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Let be the power radiated by a black-body at frequency
and temperature . It is always possible to define in a conventional way
a Rayleigh-Jeans temperature
It happens that
has a direct physical meaning, i.e.
can always be defined (even when
just loses its physical meaning. The advantage
of doing this is that all the equations of calibrations are considerably
simpler to write and to implement in source code using the conventional
Rayleigh-Jeans temperature than the black-body formula. The only constraint
is to remember to transform physical temperature (in particular hot and
cold load temperature) in conventional Rayleigh-Jeans temperature for all
the input parameters. This is what is done in GILDAS/TELCAL, in
ATM and thus in this memo.