ESA Science & Technology - No. 139 - Closing in on asteroid Lutetia

During the reporting period, mission operations have been conducted with support of the ESA New Norcia (NNO) ground station. Additional tracking passes were performed with the NASA DSN ground stations in Goldstone (DSS-15 and DSS-24), as part of the navigation campaign for asteroid Lutetia:

At the end of the reporting period (DOY 178) Rosetta was at 415.8 million km from Earth (2.63 AU) and the one-way signal travel time was 1387 seconds (22 minutes and 47 seconds). The distance to the Sun was 391.56 million km (2.61 AU). Rosetta was at 16.5 million kilometres from asteroid Lutetia.

Optical Navigation Campaign

On 10 July (DOY 191) Rosetta will fly by asteroid (21) Lutetia at a distance of less than 3200 km from the asteroid. In addition to the spacecraft tracking and usage of radiometric data for navigation purposes, Rosetta's on-board cameras are visually tracking the asteroid in an optical navigation campaign. The observations are fed into the orbit determination process to refine Lutetia's predicted location and to optimise Rosetta's trajectory for the upcoming flyby.

The three cameras that are used for these observations are Rosetta's two navigation cameras (NAVCAM A and B) and the narrow angle camera (NAC) of the OSIRIS instrument.

A series of time slots have been allocated for the optical navigation campaign, with seven slots completed up to now. The first slot was on Monday 31 May, followed by two slots every week in the following three weeks (on 7, 9, 14, 16, 21 and 23 June). From the start of the next reporting period, the frequency of observations is increased, with images of asteroid Lutetia being acquired every day instead of twice a week.

NAVCAM A and B are permanently ON already since 30 May 2010. Since 18 June the CCD temperature of both cameras is maintained at -30°C to reduce the number of warm pixels. OSIRIS-NAC is ON since 2 June (DOY 153).

Spacecraft

Payload

ALICE
The instrument is currently OFF.

CONSERT
The instrument is currently OFF.

COSIMA
The instrument is currently OFF.

GIADA
The instrument is currently OFF.

MIDAS
The instrument is currently OFF.

MIRO
The instrument is currently OFF.

OSIRIS
Since 2 June 2010 (DOY 153) the instrument has been ON and the NAC regularly takes images of asteroid Lutetia as part of the optical navigation campaign.

ROSINA
The instrument is currently OFF.

RPC
The instrument is currently OFF.

RSI
The ultra-stable oscillator (USO) is ON/muted since DOY 032/2010.

VIRTIS
The instrument is currently OFF.

LANDER Philae
The instrument is currently OFF.

SREM
The instrument is ON with standard settings since DOY 032/2010.

Future Milestones

Starting in the next reporting period, the optical navigation campaign will proceed with images of asteroid Lutetia being acquired every day instead of twice a week.

The remaining four slots that have been reserved for possible trajectory correction manoeuvres, should they be required to adjust Rosetta's course towards Lutetia, are at 1 week, 3 days, 40 hours, and at 12 hours before the closest approach on 10 July.

---
Legal disclaimer
This report is based on the ESOC mission operations report, WOR #139. Please see the copyright section of the legal disclaimer (bottom of this page) for terms of use.