Adding Non-Temporal Gain Correctons

CASA Modification Request 13C108, November 2007



1. Introduction

Casa should add the ability to apply several important non-temporal gain corrections to the data. The most important is the phase correction due to an antenna location error.

2. Background

3. Requirements

Additional gain corrections (mostly in phase) are needed for complete calibration of the data. The task CLCOR in aips gives an example of the many types of such calibrations that may be needed. In decreasing order of priority, here are suggestions of calibration types to add.

1. Antenna location changes: This task will be needed with early EVLA and ALMA data, including antenna axis-offset geometry and for a lot of archival VLA data.

2. Field position changes: The phase modification associated with a change of the field center position.

3. Gross temporal phase changes: Large phase/delay/rate changes that must be removed from the data before normal calibration. This kind of calibration will be necessary for early ATF and ALMA data analysis.

4. Ionosphere correction: The ability to correct the phase given an input ionosphere refraction model. Important for the EVLA data

5. Troposphere correction: The ability to correct the phase given an input tropospheric delay model. Important for ALMA data.

6. Astrometric reductions: The ability to correct the phase for small earth-orientation and nutation errors. Could be important for ALMA astrometric data.

4. Design

These kinds of corrections have not been well-thought out in the design of casa. There should be an integrated plan which can deal with the above (and other) corrections in a unified manner. Good plotting capabilities may also be necessary.

5. Deployment Checklist

6. Test Plan

6.1 Internal Testing

6.2 Sponsor Testing

Some changes can be easily tested (field position change), others require more ingenuity. The best method is to compare with the same type corrections that are made in AIPS.

6.3 Integration/Regression Tests

A regression test specifically designed for these calibration functions may not be necessary.

6.4 Testing for Scientific Validity

See 6.2


Signatures

APPROVED: I acknowledge that my request is fully contained in this MR, and if the CASA development group delivers exactly what I specified, I will be happy.

ACCEPTED: I acknowledge that I have validated the completed code according to the acceptance tests, and I am happy with the results.

Written - - - - -
Checked - - - - -
Approved by Scientific Sponsor - - - - -
Accepted/Delivered by Sponsor - - - - -

Symbols:
  • Use %X% if MR is not complete (will display ALERT!)
  • Use %Y% if MR iscomplete (will display DONE)


Discussion Area

-- NicoleRadziwill - 30 Oct 2007

-- EdFomalont - 06 Nov 2007
Topic revision: r3 - 2007-11-06, EdFomalont
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