From R.Lucas lecture 7, Eq. 7.1), the baseline-based observed
visibility
is linked to the true visibility Vij 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 7. At Bure, the
receivers and the IF chain are very stable and these values are constant with time
(and equal to GiUL, GiU and GiL, respectively, since we also
neglected their frequency dependence). They are measured at the beginning of each
project on a strong astronomical source. Moreover in Eq.10.3-10.4, 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 10.2 will focus on the corrections for the atmospheric absorption ( TcaliU(t), TcaliL(t)) 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, TA*,
) or in Jy (flux density unit, 1 Jy
=
10-26 Wm-2Hz-1). 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 10.3 which is devoted
to the flux density calibration.
Finally Section 10.4 will deal with the understanding of the terms
and f, the amplitude calibration of interferometric data.