Ira Thorpe
- Dr, Partner Investigator
- NASA Goddard Space Flight Centre
Gravitational Waves are an exciting new tool for astronomy which can be used to study extreme astrophysical systems involving objects like black holes and neutron stars moving at velocities near the speed of light. Predicted by Einstein in 1918, Gravitational Waves were first observed by the ground-based Laser Interferometer Gravitational-wave Observatory (LIGO) in September 2015 after decades of effort in developing instrumentation. The scientific impact of LIGO’s first few detections has been immense including suggestions of a new population of black holes, confirmation of the mechanism behind short gamma-ray bursts, tight constraints on alternative theories of gravity, and, in concert with a suite of electromagnetic instruments, the discovery of the origin of heavy elements in the universe.
I’m interested in extending this new window on the universe to longer-wavelength gravitational waves, which requires placing the detector in space. The Laser Interferometer Space Antenna (LISA) mission has been studied for nearly 20 years and has recently been selected by the European Space Agency as a flagship mission for the early 2030s. NASA is collaborating with ESA to contribute to this mission and I am the lead scientist at NASA for this effort. LISA will use optical interferometry to monitor the separations between three spacecraft in a triangular constellation billions of meters on a side. The interferometric system will be sensitive enough to detect fluctuations in the spacecraft separation at the tens of picometer level that are produced by passing gravitational waves.
The science potential for a space-based gravitational wave observatory is particularly strong due to the high density of sources in the milliHertz frequency band, a band that is only accessible from space. I’m interested in the details of how to realize such a detector including the instrument technologies, mission design, data analysis, and science interpretation.
Previously, I worked on the LISA Pathfinder (LPF) mission, a technology demonstrator for gravitational wave missions that was also led by ESA and had significant contributions from NASA and a number of European National agencies. The primary goal of LPF was to demonstrate a low-disturbance test mass via the technique of drag free control. On LISA, these test masses will serve as the fiducial point for measuring the gravitational wave signal. Ideally, these test masses would be inertial particles but in practice their trajectories can be disturbed by non-gravitational forces. The single LPF spacecraft was be sensitive to gravitational waves, but was be sensitive to many of the same noise sources. LPF was a fantastic success, demonstrating that the test masses could be isolated more than well enough to meet the LISA requirements.
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