1. “Lunar UHE Neutrino Astrophysics with the Square Kilometre Array”
LUNASKA
Status Report and Future Prospects on LUNASKA Lunar Observations with ATCA
R. Ekers (CSIRO ATNF)
C. James (U. Adelaide)
R. McFadden (U. Melbourne)
C. Phillips (CSIRO ATNF)
R. Protheroe (U. Adelaide)
P. Roberts (CSIRO ATNF)
“Lunar UHE Neutrino Astrophysics with the Square Kilometre Array”

2. The Australia Telescope Compact Array
ATCA
6x22m dishes in NSW, Australia
Aperture synthesis antenna
6km E-W Baseline
We are using this to develop methods and technology scaleable to the SKA
Why ATCA?
Beamwidth at 1-2 GHz matched to lunar disk.
Array
RFI rejection
Techniques scalable to SKA
CABB upgrade
FPGA-based back-end
Current 600 MHz Bandwidth
It’s close!
Development
Dedispersion
Triggering (fast logic)
RFI discrimination
Observations!

3. Experimental Set-Up 1 Gbit Ethernet Link (TCP/IP) Offline Processing
Data Channels:
3 antennas.
Dual linear polarisation.
600 MHz Bandwidth ( GHz).
8-bit, 2 GHz sampling
Triggering:
Independent at each antenna.
Adjustable threshold trigger on each polarisation.
If either polarisation exceeds the threshold, 128ns buffers from both are recorded.
256 MHz clock time also recorded.
Saturation rate 1 kHz / antenna.
1 Gbit Ethernet Link (TCP/IP)
Baseband
Buffer
Offline Processing

4. System Detail at Each Antenna
LNA
1.5 Ghz
2.3 Ghz
1.5 GHz
Polarisation and Band
Splitter
L-Band RF Splitter
Module (F10)
S-Band Splitter
(C23)
L-Band Splitter
(C22)
S-Band RF Splitter
Module (F11)
1.2 – 2.5 Ghz Horn
Pol A
Pol B
Receiver (we use L-band: nominal GHz)
Standard ATCA Receiving Path
Customised Hardware
Analogue De-dispersion Filters
3 – 8 ns (night – day)
2.048 Gs/s
8 bit
ADC
Buffer
Ethernet Connection
Adjustable Threshold Detection
5.1 σ
4096 samples, 2μs
ATNF BCC Interface 100Mb/s
CABB Sampler Board
( McFadden et al)

5. Dedispersion Method Typical Night-time Dispersion
We cannot digitally de-disperse or measure TEC in real time.
VTEC at ATCA during May 2006:
The ionosphere is stable between sunset and sunrise.
Mean vertical dispersion ~4ns over Ghz for 10pm-6am
Hardware De-dispersion Filter
Designed by Paul Roberts
Correct for dispersion using an analogue microwave filter with a continuously-changing profile.
Filters set for
characteristic VTEC
at 600 elevation.
Thick
Thin

6. Dispersion as RFI Discrimination
Observed Trigger
Results from May 2007
We can use the dispersion to discriminate against terrestrial RFI
E.g. we were observing regular, strong triggers of ~20ns duration (opposite).
Was the origin:
A) Terrestrial (no dispersion)
B) Lunar (characteristic dispersion)
C) Satellite bounce (double dispersion)?
A) Terrestrial Impulse?
B) True Event?
C) Satelite-bounce?
Predictions – from a 3am Analysis

7. Correlation Str (arb units)
Timing Calibration: 3C273
Correlation Str (arb units)
NOTE: x-scale should read ns

8. ATCA Run Summary May 5th-7th 2007 (5 hr) 2007 Data Reduction
10pm-6am.
Simultaneous baseband recording (64 Mhz at 1.2 GHz).
Targeted Sag A region.
Centre-pointing.
Only ms timing available!
Feb 26th-28th 2008 (14 hr)
Repeat of ’07 set-up.
14 hrs stable configuration.
March 17th-19th 2008 (20 hr)
Targeted Cen A.
Pointed at limb to maximise Cen A sensitivity.
2007 Data Reduction
120,000 candidates per antenna.
300 remain after 1 ms coincidence and ‘dumb’ RFI cuts.
4 remain after polarisation + ‘smart’ RFI cuts.
We expect ~6 false events.
ASSUME: No neutrinos.
2008 Analysis Pending…
Relative nanosecond timing will give 4/1012 chance of a false detection.
More RFI shielding on equipment, faster network => more sensitivity.

9. ATCA Sensitivity ATCA Sensitivity Simulations results:
600 MHz Bandwidth ( GHz)
Dual Polarisation
3 Antennas
Threshold F.O.M.:
Parkes: MHz m2 /K
GLUE: Mhz m2/K
ATCA: MHz m2/K
Other Factors:
Beam views entire lunar limb.
lower.
Independent triggering! Sensitivity of approx 2 beams only.
Simulations results:
Threshold comparable to Parkes, GLUE, Kalyazin etc.
Relative improvement with energy.
Calculated explicitly for 2007 only.
Slight improvement in 2008.
(my calculations)
PRELIMINARY!

10. Expected ATCA Limit ATCA We have not finished analysing 2008 data.
Plot approximate limit on an isotropic flux assuming no detections.
Range reflects the regolith depth (upper: 10m, lower: ~ )
ATCA
PRELIMINARY!

11. Other Notes Triggering Next Steps: Future:
Independent triggering now limits our sensitivity.
We await improved methods to go to >3 antenna.
The ns radio environment is strange
Most short-duration RFI unexplained.
Can dominate individual trigger rates.
This makes it hard to predict experimental sensitivity in advance!
Offline vs Real Time processing
Offline data reduction is easy.
Real-time logic is hard.
Sensitivity is limited by triggering logic.
Next Steps:
Real-time coincidence detection between antennas, RFI filtering.
1 week planned Feb/March 09
Future:
Utilise full 1-3 GHz bandwidth
28+ day observations.
Coherent beamforming?
>3 antenna?
Parkes Multibeam:
13 separate receivers.
Any 3 match the lunar limb.
Use 500 Mhz b/w.
12,000 MHz m2/K

12. In Conclusion…
Primary goal – to learn lessons which can be extended to the SKA.
Our effective aperture is higher than previous experiments, and has been improving – but soon we will come against limits of technology.
Isotropic sensitivity currently well below ANITA.
(but as for targeted observations – see my next talk!)
Sensitivity to UHE CR unknown – more theoretical work needed here.
LUNASKA is an ongoing project – we’ll keep you posted.