Observing time estimates

This matter needs special attention as a serious time underestimate may be considered as an indication of sloppy proposal preparation. We strongly recommend to use the web-based Time Estimator (URL: ./IRAMES/obstime/time_estimator.html), whenever applicable. It handles heterodyne (single pixel and HERA) as well as bolometer observations with updated instrumental parameters. Suggestions and questions can be addressed to Axel Weiß (aweiss@iram.fr).

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 $T_{\rm sys}$, 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. A technical report explaining how to estimate the telescope time needed to reach a given sensitivity level in various observing modes was published in the January 1995 issue²of the IRAM Newsletter [5]. It has been included in the 30m telescope Manual [6].

Proposers should base their time request on normal winter conditions, corresponding to 4mm of precipitable water vapor. Conditions during afternoons can be degraded due to anomalous refraction. The observing efficiency is then reduced and the temperature calibration is more uncertain than the typical 10 percent. If exceptionally good transmission or stability of the atmosphere is requested which may be reachable only in best winter conditions, the proposers must clearly say so in their time estimate paragraph. Such proposals will however be particularly scrutinized.