ESA Science & Technology - No. 86 - 6th Payload Checkout

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).

Spacecraft

Payload
The reporting period has been characterised by the PC6 activities. In general the activities have been conducted according to the plan.

ALICE
Activities have been conducted as planned

CONSERT
Consert activities have been conducted as planned. The only small problem observed in the frame of these tests was that the procedures used did not foresee the stopping of the time synchronisation services after CONSERT had been switched OFF. This will require a slight review of the switch OFF procedure.

COSIMA
COSIMA activities have been conducted according to the plan .

GIADA
GIADA activities have been conducted according to the plan.

MIDAS
MIDAS early activities have been conducted according to the plan, however due to an unexpected behaviour of the newly uplinked software remaining operations have been cancelled. The problem has been understood by the PI team and a recovery slot has already been identified in the near future.

MIRO
Activities have been conducted according to the plan.

OSIRIS
OSIRIS activities have been characterised by the re-occurrence of problems already seen with the thermal control and the shutter. After a preliminary analysis the PI team requested to disabled the remaining operations. Part of the problems seem to have been understood and a recovery slot has already been identified.

ROSINA
ROSINA activities have been conducted according to the plan.

RPC
RPC activities have been conducted according to the plan. Already before PC6 the test plan had been descoped due to problems in ground validation tests.

RSI
RSI PC6 activites will be executed in the next reporting period.

VIRTIS
VIRTIS activities executed according to the plan without any problem.

LANDER Philae
LANDER activities have been conducted according to the plan. The only problem observed during the test slot was the CIVA SW upload which failed due to a known issue with missed TCs inside the LANDER. The activities have been re-scheduled to take place just after the end of PC6 in order to prepare the CIVA instrument for the upcoming Earth Swing-by phase.

SREM
Since DoY 248/2007 the accumulation settings are configured for active cruise mode.

Future Milestones

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.