From Lucas lecture (Chapter 9), Eq. 9.1, the
baseline-based observed visibility
is linked to the
true visibility
of the source by:
and
are the electronics gains (IF
chain+receiver) in the lower and upper sidebands, respectively.
The receiver sideband gain ratio is defined as
. The sideband gain ratio is to first
order independent of the frequency
within the IF bandwidth.
The derivation of the receiver gains is given in
Chapter 9. At Bure, the receivers and the IF chain are
very stable and these values are constant with time (and equal to
,
and
, respectively, since we also
neglected their frequency dependence within the IF bandwidth).
They are measured at the beginning of each project on a strong
astronomical source. Moreover in Eq.12.3-12.4, we use
the fact that for a given tuning, only the receiver gains and the
atmospheric absorption have a significant dependence as a function
of frequency.
Section 12.2 will focus on the corrections for the atmospheric
absorption (
,
) and the possible biases they
can introduce in the amplitude.
In the equations above, the amplitudes can be expressed either in
Kelvin (antenna temperature scale, ,
) or
in Jy (flux density unit, 1 Jy
Wm
Hz
).
The derivation of the conversion factor between Jy and K, in Jy/K,
(single-dish mode) and
(interferometric
mode) and its biases will be detailed in section 12.3
which is devoted to the flux density calibration.
Finally Section 12.4 will deal with the understanding
of the terms
and
, the amplitude calibration of
interferometric data.