! beam_eff.class

! Calculate CSO beam efficiency
! D. C. Lis

! S. Radford 2013-05-09

! CSO receivers are DSB; Data are calibrated for lines with signal in only one SB.
! Planets have signal in both SB, so must halve observed temperature.

say "Input parameters:"
say "&1: observing frequency (GHz)"
say "&2: planet diamater (arcsec)"
say "&3: (ssb) planet antenna temperature (K)"
say "&4: planet brightness temperature (K)"
say "&5: beam size (arcsec) (<0=diffraction beam)"
let obs_freq &1 /new double
let pla_diam &2 /new double
let ssb_temp &3 /new double
let pla_temp &4 /new double
let fwhm &5 /new double
!
! Kooi 24.4 @ 345 GHz; diffraction limited 21 => times 1.16

if fwhm.lt.0 then
  let fwhm 1.22*3e10|10.4e2|1e9|obs_freq*206265.!*1.16
endif
let round int(10*fwhm) /new double
say " "
say "Assumed beam size: "'round|10'" arcsec"
let cfac 1-exp(-log(2.)*(pla_diam|fwhm)**2) /new double
let mbef ssb_temp|2.|pla_temp|cfac*100. /new double
let round int(mbef*10)
say "Beam efficiency  : "'round|10'" %"