Elapsed telescope time

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

$$\ensuremath{t_\ensuremath{\mathrm{onoff}}}= \ensuremath{\et... ...h{\mathrm{tel}}}\, \ensuremath{t_\ensuremath{\mathrm{tel}}},$$ (4)

where is the efficiency of the observing mode, i.e. the time needed 1) to do calibrations (e.g. pointing, focus, temperature scale calibration), and 2) to slew the telescope between useful integrations.

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.