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April's
ASKAP update
describes
plans to resume survey operations and assess the performance of Setonix as the new data processing platform,
summarises a new ASKAPsoft release, and
gives details of an investigation into ASKAP's astrometric accuracy.
The figure above shows the average astrometric errors with respect to the RACS-low catalogue
for a series of VAST epochs taken during full survey observations over the last few months.
The offsets are usually less than the indicated 2 arcsecond level, but poor weather conditions can
cause more rapid departure from the phase solution of a given bandpass observation,
leading to larger errors on occasion.
The 2 arcsecond accuracyis due to the fact that with ASKAP's wide field of view,
we currently do not phase reference in the same way that single-beam interferometers
typically do. Regularly placing a phase reference source in each beam one by one
would add significant overhead to ASKAP observations.
The Update describes several other options that are under consideration.
(Image credit: Emil Lenc)
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