The most usual instrumental mode for a radio-interferometer is to observe with a single band of receiver a single LO frequency. This mode will be called “standard” mode hereafter. NOEMA introduces two other possibilities:
As the dichroic can be removed from the optical path when doing single band observations, this receiver noise increases will only happen when the sensitivity estimation is done in dual band mode.
After the setup phase, each cycle observed at a given frequency must be surrounded by gain calibration observations at the same frequency. This means that the observing efficiency decreases with respect to the standard instrumental mode: in practice this is like doubling the number of calibrators, since each calibrator will have to be observed at the 2 frequencies (the frequencies of the previous and of the next cycle, whatever the number of cycles).
This memo describes how the sensitivity estimator tool used in the Proposal
Management System (https://oms.iram.fr/oms/?pms) encodes the
sensitivity estimation for these three instrumental
modes. Sections
,
, and
first
reminds the basic equations used to compute the sensitivity of a
radio-interferometer, namely, the interferometric point source and
extended sensitivity, as well as the system temperature that characterizes
the noise added by the receiver, the telescope optics, and the
atmosphere. Section
details the actual computation as
a function of the observing mode.