Five down, five to go! We’re now half way through the rendezvous burn manoeuvres needed to put Rosetta on course with comet 67P/Churyumov-Gerasimenko, and tomorrow will check off the sixth.

Tomorrow’s burn is also the second of four so-called ‘Far Approach Trajectory’ (FAT) burns that are being conducted once a week in the period 2-23 July.

Last week’s FAT burn performed well: it ended about one minute earlier than expected but the target change in velocity of 58.7 m/s was achieved.

Now the team are looking ahead to tomorrow’s burn, which will get underway at 11:29:58 UTC (13:29:58 CEST) and is predicted to last 46 minutes 32 seconds. The one way signal travel time tomorrow will be 22 mins 51 seconds.


Temperature profile of Rosetta’s thrusters during the last of the three ‘big burns’

The team will be looking for the rise in thruster temperature to indicate that the burn has begun; similarly, a decrease indicates it is complete. The plot shown above is from the last of the three “big burn” manoeuvres, on 18 June.

Tomorrow’s burn will reduce Rosetta’s velocity relative to the comet by 25.7 m/s. In total, Rosetta has to slow down by 775 m/s to reach a relatively velocity of less then 1 m/s by 6 August.

Today, 8 July, there’s 25 000 kilometres between the spacecraft and the comet, and the relative velocity is 44.4 m/s; the remaining 18.7 m/s will be reduced in smaller and smaller increments between now and arrival. However, despite their diminishing size, the remaining burns are no less important; if no further manoeuvres were carried out, the closest approach to the comet would occur on 14 July at distance of 4912 km, that is, we would have a flyby!

We’ll let you know how the burn went as soon as we can afterwards via our twitter spacecraft @ESA_Rosetta. And we’ll have a new image of the comet to share on Thursday!


Update as of 8 Jul
Date Delta-V
7 May 20 41 Complete
21 May 290 441 Complete
4 Jun 270 406 Complete
18 Jun 91 140 Complete
2 Jul 59 94 Complete
9 Jul 26 46
16 Jul 11 26
23 Jul 5 17
3 Aug 3 13
6 Aug 1 very brief


More about the FAT burns in last week’s post: Burning down to comet rendezvous