LISAPathfinder arrives at its destination

After a six-week journey, LISA Pathfinder arrived today at its destination, the Lagrange point L1, a point on the virtual line joining the Earth to the Sun, some 1.5 million km from Earth, where the gravitational effects are balanced by the centrifugal force.

LISA Pathfinder’s arrival came after a final thruster burn using the spacecraft’s propulsion module on 20 January. The small, 64-second firing was designed to slightly change its speed and just barely tip the craft onto its new orbit about L1. “We had planned two burns to get us into final orbit at L1, but only one was needed,” says Ian Harrison, Spacecraft Operations Manager at ESA’s ESOC operation centre in Darmstadt, Germany, where the mission control and science teams are located.

LISAPathfinder journey from the Earth to L1

LISAPathfinder journey from the Earth to L1

Since launch, the propulsion module raised the orbit around Earth six times, the last of which kicked it towards L1.


The propulsion module separated from the science section at 11:30 GMT (12:30 CET) after the combination was set spinning for stability.

“Heat and vibration from the regular, hot thrusters on the propulsion module would cause too much disturbance during the spacecraft’s delicate technology demonstration mission,” notes Ian. “Primary propulsion during the rest of the mission will be provided by microthrusters to keep us at L1.”

These small thrusters were used in the hours after separation to kill the spin and stabilise the spacecraft.

Next week, LISA Pathfinder’s trajectory will be fine-tuned with a series of three micro-thruster bursts, taking it onto its final orbit, a 500 000 km × 800 000 km orbit around L1.

The next delicate step will be the final release of the test masses on 15 and 16 of February.



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