Argus has been fully implemented into the GBT sensitivity calculator. The numbers provided below are based on version 2.4.1 of the Sensitivity Calculator. *** As a general approximation, the total requested time, including all overheads (AutoOOF's, points, focus, vanecals, calibration, setups, configurations, scan-overheads, mapping overheads) should be about 2x the required observing time, independent of observing mode. *** ---------------------------------------------------------------- Example of estimating the observing time for Argus using the GBT sensitivity calculator tool: https://dss.gb.nrao.edu/calculator-ui/war/Calculator_ui.html o Select Observing Time from Desired Sensitivity o Select Sensitivity Units:, e.g., Tmb(mK) o Select Desired Sensitivity (1-sigma), e.g.,: 100 mk o Select Backend: VEGAS (VErsatile GB Astronomical Spectrometer) o Select Mode: Spectral Line o Select Receiver: ARGUS (75.0-115.5GHz) o Select Beams: 16 o Select Bandwidth (MHz): e.g., 23.44 o Select Number of Spectral Windows: e.g., 1 o Select Switching Mode: In-Band Frequency Switching Use position switching for broad extragalactic lines or complex spectral regions with many lines, or frequency switching for Galactic narrow-lines and/or large extended regions without a clean spatial off. o Enter frequency -- Rest Frequency (MHz): 110000. (for 110 GHz, enter in units of MHz) o Enter Source Declination (Deg): e.g., 0. o Enter minimum elevation -- Minimum Elevation (Deg): 30. (avoid the default 5 deg or the tool will assume observing at high airmass which will overestimate the observing time) o Make sure "Average Orthogonal Polarizations" is not selected since Argus has only one polarization per beam. o Ratio of observing time spent on-source/on-frequency vs reference positions/frequency (leave default of 1). o Number of reference observations used in reduction. Leave as 1 for frequency switching observations. For position switching mapping observations where the edges of the maps are clear of any signal, then one can choose to average multiple edge integrations of each scan to be used as the off of each scan integration/sample; in this case one can enter 10-20 depending on how much of the map edges are void of signal. For OnOff or NOD/subBeam/Nod observations, leave as 1. o Select Difference Signal and Reference Observations (normal on-off reduction) o Select Smoothing to desired velocity or frequency resolution: e.g., 1 km/s. Click the "Update Results" button in the right control panel to return the results. Example: Say an observer wants to reach an rms of 100.0mK in Tmb at 110.0 GHz smoothing to 1.0 km/s spectral resolution using in-band frequency switching. The calculator derives a total observing time of 159sec with the above settings. The value of 100mK on Tmb scale corresponds to 20mK in Ta and 26mK in Ta*, so it is crucial that proposers explicitly state which temperature scale they are using for their time estimation. In this example, the calculator uses a main-beam efficiency (eta_mb) of 0.26, where Tmb eta_mb = Ta exp(tau_zenith*AirMass) = Ta* et_l. --------------------------------------------------------------------- If the observer wants to map a region, they can estimate the mapping time using the GBT mapping calculator. http://www.gb.nrao.edu/~rmaddale/GBT/GBTMappingCalculator.html Say the observer wants to map 5 arcmin x 5 arcmin to the depth of 100mK in Tmb at 110GHz (as given above) using on-the-fly in-band frequency switching mapping. The observing time from the sensitivity calculator is 159 sec), but the mapping calculator is for one beam, so the "Integration Time Per Beam" on the sky to enter into the mapping calculator is 159sec/16 = 10sec, since Argus has 16 feeds. For Argus mapping, you can choose TINT/SWPER=1 (instead of default of 4). For 5'x5' enter 0.0833 Deg x 0.0833 Deg for rectangle map size. The calculator will return a "Time for Map" of 5.3hrs or a "Total Time" of 5.8hrs including the mapping overheads between scan legs. Factoring in all overheads, the total requested time should be about 11hrs (~2x5.3 = 10.6), depending on how the time is divided into sessions (each session needs to be a multiple of 15minutes for scheduling and session lengths are typically 3-6hrs). Mapping restrictions: o For frequency switching SWPER>=0.4 sec. o Observers are limited to only 2 turn-arounds/accelerations per minute while mapping. 2021.01.20 -- D. Frayer