Deploying ASKAP's Phased Array Feeds Lessons from the Field Dr. - - PowerPoint PPT Presentation

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Feb 12, 2023 167 likes •316 views

Deploying ASKAP's Phased Array Feeds Lessons from the Field Dr. Aaron Chippendale | 16 Sept. 2019 Australias National Science Agency 36 Reflector Antennas Australian Square 12 m diameter aperture Kilometre Array 22 m to 6 km baselines

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Australia’s National Science Agency

Deploying ASKAP's Phased Array Feeds

Lessons from the Field

Dr. Aaron Chippendale | 16 Sept. 2019

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Australian Square Kilometre Array Pathfinder

(...and most complex) World's fastest survey radio telescope 36 Reflector Antennas

12 m diameter aperture 22 m to 6 km baselines 3-axis mounts

Phased Array Feeds

188 receptors per reflector 6,768 radio signals × 600 MHz bandwidth Radio frequency over fibre

Digital Signal Processing

6,912 direct sampled inputs 72 beams × 36 PAFs × (336 × 1 MHz) 3,690 DSP FPGAs, 130 Tbps raw IO, 210 kW

Data rate of a megacity!

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BYO water, electricity, hum

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Key lessons

… in building large, complex systems with major subsystems that are first of kind Prototypes

Things that work in prototypes cause less trouble.

Staging

Plan a design refresh after deploying and

perating a 10% system
r risk a drastic pivot.

Plan and heed robust reviews.

Test Systems

Complete 1-antenna and partial 3-antenna test platforms are indispensable.

Scaling

Scaling to production before prototype integration causes

headaches. Expect new

problems at full scale.

Flexibility

Flexibility of subsystems can inhibit full-system

flexibility. Specify

standard modes and configs early or risk delays.

Automation

Continuously integrate, test and deploy

everything. Script, log,

visualise and learn from everything.

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Synchronisation challenges over 36 PAFs

Massive distributed systems dictate asynchronous data transport.

Advantages:

opportunity for COTS hardware
free running clocks don't correlate

But data synchronisation is:

far more complex
harder as system scales

Problems manifest as:

setup/hold violations on FIFO resets
buffer over/under-runs
clock-domain crossing issues
intermittent and distributed issues

that don't show up until the system reaches a certain size We are working to reduce the likelihood of errors and automate their detection and correction with an on-dish noise source.

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95% work fine!
1.7% failed LNAs (lightning)
Replacing 2-channel receiver module (domino) fixes most issues

RF Link Problems for 36 PAFs (10 Apr 19)

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LNA Failures for 36 PAFs (10 Apr 19)

'Red' leg 4 (service)

LNA bias abnormally high

(by 13 mA)

Distorted bandpass
Confirmed lightening event on

worst affected antenna

Affects edge elements
Low impact on FOV
Letting it be for now

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Domino RF TX power suddenly high/low on many ports
Affects approximately 1 of 36 PAFs each day
Some antennas affected more frequently
Automatically flag affected antennas
Planning to automatically restart affected PAFs
Investigating root cause (power/comms glitches?)

RFoF Transmitter Dropouts

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Comms Issues

Production/deployment

commenced before completing design of the PSU and TEC subsystems -> several modifications required

Now losing comms to about
ne PAF/PSU/TEC unit every

few months

RFoF control link to PAF meets
riginal temperature spec but

controlling rack temperatures has been harder than expected

Designed bespoke linear PSUs

for the PAFs and TECs, minimising transmission losses and amount of equipment in antenna pedestals

Backtracked to a COTS

switched-mode lab supply for the TEC subsystem

A COTS PAF PSU would have

significantly reduced debugging time at the cost of higher ongoing electricity use

COTS vs Bespoke PSU

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SLIDE 11

GAMA-23 Multi-beam Image interactive version

Galaxy and Mass Assembly, 215 megapixels, 2 ×8 h, 36 antennas

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3D Image of a Complex Field

50 TB raw data, 36 antennas, 10 h, 7 galaxies rich in HI,

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