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Green Bank Observatory Call for Proposals: 2021A Semester

The Green Bank Observatory (GBO) invites scientists to participate in the 2021A Semester Call for Proposals for the Green Bank Telescope (GBT).  The entire proposal call can be found on this page.   The submission deadline for Semester 2021A proposals is Monday, 3 August 2020, at 17:00 EDT (21:00 UTC).

The GBT is happy to announce a new opportunity for joint observations with SOFIA. Up to three percent of the U.S. Guest Observer time on SOFIA will be made available for requests in GBT proposals.

Receiver availability for the 2021A semester will be determined by those highly ranked proposals accepted in Group A.

The GBT only accepts large proposals once per year at the February proposal deadlines.  We no longer accept GBT large proposals at the August proposal deadlines.  The next large proposal deadline for the GBT after this call will be for the 2021B semester.  This new policy ensures equality for the reviews of all large proposals that can be scheduled across a full year.

Recall that all large proposals are restricted to using no more than 50% of the open skies time available under any weather category (poor, good, excellent) at any LST during any semester.

New Regular, and Large proposal size definitions for the GBO:

  • 0-8 GHz (Any weather)
    • Regular:  < 400 hours and lasting  ≤ 1 year
    • Large: ≥ 400 hours or lasting >1 year
  • 8-18 and 27.5-50 GHz (Good weather)
    • Regular:  < 200 hours and lasting ≤ 1 year
    • Large: ≥ 200 hours or lasting >1 year
  • 18-27.5 and > 50 GHz (Excellent weather)
    • Regular:  < 100 hours and lasting ≤ 1 year
    • Large:  ≥ 100 hours or lasting >1 year
  • Fixed and Monitoring proposals
    • Regular:  < 200 hours and lasting ≤ 1 year
    • Large:  ≥ 200 hours or lasting >1 year

The GBO encourages proposals that take advantage of the GBT’s unique capabilities across 0.29 to 116.2 GHz frequency range.  (Coverage is not available for 2.65-4.0 GHz, 15.8-18.0 GHz, and 49.9-67.0 GHz)

Key science areas include, but are not limited to:

  • Low column density HI (NHI ≈1017 cm-2 galactic and extragalactic)
  • astrochemistry
  • cosmology
  • fast radio bursts
  • galaxy and cluster evolution
  • pulsars (searches and timing)
  • radio recombination lines
  • solar system science

The GBO also encourages the submission of high risk, high reward proposals requiring GBT observing time.

There are approximately 1000 hours of excellent weather (18-27.5 and > 50 GHz) available each semester for both open skies and sponsored time.    Prior commitments typically account for half of this time which leaves only 500 hours available for new requests each semester. 

Instrumentation news:

  • The PFS radar backend has been retired.
  • A new X-band receiver is expected to begin commissioning in the 21A semester. 
  • There will be two new prime focus receivers undergoing testing and commissioning on the GBT during the 21A semester.  As a result the Prime Focus 342 MHz feed is not expected to be available on a regular basis during the 21A semester.

Filler time proposals which can take advantage of gaps in the GBT schedule are also encouraged.

Triggered proposals can be submitted for studies of transient objects such as fast radio bursts, near Earth asteroids, comets, and other transients.                   

All proposals should state why the GBT is necessary for the requested observations in both the abstract and science justification.

We strongly encourage proposers to carefully read through the “News and Opportunities” section of the proposal call.  

Proposals requesting the GBT as part of High Sensitivity Array (HSA), and Global 3mm VLBI Array (GMVA) should be submitted through the Very Long Baseline Array’s call (available here).

We wish to remind proposers of continuing opportunities for joint observations with the Chandra X-ray Observatory, the Hubble Space Telescope, the Swift Gamma-Ray Burst Mission, the Fermi Gamma-ray Space Telescope and XMM-Newton.

Proposal preparation and submission remain via the NRAO Proposal Submission Tool (PST) available at NRAO Interactive Services. Note that use of the PST requires registration.  Proposers who need assistance with proposal preparation or have questions regarding the Call or GBT capabilities should contact Observatory staff via the Helpdesk.

Please note that the GBT is scheduled in 15 minute (0.25 hour) increments and that all proposals should request time appropriately.   Time requests will be rounded down to the nearest 0.25 hour increment. 

News and Opportunities

Proposal Deadline

The 3 August 2020 deadline (21:00 UTC) is for the 2021A Semester observing period on the GBT: 1 February 2021 – 31 July 2021.

Details of all GBT observing modes are inThe Proposer’s Guide for the Green Bank Telescope. Proposers should also consult the more general document The Performance of the GBT: A Guide for Planning Observations. Proposers should make sure that they are familiar with the latest versions of these documents before writing their proposal.

Joint Observations with SOFIA

By agreement with the GBO, SOFIA may award up to 5% of GBO open skies observing time. Similarly the GBO Time Allocation Committee may award up to  3% of the U.S. Guest Observer Time on SOFIA. See the Joint Observations with SOFIA page for details.

Large Proposals

Beginning with the 2020B semester the GBT will only accept large proposals once per year at the February proposal deadlines.  We will no longer accept GBT large proposals at the August proposal deadlines.  There will not be a large proposal call for 2021A for the GBT.  The next large proposal deadline for the GBT after this call will be for the 2021B semester.  This new policy ensures equality for the reviews of all large proposals that can be scheduled across a full year.

Instrumentation

The GBT receivers, backends, and observing modes that are available for Semester 2021A proposals are listed in Tables 1 and 2 below.

Table 1

ReceiverFrequency Range
Prime Focus 1   290-395 MHz, 385-520 MHz, 510-690 MHz and 680-920 MHz
Prime Focus 2 910-1230 MHz
L-band 1.15-1.73 GHz
S-band 1.73-2.60 GHz
C-band (linear only – see below) 3.8-7.8 GHz
X-band 7.8-11.6 GHz
Ku-band 12.0-15.4 GHz
K-band Focal Plane Array (7 pixels) 18.0-26.5 GHz
Ka-band 26.0-39.5 GHz
Q-band 38.2-49.8 GHz
W-band 67-93.3 GHz
ARGUS (shared-risk – see below) 75-115.3 GHz
MUSTANG2 (shared-risk – see below) 90 GHz, Shared Risk

Table 2

Backend Observing Modes
Versatile Green Bank Astronomical Spectrometer (VEGAS) Continuum (see below), spectral line, pulsar
Digital Continuum Receiver (DCR) Continuum
Caltech Continuum Backend (CCB)Continuum (Ka receiver only)
Mark6 Very Long Baseline Array Disk Recorder Very Long Baseline Interferometry
JPL Radar backend Private PI Instrument – Open for Public Use
Breakthrough Listen Private PI Instrument, Shared Risk

C-band

Proposals wishing to use the GBT C-band receiver should only use linear polarization outputs.  The circular polarization of the receiver is currently not preforming correctly and we will not accept any proposals to use the circular polarization output of this receiver.

C-band VLBI on the GBT

The GBO will only accept proposals using the GBT C-band receiver for VLBI Stokes I continuum observations (the observations will need to be done using full Stokes just to calibrate Stoke I). Please see the HSA section of the Long Baseline Observatory call (available here) for proposals for more details.

VEGAS

Continuum: All modes of VEGAS may now be used for continuum observations.  The Proposal Submission Tool has not been updated to reflect this situation.  Proposers should use the spectral line modes of VEGAS to choose the desired bandwidth and then note in the technical justification that the observations will be for continuum measurements.

Pulsar: VEGAS pulsar modes have been released.

ARGUS

Observers interested in using the ARGUS instrument should see http://www.gb.nrao.edu/argus/ for further information. 

VLBI

Proposers should clearly justify the need for the GBT in the text of the proposal. All Very Long Baseline Interferometry (VLBI) proposals requesting the GBT should include any needed setup and overhead time in the time request of their proposals. C-band VLBI observers should see the C-band VLBI note above.

MUSTANG2

The GBO will accept proposals for shared risk observations using the MUSTANG2 instrument at the proposal deadline. The GBO cannot guarantee that MUSTANG2 will be cold at the start of scheduled observing due to low observing elevations or rotations of the turret from prior observations. Cool down time for MUSTANG2 observations should be included in the overhead for MUSTANG2 observations. All MUSTANG2 proposals must have permission from the instrument development team.

Breakthrough Listen backend

The Breakthrough Listen project is making its backend available for shared-risk observations during the 2021A semester. The instrument consists of a cluster of 64 Titan X and 1080 GPU-based servers capturing 8-bit baseband voltages over up to 12 GHz of instantaneous bandwidth. Data rates are typically tens of TB/hr but a pipeline is available to generate spectra with adjustable frequency (> 3 Hz) and time (> 350 μs) resolutions, with possible science applications including fast radio transients, pulsar observations, stellar flares, SETI, etc. Before submitting a proposal, proposers must obtain permission from the Breakthrough Listen team at Berkeley SETI Research Center. The team will consult on proposal preparation and data analysis. Any data acquired using the backend will be proprietary to the proposer per the standard GBO policies.

More information including a technical description of the backend and team contact details can be found here.

Observing and Scheduling Constraints

The GBT is scheduled by the Dynamic Scheduling System (DSS). The DSS system is fully described in the GBT Proposer’s Guide and the GBT Observer’s Guide.

Session lengths:  Proposers should be aware that long scheduling blocks (more than 6 hours) become increasingly difficult to schedule as a result of the transition to reduced open skies time by the NSF.  Proposers must clearly state in the technical justification section how their project could be scheduled in smaller observing blocks that would more easily fit within the GBT scheduling constraints.   This is especially critical for proposals that require fixed or coordinated observing dates, e.g. VLBI observations, pulsar monitoring, radar, etc.

Mapping: If you are considering mapping with the GBT such that there are major turns or moves (end of rows in raster map, change in position for pointed maps, etc.) that occur with a cadence faster than every 30 seconds, you will need to consult with a GBT support scientist to ensure that the GBT can safely withstand the stresses induced by the mapping motions.

“Fixed” and “Windowed” Observations

Due to varied pressures on the GBT’s scheduling resulting from the transition to reduced open skies by the NSF, fixed time observations (e.g. VLBI, pulsar transit observations, etc.) and windowed observations (e.g. monitoring observations) will likely have to be ranked at least in or near the top 10-15% of all AUI telescope proposals in order to be accepted.

Instrument Availability

The availability of GBT Gregorian receivers and prime focus feeds will be based on demand from the highly ranked (Group A) proposals.  Some receivers and feeds may be available only for a few short, two or three week periods during the semester

Observing Team Members

We would like to remind all project teams of the Green Bank Observatory policy that all observers must be listed as a member of the project team in the GBT Dynamic Scheduling System. 

Also, we would like to remind all observers that they should not log into any GBO computing system using another person’s account.  Co-Is and students are required to have their own GBO login and account if they are to participate in observing and data reduction. 

Scheduling Increments

Please note that the GBT is scheduled in 15 minute (0.25 hour) increments and that all proposals should request time appropriately. Time requests will be rounded down to the nearest 0.25 hour increment.

GBT Proposal Preparation

Proposers should consult the The Performance of the GBT: A Guide for Planning Observations and the GBT Observer’s Guide. All proposers, including pulsar proposers, should use the GBT Sensitivity Calculator. Please see the Calculator’s User’s Guide for instructions. The Sensitivity Calculator results can be cut and pasted into the Technical Justification section of the proposal. This will streamline the creation of your Technical Justification and will lessen the chances for error.  If you are planning on making maps with the GBT, you should use the GBT Mapping Calculator tool.

The GBT observing policies describe the telescope’s remote observing restrictions.

Proposers requesting GBT participation in High Sensitivity Array (HSA), Very Long Baseline Array (VLBA), or Global Millimeter Very Long Baseline Interferometry (GMVA) observations should consult the VLBA, HSA, and GMVA Proposal Call.

RFI

RFI Monitoring Scans

The most recent RFI monitoring scans for the GBT can be found here.  These scans provide information on the frequencies that may encounter RFI.

470-700 MHz RFI

Digital TV transmissions above 470 MHz will make observing very difficult with the 450 and 600 MHz feeds of the PF1 receiver. Available RFI plots do not show the strength of these signals as the RFI overpowers the system: the plot intensities are estimated to be too low by a factor of up to 10 to 50. Observers should consult the GBT support scientists before submitting a proposal for these feeds.  Also, “TV Whitespace” usage of these frequencies is expected to begin in 2018.

Schools and Workshops

Observer Training

The Green Bank Telescope (GBT) Remote Observer Training Workshop will provide the essential skills and knowledge needed to use the GBT and maximize its scientific output. It is intended for experienced astronomers who need to learn the specifics of observing with the GBT. After completing the workshop, an attendee will be certified to use the GBT as a remote observer. The workshop will focus on hands-on training in the observing techniques most relevant to participants (e.g. high frequency map, continuum, pulsar, etc.).

These workshops will be held several times a year and will complement traditional on-site training.  The next workshop will be held October 13-14, 2020 and will be held virtually.

More information can be found here.

Single Dish Training Workshop

 The Green Bank Telescope (GBT) Single Dish Training School will provide graduate students, post-docs, and experts in other fields of astronomy with both knowledge and practical experience of the techniques and applications of single-dish radio astronomy using the GBT as the primary example. The school will be based around an intensive series of lectures from experts, as well as hands-on radio-astronomy projects and tutorials.  Topics to be covered include radio telescope fundamentals, key single-dish science areas, observing and calibration techniques, the impact of weather, the GBT observing procedures and software, and data reduction.

The school will be held once per year. An intensive GBT remote observer training workshop will be held immediately following the school for those who wish to obtain remote observing certification. The next school will be held in Summer 2021.

More information can be found here.

Continuing Opportunities

Joint Observations with SOFIA

By agreement with the Green Bank Observatory, SOFIA may award up to 5% of GBT open skies observing time. Similarly the GBT Time Allocation Committee may award up to 3% of U.S. Guest Observer Time on SOFIA. See the Joint Observations with SOFIA page for details.

Joint Observations with XMM-Newton

By agreement with the Green Bank Observatory, detailed in a Memorandum of Understanding, the XMM-Newton Project may award up to 3% of GBT open skies observing time. Similarly the GBT Time Allocation Committee may award up to 150 ks of XMM-Newton time per year. See the Joint Observations with XMM-Newton page for details.

Joint Observations with Chandra X-ray Observatory

In previous semesters, the community has had the opportunity to propose for observing time on NRAO facilities through a joint program with the Chandra X-ray Observatory. The Green Bank Observatory will continue with this program and will allocate up to 3% of the open skies time to highly ranked proposals that request time on both HST and the GBT.  Proposers to the GBO will have the opportunity to request time on Chandra, to be awarded on the recommendation of the GBO Telescope Allocation Committee (TAC) and approved by the GBO Director. Up to 120 ksec will be made available to GBO/LBO/NRAO proposers annually.  See the Joint Observations with Chandra page for details.

Joint Observations with the Hubble Space Telescope (HST)

By agreement between the NRAO (and continued honoring by GBO) and the Space Telescope Science Institute, STScI will be able to award up to 3% of the available open skies time to highly ranked proposals that request time on both HST and the GBT.  In return, STScI has offered 30 orbits of HST time for allocation by the GBO/LBO/NRAO TAC to proposals submitted for the GBO deadlines for Semester 2020B and Semester 2021A.   See the Joint Observations with HST page for details.

Joint Observations with Swift Gamma-Ray Burst Mission

To foster correlative observations, a joint Swift/NRAO observing program was established, detailed in a Memorandum of Understanding. The GBO will continue to honor this agreement.  By this agreement, the Swift Program permits GBO/LBO/NRAO to award up to 300 kiloseconds of Swift observing time per year.   Similarly, GBO/LBO/NRAO permits the Swift Guest Investigator (GI) Program to award GBO observing time.  See the Joint Observations with Swift page for details.

Joint Observations with Fermi Gamma-ray Space Telescope

We remind the community that it is possible to propose for observing time on the GBT through the Fermi Gamma-ray Space Telescope Joint Proposal Opportunity or the Cooperative Proposal Opportunity.  See the Joint Observations with Fermi page for details.

Joint Proposals Between the GBT and NRAO

Observing programs that require combinations of the GBT, VLBA, and/or the VLA should submit a proposal for each of the requested telescopes, with a clear justification for each, as has been the case to date. The proposals will be reviewed as before and considered jointly by the Time Allocation Committee. VLBI proposals which request the GBT or VLA (or the HSA, for example) as elements of the VLBI array do not need separate proposals—those telescopes can be selected as separate VLBI stations from a VLBA/HSA proposal.

Other Proposal Opportunities

The GBO would like to make users aware that there are additional proposal opportunities as follows:

High Risk Proposals

As a means of maximizing its scientific impact through cutting-edge observations, the Observatory encourages the submission of high-risk/high-reward proposals.  The high risk/high reward should be designated in the abstract of the proposal and in the science justification.

Filler Programs

Some programs that are not time critical or require highly subscribed LST ranges can request designation as a “filler program.” Such programs may be able to take advantage of gaps in the GBT schedule, but there no guarantee that any GBT time will be allocated. Proposals requesting a designation as filler should do so in the proposal abstract and in the science justification.  All filler programs will be given a ranking of C.

Triggered Proposals

Observations for unknown sources that would be triggered by a celestial event (e.g. near Earth asteroid, comet, fast radio burst, etc.) can be submitted as a triggered proposal.  Any accepted triggered proposal will have proprietary rights to observations over any DDT proposal.

Further information about each of these programs can be found here.