Andrew Siemion SSL Colloquium April 10, 2009 Andrew Siemion SSL Colloquium April 10, 2009 Searching...
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Transcript of Andrew Siemion SSL Colloquium April 10, 2009 Andrew Siemion SSL Colloquium April 10, 2009 Searching...
Andrew SiemionSSL ColloquiumApril 10, 2009
Andrew SiemionSSL ColloquiumApril 10, 2009
Searching for Radio Ephemera:
The Fly’s Eye AstroPulse
Searching for Radio Ephemera:
The Fly’s Eye AstroPulseand Beyond...and Beyond...
Orthogonal Searches- Fly's Eye -
Allen Telescope ArraySolid Angle: wide, 200 deg2
Time Resolution: 0.6 ms (Incoherent Dedispersion)
Dispersion Measures [0, 2000]Search Algorithms: Single pulses only
- AstroPulse -
Arecibo Multibeam Sky SurveySolid Angle: narrow, 0.04 deg2
Time Resolution: 0.4 us (Coherent Dedispersion)Dispersion Measures [-830, 830]
Search Algorithms: Single and Periodic Pulsesuses Distributed Computing
Both AstroPulse and Fly’s Eye are Ongoing
Fly’s Eye
Acknowledgements
Don Backer, Henry Chen, Matt Dexter, Terry Filiba, Rick Forester, Colby Kraybill, David MacMahon, Oren Milgrome, Mel Wright + ATA Staff, et al.
AstroPulse
Dave AndersonBob BankaySteve BoggsJeff Cobb Eric Korpela Matt Lebofsky Josh Von KorffDan Werthimer
Geoff BowerJim Cordes Griffin Foster Joeri van Leeuwen William Mallard Peter McMahon Mark Wagner Dan Werthimer
And Copious Assistance From:
Josh Von Korff Space Grant
Summer Fellowship Program
Center for Astronomy Signal Processing and Electronics ResearchCenter for Astronomy Signal Processing and Electronics ResearchHenry Chen, Daniel Chapman, Terry Filiba, Griffin Foster, Suraj Gowda, William Mallard, Jason Manley, Peter McMahon, Vinayak
Nagpal, Aaron Parsons, Andrew Siemion, Laura Spitler, Mark Wagner, Dan Werthimer
UC Berkeley Radio Astronomy LaboratoryDon Backer, Matt Dexter, Joeri van Leeuwen, David MacMahon, Oren Milgrome, Mel Wright, Lynn Urry
Berkeley Wireless Research Center
Bob Broderson, Chen Chang, Kevin Chao, Borivoje Nikolic, Brian Richards, John Wawrzynek
Industrial and Academic CollaboratorsXilinx, Fujitsu, HP, Sun Microsystems, NSF, NASA, NRAO, NAIC, Chris Dick, CfA, Haystack, Caltech, Stanford, Cornell, WVU, CSIRO/ATNF, UNCA/PARI, JPL/DSN, South
Africa KAT, University of Oxford, Manchester/Jodrell Bank, GMRT, Bologna (SKA), Metsahovi Observatory/Helsinki University, Chalmers (Sweden), The National Astronomy Observatory Chinese Academy of Sciences, Nancay, NCRA/TIFR
CASPER The Friendly...Group Helping Open-source Signal-Processing Technology? (GHOST)
✴ Goal is to Develop High Performance Signal Processing Infrastructure for the Astronomy Community and Beyond.
✴ Open Source Everything.
✴ Use Commodity Off-the-shelf Hardware Where Possible.
✴ Provide Training and Tutorials (Wiki, Video Lectures, Workshops etc...)
✴ Promote Collaboration (30+ Universities and Observatories.
✴ Do Not Necessarily Concentrate or Specialize in Turn-Key Instruments.
TIME (mS)
FRE
QU
EN
CY (
MH
z)
Δt=29 mS
Δν =νhigh −ν low =208 MHz
Interstellar Dispersion
Crab Pulsar
Assuming a model of free electron density in the ISM, we can infer a distance of ~2000 pc.
Undoing Dispersion
Coherent Dedispersion
Incoherent Dedispersion‣Most common method.
‣Performed post-detection.‣Relatively cheap computationally.‣Useful for millisecond pulses.‣Uncertainty limits sensitivity.
‣Performed pre-detection.‣Very computationally intensive.‣Sensitive to pulses as short as
bandwidth-1
In Both Cases:
★Dedisperse at a number of trial dispersion measures.
★Threshold resulting time series.
Known Sources‣Repeating Signals from Pulsars
‣Giant Pulses from Pulsars
‣RRATs or Nulling Pulsars
Jocelyn Bell
M. McLaughlin et al. 2005
Graphic Courtesy Sabine Hossenfelder
Theoretical Sources
Rees, 1977
According to Hawking (1974), black holes emit radiation at a rate inversely proportional to their mass, eventually leading to a very rapid release of energy as they finally wink out.
As suggested by Rees (1977), this final explosion could include a large electromagnetic pulse (EMP).
Observational Results
Parkes Multibeam Pointing During Lorimer Detection
(Lorimer 2007)
Frequency vs. Time Waterfall (Lorimer 2007)
‣Announced September 2007‣Single pulse at L-band‣30 Jy, saturated digitizer in one beam‣Located 3° from the SMC‣DM = 375 pc/cm3 implies D ~ 1Gpc
Exciting Results From Lorimer et al.• Lorimer, et. al., “A Bright Millisecond Radio Burst of Extragalactic Origin.” Science, 318, 2007.
If this is a real event, pulses of this type could serve as an invaluable cosmological probe of the intergalactic medium.
The Fly’s EyeThe Fly’s EyeA Search for Highly Energetic Dispersed A Search for Highly Energetic Dispersed
Radio Transients using the Allen Radio Transients using the Allen Telescope ArrayTelescope Array
Fly’s Eye Timeline
‣November 19, 2007 - Dan Werthimer and Geoff Bower have lunch to discuss transient search projects using the ATA.
‣November 20, 2007 - Dan Werthimer tasks a group of mostly undergraduate students to begin building a transient instrument.
‣December 22, 2007 - Fly’s Eye Team installs Fly’s Eye at ATA.
‣February, March 2008 - Conducted 500 hours of weekend observations.
‣April 2008 - Present - Data analysis underway
• Lorimer, et. al., “A Bright Millisecond Radio Burst of Extragalactic Origin.” Science, 318, 2007.
September 27, 2007
• Fly’s Eye First Light
December 22, 2007
Fly’s Eye Basics44 independent spectrometers - constructed using a system of eleven iBOB/iADC quad spectrometers
Built using open-source CASPER hardware and software libraries in about one month.Sky Coverage:
22 - 42 beams100-200 square degrees
Spectrometer Specifications (each):208 MHz bandwidth, at 1430 MHz128 spectral channels0.625 mS readout
Distributions:Spatial, DM, Power, Pulse Width
Sky Coverage:22 - 42 beams100-200 square degrees
Spectrometer Specifications (each):208 MHz bandwidth, at 1430 MHz128 spectral channels0.625 mS readout
Distributions:Spatial, DM, Power, Pulse Width
Fly’s Eye Rack at ATA
IBOBs
Clock source
EthernetSwitch
Control Computer
Storage Server
Fly’s Eye Rack at ATA
High Level Fly’s Eye Diagram
Fly’s Eye Instrument Rack
PSR B0329+54 DetectionFE Instrument Diagnostics I
PSR B0329+54 Detections in 41/44 Beams (15 minutes folded)
PSR B0329+54 (36 beams summed, 15 minutes folded)
PSR B0329+54 detected in 41/44 signal paths.
Giant Pulses From PSR B0531+21FE Instrument Diagnostics II
Giant Pulses from PSR B0531+21 (35 beams)
Giant Pulse from PSR B0531+21 (single beam)
The Crab pulsar was observed for one hour, during which close to a dozen detectable pulses were detected (in summed data), the brightest of which was distinguishable in approximately half of single dish observations.
Observations
Total observing time thus far is approximately 480 hours.
Both North and South pointing observations were performed, primarily North due to kinder RFI environment.
Total dataset is approximately 17 terabytes.
Total observing time thus far is approximately 480 hours.
Both North and South pointing observations were performed, primarily North due to kinder RFI environment.
Total dataset is approximately 17 terabytes.
Fly’s Eye Beam Pointing Diagram
Drift scan Fly’s Eye observations were conducted in campaign mode on weekends between February and April 2008.
Initial plan was for “fly’s eye” sky patch observing, eventually transformed to “horseshoe” constant declination strip. This pattern was chosen such that a known pulsar would traverse through all beams during an observation run, to be used for sanity checks and calibration during the analysis stage.
High Performance Storage System MySQL Database
MySQL Database
Data StorageData is stored in 36 GB (58 minute) .pcap ethernet capture files on a remote high performance storage system. Pointers to data files are stored in a local MySQL database
Data is stored in 36 GB (58 minute) .pcap ethernet capture files on a remote high performance storage system. Pointers to data files are stored in a local MySQL database
Data Analysis‣Data are broken up into
~10 minute single-spectrometer chunks
‣DM search range: 50-2000 pc/cm3 (with decimation, non-integer spacing)
‣Computing grids used: 5 (Berkeley Wireless Research Center, UC Berkeley EECS, DOE NERSC)
‣Total cores (peak): ~200 (Itanium64, Xeon, Sparc, Opteron)
‣Total throughput (peak): ~200 Mbits/secondFly’s Eye Data Analysis Pipeline
SigProc
RFI Rejection ISome narrow band intermittent RFI can be identified based on the variance of the powers of the frequency channel.
These channels can then be ignored in dedispersion and pulse searching.
Post Processing RFI Removal
Two basic criteria used for excision:
An event is detected at the highest s/n at a low DM (< 50 pc/cm3)
-or-
An event is detected at too broad a range of DMs
Example Preliminary Results
Example Time vs. Sigma Plot Example Time vs. DM Plot
Result Browser
480 hours of observations, 44 spectrometers, 10 minute sets, 9 plot types == over a million plots!
Automated First PassA quick search through our data to find interesting high S/N
events. Method:
- Filter data to select sets with a low average detection S/N.- Tag events with a S/N greater than 8.5.
Method:
- Filter data to select sets with a low average detection S/N.- Tag events with a S/N greater than 8.5.
Fly’s Eye Status and Summary‣ Current data will allow us to place significant constraints on
the rate and distribution of bright short-duration transient events.
‣ Detection of Crab Giant Pulses has given us confidence that the Fly’s Eye instrument and processing pipeline are functional.
‣ A search through 480 hours of processed results found about 50% suitable for automated analysis (low rfi). Approximately 100 events with dispersion measure > 50 pc/cm3 were found above 8.5 sigma. None appear to be of astrophysical origin.
‣ Plans for reprocessing of existing data, as well as instrument improvements to enable more precise localization.
AstroPulseAstroPulseA Multibeam Sky Survey for Microsecond Transient A Multibeam Sky Survey for Microsecond Transient
Radio Signals using Arecibo ObservatoryRadio Signals using Arecibo Observatory
Arecibo ALFA Receiver
Arecibo L-band Feed Array (ALFA) Receiver System:
‣1.4 GHz‣7 dual-polarization feeds‣2.5 MHz Bandwidth‣Used for various surveys: PALFA, ALFALFA‣AstroPulse observes commensally
ALFA Receiver (NAIC)
ALFA Receiver and Gregorian Dome (NAIC)
AstroPulse @ Arecibo
RF Downconverter
Data Recorder PC
Multibeam Datarecorder Installation
Multibeam Datarecorder Instrument Rack
AstroPulse records raw voltage data (just like SETI@Home), not detected spectra.
AstroPulse records raw voltage data (just like SETI@Home), not detected spectra.
‣Bandwidth: 2.5 MHz‣Centered at: 1420 MHz‣Portion of the sky visible from Arecibo: 1/3‣Beam width: 3.5'‣Beam transit time: 12 seconds‣Sky coverage rate: 1/3 of the sky in 8 months‣Sample rate: 2.5 MSamp/sec, 1 bit sampling ‣Disk space required: 200 GB per day for 1 yr = 70 TB
Data Pipeline
NERSC HPSS data storage silo(National Energy Research Scientific Computing Center)
Arecibo Observatory
SSL Computer ClosetParticipant PCs
TOGS Sky Coverage
Turn-on GALFA Survey (TOGS) Sky Coverage 2005-2007
Operating commensally, AstroPulse takes data nearly continuously.
Computing Power
To process existing 70,000 hours of data in 6 months, AstroPulse requires 240 TFLOPS/s.
BOINC’s 1,000,000 volunteers provide nearly 300 TFLOP/s, equivalent to some of the world’s most powerful supercomputers.
Client-based RFI Rejection
Dispersion Measure
Puls
e C
ount
Dispersion Measure
Puls
e C
ount
Before and after RFI rejection
TIME
FRE
QU
EN
CY RFI due to an
air route radar system
Evaporating Black Holes
Year
log[d
ete
ctab
le r
ate
] (p
c-3 y
r-1)
Phinney & Taylor, "A Sensitive Search for Radio Pulses from Primordial Black Holes and Distance Supernovae" Nature Vol. 277, 11 January 1979
O'Sullivan et, al. "Limits on Cosmic Radio Bursts With Microsecond Time Scales", Nature vol. 276, 7 December 1978
Katz & Hewitt 2003, “A Search for Transient Astronomical Radio Emission”, Pub. Astr. Soc. Pac., 115:675-687, 2003 June
Amy, Large & Vaughan “ A Search for Transient Events at 843 MHz”, Proc. ASA 8 (2) 1989
AstroPulse will either detect evaporating primordial black holes, or place the most stringent limits yet on EPBH event rates.
AstroPulse Status
‣AstroPulse data is currently being distributed with SETI@Home
‣Over 100,000 volunteers currently processing data.
‣RFI, RFI, RFI
Future Fly’s Eye
Angular Localization of Transient Radio Bursts
‣Reprocess! - Improve RFI rejection, implement new pulse search algorithms, search negative DMs - underway
‣Improve ability to localize detections
Fly’s Eye 44 input fast readoutspectrometer becomes...
Fly’s Eye 11 x 4 input fast readoutcorrelator
QuickTime™ and a decompressor
are needed to see this picture.
PSR B0329+54 @ 700MHz
Casey Law / ATA 2009
2.5o
2.5o
Interferometric detection of PSR B0329+54 based on a 5-minute ATA observation at 700MHz sampled at 0.1 sec.
Real Time Processing
4.5m Leuschner Observatory Radio Telescope
Real time processing will enable the transmission of event notifications to observatories operating at other wavebands.
Prototype system at Leuschner Observatory
Eventually will operate commensally on incoherent sum at ATA (~3 deg FOV)
ATA-42