No. 86 - 6th Payload Checkout
02 October 2007 18:00Report for Period 8 September 2007 to 29 September 2007
The reporting period covers a period of 3 weeks of Active Cruise Mode. The reporting period has been characterised by a very high activity load with the spacecraft instruments as part of the 6th payload check-out.
A reconfiguration of the AIU took place very likely due to an overload of the data traffic, however this had not impact on the operations. Few anomalies have been recorded in the area of the instruments however none if them is of particular concern.
At the end of the reporting period (DOY 272) Rosetta was at 43.1 million km from Earth (0.28 AU; one-way signal travel time was 2 minutes and 24 seconds). The distance to the Sun was 185.7 million km (1.24 AU).
With the end of the active payload check-out #6 the preparation of the Earth Swing-by phase enters its period mainly dedicated to navigation activities. The coming weeks will be characterised by more frequent tracking passes. The orbit determination and manoeuvre optimisation teams will focus on the eventual trajectory corrections required to properly phase and executed the swing-by manoeuvre to take place on the 13th of November at around 21:00 UTC.
Earth Swing-by 2 Targeting
On the plot below, the red cross and surrounding 3-sigma error ellipse were the estimates for the location in the Rosetta B-plane, corresponding to the 2nd Earth swing-by, that were made on the basis of a long arc solution up to 06 June, at entry into NSHM.
From a short arc orbit determination using data acquired since exiting NSHM and up to the end of the pass on 19 September, and a subsequent orbit prediction, the blue cross and surrounding 3-sigma error ellipse shows the current estimate in the B-plane. This estimate is 67 km from the target. The target location corresponds to a perigee altitude of 5299 km (relative to the Earth's equatorial radius). The estimate corresponds to an altitude of 5362 km with a 3- sigma uncertainty of 101 km.
The estimated time of closest approach (perigee passage) is 20:57:23 UTC on 13 November (9 seconds earlier than the previous estimate). The 3-sigma uncertainty is now 14 seconds. Based on the present solution, a manoeuvre at arrival minus 4 weeks, on 18 October, would have a delta-V of between 3 and 4 cm per second.
At present the target lies within the 3-sigma error ellipse.However, over the last couple of weeks the solutions have remained quite stable and the error ellipse is diminishing in size quite rapidly. It appears to be quite likely that in another couple of weeks the target will be outside the error ellipse, thus making use of the -4 weeks slot for a correction manoeuvre very probable.