Argus Observer's Web Page


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).

Figure: 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.

Key Information for GBO call for proposals

Information for Argus Observers

Argus has successfully completed its commissioning and has been carrying out science observations on the GBT since 2017. 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.

Important Data Issue

All Argus data collected before 2018.10.22 19:30 UT will need to swap the positional information between Beam-2 and Beam-3 to be consistent with the actual positions on the sky for these beams. This was due to a cable mis-match for these beams in the equipment room. (link for more information)

Note: Beam2 and Beam3 are for the instrument beam numbering system (1-16). This corresponding to fdnum1 and fdnum2 using GBTIDL numbering system (0-15).

Figures: (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. The First and 2nd Light spectra are the first time the GBT has observed above 100 GHz.

Commissioning and First Light

Argus finished its intial commissioning 2016.12.04 and is now carrying out shared-risk science observations on the GBT.
  • 2017.06.27 TGBT15A_901_49: USB vs LSB Tsys measurements. USB and LSB has similar performance except at the high end of the band where USB is better on average. Much of the improved performance in USB at high-frequency is due to beam-8 which does not have any side-band rejection so that the LSB Tsys values are doubled in compared to USB at 115 GHz. Below 100 GHz, users will get slightly better performance in LSB. At 100-110 GHz the performance is similar and above 110 GHz, USB should be used.

    VEGAS Bandpass with Argus

    VEGAS is the new GBT spectrometer and supports several modes. Here we show the VEGAS bandpass performance as a function of bandwidth/mode for Argus. The bandpass shapes shown here are similar to those seen with other GBT receivers. The narrow-bandwidth modes (11-24 MHz) have a smoother bandpass and are good for frequency switching, while the larger bandwidth modes (100-1500 MHz) show signficant ripples/structure across the bandpass.
    Mode Bandwidth [MHz] Useable Bandwidth [MHz] Notes Figure
    1 1500 +/-650 15-40 MHz structures Fig.
    3 1080 +/-400 44 MHz ripple Fig.
    4 187.5 +/-80 12.5 MHz ripple Fig.
    7 100 +/-45 6.7 MHz ripple Fig.
    10 23.44 +/-9.5 smooth passband Fig.
    15 11.72 +/-5 smooth passband Fig.
    20 23.44 +/-9.5 small bump in middle Fig.
    25 16.9 +/-7 small bump in middle Fig.

    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.

    Last updated 04 February 2020 by David Frayer