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 (Summer 2003; superseded by tests made in September for which see below).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