Early indications of performance Max Voronkov Software Scientist – ASKAP 13th May 2009

Performance tests - Main questions Typical delay scatter in vis plot and its stability Wide bandwidth allows to estimate delays better May see weak effects we have never seen before Flux scale calibration Bandpass shape, spectral indices and software can affect it Using 1934-638 at 7mm? Astrometric accuracy Systematic effects (e.g. baseline solution)? Accuracy of the pointing solution Greater sensitivity may improve the solution Bandpass shape and spectral indices can make it worse Could we use weaker sources?

Delays in vis plot

Delays in vis plot (cont’d)

Flux scale calibration We didn’t have a chance to study this in detail More information will probably come from the calibrator monitoring Be prepared to see systematic effects Wide bandwidth effects are more serious for CX-band (3 and 6 cm). Probably the uncertainty is not worse than a few per cent for CX-band, 10% for 12mm, a few tens per cents for 7mm and 3mm bands. Paddle measurement at 3mm Frequency-dependent Tsys measurement Does not converge amplitudes in vis. Can 1934-638 be used instead of the planet at 7mm? The source is easily detectable at the level of about 0.3 Jy There is a factor of 1.8 difference in fluxes if calibrated on Uranus and 1934-638! The difference is present for narrow bandwidth too. Flux model? Previous such experiments with the old system at 36 GHz gave a factor of about 1.3.

Interference spikes Things improved a lot since this picture was taken!

Observations of G19.61-0.23 at 7mm

Recombination lines in G19.61-0.23 at 7mm H53 42951.47 MHz

Pointing accuracy Important for mm bands where wide band effects are small (for general users) Pointing solution is done at 3/6cm after reconfig (staff) Wide-band effects (spectral index and primary beam dependence on frequency) are not taken into account Iterative solution for pointing should converge Did a number of pointing scans with a 10’’ offset in positions Compared solutions with 10’’

Pointing accuracy (contd.) Antennas 3 (technical problems) and 6 were excluded from the analysis Found 3.9 arcsec accuracy This is similar to the accuracy obtained with the old system Strangely enough, the pointing procedure always underestimates the offset It would be interesting to repeat the same experiment in C/X and/or with narrower tvch It is advisable to use the old strategy to choose pointing calibrators.

W33 - combining old and new data Blue contours - old system, 6km array Red contours - the same 6km array data combined with the new CABB data (using H168) Grayscale - VLA ammonia data (Keto & Ho, 1989) CABB data completely outweigh the data from the old system

Summary Usually delays are spread by less than 10 ps or so Baseline errors can give a residual delay of the order of tens of picoseconds (especially 6km baselines at 7mm). This should not be a problem for a typical science experiment The weather and other effects we don’t yet understand usually give a smaller delay Flux scale calibration and ATCA astrometry need further study Calibration on 1934-638 and Uranus at 7mm gives different result There are interference spikes and lines in the spectra (flagging) Always observe bandpass calibrator for every frequency setup Pointing accuracy is no better than before Use the same strategy as before (1 Jy or brighter source close to the target) Merging old correlator data with CABB data is non-trivial

Thank you Australia Telescope National Facility Max Voronkov Contact Us Phone: 1300 363 400 or +61 3 9545 2176 Email: enquiries@csiro.au Web: www.csiro.au Australia Telescope National Facility Max Voronkov Software Scientist (ASKAP) Phone: 02 9372 4427 Email: maxim.voronkov@csiro.au Web: http://www.narrabri.atnf.csiro.au/~vor010 Thank you