Tài liệu The Proposer''''s Guide for the Green Bank Telescope: GBT Support Staff pdf

The Proposer’s Guide for the Green Bank

Telescope

GBT Support Staff

December 19, 2012

This guide provides essential information for the preparation of observing

proposals on the Green Bank Telescope (GBT). The information covers

the facilities that will be offered in Semester 13B.

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Important News for Proposers

Deadline Proposals must be received by 5:00 P.M. EST (22:00 UTC) on Friday, 1 February 2012.

Technical Justification is Required All GBT proposals must include a Technical Justifica￾tion section (see Section 8.2)). Any proposal that does not include a technical justification may

be rejected without consideration.

VErsitile GBT Astronomical Spectrometer (VEGAS) We will accept shared-risk ob￾servations using the new VErsitile GBT Astronomical Spectrometer (VEGAS) which is an FPGA

based backend (see Section 3.3.2)).

PF1/450 Feed RFI Digital TV signals at frequencies above 470 MHz will make observing very

difficult with this receiver. Available RFI plots do not show the strength of these signals very well

as they overpower the system. Observers should consult the support scientists before submitting

a proposal for this feed.

PF1/600 Feed RFI Digital TV signals at frequencies covering most of this feed will make observ￾ing very difficult with this receiver. Available RFI plots do not show the strength of these signals

very well as they overpower the system. Observers should consult the support scientists before

submitting a proposal for this feed.

C-band Receiver The C-band receiver will be upgraded to include the 6-8 GHz frequency range.

We will consider shared-risk proposals for the 1 February 2013 deadline for observations in the 6-8

GHz range.

Ku-wideband Receiver The Ku-wideband receiver has nominal frequency range to cover 12.0

- 18.0 GHz. We will consider shared-risk proposals for this new feed (Ku-wideband) at the 1

February 2013 proposal deadline. When proposing, please use the nominal system temperature for

the ”old” Ku receiver. Please note that this feed was built for continuum and pulsar observations

and is expected to have very poor baseline structures for spectral lines. The feed does not have a

noise diode so close attention must be paid to calibration.

Pulsar Proposals All proposals requesting pulsar observations should use the GBT Sensitivity

Calculator available at https://dss.gb.nrao.edu/calculator-ui/war/Calculator ui.html to estimate

their observing times.

Sensitivity Calculator New All proposers should use the new and improved GBT Sensitivity Cal￾culator. Please see the GBT Sensitivity Calculator available at https://dss.gb.nrao.edu/calculator￾ui/war/Calculator ui.html for further instructions. The new 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 increase your chances of getting a positive technical

review.

The Dynamic Scheduling System (DSS) The GBT will be scheduled by the DSS during

the 13B semester. Further information on the GBT DSS can be found at: http://www.gb.nrao.edu/DSS

Large Proposals Large Proposals (more than 200 hours) will be accepted for the 13B semester.

Large proposals will be accepted for the fully commissioned hardware only.

New Ph.D. Support Policy Proposer’s are reminded of the NRAO policy related to the sup￾port of Ph.D. dissertations using NRAO facilities. The policy can be found at

http://www.gb.nrao.edu/gbtprops/gbtproppolicies.shtml

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Contents

1 Introduction to the GBT 1

2 Submitting a proposal 2

2.1 Latest Call for Proposals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Joint Proposals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.3 Travel Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.4 Student Financial Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.5 Observing Policies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.6 Page Charge Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 GBT Instruments 4

3.1 Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.1.1 Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.1.2 Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.1.3 Efficiency and Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.2 Receivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.2.1 Prime Focus Receivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.2.2 Gregorian Receivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3.2.3 Receiver Resonances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.3 Backends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.3.1 GBT Spectrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.3.2 VErsitile GBT Astronomical Spectrometer . . . . . . . . . . . . . . . . . . . . . . 17

3.3.3 Spectral Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.3.4 DCR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.3.5 Guppi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.3.6 CCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.3.7 Mark5 VLBA Disk Recorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.3.8 User Provided Backends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4 GBT Observing Modes 21

4.1 Utility modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.2 Standard Observing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.3 Switching Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.4 Spectral Line Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4.4.1 Sensitivity and Integration Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4.5 Continuum Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.6 Polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.7 VLBI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26