This matter needs special attention as a serious time underestimate may be considered as a sure sign of sloppy proposal preparation. We strongly recommend to use the web-based Time Estimator at URL ../IRAMES/obstime/time_estimator.html , whenever applicable. Versions 2.6 and higher handle heterodyne (single pixel and HERA) as well as bolometer observations with updated instrumental parameters.
If very special observing modes are proposed which are not covered
by the Time Estimator, proposers must give sufficient technical
details so that their time estimate can be reproduced. In
particular, the proposal must give values for 
, the
spectral resolution, the expected antenna temperature of the signal,
the signal/noise ratio which is aimed for, all overheads and dead
times, and the resulting observing time. The details of the
procedures on which our time estimator is based are explained in a
technical report published in the January 1995
issue2
of the IRAM Newsletter [5].
Proposers should base their time request on normal summer conditions, corresponding to 7mm of precipitable water vapor. Conditions during afternoons can be degraded due to anomalous refraction. The observing efficiency is then reduced and the flux/temperature calibration is more uncertain than the typical 10 percent (possibly slightly more for bolometer observations). If exceptionally good transmission or stability of the atmosphere is requested which may be reachable only in winter conditions, the proposers must clearly say so in their time estimate paragraph. Such proposals will however be particularly scrutinized.