[mmaimcal] Q for Monday discussion

[Al Wootten]

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From: Wolfgang Wild <wild at astro.rug.nl>
To: Al Wootten <awootten at NRAO.EDU>, "S. Guilloteau" <guilloteau at iram.fr>
Subject: phase calibration
Date: Fri, 27 Aug 1999 09:42:15 +0200

Dear Al and Stephane,

during discussion about ALMA receiver issues in Toronto, a few questions
came up concerning phase calibration using the 3mm band. The overall
receiver design may be influenced by the answers to these questions. I'd
be grateful if you could let me know fairly soon what you think about
this. Here are the questions:

- - It is understood that phase calibration will be done by observing a
phase calibrator (e.g. a quasar) at 3 mm by fast switching. How often
will this calibrator be observed (every x min/sec) ? For how long
typically ? The time to switch from the observing freq to the phase
calibrator is 1.5 sec, is that right ?
- - At what 3mm frequency needs the observation be done ? Can it be any
frequency in the 3 mm band, or does it have to always the same freq ?
- - What sensitivity do we need in the 3mm channel (or in other words:
what would be the weakest source ?)? What stability ? Would a dedicated
3mm channel for phase calibration be necessary (e.g. SIS for phase
calibration, HFET for observing at 3 mm) ?
- - Is dual linear polarization needed for phase calibration ? Or would a
single polarization observation be enough ?

Thank you for some answers, or, if it is not clear at the moment, some
input and opinions.

Best regards,

Wolfgang

PS: There are a few more things important for the receiver group which
should be addressed in the system group. When is the next meeting of the
science and system group ?
 
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Wolfgang Wild              e-mail wild at astro.rug.nl
NOVA/SRON                  Tel.   +31-50-363 6243 (direct)
P.O. Box 800                             363 4074 (secr.)
NL-9700 AV Groningen       Fax    +31-50-363 4033
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