LISA Pathfinder - Laser Interferometer Space Antenna Pathfinder
Observation of gravitational waves from space will revolutionize astrophysics, opening a whole new window on the Universe. The ESA mission LISA Pathfinder represents an in-flight experimental verification of most aspects of this kind of observatory, as well as an orbiting laboratory for understanding the limits of the most ambitious measurements in spacetime physics and of small forces.
The Science
Observation of low frequency gravitational waves from a space observatory such as eLISA - proposed for the ESA Gravitational Universe large mission (L3) theme selected for the 2030 timeframe - will revolutionize astrophysics, opening a whole new window of discovery for the physics and astronomy of massive black holes at galactic centers, stellar mass compact objects, and the interactions among and between these disparate astrophysical populations.
The gravitational waves produced by these distant sources produce a measurable time varying differential force that on a constellation of free-falling test particles, a “tidal deformation” that alternately shrinks and expands their effective separation.
LISA Pathfinder is an ESA mission dedicated to performing a relative acceleration measurement between two “geodesic reference” test masses in near-perfect free-fall. The two free-falling test masses inside a single spacecraft at 40 cm separation, and an optical interferometer measures their differential displacement. The target precision of 3 10-14 m/s2/√Hz – 30 fm/s2/√Hz with 1 fm = 1 femto-meter – at 1 mHz, or a resolution of 1 fm/s2 in one cycle of 1000 s period. This is within an order of magnitude of the eLISA sensitivity goal and would guarantee most of the eLISA science return. This is also a several order of magnitude improvement on the current state of the art for gravitational gradient measurements.
This mission represents an in-flight experimental verification of most aspects of the eLISA relative acceleration measurement, as well as an orbiting laboratory for understanding the limits of the most ambitious measurements in spacetime physics and of small forces.
It will demonstrate:
• Test masses in near perfect free-fall
• First high precision interferometric displacement measurement in space
• Drag-free spacecraft control at the nm level
• Flight verification of the eLISA “Gravitational Reference Sensor”
• Physical model of the limits for differential acceleration measurements for gravitational physics
The Laboratory of Experimental Gravitation at the Università di Trento /TIFPA has worked towards the development of an orbiting gravitational wave observatory since the joint NASA – ESA studies of LISA – Laser Interferometer Space Antenna – in the 1990s. We have been a leader for a metrology demonstrator mission since its approval – as the LISA Technology Package aboard SMART-2 – as an ESA mission in 2002, and one of us (Stefano Vitale) serves as the LISA Pathfinder mission principal investigator (PI).
Our primary eLISA / LPF research activities and main contributions include:
• Designing and analyzing an in-orbit experiment to demonstrate sub-femto-g free-fall
• Designing and prototyping “Gravitational Reference Sensors” for eLISA and LISA Pathfinder
• Probing the limits of free-fall in the lab with femtoNewton torsion pendulums
TEAM
• Involved external institutions: Max Planck Institut (DE), Imperial College - London (UK), ETHZ - Zurich (CH), Universidad de Barcellona (ES), ASI (IT), NASA (US), ESA (EU)
• INFN groups: Firenze/Urbino, Napoli, Roma II, TIFPA
• Principal Investigator: Stefano Vitale - TIFPA-INFN and Università di Trento (IT)
• INFN Project: CSN II
• Duration: 16 years (2000-2016)
TIFPA Team
• Local responsible for TIFPA: Rita Dolesi, TIFPA-INFN e Università di Trento
• Involved TIFPA people: Bortoluzzi Daniele, Cavalleri Antonella, Cesarini Andrea, Ferroni Valerio, Gibert Ferran, Giusteri Roberta, Hueller Mauro, Liu Li, Pivato Paolo, Russano Giuliana, Vetrugno Daniele, Vitale Stefano, Weber William Joseph
Images
LISA Pathfinder - Exploded View Annotated
LISA Pathfinder - Sensors VC
LISA Pathfinder - LTP core assembly trans