En route to nothing

It’s official! LISA Pathfinder is safely en route to a virtual point in space called the Sun-Earth Libration Point 1 (SEL1), 1.5 million km from Earth.

A main engine burn during the weekend provided the thrust needed to get there (see roughly the 22 second point in the animation), and took place as planned on Saturday, 12 December, at 06:18 CET. This was the 6th and final of the orbit-raising manoeuvres (#ARM6), and this one will take the craft all the way ‘up’ to L1.

Once there, without any further action, LISA pathfinder would ‘fall back down’ to Earth under the tug of our planet’s gravity, so the mission operations team will have to perform a regular station-keeping manoeuvre (about once per week) to keep it ‘up’ at L1.

After Saturday’s manoeuvre, an assessment of the actual burn results conducted by the flight dynamics team at ESOC showed an under performance of the planned change in speed by less than 1%, which is well within expectations. This means that a follow-on burn slot planned for the following day (Sunday) was used to give an additional push of 7 m/second.

This burn, too, was analysed and was found to have delivered a slight over performance of about 1-2% – and so there will be a further small transfer correction manoeuvre in approximately one week (which also provides time for a very detailed trajectory analysis).

LISA Pathfinder is now on a transfer orbit for a free drift into L1 orbit.

The activity this weekend marked the formal end of the critical Launch and Early Orbit Phase (LEOP), and the start of approximately three months of commissioning.

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