ASKAP Early Science WorkshopLisa Harvey-Smith & Aidan Hotan | ASKAP Project Scientists

August 5th 2013

ASTRONONY & SPACE SCIENCE

ASKAP funding, fabrication, integration, commissioning is phased.Science can also be phased.

Reasons to do early science observing:1. Provides stringent early test of techniques & technology2. Takes place in parallel with construction3. Many super science fellows, postdocs available now-2016

Rationale

ASKAP Early Science | Lisa Harvey-Smith

Early science will be a 'best-efforts' affair

Priority continues to be: • Completing ASKAP to scope and • Enabling the original survey science projects to take place

Early science plans may evolve as we 1. Refine the build-out schedule and 2. Learn and improve the capabilities of the telescope

Guiding Principles

ASKAP Early Science | Lisa Harvey-Smith

• Gauge the interest of user community • Identify a range of possible observing strategies• Plot a course – a plan for early science (via advisory bodies, CASS Chief)

• Assignment of observing time• Scheduling of specific projects• Provision of certainty

This workshop will allow us to

ASKAP Early Science | Lisa Harvey-Smith

This workshop will not lead to

Dear Colleague,

I am pleased to inform you that your abstract for the ASKAP early science workshop has been accepted.

Please note that this is a workshop with a very specific focus, so take the time to re-read the attached information in order to make the workshop a successful as possible. In particular, your talk should address the following questions where relevant:

• What unique discovery space can be explored with ASKAP-12?

• What are the minimum requirements in your area of interest?

• What science topics could be tackled with a short (~hours) amount of observing time?

• Are there short observations that can tackle a number of different topics simultaneously?

• What could be achieved with a longer survey?

• What is the potential for commensal science?

• How does ASKAP-12 compare with other existing telescopes?

• What is the likely scientific impact of the observations?

• Are observations ‘high-risk’ or ‘low-risk’ in terms of implementation?

• What are the likely minimum requirements with respect to observing time?

• Do the observations have advanced data processing, imaging or calibration requirements?

• Are there any requirements that are different from those of the ASKAP SSPs or the intended specifications or deliverables?

[…]

Best wishes,

ASKAP Early Science | Lisa Harvey-Smith

How do we maximise the impact of early science?• Do one thing really well?• Lots of small, single-target or single-field observations?• One large survey?

How do we measure the impact of ASKAP early science?• Number of papers?• Scientific discovery potential?• Training opportunities provided?

How would you like to interact with CSIRO during early science?

What I want to know

ASKAP Early Science | Lisa Harvey-Smith

ASKAP Commissioning Update | Aidan Hotan

ADE-12 System Overview

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Phased Array Feed188 chequerboard elements

Low-noise amplifiersBand-select filters

RF over Fibre transmission

Digitiser / PFB300 MHz bandwidth

1 MHz channels

Correlator5-second visibilities18.5 kHz channels

Central Processor / ArchiveIngest Pipeline: CASA measurement sets

Image pipeline: Calibration & deconvolution

MRO Central Building

Beamformer36 dual-pol beams

ASKAP Antenna

Pawsey Centre

ASKAP Commissioning Update | Aidan Hotan

Hardware Capabilities

12 ADE PAFs with 50K intrinsic Tsys across the ASKAP band. Allow for imperfect illumination efficiency on the antennas.

36 simultaneous beams (2 polarisations each) per PAF.

300 MHz of instantaneous bandwidth.

18.5 kHz fine channel resolution.

No initial support for transient capture, zoom modes, etc. (Anything that requires changes to the basic firmware).

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ASKAP Commissioning Update | Aidan Hotan

Software Capabilities

Automated monitoring and safety overrides. Wind / storm stow, cooling systems, power supply, etc.

Control of telescope via scheduling blocks (python based). Tracking, scanning, frequency selection.

Ingest pipeline that produces measurement sets (with metadata) from correlator output in real time.Image pipeline that calibrates and images the measurement sets. Includes a suite of software tools that can be run manually, but with limited

documentation. Advanced features like source catalogue creation & sky model will still be in

experimental stages.

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ASKAP Commissioning Update | Aidan Hotan

Expected Limitations During Early Science

Beam setup / maintenance will probably be a manual operation.Imaging pipeline calibration will be marginal with 12 antennas. Manual intervention required to make best images.

ASKAP imager assumes beam shape is uniform and unchanging. Early images will have artefacts. Errors likely to be time variable.

Full-resolution measurement sets will be large. Disk / memory / network requirements mean that bulk processing needs to be done on

the Pawsey machine. Accounts, queue scheduling required. Some scope for the extraction of subsets and local caching at the MRO.

Support and training resources for SST members will be limited. Interface to be decided. Nominate 1-2 representatives from key SSTs?

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ASKAP Commissioning Update | Aidan Hotan

The Need for BETA

Over the next 12-18 months, we will be learning many things: How to best measure the characteristics (pattern shape, etc.) of a PAF beam. How to optimise a PAF beam for circular symmetry, low side-lobe levels, low polarisation

leakage, etc. How often beamformer weights must be updated to keep all of the above properties as

constant as possible. How to best synthesise a uniform field consisting of multiple beams (which of the above

beam characteristics results in the best image?). How to best calibrate an array with a small number of antennas (low sensitivity and poor

UV coverage makes self-cal difficult). How much of the total observing time will be required for beamforming and calibration

work.

This learning process will extend into the ADE early science period.

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ASKAP Commissioning Update | Aidan Hotan

Radio Frequency Interference

The MRO is a fantastic radio quiet site, but it is not RFI-free.

Thuraya 3 – mobile telecommunications. Broadcast capability over 1525-1559 MHz

and 1626.5-1660.5 MHz bands. Observed at MRO around 1550 MHz.

ADSB transponders – onboard aircraft position broadcast. 1090 MHz transmission.

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ASKAP Commissioning Update | Aidan Hotan