Successful Rosetta swing-by – next stop Earth

The critical gravity assist manoeuvre around Mars has helped Rosetta change direction – putting it on the correct track towards Earth its next destination planet whose gravitational energy Rosetta will exploit in November this year to gain acceleration and continue on its ten-year journey to the comet which it will reach in 2014.

At 2.57 GMT mission controllers at ESOC, ESA’s Space Operations Centre in Germany confirmed that Rosetta had successfully completed the swing-by manoeuvre. At its closest approach (around 2.15 GMT) Rosetta passed the surface of Mars at a distance of 250 km (155 miles) travelling at a mere 10.1 km/second relative to the centre of the planet.

During the swing by there was a 25 minute period when Rosetta passed into the shadow of Mars denying the probe the ability to generate power using its solar arrays. At this time the spacecraft was put into “eclipse mode” with no science operations taking place on the orbiter instruments.

However, during the lead up to the closest approach and after the eclipse period the flyby presented scientists with a golden opportunity to calibrate the payload with instruments on other orbiting spacecraft such as Mars Express and Mars Reconnaissance Orbiter. Prior to the orbiter’s instruments being switched off the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) captured some detailed images showing the atmospheric features of Mars, including cloud systems above the North polar cap.

Professor Keith Mason, CEO from the Particle Physics and Astronomy Research Council (PPARC), said, “Rosetta has provided some amazing images of Mars from a completely different perspective. Data gathered during the swing-by will complement that collected by other current missions enabling us to build up a comprehensive picture of the make up of Mars.”

UK scientists from 10 institutions are involved in the instruments on both the Rosetta orbiter and lander. Chris Carr leads the Imperial College London team that operates the Rosetta Plasma Consortium (RPC) instruments, “Our instruments operated near continuously both sides of the flyby – allowing simultaneous measurements with its identical twin instrument on Mars Express. With Rosetta and Mars Express together, we hope to understand more about the vast and complex plasma environment around the red planet.”

Dr Andrew Coates from UCL’s Mullard Space Science Laboratory is a co-investigator on instruments on both Rosetta and Mars Express. He comments, “It's great to see that this important milestone in this marathon mission has gone so well – and we will learn more about Mars on the way. Now, Rosetta can continue its long journey via 2 Earth flybys and passing 2 asteroids, en route to becoming the first ever mission to orbit and land on a comet. A triumph for the ESA and international teams involved.”

Professor Ian Wright from the Open University is Principal Investigator for Ptolemy, a miniaturised mass spectrometer on the lander – whose instruments were able to operate during the whole period of the close approach. He said, “This is the first time that the Philae lander has operated autonomously, completely relying on the power of its batteries. It is reassuring to know that so many miles away from home all instruments operated as is planned. This was a great rehearsal for 2014 and touch down on the comet when Philae will conduct its scientific measurements independent from the Rosetta orbiter.”

The camera onboard the lander (CIVA) provided a stunning image showing sections of the spacecraft and one of its solar arrays with Mars in the background. The ROMAP instrument was also switched on to collect data about the magnetic environment of Mars.

Chris Lee from SciSys UK Limited, who are responsible for the implementation of the Rosetta Mission Control System, monitored events from mission control in Germany. He comments, “The most critical time from our point of view came a few days before the actual manoeuvre when the on-board timeline was loaded with commands to execute the necessary actions for the swing-by. All went to plan and for the flyby itself it was a case of sitting back and letting Newton take over.”

EADS Astrium in the UK was responsible for the design, development and supply of the spacecraft platform including the structure and mechanical, thermal, propulsion, power and RF communications equipment. Rod Emery head of Astrium’s Rosetta team said: “Rosetta was a key major project and its success heralded a growth in scientific and Earth observation activities including prime management of Aeolus and Lisa Pathfinder and major roles in Gaia and Swarm. Rosetta is an extremely challenging mission and Astrium’s ex Rosetta team are tracking its success with great pride.”