Developments in Nanosecond Pulse Detection Methods & Technology UHE Neutrino Detection using the Lunar Cherenkov Technique. Lunatics - those who search for lunar ticks. Prof Ron Ekers Dr Paul Roberts Dr Chris Phillips. Rebecca McFadden (PHD). Prof Ray Prthoeroe Clancy James (PhD).
Developments in Nanosecond Pulse Detection Methods & TechnologyUHE Neutrino Detection using the Lunar Cherenkov Technique
Prof Ron EkersDr Paul RobertsDr Chris Phillips
Prof Ray PrthoeroeClancy James (PhD)
A/Prof Steven TingayDr Ramesh Bhat
Technique first proposed by
Dagkesamanskii & Zhelezynkh (1989)and first applied by Hankins, Ekers and O'Sullivan (1996)
using the Parkes radio telescope
Image courtesy of R Ekers
(See #0341 Clancy James for more details)
Broad receiver bandwidth for ns time resolution
High speed sampling
Real time trigger to avoid excessive storage requirements
Real time dedispersion to maximise SNR for trigeer
A rray geometry allows RFI discrimination based on the signal direction of arrival.
The system temperature is dominated by thermal emission from the moon so there is little improvement in signal to noise ratio to be gained by larger apertures.With many small dishes, their spatial separation can be used to ensure that thermal emission from the moon is incoherent between elements thus increasing the signal to noise ratio.
At frequencies in the 1-2GHz range, the primary beam produced by a 22m aperture (such as the Compact Array) can see the entire moon. Beamwidth is inversely proportional to aperture size, therefore a larger dish will see less than the entire moon and any minimal improvement in sensitivity from the larger aperture will be offset by decreased coverage of the moon.
1 Gbit Ethernet Link
1.2 – 2.5 Ghz Horn
Polarisation and Band
L-Band RF Splitter
S-Band RF Splitter
4096 samples, 2μs
Coincidence Test and Threshold Detect
Standard ATCA Receiving Path
Analog Dedispersion Filters
3 – 8 ns (night – day)
ATNF BCC Interface 100Mb/s
CABB Sampler Board
Histogram of VTEC for May 2006
Signal dedispersion is performed in analog microwave filters with a fixed dispersion characteristic.
These filters were designed using a new method of planar microwave filter design based on inverse scattering .
This results in a filter with a continuously changing profile, in this case a microstrip line with continuously varying width.
The width modulations on the microstrip line produce cascades of reflections which sum to produce the desired frequency response.
TEC data from NASA’s Crustal Dynamics Data Information System
Δt = 0.00134 TEC (1/flo2 – 1/fhi2 )
Restricting data set to night-time hours (8pm-6am):Average TEC of 7.06 VTECU (May 2006) and 7.01 VTECU (May 2007)Over the 600MHz bandwidth (1.2-1.8 Ghz) this corresponds to an average differential delay of 5ns (May 2006) and 4.39ns (May 2007)
D Path = D sin q
Delay = D/c sin q
We can form multiple Beams to Cover the Limb of the Moon
It will also be possible to implement real time dedispersion algorithms in this hardware and we have developed a technique for obtaining measurements of the ionospheric TEC which are both instantaneous and line-of-sight to the lunar observations. The ionospheric TEC can be deduced from Faraday Rotation measurements of a polarised source combined with geomagnetic field models, which are more stable than ionospheric models when the direction of signal propagation is parallel to the geomagnetic field vector.We propose to use this technique, with the polarised thermal radio emission from the lunar limb as our polarised source, to obtain instantaneous and line-of-sight TEC measurements.
Lunar UHE Neutrino Astrophysics with the Square Kilometre Array (LUNASKA)
Work conducted by the Lunatic team will form a pathway for UHE neutrino detection using the proposed SKA radio telescope.The Square Kilometre Array will be 100 times more sensitive than the best present day radio instruments.The current designs proposed for the SKA consist of large numbers (~104) small dishes (6-12m) to achieve a square kilometre of collecting area in the 1-3GHz range.