12 Meter Atmospheric Model
Until the end of the 2003-2004 season, spectral line data taken with the KP
12m telescope were converted to temperature units using a nominal fixed value
for the calibration scale temperature. This value was relatively accurate for
typical atmospheric conditions and frequencies not very close the edges of the
different atmospheric windows accessible by the current facility receivers.
To improve the calibration precision for observations under varying weather
conditions, covering wide ranges in elevation and for lines close to the edges
of the atmospheric windows, we have implemented a real-time calibration system
based on the ATM atmospheric model. Weather data (%RH, Tamb, Pamb, tipper tau)
at the time of each calibration is sent to a program that calculates, for a
given frequency and telescope elevation, a more accurate value for the
calibration scale temperature. Tests of this procedure at the start of this
season have shown a higher stability and repeatability of the intensity scales
in the final calibrated spectral data.