Observing time estimations

Most proposals submitted for the 30 m telescope underestimate the observing time needed to carry out the programme, even during excellent weather. Observing time estimates must take into account:

• receiver tunings (allow 20 min. per receiver)

• pointing, focus, receiver alignment, continuum and line calibrations,

• telescope motions when changing sources as well as dead time due to telescope motion and/or data writing between ON and OFF subscans (count 2 sec per degree for slew mode motions and an additional 8 sec for telescope acceleration and deceleration; count 8 sec of dead time between subscans),

• integration time on source and comparison field(s). The total integration time should be derived using the standard formula:

  

  where and are the telescope forward and main beam efficiencies, is the system temperature above the atmosphere (in the antenna temperature scale), B the channel bandwidth, and t the total (ON + OFF) integration time. should be estimated for an `average' winter humidity for 3mm, 2mm and 1.3mm observations (3mm of precipitable water, or at 230 GHz), and for dry weather conditions for the 0.8mm observations which will be scheduled in January (1.5mm of precipitable water, of at 350 GHz).

For additional help on this matter, please, contact IRAM Granada or IRAM Grenoble (Mrs. C. Berjaud). Several examples of observing time request estimates are at your disposal.