ESA Science & Technology - Rosetta Second Earth Swing-by

Updates on the progress of the flyby can be found on the ESA Rosetta Swing-by site.

Position of inner Solar System planets and Rosetta's orbit (green) as it approaches the Earth for a second swing-by. (click for animation)

This second Earth swing-by occurs nearly 9 months after the Mars swing-by in February 2007 which slowed down Rosetta to direct it back into the inner Solar System towards Earth. The second Earth swing-by, plus the third Earth swing-by in two years time, will be used to increase Rosetta's velocity and provide it with the energy needed to journey out to nearly the orbit of Jupiter to rendez-vouz with comet 67P/Churyumov-Gerasimenko.

Swing-by Details

View of Earth around closest approach (click for animation)

Rosetta will swing by the Earth at a distance of 5301 km (compared to Earth's equatorial diameter of ~12 760 km), with closest approach at 20:57 UTC. At that time the spacecraft will be over the Pacific Ocean, south-west of Chile, at 74° 35' W, 63° 46' S. It's velocity relative to Earth will be 45 000 kmh^-1 (12 500 ms^-1).

During the swing-by, the highest priority will be given to spacecraft operations, as the manoeuvre is critical for the success of the overall mission. However, a few instruments both on the Rosetta orbiter and the Philae lander are and will be activated (see also the Rosetta status report from 12 November) for calibration, scientific measurements and imaging purposes. Observations of the Earth-Moon system will take place for about two weeks around closest approach, from 7 November, 00:00 UTC, until 20 November, 14:00 UTC.

Planned Science Activities

On the swing-by incoming and outgoing trajectory Rosetta will be in unfavourable solar illumination conditions, with thermal constraints for pointing, resulting in only limited time slots for the instruments to be safely used.

Each observation by the instruments that require pointing will start at the end of a slew manoeuvre that will orient the spacecraft correctly. A few instruments (ROMAP, RPC, SREM and Radio Science) do not require pointing to be operated.

Around closest approach, imaging by Rosetta's navigation camera is also foreseen, on a non-interference basis with OSIRIS and VIRTIS observations.

Scientific objectives

• ALICE - orbiter's UV imaging spectrometer
  Spectra of illuminated Earth for calibration purposes.
  Spectra of illuminated Moon for calibration purposes.
• ROMAP - lander's magnetometer
  Measurements of the Earth magnetosphere.
• RPC - orbiter's plasma consortium
  Measurements of the Earth magnetosphere. In the case of RPC the measurements are also used for calibration purposes.
• MIRO - orbiter's microwave experiment
  Earth and Moon observations for calibration purposes.
  Earth observation around closest approach to test the 'asteroid mode sequence': ensure that the microwave radiation emitted by the 4 volatile molecular species MIRO is to study at the asteroids Steins and Lutetia will be in the bandwidth of the instrument (considering the Doppler shift due to the fact that the spacecraft is first approaching and then flying away from the target).
• RSI - orbiter's radio science investigation
  Investigation of anomalous acceleration during swing/fly-bys.
• SREM - radiation monitor experiment
  Measurements of Earth's radiation belt.
• OSIRIS - orbiter's Optical, Spectroscopic, and Infrared camera
  Earth night-side pointing: includes imaging of urban regions in Asia, Africa and Europe at night (WAC) and a search for shooting stars from space (Rosetta will pass close to the Leonids clouds).
  Lunar disk spectro-photometry.
  Distant images of the Earth-Moon system when both are in the field of view of the Wide Angle Camera (WAC).
• VIRTIS - orbiter's visual and infrared mapping spectrometer
  Study of fluorescence emission of CO₂ and O₂ through Earth atmospheric scan (300-0 km from the surface, total of seven scans) at Earth limb on sunset side.
  Spectra of the Moon for calibration purposes.

Observation plan

On 7 November at 00:00 UTC the Philae Lander and its instruments were initialised for observations. The lander's ROMAP instrument, and the orbiter's RPC instrument started making observations of the Earth's magnetosphere, and will continue these until 20 November.

The Closest Approach Earth pointing slot will start on 13 November at 18:00 UTC and will be concluded at 21:02 UTC. During this time frame, seven slew manoeuvres will be performed. The first of these slews (18:00-18:45 UTC) will bring the spacecraft into Earth pointing attitude. The planned observations include:

The Closest Approach Moon pointing slot will start on 13 November at 21:02 UTC and will be concluded at 10:02 UTC on 14 November. Two slews will be performed in this time frame; the first one (13 November, 21:02 UTC - 22:02 UTC) will change Rosetta's attitude to be Moon-pointing. The second slew (14 November, 08:32 UTC - 10:02 UTC) will conclude the Closest Approach Moon pointing slot. The planned observations include:

After closest approach, the ROMAP and RPC observations of the Earth magnetosphere will be on-going. Other planned observations include: