Fitting Tsys for the alfa receiver.


      The system temperature for the Alfa receiver is computed by month using all of the spectral line cal on/offs (wapp data) taken  (see computing tsys from the archive for a description of how it is computed). A model is then fit to this data. The fitting procedure is iterative. It does the fit, and then throws out any points whose residuals are greater than 3 sigma.

The model used:

    The model for the fit is:
Tsys=c0 + c1*za + c2*(za-14)^2 + c3*cos(az) + c4*sin(az) +c5*cos(2az) +c6*sin(2az) + c7*cos(2rotA) + c8*sin(2rotA) + c9*(freqGhz-1.36) + c10*(freqGhz-1.36)^2



Model notes:

Model fits: 01jan05 thru 31jan07

    There were between 15000 and 17000  good calon/offs in this date range (depending on pixel and polarization). The fit sigma's ranged from .47K to .67 There are 14 plots in all (one for each pixel/polarization). The plots contain: The  plots for each pixel/polarization: (.ps files about 10 Mb, .pdf files about 3 Mb)
  • pixel0A (.ps)  (.pdf)
  • pixel0B (.ps)  (.pdf)
  • pixel1A (.ps)  (.pdf)
  • pixel1B (.ps)  (.pdf)
  • pixel2A (.ps)  (.pdf)
  • pixel2B (.ps)  (.pdf)
  • pixel3A (.ps)  (.pdf)
  • pixel3B (.ps)  (.pdf)
  • pixel4A (.ps)  (.pdf)
  • pixel4B (.ps)  (.pdf)
  • pixel5A (.ps)  (.pdf)
  • pixel5B (.ps)  (.pdf)
  • pixel6A (.ps)  (.pdf)
  • pixel6B (.ps)  (.pdf)
  • Fit residuals (degK)
    SigPolA (K)
    SigPolB (K)


  • Tsys contains the contribution from the sky. It will vary depending where the person was looking.
  • The fit coefficients are supplied in the idl distribution of phil's routines (see downloading the idl routines). At AO this is located in /pkg/rsi/local/libao/phil/data/tsysdatR17.
  • The idl routine alfatsysget() (in the ./gen directory) will evaluate tsys for a given freq, az,za, and rotation angle.
  • History:

    processing: x101/mbeam/tsys/archive/fit/