Documents on System Gain Stability and Phase Stability
The primary document defining specifications for ALMA Front End Systems
is the Front End Specifications, which has evolved considerably since
it
was first drafted following the Front End Review in Feb 2001.
There
was a version
at ALMA Week in June, which had specifications agreed upon at a meeting
in Charlottesville in November of 2002. After some measurements
were done on an early version of B6, this was modified in the Proposed Specs
officially submitted to ALMAEDM. A much
more precise statement of the requirements than in the proposed FE
Spec
is available at the link, to Larry D'Addario's document. He
notes:
"This gives the specification as a test procedure, with limits on
the
Allan variance over a wide range of time intervals. The FE Spec
uses
the vague "time scale" instead of the well-defined time interval and
integration
time used in the Allan variance".
Background documents
Science:
Draft ALMA
Science Requirements.
Engineering:
D'Addario: ALMA Memo
No. 466.
J. Effland tests
of Band 6. (Summer 2003; superseded by tests made in September for
which see below).
Andrey's version of Band 6 tests
Andrey's measurements
at 681 GHz
Paper "Influence
of Temperature Variations on the Stability of a Submm Wave Receiver"
Measurements
on NRAO amplifier illustrating onset of 1/f noise. New (Sept 03) FE
Measurements give much better results on Gain Stability.
Also see the Old
memo.
Simulations:
Holdaway simulations
of effects of atmospheric noise, thermal noise and receiver gain
stability on OTF image noise.
ASAC Comments, 3-4 November ALMA Board Meeting:
This has not yet been released, but the report
discusses these measurements.
Background:
Wolfgang Wild's compilation
of two years ago (Welch memos, etc.; background information)
Phase Stability:
A telecon on 13 November will cover phase stability as well. For
the
SE view please see section 3.1.1.2 of the draft "System
Design Description" .
See also D'Addario proto-memos Phase
Calibration, Atmosphere
(with Holdaway).
A Science IPT view may be found in the 'Calibration
of ALMA' document.
Al Wootten revised 2003-November-10