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Basic Information on obstau
Task: obstau
Purpose: Computes tau and sky temperature from atmospheric model
Categories: utility
OBSTAU computes tau, sky temperature and single sideband
systemp from an atmospheric model.
The program assumes scale height for water is 1.6 km.
You must specify the water content of the atmosphere.
This can be input as precipitable water (mm),
or relative humidity (%) and temperature (C).
Output: zenith opacity, estimated skytemp at current airmass,
and single sideband system temperature, Tsys.
Key: altitude
Altitude of observatory (km). Default=1 km.
Key: freq
freq (GHz). Default=100 GHz.
Key: mmh2o
precipitable water (mm). Default=10 mm.
Key: relhumid
ground level relative humidity (%). Default=0. Uses mmh2o.
A non-zero relhumid is used to calcuate mmh2o.
Key: airtemp
ground level temperature (C). Default=0.
Key: airmass
airmass in units of zenith airmass. Default=1 airmass.
Key: elev
elevation in degrees used to compute airmass if elev.ne.0.
Default elev=0, i.e. use given airmass.
Key: trx
Double sideband receiver noise temperature. Default=40 K.
or if (freq.gt.120) trx=80 K is default.
This is used to calculate the single sideband systemp as:
systemp = 2.* (skytemp+trx) * exp(airmass*tauzenith)