LIGO and GriPhyN
Caltech
Roy Williams
Peter Shawhan
Albert Lazzarini
Kent Blackburn
LIGO-G9900XX-00-M
USC/ISI
Carl Kesselman
Ewa Deelman
Sachin Chouksey
LIGO Virtual Data Grid
LIGO Hanford
MIT
LIGO Livingston
Caltech
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
2
Pictures
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
3
LIGO Overview


To detect gravitational waves predicted by
Einstein’s theory of relativity.
Waves created from
»
»
»
»
»

Rapidly spinning asymmetric compact objects eg. pulsars
Mergers of black holes, neutron stars -- gamma bursts?
Supernova collapse (and post-collapse R-modes)
Starquakes in neutron stars
Primæval GW from early universe
Installation in Louisiana and Washington State
» Other projects: Virgo (Italy), GEO (Germany), Tama
(Japan)
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
4
Physics and Virtual Data
time
Supernova
frequency
Merger
Ringdowns
Primeval GW Background
Each source type has
different freq/time
charactaristics
 different virtual
data requirements
CW (eg pulsar)
Mergers BH/NS
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
5
LIGO Data

Time series, 16 kHz down to 1 Hz

~1000 channels:
» Gravity wave
» seismic, magnetometer, microphone, engineering, …


Power spectra, cross spectra, sonogram, …
Events
»
»
»
»
Each has time and SNR (signal to noise ratio)
Candidate inspiral events from matched filter
Other pattern matching
“Examine the big ones, histogram the small ones”
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
6
LIGO vs NVO vs HEP

Processing
detector
datacube
detector
filter
reduce
1D,2D
filter
reduce
events
RDBMS
pattern
matching
events
LIGO, NVO
objects
pattern
matching

HEP
Network
» NVO is federation, LIGO is coincidence
» In both cases registration is important
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
7
Data Access

LDAS (Ligo Data Analysis System)
»
»
»
»
Script (Tcl) based
Primarily for onsite analysis and archiving
Talks to local files, Hanford/Livingston
Has a filtering language
– stack-based, like Matlab
– functions eg power spectrum, fft, resample

LARS
» Can talk to local, HPSS files
» Can do subsetting
» Simple program, simple protocol
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
8
Activities
1.
Virtual Data
»
»
2.
Replication
»
»
3.
A: Language & Architecture
– Naming is Time/Channel/Transformation
– Smart subsetting
B: LigoVista web display
– Archive at-a-glance + drill-down
A: Realtime mirror
– Hanford/Livingston/Virgo nternational coincidence study
B: Fault-tolerant mirror
– from Caltech to UW/Milwaukee
Pulsar search
»
backfill on Condor farms
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
9
1A: Virtual Data: Language

Virtual Data:
» Times + Channels,
– eg 668371475-668372499 (GPS time, seconds since 1981)
– L0: PEM-LVEA_SEIS*, L1:LSC-AS_Q
» Transformations to Virtual Channels
– eg. L0:PEM-EX-SEISX- L0:PEM-LVEA-SEISX / resample(L1:LSC-AS_Q, 1, 64)


Use LARS and Globus Replica Catalog
For each requested data value, need to
» Determine if it is instantiated; if so, where; if not, how to compute it
» Plan data movements and computations required to obtain all results
» Execute this plan
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
10
1A: Virtual Data: Architecture
P. Charlton
Power spectrum of seismic channels
LIGO Application
Channel, start time, stop time
Request Manager
Replica Management
Replica Selection
LARS Prot.
Virtual Data URL
LDAP
GridFTP
existing
FTP
in development
planned
Connectivity
“local”
storage
LIGO-G9900XX-00-M
HPSS
at Caltech
Other
Remote
Storage
Replica
Catalog
Transformation
Catalog
LIGO Scientific Collaboration
Derived
Data
Catalog
11
1B: Virtual Data: LigoVista

Overview of archive in a web browser
» Time based
– month, week, day, hour, ....
» Machine state
– lock status, science run, event density, ....
» Drill down to raw data
– Transformed data
» Uses Virtual Data framework
– compute on the fly and cache
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
12
2A: Replication:Realtime

Look for coincidence in Ligo-Virgo data
LDAS
analysis
event
stream
Interferometer,
seismic. etc
Interferometer,
seismic. etc
streaming
bidirectional
transatlantic
replication
Virgo
LIGO
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
13
2A: Whistlers from Lightning?
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
14
2B: Replication: Fault-tolerance
Master archive replicated at LSC sites
•
Fault tolerant
GridFTP
HPSS@Caltech
Beowulf@UWiscMilwaukee
Replication API
Penn State
UT Brownsville
LIGO-G9900XX-00-M
LIGO Scientific Collaboration
Replica Catalog
15
3. Pulsar Search
Frequency modulation by Earth movement

Infinite computation on finite data!
» Tiny, precise signals in deep noise
» Search on 4D space: sky position, pulsar frequency, spindown,
0.5 TByte “image”
Frequency (Hz)
frequency
frequency bins
Time (months)
LIGO-G9900XX-00-M
Condor farms
LIGO Scientific Collaboration
UT Brownsville
UW Milwaukee
Caltech CACR
UW Madison
frequency
6 months data
time
time
16
frequency
frequency
time
LIGO-G9900XX-00-M
time
LIGO Scientific Collaboration
17