21 Oct 2009 11:29

Mission operations have been conducted with support of the ESA New Norcia (NNO) ground station.

In preparation of the Earth swing-by activities and the intense tracking campaign, proficiency passes have been taken with the ESA Kourou and Maspalomas ground stations, as well as the NASA DSN ground stations Canberra, Madrid, and Goldstone. All activities were nominal and radiometric data of the expected quality.

At the end of the reporting period (DoY 289) Rosetta was at 24 million km from Earth (0.16 AU) and the one-way signal travel time was 80 seconds. The distance to the Sun was 170.87 million km (1.14 AU).

Navigation Campaign

On 13 November 2009 Rosetta will perform its third Earth swing-by. It is the mission's fourth and final gravity assist that will boost Rosetta's orbit to place the spacecraft on a trajectory to its final destination: comet 67P/Churyumov-Gerasimenko. Closest approach to Earth is expected to occur at around 07:46 UT, with Rosetta passing at an altitude of under 2500 km.

The navigation campaign leading up to the swing-by is well underway. Radiometric data from the New Norcia ground station is used by the flight dynamics team to determine Rosetta's current course. Based on this data the required adjustment to the spacecraft's velocity will be determined to place Rosetta on the correct approach trajectory for the Earth swing-by.

The two figures below are B-plane plots illustrating the status of the navigation campaign in preparation for the third Earth swing-by. The B-plane is a planar coordinate system that allows targeting during a gravity assist. The first plot shows the target point (green) of Rosetta's approach trajectory relative to the Earth in the B-plane. Note: this is not the point of closest approach. Instead this virtual point corresponds to what would be Rosetta's miss-distance if the Earth had no gravity.

The second plot is a magnification of the region around the target point, with the progressively smaller navigation error ellipses plotted. The error ellipses are based on radiometric data from 21 September up to 1 October (black), 8 October (red), and 15 October (orange).

B-plane plot for Rosetta's third Earth swing-by (left), and a zoom on the target region (right) with the navigation results, up to 15 October

A trajectory correction manoeuvre (TCM) is planned for 22 October. Three additional time slots are reserved for possible refinement of the first TCM. These extra slots are at 1 week, 1 day and 6 hours before closest approach.

Spacecraft

Payload
Most instruments were OFF, with only a few instruments activated as part of the final payload check-out 10 activities. The Standard Radiation Environment Monitor (SREM) continues to run in the background.

ALICE
The instrument is currently OFF.

CONSERT
The instrument is currently OFF. It was activated on DOY 281 to monitor the RSI activities.

COSIMA
The instrument is currently OFF.

GIADA
The instrument is currently OFF.

MIDAS
The instrument is OFF.

MIRO
The instrument is currently OFF.

OSIRIS
The instrument is OFF.

ROSINA
The instrument is OFF.

RPC
The instrument is OFF.

RSI
The instrument is muted. The PC10 activities were conducted on DoY 281 and the spacecraft performance was nominal.

VIRTIS
The instrument is currently OFF.

LANDER Philae
The instrument is currently OFF. The instrument was ON at the beginning of the reporting period to complete the PC10 activities.

SREM
Since DoY 251/2009 the accumulation settings are configured for active cruise mode.

Future Milestones

The navigation campaign for the approach to the third and last Earth swing-by will continue for the next weeks. A first slot for a trajectory correction manoeuvre is planned for 22 October.

The ground segment team will conduct the short simulation campaign required to complete the validation and training plan in view of the critical mission phase that the Earth swing-by represents.

Detailed planning of the scientific observations during the Earth swing-by has also started, with finalisation of the products for the spacecraft planned for week 44.

Re-lubrication of reaction wheel B is planned for week 44.

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Legal disclaimer
This report is based on the ESOC mission operations report, WOR #121. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.