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Dead times

Telescope motions are either in the `slew' mode (when moving toward a new pointing position, or from the source to a reference field), or in the `tracking' mode. Data acquisition is not allowed during `slews'. Similarly, when wobbling the subreflector (WSW mode), there are blanking intervals during the subreflector motions. These dead times have to be included in the telescope time evaluation. They can be estimated with the following formulas:

  1. where D is the AZ or EL angle (whichever is the largest) between the two positions, expressed in degrees, and is deg/sec.

  2. In the standard wobbling mode (WSW= or , Phase= 2s), the blanking time is , where N is the number of 2s integration phases and s.

To these times, one must add the deadtimes between subscans, = 2s (but only when the telescope does not move, otherwise this time is included into ), and the time needed to initiate and close a scan ( = 8s).

Robert Lucas
Thu Mar 9 12:14:01 MET 1995