Measurement ●

We are now entering the wide field era



Single gains no longer adequate



Gains are direction dependant

Components of DDEs ●

Beams



Pointing errors



Atmosphere

Open Loop vs Closed Loop ●



Open Loop –

Measurement seperated from target observations



Holography, pan & scan

Closed Loop –

Beam determined by the target field

Smirnov's DDEs ●

Extensive analysis of WSRT DDEs with MeqTrees

Differential Gains

V. High Dynamic Range

dE ●



The Good –

Fly swatter approach



Great maps

The Bad –

Rolls up beam, atmosphere, source structure



Comutational cost



Degrees of freedom

Seperating beam and sky ●



The beams can only be determined realatively with a good sky model Brisken suggested scanning around the sky to trace the flux over the beam by linked tracks of sources

Pointing Self-Cal ●

Given a beam model solve for pointing errors



Low number of solvable terms –



2 reals per antenna vs. 1 complex per source

Our beam models are quite poor, does not consider the atmosphere

Pointing Self-Cal ●

Resutls were poor

Pointing Self-Cal ●

Not sufficient to model the effects



Scale parameter aborbs some of this



Need better beam models and combine with atmospheric models

Pointing Self-Cal success story ●

WSRT pointing analysis



The WSRT wobble

ATA Beams ●

Open loop measurements

ATA Beams

ATA Squint

Summary ●

Beam measurement is not easy



Can constrain our calibration models



Limits degrees of freedom in our solutions

Measurement - GitHub

Measurement. ○ We are now entering the wide field era. ○ Single gains no longer adequate. ○ Gains are direction dependant ...

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