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Glossary

attenuators There are a number of attenuators controlling the power levels into the samplers. These levels need to be set before the start of observing.
(See fine attenuators, coarse attenuators and mm attenuators)
caobs the main ATCA observing program
coarse attenuators Coarse attenuators help control the power levels into the samplers.
There are 4 fine attenuator steps (0 - 3) which are 6dB steps (except the last step (step 3) which is 5dB)
Coarse attenuators effect the phases and amplitudes, so caobs will not automatically set coarse attenuators. Changes have to be commanded explicitly:
caobs> set coarse ca0# a1b1a2b2
To determine current attenuator settings, check on page 7 and 8 of camon or in caobs
caobs> show coarse
(See also attenuators, fine attenuators and mm attenuators)
fine attenuators Fine attenuators control the power levels into the samplers.
There are 8 fine attenuator steps (0 - 7) which are 2dB steps
these attenuators are usually automatically set by caobs, however levels can explicitly be set with the caobs command
caobs> set atten ca0# a1b1a2b2
Fine attenuators do not effect the phases or amplitudes, so can be set without disrupting observing.
To determine current attenuator settings, check on page 7 and 8 of camon
(See also attenuators, coarse attenuators and mm attenuators)
mm attenuators mm attenuators are available to help control the power levels into the samplers.
There are 16 mm attenuator steps (0 - 15) which are 1dB steps
mm attenuators control both a and b polarisations (i.e. a1 and a2 are not controlled separated, similarly b1 is driven at the same time as b2). Like coarse attenuators mm attenuators effect the phases and amplitudes, so caobs will not automatically set mm attenuators. Changes have to be commanded explicitly:
caobs> set mm ca0# ab
To determine current mm attenuator settings
caobs> show mm
(See also attenuators, fine attenuators and mm attenuators)
scan the set of parameters that define an individual pointing in an ATCA observation (e.g. source name, RA, dec, frequency, bandwidth etc.) A schedule will generally include a number of scans.
Original: Robin Wark (14-Aug-2006)
Modified: Robin Wark (17-Aug-2006)