No. 87 - Ongoing Payload Checkout
15 October 2007 18:00Report for Period 30 September 2007 to 12 October 2007
The reporting period covers a period of 2 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.
At the end of the reporting period (DOY 285) Rosetta was at 29 million km from Earth (0.19 AU; one-way signal travel time was 1 minute and 37 seconds). The distance to the Sun was 175.6 million km (1.17 AU).
The preparation of the Earth Swing-by phase is proceeding according to the plan. Latest orbit determination indicates that a trajectory correction manoeuvre will be very likely needed at on the 18th of October. The swing-by manoeuvre will take place on the 13th of November at 20:57 UTC.
Earth Swing-by 2 Targeting
On the plot below, the blue 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 short arc solution using data from the time of NSHM exit up to 19 September.
From a longer arc orbit determination using data acquired since exiting NSHM and up to the end of the pass on 04 October, and a subsequent orbit prediction, the red cross and surrounding 3-sigma error ellipse shows the current estimate in the B-plane. This estimate is 68 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 5364 km with a 3-sigma uncertainty of 39 km.
The estimated time of closest approach (perigee passage) is 20:57:23 UTC on 13 November (the same as the previous estimate). The 3-sigma uncertainty is now 7 seconds. Based on the present solution, a manoeuvre at arrival minus 4 weeks, on 18 October, would have a delta-V of about 4 cm per second.