EADS Astrium to Build Technology Pathfinder Spacecraft for the LISA Gravity Wave Observatory

* LISA Pathfinder – Europe’s test bed for gravity physics in space
* Precision Technology will help open a New Window on the Universe

Stevenage, UK, 23 June 2004

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.”

LISA Pathfinder

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 Team

LISA 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 Scientists

The 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

Press contact:
Rémi ROLAND
EADS SPACE (FR)
Tel.: +33 (0) 1 34 88 35 78

Alistair SCOTT
EADS SPACE (UK)
Tel.: +44 (0) 1438 77 3698

Mathias PIKELJ
EADS SPACE (GER)
Tel.: +49 (0) 7545 8 91 23
www.space.eads.net
Editor note:

Why Study Gravity Waves?

A consequence of Einstein’s famous Theory of General Relativity, published in 1915, in which he proposed that matter, space and time are all linked, is the idea that the force of gravity also produces waves. For small masses moving at slow speeds – every day things like cars, aircraft and even spacecraft – the predictions of Einstein’s theories are the same as those of Isaac Newton’s laws of gravity dating back to 1665.

But when considering the movement of massive bodies, such as black holes or colliding galaxies travelling at enormous speeds, strange things start to happen. Einstein’s theory predicts that the movements of these massive bodies will disturb the ‘fabric of space-time’ around them, sending ripples of gravity waves in all directions.

In practice, these fluctuations are extremely small and difficult to detect. Up until now, gravity waves have not been directly measured, though large Earth-bound facilities are currently being built.

Scientists predict that gravitational waves should still be echoing from the very first second of the formation of the Universe. Detection of these waves would be the most fundamental discovery that LISA could make.

LISA will also study super-massive black holes and pairs of black holes merging deep in our own galaxy and beyond. These measurements provide a new yardstick with which to measure the Universe, as well as a new understanding of the behaviour of space-time near black holes. Although Einstein himself may only have dreamed the possibility of detecting these waves, the technology will soon exist to do so.

How will LISA Work?

LISA, will be launched within the next decade as the World’s first space-based gravitational wave observatory. It will rely on three core technologies, Gravitational reference sensors, Micro-Newton thrusters and Laser interferometry.

Working together, they must overcome the mission’s central challenge, which is to cancel out all the other disturbances that could prevent the gravitational waves being detected.

Unfortunately, there are many sorts of noise, from both the environment of space (external disturbances), and the spacecraft itself (internal disturbances).

External disturbances include the gentle pressure of the light coming from the Sun, the effect of its magnetic field and Earth’s gravity. Internal disturbances include changes in the temperature within the spacecraft, interaction with the computer and other electronics on-board and any changes in the gravity field of the spacecraft itself, e.g. caused by equipment movement or the sloshing of rocket fuel. An extraordinary consequence of the need to minimise all these effects is that each LISA spacecraft must ‘follow’ the test masses contained inside to an accuracy of ten nanometres.

To achieve this almost-perfect ‘shadowing’ of the test masses, LISA will use tiny Micro-Newton thrusters which will each only produce up to 50 thousandths of a Newton thrust and deliver it in finely adjustable increments, like the dimmer switch in domestic lighting.

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