The test map of 13CO in DR21 shown at the right was taken with an opacity of 0.42 (marginal conditions) in about 40 minutes of mapping using all 16 beams of Argus. The map is the result of the default data processing without any data editing. The small beam of the GBT is shown in white to the lower-right of the image for comparison.

Argus is a 16-pixel W-band focal plane array for millimeter spectroscopy that has been deployed on the Green Bank Telescope (GBT). The array is designed to operate in the 85-116 GHz range (Sieth et al. 2014, SPIE 9153; doi:10.1117/12.2055655 (pdf)). Argus is a collaboration between Stanford U. (PI Sarah Church), Caltech, JPL, Univ. Maryland, Univ. Miami, and the Green Bank Observatory (GBO).

Information for Argus Observers

Argus has successfully completed its initial phases of commissioning and is ready for shared-risk science observations on the GBT. The normal DSS scheduling system applies, and priority for observations will be given to teams that visit Green Bank to carry out the observations. Example Argus observing scripts are located at: /home/astro-util/projects/Argus/OBS while example Argus GBTIDL reduction scripts are located at: /home/astro-util/projects/Argus/PRO. The information contained here will expand significantly as it becomes available, but the details related to observing can wait until you visit Green Bank for observations.

Key Information for GBO call for proposals

ARGUS is a “shared-risk” instrument for the GBO 17B call for proposals (due 2017-Feb-01) . Argus shared risk policy: [pdf file].

  • Proposers must contact the instrument team for permission to use the instrument; email address: “”
  • Good frequency range: 74–116 GHz
  • Receiver noise: 40–80 K
  • 4×4 element focal plane array with beam separation of 30.4 arcsec on the sky in both the elevation and cross-elevation directions.
  • Single linear polarization per feed
  • Instananous instrument bandwidth is 1.5 GHz (which is similar to the VEGAS spectrometer bandwidth)
  • All 16 beams of ARGUS can be connected to the 16 VEGAS channels (VEGAS has 8 dual polarization banks [16 spectrometer channels])
  • Users can observe multiple lines simultaneously using VEGAS sub-banding modes (
  • Double-side-band instrument with IQ-mixer scheme to separate the USB and LSB. The user can select one of the side-bands to connect with VEGAS. Sideband isolation is about 10-20 dB.
  • Instructions estimating the observing time needed for Argus using the GBT sensitivity and mapping calculators (example of time estimation).
  • NRAO Proposal Submission Tool (PST)
  • GBT Sensitivity Calculator
  • GBT Mapping Planner
  • GBT Proposer’s Guide

Argus 1st and 2nd Light Spectra This represents the first time that the GBT has observed above 100 GHz.

Noise Temperature as a function of frequency measured for Argus during good weather conditions during a maintenance day (zenith tau(90GHz)=0.057). The small “+” are individual Tsys measurements for each of the 16 beams, where Tsys corresponds to the total system temperature applicable for Ta. The median over all the beams of these values is shown by the squares. The median of the effective Tsys* corresponding to the system temperature associated with the measured Ta* is shown by the triangles, while the median values for the implied receiver noise temperature is shown by the diamonds.

This is the public Argus web page. Users can contact David Frayer with questions about observing.

Argus team members should contact David Frayer for the location of the team web page(s) with more detailed information.

Contact David T. Frayer via e-mail.

Last updated 12 January 2017 by David Frayer

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