Today’s update continues our 18 August post, What’s Up with Rosetta.
Here are some interesting numbers related to Rosetta’s path around the comet. Note that, in this post, we’re citing numbers as planned; reconstructed values are not available until after the flight dynamics teams do their detailed orbit determinations.
All times shown in UTC = CEST – 2
From 6 to 17 August, 09:00 UTC (during the first 100km pyramid orbit, also called ‘Big CAT’ in our last post) the minimum distance from the comet achieved by Rosetta was ca. 90 km on 11 August around 21:00 UTC.
On 17 August, starting at 09:00 UTC, we started the descent toward the next triangular orbit (‘LittleCAT’) as follows:
- During the orbital arc from Sunday, 17 August to Wednesday, 20 August at 09:00 UTC, the minimum distance achieved was ca. 79 km on 19 August around 07:00 UTC.
- On 20 August at 09:00 UTC, Rosetta conducted a manoeuvre to go further ‘down’; the distance at the time of the burn was ca. 92km.
- Rosetta crossed the 79 km distance between 02:00 and 03:00 UTC on 21 August; and will be on a continuous decay until late in the evening of 22 August, when we reach ca. 60 km
- On Sunday, 24 August at 09:00 UTC, we will do the manoeuvre to start the first arc of the second pyramid (‘Little CAT’); we will be at about 72 km.
- At the crossing (point of closest approach) between 24 and 25 August, we will go below 60km
During the second pyramid (24 August until 3 September 09:00 UTC), the minimum distance will be about 52-53 km and will be reached on 25 August and 29 August (at ca. 09:00 UTC) and on 1 September at ca. 22:00 UTC, i.e. the mid-points of the three arcs.
On 3 September at 09:00 UTC (the end of the second pyramid), Rosetta will be again at about 72 km; from there onwards will be on an (almost) continuous decay toward the 30 km orbit. For this next leg we do not yet have the operational orbit – it is being prepared right now!