LISA Pathfinder – Europe’s test bed for gravity physics in space
Precision Technology will help open a New Window on the Universe EADS
Astrium and the European Space Agency (ESA) to sign the LISA Pathfinder
contract to demonstrate, in orbit, the technologies for LISA, the ESA/NASA
Laser Interferometry Satellite Antenna gravity wave observatory.

LISA Pathfinder, originally named SMART 2 (one of ESA’s Small Missions for
Application Research and Technology), is a new ESA space science mission. To
be launched in 2008, LISA Pathfinder will be packed with radical
instrumentation and technology to prepare the way for LISA, the world’s
first space-based gravity wave detector.

Professor David Southwood, ESA’s Director of Science and Colin Paynter,
Managing Director, EADS Astrium Ltd. will sign the 80M? contract to build
this small but remarkable spacecraft that will eventually lead to a whole
new way of looking at the Cosmos.

Colin Paynter said, "The LISA Pathfinder mission will test a series of
ultra-high precision technologies that will be used on a later and much
larger international project called LISA, for which the European Space
Agency is preparing a leading European role. LISA will open a new window on
the Universe by measuring gravitational waves generated by exotic objects
such as collapsing binary star systems and massive black holes. Through LISA
Pathfinder, EADS Astrium will augment its existing capability in astronomy
and planetary exploration by developing know-how for space-based fundamental
physics."

The basic principle of LISA is to measure the changes in distance between
freely floating ‘test masses’, literally, small gold blocks held in place by
carefully controlled electrostatic fields. The six test masses will be
contained in 3 separate spacecraft (two each) arranged in an equilateral
triangle with sides of 5 million km! Each of the three arms of the
constellation will be optically linked by a system of lasers (‘laser
interferometer’) and a software control system so as to form a ‘rigid’
structure.

LISA Pathfinder is an in-orbit demonstrator of the key technologies for
LISA: a kind of physics lab in space. It will test the gravitational
reference sensors, the laser interferometry and the micro-Newton thrusters.
But instead of a separation of 5 million km, LISA Pathfinder will use test
masses only 30cm apart and placed on a single spacecraft,.

In fact, because the technology is so challenging, LISA Pathfinder will
carry two alternative packages of sensors, lasers and micro-thrusters. One
(provided by European institutes and ESA) is called the LISA Test Package
(LTP), while the other, the Disturbance Reduction System (DRS), will be
provided by NASA.

After the inertial sensor systems, the micro-propulsion is the most
innovative technology to be tested on LISA Pathfinder. Two types of
micro-Newton thrusters are under development in Europe.

Field Emission Electric Thrusters are a type of electric propulsion which
use very large electric fields to almost instantly accelerate tiny droplets
of electrically conducting-metal up to high velocity.

In contrast, micro-cold gas thrusters are tiny proportional valves; in
essence, a controlled leak of inert high pressure gas (typically nitrogen).

LISA Pathfinder will be launched on a small launch vehicle into Low Earth
Orbit. To transfer the spacecraft into its operational orbit a conventional
chemical propulsion system is needed, but this must be ejected after use,
because even a few kilogrammes of left-over fuel sloshing around within the
emptied tanks could disturb the experiments.

The operational orbit is a stable and eclipse-free orbit around the L1
Lagrange point, 1.5 million km from Earth towards the Sun. This location
helps minimise disturbances from the Earth’s gravity, magnetic field and
atmosphere. The nominal mission life is just over 1 year, allowing the DRS
and the LTP to be separately tested and also allowing special experiments
where one system will monitor the performance of the other. This in-orbit
feedback will then help the detailed design of LISA.
Industrial TeamLISA Pathfinder involves an Industrial Core Team of EADS
Astrium Ltd (system prime and platform); EADS Astrium GmbH (LTP industrial
lead and drag-free control system) and SciSys Ltd (software architecture).
The full industrial team comprising companies across Europe will be
assembled over the next year via competitive selection.
Involvement of European ScientistsThe LISA Test Package (LTP) involves
scientists and industry from Italy, Germany, the UK, the Netherlands,
Switzerland and Spain. The co-Principal Investigators are Professor Stefano
Vitale of Trento University, Italy and Professor Karsten Danzmann of the
Albert Einstein Institute in Hannover, Germany. Prof Danzmann is also the
European Co-Chair of the LISA science team. The Italian contribution is
funded by the Italian space agency (ASI) and the German contributions by DLR
and the Max Planck Society.

Several research groups in the UK are involved in research for both LISA and
LISA Pathfinder. They include the Universities of Glasgow and Birmingham,
Cardiff University, Imperial College and Rutherford Appleton Laboratory
(CCLRC). The UK Particle Physics and Astronomy Research Council (PPARC) is
providing £3.5M to develop key parts of the LISA Technology Package,
including the optical bench, the cosmic ray charge management system and the
interferometer phasemeter.

EADS Astrium is Europe’s leading satellite system specialist. Its activities
cover complete civil and military telecommunications and Earth observation
systems, science and navigation programmes, and all spacecraft avionics and
equipment.

EADS Astrium is a wholly owned subsidiary of EADS SPACE, which is dedicated
to providing civil and defence space systems. In 2003 EADS SPACE had a
turnover of ?2.4 billion and 12,000 employees in France, Germany, the United
Kingdom and Spain.

EADS is a global leader in aerospace, defence and related services. In 2003,
EADS generated revenues of ? 30.1 billion and employed a workforce of more
than 100,000.

LISA Pathfinder – Facts and Figures

  • Mass of Science spacecraft 480 kg
  • Propulsion module including fuel 1420 kg
  • Total Launch mass 1900 kg
  • Dimensions 2.9m high
  • by 2.1m diameter
  • Launch date Mid-2008