| Keyword | Description | Possible values |
| receiver | Name of GBT Receiver | Rcvr_342, Rcvr_450, Rcvr_600, Rcvr_800, Rcvr_1070, Rcvr1_2, Rcvr2_3, Rcvr4_6, Rcvr8_10, Rcvr12_18, Rcvr18_22, Rcvr22_26, Rcvr_26_40, Rcvr40_52, NoiseSource |
| obstype | Observing Type | Continuum, Spectroscopy, Pulsar, Radar, VLBI |
| backend | Name of Data Acquisition System | DCR, DCR_AF, SpectralProcessor, Spectrometer, VLBA_DAR, Radar, LLRADAR, BCPM, BCPM/SPIGOT, GASP, CGSR2, JPL_RSR |
| restfreq | A list of up to 8 frequencies in MHz. | Any frequency supported by the chosen receiver. (Note that the LO1 system can only track one frequency. The first frequency in the list will be tracked.) |
| bandwidth | Band width per backend input, in MHz. | The possible values depend on the backend and the receiver -- see Table 5. |
| Keyword | Description | Possible values | Default |
| swmode | Switching mode | tp(total power with cal), tp_nocal, sp(switched power with cal), sp_nocal | tp |
| swtype | For switching modes sp and sp_nocal, this is the type of switching. This parameter is not used for tp and tp_nocal modes. | none, fsw(frequency switching), bsw(beam switching), psw(polarization switching), tsw(tertiary switching) | Depends on Swmode. |
| swper | Switching cycle period. | A time in seconds. | Depends on Obstype. |
| swfreq | Frequency offsets used for frequency switching. | A pair of frequencies in MHz. | (-0.25*Bandwidth, +0.25*Bandwidth) for fsw, (0,0) otherwise |
| tint | Back end integration time. | A time in seconds. | Depends on the Backend. |
| beam | Beam selection: applies to multi-beam receivers. | 'B1', 'B2', 'B3', 'B4', 'B12' (both beams 1&2), 'B34', 'B1234' | B1 |
| nwin | Number of frequency windows | 1, 2, 3, 4, 6, 8 | 1 |
| deltafreq | Table of sky frequency offsets for each spectral window. Note these are applied in the topocentric frame (see explanation.) | List of Nwin frequencies, in MHz. | zero (i.e., no offsets) If specified, it must have nwin elements and be the same size as the restfreq list. |
| vlow * | minimum of all source velocities or Z(if vdef=Red) | km/sec | 0 |
| vhigh * | maximum of all source velocities or Z(if vdef=Red) | km/sec | 0 |
| vframe | Velocity reference frame. | topo bary lsrk lsrd galac cmb | topo |
| vdef ** | Velocity definition. | Optical Radio Relativistic Red | Radio |
| iftarget | desired IF power level | 0.2 to 9 volts | 1 volt for 0-12GHz receivers, 3 otherwise |
| Backend | Keyword Name | Description | Possible Values |
| Spectral Processor | sp.mode | Parallel or Cross polarization products or both | 'Square', 'Cross', 'SqrCross' |
| Spectral Processor | sp.polyco | Name of polyco file used for pulsar observing. | valid file path |
| Spectral Processor | nchan | Number of spectral channels per IF | 1024, 512, 256 |
| Spectrometer | spect.levels | Number of levels | 3 or 9 |
| Spectrometer | spect.crosspol | Turns on/off cross poloraization products | Set to 'y' for cross polarization products |
| Spectrometer | nchan | Number of spectral channels. Given the bandwidth, number of levels, number of spectral windows, and beams, there are up to 3 choices of the number of spectral channels available. This parameter chooses which of the possibilities are to be used. Refer to the SpectrometerModes page to see the number of channels corresponding to this parameter. | 'low', 'medium', or 'high' |
| Spectrometer | spect.numbanks | (optional) Requested number of spectrometer banks. In most cases there is only one choice and the config tool chooses the default. There are a few cases in which one may choose an alternate number of banks. Refer to the SpectrometerModes page for details. | None(tool choose the default), 1, 2, or 4 |
| BCPM | bcpm.submanager | The name of the computer controlling the BCPM | 'bcpm1', 'bcpm2', or 'bcpm1_and_bcpm2' |
| BCPM | bcpm.hardware | Which hardware rack is being used. | 'bcpm1', 'bcpm2', or 'bcpm1_and_bcpm2' |
| BCPM | bcpm.ch_bw | channel bandwidth | 0.5, 0.7, 1.0, 1.4, or 1.74 MHz |
| BCPM | bcpm.sample_time | The sample time | 'X1', 'X2', or 'X4' |
| BCPM | bcpm.sum_pol | Chooses whether to sum the polarizations | 'Yes' or 'No' |
| BCPM | bcpm.source_name | Name of source to be observed. | 'needs_to_be_defined' |
| VLBI | vlbi.phasecal | Turn phase cal on or off | 'off' 'M1' 'M5' |
| Keyword | Receiver(s) | Default | Possible values |
| pol | Prime Focus, Rcvr1_2, Rcvr2_3, Rcvr4_6 | Default is Circular for VLBI or Radar back ends, otherwise Linear | 'Linear' or 'Circular' |
| noisecal | All receivers but hi/lo option not available for Rcvr12_18 and higher | 'lo-ext', except for BCPM and Radar = 'off' | 'off', 'on-mcb', 'on-ext', 'lo-mcb', 'hi-mcb', 'lo-ext', 'hi-ext', 'lo', 'hi' |
| notchfilter | Rcvr1_2 | 'In' | 'In' or 'Out' |
| xfer | Beam transfer switch for Rcvr12_18, Rcvr18_26, and Rcvr40_52 | If Swtype is 'bsw', then 'ext', otherwise 'thru' | 'ext', 'thru', or 'cross' |
| polswitch | Pol transfer switch for Rcvr1_2 | If Swtype is 'psw', then 'ext', otherwise 'thru' | 'ext', 'thru', or 'cross' |
| chopper | Rcvr40_52 | 'off' | 'off', or 'on' |
| Backend | Receiver | Possible Bandwidths |
| Spectrometer | Any | 12.5, 50, 200, 800 MHz |
| Spectral Processor | Any | 40, 20, 10, 5, 2.5, 1.25, 0.625, 0.3125, 0.15625, 0.078125 MHz |
| DCR, BCPM, VLBI, or Radar | Prime Focus | 20, 40, 80, 240 MHz |
| DCR, BCPM, VLBI, or Radar | Rcvr1_2, Rcvr4_6, Rcvr8_10, Rcvr12_18 | 20, 80, 320, 1280 MHz |
| DCR, BCPM, VLBI, or Radar | Rcvr2_3, Rcvr18_26, Rcvr40_52 | 80, 320, 1280 MHz |
| DCR_AF | Any | 12.5, 50, 200, 800 MHz |