Pulsar Timing with ASKAP Simon Johnston ATNF, CSIRO

Looking to the future Pulsar timing and surveys in the last 20 years have mostly been carried out with large single dishes some with multiple pixels For surveys this is the only option computationally WSRT the honourable exception Bandwidth generally small (< 1 GHz) Limited by front end and RFI Coherent de-dispersion limited by cpu power By 2015 with SKA coming on-line most cutting edge pulsar work will be carried out on a interferometer, potentially with very large bandwidths (10 GHz). ASKAP can provide a transition between large single dishes and interferometers (at least in the south).

ASKAP - The next gen radio telescope on the path to the SKA 45 parabolic dishes, 12 m diameter 990 baseline interferometer, ~5000 m2 collecting area 30 square degree field of view on the sky Focal plane array technology and digital beamforming Frequency range 0.7 – 1.8 GHz Bandwidth 300 MHz, 16000 channels (20 kHz resolution) Tsys = 35 K (cooled) Located in Murchison Shire, Western Australia 6 element outstation in NSW ASKAP is not very sensitive but it has a fast survey speed. ASKAP observing will be dominated by surveys which can exploit the large FoV capability.

Sensitivity Instantaneous sensitivity ~ ND2/T Parkes = 1 x 642 x 0.7 / 22 = 1.0 ASKAP = 45 x 122 x 0.8 / 35 = 1.1 ASKAP will be somewhat more sensitive providing the specs can be met (N, , T) At sub GHz frequencies ASKAP will be much more sensitive than Parkes Bandwidth ~ 256 MHz for both at 1.4 GHz ASKAP has 30 square degrees FoV If you can observe more than 1 pulsar at a time the efficiency gains go up proportionally RFI conditions in WA should be better than anywhere else in the world.

Millisecond pulsar timing Only one source per Field of View Need to form tied array beam at the phase centre and sample at baseband Would like to record the full 1 GHz band Can FoV be traded against bandwidth? In any case should think about sub GHz observing Would like high frequency capability Needs good polarization calibratability Needs lots of regular observations (100 days/yr!) Parkes would still be the instrument of choice but ASKAP would be a good test bed for future work

General pulsar timing Benefits from multiple pulsars per FoV, especially in the Galactic plane Integration time determined by weakest pulsar in the FoV so the gain is not quite proportional to N Requires multiple tied array beams Beamformer capability? Off axis polarization? For e.g. the GLAST timing program ASKAP would be a factor 5 faster than Parkes ASKAP would be the instrument of choice for a big timing campaign

Summary of Requirements FRONT END Good polarization properties Would like to exploit 1 GHz bandwidth Ability to have at least 10 tied array beams BACK END Baseband recording for MSPs with at least 300 MHz possibly 1 GHz bandwidth and associated cpu power for data reduction 10 digital filterbank systems with high freq resolution, high time resolution and on-line folding mode TIMING MSP timing very competitive with 1 GHz bandwidth Timing of survey discoveries much faster with ASKAP.