almatau.g encapsulates the approximate behavior of the opacity spectrum above the Chajnantor site into a glish tool. Using the most recent version of J. Pardo's ATM program (current as of 2003-June: see http://www.aoc.nrao.edu/~bbutler/work/alma/calibration/ATM), I calculated wet and dry opacity terms for the Chajnantor site with 1 GHz resolution. The almatau.g script defines a tool which uses the wet and dry term spectra from 1 to 1000 GHz to perform various calculations. Since the site testing data archives opacity at 225 GHz, some special functions are defined on the 225 GHz opacity, scaling it to other frequencies based on the model
tau(freq, pwv) = dry(freq) + pwv * wet(freq)
Note that all frequencies are in GHz and all precipitable water vapor values are in millimeters. To use almatau.g:
download almatau.g start aips++ at the aips++ prompt, type: include 'almatau.g' # load the almatau.g code pwv := 1.1; # set a variable called pwv to 1.1 mm water freq := 345; # set a variable called freq to 345 GHz tau225 := 0.06 # set a variable called tau225 myalmatau := almatau() # create a tool called myalmatau myalmatau.plottrans(pwv) # make a plot of the atmospheric transmission myalmatau.plottrans(pwv, fmin=200, fmax=300) # make a plot myalmatau.gettau(freq, pwv) # get the opacity for freq, pwv myalmatau.getpwv(tau225) # calculate the pwv for a specific 225GHz tau myalmatau.getwet(freq) # return wet term at freq myalmatau.getdry(freq) # return dry term at freq myalmatau.totaufreq(tau225, freq) # given tau @ 225, calculate tau at freq vectau225 := [0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1] myalmatau.vectotaufreq(vectau225, freq) # given vector of tau @ 225, # calculate a vector of tau at freq myalmatau.done() # finish the almatau tool
Last Modified 2003 July 2