The goal of a time estimator is to find the elapsed telescope time
(
) needed to obtain a given rms noise, while a sensitivity estimator
aims at finding the rms noise obtained when observing during
. If
is the total integration time spent both on the on-source and
off-source observations, then

The tuning of the receivers is not proportional to the total integration
time but it should be added to the elapsed telescope time. A time estimator
can hardly anticipate the total tuning time for a project. Indeed, one
project (*e.g.* faint line detection) can request only one tuning to be used
during many hours and another (*e.g.* line survey) can request a tuning
every few minutes. In our case, we thus request that the estimator user add
by hand the tuning time to the elapsed telescope time estimation.