Gravitational Wave Open Science Center

S5 Continuous Wave 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.

Continuous Wave Injections

Continuous Wave (CW) injections were added at planned times throughout S5. Each CW injection corresponds to a simulation of a gravitational wave signal of the form expected from a rapidly rotating, isolated neutron star. These are known as gravitational wave pulsars.

The full set of injected pulsars may be seen on the pulsar injection parameters page.

The pulsar injections are defined in "sets", where each set contains parameters for several simulated pulsars. Each set has a corresponding epoch when that set of parameters defined the pulsar injections. Each epoch is further divided into segments. There are multiple, relatively short epochs near the start of S5, as injection amplitudes were adjusted to accommodate improvements in interferometer sensitivities. By far, the longest epoch is the one labeled s5try3.

The page provides lists of pulsar injection times in the form of segment lists. For each epoch, there is a list of the segments when injections were intended to be made and a list of segments (with 1-minute discreteness) when injections were confirmed to have been made by examining the data channel devoted to the injections. There were some occasions when attempted injections failed because of computer or network failures. The recovery of some of the pulsar hardware injections is described in arXiv:0909.3583 and arXiv:1110.0208.

A listing of the parameters used in each set can be seen by following the links at the top of the pulsar injection parameters page. The parameters are defined as in Dupuis & Woan, 2005. The parameters f0 and phi0 are both defined at a reference time corresponding to the beginning of LIGO's 3rd science run: GPS 751680013 == Nov 01 2003 00:00:00 UTC. Two additional parameters are also listed for each simulated pulsar:

Aplus = 0.5*h0*(1 + cos2(iota))
Across = h0*cos(iota)