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The system temperature is a summary of the noise added by the system. This
noise comes from 1) the receiver and the optics, 2) the emission of the
sky, and 3) the emission picked up by the secondary side lobes of the
telescope. It is usual to approximate it (in the
scale) with
|
(3) |
where
is the receiver image gain,
the telescope forward
efficiency,
the airmass,
the
atmospheric opacity in the signal band,
the mean physical
atmospheric temperature,
the ambient temperature in the receiver
cabine and
the noise equivalent temperature of the receiver and the
optics. All those parameters are easily measured, except
, which is
depends on the amount of water vapor in the atmosphere and which is
estimated by complex atmospheric models.
Gildas manager
2014-07-01