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Gravitational Wave
Data Analysis
 GW detectors
 Signal processing: preparation
 Noise spectral density
 Matched filtering
 Probability and statistics
 Software implementation
Gravitational Wave
Data Analysis
Gravitational Wave Detectors
Junwei Cao (曹军威) and Junwei Li (李俊伟)
Tsinghua University
Gravitational Wave Summer School
Kunming, China, July 2009
Gravitational Waves
 Gravitational waves are
prediction of Einstein’s
General Theory of
Relativity.
 No direct detection of GWs
is successful for nearly
100 years.
 A new window to observe
the universe
Strength of GWs
For the binary
system shown in
the figure, the
strain h=2δl/l
becomes
h~R1R2/Dd
For neutron stars of
1.4M⊙out at Virgo
cluster (15Mpc):
h~10-21
Crazy but within
current reach!
Binary: a typical GW source
Frequency Ranges
Laser Interferometers
 The Michelson
interferometer
measures phase
differences between
two returning beams
recombined at the
beam splitter. (Albert
A. Michelson, 18521931, Nobel Prize
1907)
 Modern
interferometers use
lasers
GW Laser Detectors
LIGO
GEO
Simultaneously detect signal
(within msec)
Virgo
TAMA
AIGO
GW Laser Detectors (Contd.)
LIGO & LSC
 LIGO: Laser Interferometer Gravitational wave
Observatory (激光干涉引力波天文台)
 U.S. NSF flagship project with largest single
investment; a joint effort of Caltech and MIT
 LSC: the LIGO Scientific Collaboration over 500
scientists from over 60 institutes worldwide
LIGO Hanford Observatory (H1, H2)
LIGO Livingston Observatory (L1)
LIGO Experiences
LIGO Status
 LIGO deliverable – S5
run with over 1 year
triple coincidence, no
gold-plated detection
 Enhanced LIGO – 2
times sensitivity
improvement, S6 starts
in July 2009
 Advanced LIGO – 10
times sensitivity
improvement, 103
times signals and
frequent GW
detections are
expected
Struggle Against Noises
LIGO Data
 Data are comprised of:
 Gravitational Wave channel (AS_Q)
 Physical Environment Monitors
 Internal Engineering Monitors
 Multiple data products beyond raw
data
 RDS_R_L1, including both GW and
environmental channels
 RDS_R_L3, including only AS_Q channel
L-RDS_R_L3-751658016-16.gwf
Site (H,L)
Data Type
Duration
GPS Start Time
GW Data Analysis
Burst, Inspiral, Stochastic,
Continuous
Signal processing, probability,
statistical analysis
Online, offline, real-time
Matlab, DMT(C++), Scripts (Python)
Clusters, grids, …
Gravitational Wave
Data Analysis
Junwei Cao
[email protected]
http://ligo.org.cn