S5 Stochastic Hardware Injections
Hardware Injections
During LIGO's 5th Science Run (S5), simulated signals were added to the
LIGO detectors for testing and calibration. The simulated signals are
known as hardware injections, because they were created by manipulating
mirrors in the arms of the interferometers. Times of hardware injections
are marked in LIGO data files by injection data quality channels. See the
injection bit mask definition
for details.
Stochastic Injections
The S5 stochastic hardware injections are reported in
the
S5 stochastic search paper:
"A stochastic background of gravitational waves is expected to
arise from a superposition of a large number of unresolved
gravitational-wave sources of astrophysical and cosmological origin.
It is expected to carry unique signatures from the earliest epochs in the
evolution of the universe, inaccessible to the standard astrophysical
observations."
To simulate this background, stochastic signals were injected
into all three LIGO interferometers at planned times during S5.
Each stochastic injection is generated with a flat energy spectrum,
and is characterized by an energy density
Ω0,
which is normalized by the critical energy density of the universe.
The procedure is described in the
S5 stochastic search paper.
The parameters of the S5 stochastic
injections are:
| GPS Start | GPS End | Ω0 |
| 822198733 | 822199838 | 2 |
| 822200170 | 822202224 | 0.02 |
| 838748736 | 838766387 | 0.0065 |
The injection segments can also be seen in these timelines:
