Rosetta’s night-time excursion and a ‘Go’ for 20 km

For the last two weeks, Rosetta has been orbiting comet 67P/C-G at a distance of about 30 km on the “Global Mapping Phase” (GMP), and is now set to go even lower. The aim of the GMP was to gather high-resolution science data to help characterise the potential landing sites for Philae, while also continuing to monitor how the spacecraft responds to the environment of an active comet, before getting closer still. See the table below for a recap of the manoeuvres conducted this month, starting with the transfer to the global mapping phase (TGM), and refer to the animation to help visualise these changes in trajectory. Burn Date DV (m/s) Duration (min:sec) TGM1 03/09 0.56 04:55 TGM2 07/09 0.45 04:18 GMP1 10/09 0.193 02:19 GMP slot 1 14/09 0.025 00:32 GMP2A 17/09 0.085 01:23 GMP2B 17/09 0.087 01:25 GMP slot 2 21/09 0.018 00:25 (DV = delta v; TGM = transfer to global mapping; GMP = global mapping phase; two more burns scheduled this month for 24/09 and 29/09) In fact, as we discussed in an earlier blog post, rather than fly one complete orbit, the spacecraft conducted two seven-day-long half orbits at about 30 km, in different planes. That is, on 10 September, the spacecraft was at the terminator plane (the boundary between day and night, which is itself the 06:00/18:00 plane), and performed a thruster burn to insert onto the 30-km circular orbit. The orbital plane was then 60 degrees away from the Sun’s direction, such that the spacecraft orbited over areas of the comet in their ‘morning’ hours. Seven days later, when the spacecraft was again on the terminator plane, it conducted another thruster burn to change the orbital plane such that it had the same characteristics as the previous orbit – but instead was flying […]



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