;+ ; Function to return a default zenith opacity, given an ; observing frequency. Used in the calibration routines. ; ; These values are simply best guesses. The user should replace ; this routine as required for the program at hand. ; ; @param freq {in}{required}{type=float} Observing frequency in GHz ; @examples ;
; apeff = get_ap_eff(18.5,45.0) ; tau = get_tau(18.5) ; print, apeff, tau ;; ; @version $Id: get_tau.pro,v 1.1 2005/05/26 21:19:13 jbraatz Exp $ ;- function get_tau,freq compile_opt idl2 ; Check parameters if n_elements(freq) ne 1 then begin message,"A frequency must be supplied.",/info return, 0 endif if freq gt 115.0 then begin message,"Frequency out of range.",/info return, 0 endif ; Set the aperture efficiency if freq gt 52.0 then $ tau = 0.2 $ else if freq gt 18.0 and freq lt 26.0 then $ tau = 0.008 + exp(sqrt(freq))/8000.0 + exp(-(freq-22.2)^2/2.0)/40.0 $ else $ tau = 0.008 + exp(sqrt(freq))/8000.0 return,tau end