A technology demonstrator mission for the Laser Interferometer Space Antenna (LISA), a space-based gravitational wave detector due to be launched during the mid-2030s. RHEA was involved in the mission throughout the development, operations and post-operations phases.

LISA Pathfinder mission timescale

Mission launch: 3 December 2015
End of operations: 18 July 2017

About the LISA Pathfinder mission

LISA Pathfinder ready for launch. Image copyright: ESA–M. Pedoussaut, 2015
LISA Pathfinder ready for launch. Image copyright: ESA–M. Pedoussaut, 2015

LISA Pathfinder was a joint European Space Agency (ESA)/NASA mission. The aim was to demonstrate a number of novel technologies that would be key to the success of a future space-based gravitational wave interferometer (a tool that measures and analyzes the interference caused when two or more waves are merged or superimposed).

The mission housed the LISA Technology Package (LTP), delivered by a consortium of European research institutions and industry, and the Disturbance Reduction System (DRS) provided by NASA.

The LTP was designed to demonstrate the possibility of having two freely falling test masses in space with very low noise. Each 2kg mass was confined inside a separate enclosure in order to remain in free fall with no physical contact with the satellite. This is an essential step in order to be able to detect gravitational waves using laser interferometry in space – the goal of LISA.

The DRS was a set of colloid thrusters delivering forces of between and 5 and 30 micronewtons in order to precisely steer the satellite around the free-falling test masses.

At the core of LISA Pathfinder are the two test masses: a pair of identical 46 mm gold–platinum cubes, floating freely, several millimetres from the walls of their housings. The cubes are separated by 38 cm and linked only by laser beams to measure their position continuously. Image copyright: ESA/ATG medialab
The two test masses are identical 46mm gold–platinum cubes, floating freely several millimetres from the walls of their housings, linked only by laser beams to measure their position continuously. Copyright: ESA/ATG medialab

LISA Pathfinder’s main technical achievements

The results show that the test masses were almost motionless with respect to each other, with a relative acceleration lower than 1 part in 10 millionths of a billionth of Earth’s gravitational acceleration. This corresponds to the weight of a virus on Earth.

LISA Pathfinder’s main scientific achievements

LISA Pathfinder was used to test two different methods to measure Newton’s gravitational constant G, which is used to determine the force between two objects caused by gravity. The results obtained are consistent with the recommended CODATA (Committee on Data of the International Science Council) value. One of the methods uses electrostatic suspension forces to measure a change in acceleration of a test mass due to a displaced source mass. The second method measures a change in relative acceleration between two test masses due to a slowly varying fuel tank mass.

Data acquired by LISA Pathfinder also allowed scientists to improve our understanding of the collapse of the wave function, the still poorly understood process responsible for driving physical systems from a quantum to a classical regime. (Read more about the contribution of LISA Pathfinder to calculations of wave function collapse models.)

Strange but true

The noise affecting the free falling test masses was so low, we can confidently say LISA Pathfinder scientists and engineers created the quietest place known to humankind.

How RHEA contributed to the LISA Pathfinder mission

RHEA personnel played key roles at the LISA Pathfinder Science and Technology Operations Centre at the European Space Astronomy Centre and were involved in the mission through part of the development and the entire operations phase, as well as the post operations phase.

Our LISA Pathfinder team included:

  • One of the operations engineers responsible for the development testing and validation of the planning software and the telemetry unwrapping software to be used during the mission. He was also responsible for designing several simulations and test campaigns used to train the team that was later involved in operations.
  • An operations engineer for the operations phase. One of his duties was to guarantee the experiments to be performed on board LISA Pathfinder, as requested by the scientists, were correctly translated onto commands that could be sent to the satellite after testing and validation.
  • The archive scientist for the post-operations phase, who was responsible for overseeing the development of the LISA Pathfinder Legacy Archive and its population with validated LISA Pathfinder data.

In addition, RHEA’s MOIS software was used for mission procedure preparation and management.

The LISA Pathfinder Dedicated Control Room is located at ESOC, ESA's European Space Operations Centre, Darmstadt, Germany. Image copyright: ESA/J. Mai
The LISA Pathfinder Dedicated Control Room at ESOC, ESA’s European Space Operations Centre, Darmstadt, Germany. Image copyright: ESA/J. Mai

Main image: LISA Pathfinder will operate from a vantage point in space about 1.5 million km from Earth towards the Sun, orbiting the first Sun–Earth Lagrangian point, L1. Image copyright: ESA–C.Carreau