if the dynamic constraints are no longer satisfied, they may be returned to the scheduling queue, provided the project is in the General Observing category. Re-observation is not guaranteed in such a case. If observers believe that an observation should be failed after inspecting their data they should submit a ticket to the NRAO Science Helpdesk as soon as possible and in all cases prior to the expiry of the period of eligibility for scheduling. Please contact the NRAO Science Helpdesk for clarification concerning specific projects.
Generally, approved Large proposals are accepted in their entirety for the duration of the program; that is, the Observatory will commit the resources required to discharge the proposal within the constraints imposed by scheduling guidelines even though it may take multiple semesters to do so. The Observatory requires annual progress reports from all Large proposals and reserves the right to revisit allocations made to a given Large proposal if insufficient progress is demonstrated. Specifically, the following aspects of the proposal are considered:
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A project connected to a Large proposal is required to maintain and provide timely updates to their online resources, otherwise their project may be terminated or future proposals rejected. An approved Large proposal must provide a web link for the Large proposals page7 before observations are scheduled. Initially, this can be a simple web page that describes the project but this page is expected to be kept up to date.
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A project connected to a Large proposal is required allocate sufficient resources (e.g., observers) for successfully completing the project, otherwise their project may be terminated or future proposals rejected.
As much as 25% to 50% of available Open Skies observing time on Observatory telescopes is allocated to Large proposals. The final percentage will depend on proposal pressure and scientific merit, as determined by peer review. Large proposals will be further constrained to a maximum of 50% of the available Open Skies observing time in any LST range during any semester (or array configuration for the VLA).
The Observatory allocates telescope time and therefore does not guarantee that a specified sensitivity will be obtained. For qualifying programs, the data are run through the Science Ready Data Product (SRDP) pipeline and the proposers are notified of the available pipeline datasets; see the resources online https://science.nrao.edu/srdp/home for more information.
Further details pertaining to scheduling are available online:
7 For VLA and VLBA Large proposals, see https://science.nrao.edu/science/science-program/large-proposals. For GBT Large proposals, see https://greenbankobservatory.org/science/gbt-surveys/.
4. PI Errors in Preparation and Execution
The Observatory is not responsible for errors in tuning or pointing (e.g., wrong or outdated ephemerides) due to incorrect information provided by the PI. If unexecuted parts of the project are found to contain similar (or any other) errors before the project execution has been completed, the PI should immediately adjust their prepared scheduling blocks in the relevant tools (e.g., OPT).
5. Data Delivery and Data Rights
5.1. Data Property
The original contract between the National Science Foundation (NSF) and AUI states that
All scientific information which the Contractor deems to be of record value, prepared by, or otherwise under the control of, the Contractor, in connection with the performance of work hereunder, shall remain the property of the Government, but the Contractor shall have the right to use, disseminate and publish such information, subject to all the provisions of the Articles entitles “Security Requirements” and “Patents”.
5.2. Data and Metadata
Proposal data, proposal metadata, observational data, and observational metadata are defined as follows.
- Proposal data consist of material submitted by the PI (title, abstract, author information, scientific and technical justifications, source/resource information and related sessions) and a disposition letter, which contains scheduling priorities and review feedback.
- Proposal metadata consists of source positions, observation frequencies, and integration times.
- Observational data include visibility data and all resulting data products.
- Observational metadata include the positional and sky coverage information, frequency settings, frequency coverage and resolution, angular resolution, uv-coverage, antenna lists, source and calibrator names, polarization, observation date(s) and start/end times, time on source and sampling rate, weather information and PI name.
For projects with scheduling priorities of A, B, C, or D the name of the PI, proposal ID, title, hours awarded, proposal type, expiration date for Trigger proposals, and the aggregate time observed for Large proposals are made public immediately in the relevant observatory Science Program. This information plus the list of co-Is and the abstract is made available from the Proposal Finder Tool (PFT). The information submitted as part of proposals that are rejected or not observed will remain confidential. The scientific and technical justification, figures, references, and review rankings and reviews are never made public for any proposal.
While proposal source lists are not made public directly, proposal metadata are available publicly from the Archive Access Tool once the data for a proposal have been collected. Observational metadata will be made available without restrictions when an observation is archived. Additionally, Operator Logs are made available once the data have been collected at http://www.vla.nrao.edu/cgi-bin/oplogs.cgi.
5.3. Confidentiality of Proposal Data
Both Observatory staff and external members of the scientific community participate in the Observatory proposal evaluation and time allocation process. They will regularly be exposed to confidential information and proprietary data and ideas. The information, data, and ideas must be held in confidence and not disclosed to others. However, several exceptions apply according to the role of the individuals in question.
- Members of a given Science Review Panel may disclose and discuss the contents of any proposal assigned to them with one another, consistent with the conflicts of interest policy.
- Members of the Time Allocation Committee may disclose and discuss the contents of any proposal under consideration with each other, consistent with conflicts of interest policy.
- Observatory staff serving as technical reviewers may need to consult with each other to ensure a fair and complete assessment of technical elements of the proposal. Hence, technical details may be disclosed and discussed internally by relevant Observatory staff as needed.
- Observatory staff members that participate in the Director’s Review may disclose and discuss the contents of any proposal under consideration with each other, consistent with the conflicts of interest policy.
5.4. Proprietary Periods and Observational Data Access
The observational data are reserved for the exclusive use of the proposing team for a fixed period of time, after which they become publicly available. The proprietary period for Regular, Large, and Triggered proposals is normally a maximum of 12 months after the last observation. For data acquired by the VLBA, HSA, or GMVA, the nominal proprietary period begins when the correlated data are entered into the data archive by Observatory science operations. At its discretion, the TAC may recommend a proprietary period that differs from the nominal 12 month period. For Large proposals, the proposing team is encouraged to make their data available to the public after a shorter proprietary period. The TAC recommendation regarding any change in the normal proprietary period is considered as part of the Director’s Review. If the recommendation is accepted, the proposers will be informed and the reason will be provided.
The proprietary period for data acquired by DDT proposals will normally be no more than 6 months and may be waived entirely; i.e., under certain circumstances, the data will be available to other teams or the public as soon as they are acquired. The proprietary period for data obtained by ToO proposals will be assessed on a case-by-case basis but will be no more than 6 months. An example where this option might be exercised is when the announcement of a transient event by one team triggers an active proposal of another team. The data would be made available to both teams immediately. The relevant Director’s office, in consultation with the NRAO Director or designee, will assign a proprietary period for the data based on scientific and programmatic considerations.
The Observatory staff will have access to observational data at all times as necessary for technical analysis and performance tuning. In addition, if a project qualifies to be run through the Science Ready Data Products (SRDP) pipeline, then Observatory staff can download and reduce project data for this purpose. Until the proprietary period expires, Observatory staff may not disclose or scientifically use the observational data from projects for which they are not a PI or co-I, including projects they support, without explicit recorded permission from the PI.
For the VLA and VLBA, the observational data is released to the PIs soon after the data are collected via the Archive Access Tool. Users must log-in to access their data. Qualified datasets are run through the SRDP pipeline and can be accessed through the Archive Access Tool as well. For the GBT, the observational data are immediately available.
5.5. Extension of Proprietary Periods
Requests for extensions will be considered for extenuating circumstances outside the control of the PI. The most common circumstances where proprietary time extensions have been approved include parental/personal leave, sick leave, or military service. PIs may submit their request through the NRAO Science Helpdesk and justify that the approved leave takes significant time away from the office. Decisions on requests for an extension of the propriety period are made by the Assistant Director for Science Support and Research. The length of the extension will be considered on a case-by-case basis based on the conditions of the approved leave. For these cases, the extensions must be requested at least one month before the end of the proprietary period. An extension will not be granted if requested within 30 days before the data are scheduled to become public. Vacation, science, sabbatical leaves will not be considered for an extension. The proprietary period of Large proposals will not be extended in the cases of approved leave. The proprietary period may be extended without PI consultation if errors are found in the data by Observatory staff or extenuating circumstances occur (e.g., Archive Acess Tool is unavailable for a long period of time).
5.6. Calibration Data
Standard calibration data are observations of calibrators needed to perform the correct calibration of the scientific data. They include the flux, bandpass, amplitude, phase and polarization observations taken during PI observations. This definition extends to data that are resultant from the Accurate Position Service (see Section 5.1).
All standard calibration data have no proprietary period even if they are the result of PI observations. However, there does not yet exist a mode independent of the Archive Access Tool to acquire calibration data that is associated with proprietary data. In the future, the Observatory may make such data accessible separately from the Archive Access Tool. If the Accurate Position Service (Section 5.1) is leveraged, the results will be public domain immediately and source positions, and in many cases, even images will appear on the geodetic web sites.
5.7. Test and Science Verification data
Data obtained during commissioning, engineering tests or science verification (SV) activities will be used to characterize and develop the facility systems, including hardware and software. The data will be released through the archive, technical memos, or publications.
Science Verification projects may not duplicate an approved PI or DDT proposal that is in the observing queue or during their proprietary period. If a PI proposal is approved that duplicates a SV observation planned after the proposal submission deadline, the corresponding SV project must be changed to avoid duplication. DDT proposals that duplicate a SV observation already planned and announced on the relevant observatory Science Program before the submission of the former will be rejected.
