The crucial series of six major engine burns – needed to get LISA Pathfinder to its final science orbit around L1 – continues to go well. Since the last blog post, the mission control team at ESOC have conducted the 5th burn as well as a smaller ‘test’ burn using the reaction control thrusters. Here’s the latest update from Spacecraft Operations Manager Ian Harrison, sent in at 04:30 CET today:
LISA Pathfinder apogee-raising orbits, prior to departure for SEL1. We’re now on the big one! Credit: ESA
The fifth orbit-raising engine burn, ARM#5, has been executed successfully and LISA Pathfinder is now in a highly elliptic orbit with apogee above 120 000 km. We also conducted a functional check of the ‘CTCM’ mode, which uses the reaction control thrusters to generate a push (aka ‘delta-v’) rather than the main engine*; this system will be used for small manoeuvres in the future.
The ARM#5 and CTCM burns both over-performed, and so during this long final orbit, all the burn performances are being analysed to plan the final Earth-escape burn with the best possible accuracy.
During the weekend, LISA Pathfinder will escape the Earth and be guided into a free-drift orbit towards L1.
Note*: The main engine delivers a thrust of around 400N, whereas the smaller thrusters provide around 10N thrust
Discussion: 4 comments
What is the possible reason for the over-performance of the last burns?
I am looking at the live tracking at n2yo.com, but that doesn’t seem to correspond to the orbit it should be having after the last burn. Are they several days behind?
Hi Jens: Yes, you are correct. I will check this out later today. — Daniel
ny2o.com I am pretty sure gets its data from the JSPOC TLEs, as do other sites that let you look at where satellites are. US tracking hasn’t picked LPF up since it was in the 44000 km apogee orbit, and I don’t expect they will ever do unless you send them some state vectors to clue them in. They don’t care much about stuff beyond GEO.