The Flight Control Team

Andrea Accomazzo

The Flight Control Team (FCT) at ESOC operates from the same Dedicated Control Room (DCR) as Mars Express and Venus Express. Spacecraft Operations Manager (SOM) Andrea Accomazzo, from Italy, oversees a team of four flight control engineers working full-time on Rosetta. The team is further composed by analysts and SPACONs (spacecraft controllers), who support all three ESA interplanetary missions via integrated ground software and daily operations.

Other ESOC teams provide additional support in the areas of Flight Dynamics, Ground Facilities and Software Support.

Mission operations overview

Launch of Ariane-5 flight V138 from the European Space Centre, Kourou, French Guiana, 19 December 2000.

During its 10-year journey to Comet 67P/Churyumov-Gerasimenko, Rosetta will circle the Sun almost four times. It will also cross the asteroid belt twice and gain velocity from gravitational 'kicks' provided by close swing-bys of Mars (2007) and Earth (2005, 2007 and 2009).

The launch and early orbit phase (LEOP)

The planned launch date for Rosetta was 07:36:49 UT on 26 February 2004. However, an initial delay due to adverse weather, and a subsequent delay due to a technical issue with the launch vehicle, pushed the launch date back by five days, to 2 March 2004.

After burn-out of the lower stage, the spacecraft and upper stage remained in Earth parking orbit (4000 x 200 km) for about two hours. Ariane's upper stage then ignited to boost Rosetta into its interplanetary trajectory, before separating from the spacecraft.

Earth swing-bys

Rosetta first travelled away from its home planet, before returning a year after launch, in March 2005. Rosetta then headed to Mars and returned to Earth in November 2007 for its second swing-by of our planet. In November 2009 Rosetta will fly past the Earth for the third and last time to receive the final boost required to reach its final target.

Rosetta alternates periods of active and passive phases during the cruise to Earth. The distance at closest approach is between 300 and 5300 km. Operations are mainly focused on orbit determination for the fundamental swing-by manoeuvres; however payload check-out, calibrations and scientific observations are also performed. If required, orbit correction manoeuvres take place before and after each swing-by.

Animation showing Rosetta's approach and swingby at Mars

Mars swing-by

Rosetta flew past Mars in February 2007 at a distance of about 250 km, phasing its trajectory for the next Earth swing-by and, as a spin-off, obtaining some science observations. During the swing-by, Rosetta had to survive an eclipse for which, due to the mission target change, the spacecraft was not specifically designed to handle. This operation required a significant effort by the FCT, but was entirely successful; during the swing-by itself, a communications black-out was also caused by an occultation as the spacecraft passed behind Mars with respect to the Earth.

Asteroid fly-bys

During the cruise phase, Rosetta alternates between phases of passive and active operation, depending on mission needs. As a secondary scientific objective, Rosetta has observed asteroid Steins in 2008 from a distance of 800 km. In July 2010 only 3160 km will separate Rosetta from asteroid Lutetia when it will fly past. Science data recorded onboard will be transmitted to Earth afterwards.

Deep-space hibernation

Following a planned deep-space manoeuvre using the engine to achieve a change in speed of approximately 800 m/s, the spacecraft goes into hibernation between June 2011 and January 2014, due to the very limited power that will be available - which would not allow safe spacecraft operations. Almost all electrical systems are switched off, except for the thermal subsystem, on-board computer, radio receivers, command decoders and power supply.

During this period, Rosetta should record its maximum distance from the Sun, about 800 000 000 km, and Earth, about 1000 000 000 km.

Artist impression-the Rosetta orbiter swoops over the lander soon after touchdown on Comet 67P/Churyumov-Gerasimenko.

Arrival

In May 2014, Rosetta's thrusters will brake the spacecraft so that it can match Comet 67P/Churyumov-Gerasimenko's orbit. The spacecraft will arrive in the comet's vicinity a few weeks later.

Over the following six months, it will edge closer to the black, dormant nucleus until it is only a few kilometres away. The way will then be clear for the exciting transition to global mapping, lander deployment and the continuing 'comet chase' toward the Sun.

The ground station - New Norcia

New Norcia antenna

Since launch, the Rosetta mission has been controlled from a single control centre, the Rosetta Mission Operations Centre (MOC) at ESOC, Darmstadt, using ESA's DSA 1 deep-space ground station at New Norcia.

During critical mission phases (launch, planet swing-bys, etc.) it is supported for tracking, telemetry and command by other ESA ground stations at Kourou and Cebreros, and by the NASA Deep Space Network (DSN) stations at Madrid, Spain, and Goldstone, USA.

Ground segment & mission control system

This mission uses SCOS-2000

The Rosetta ground segment is designed to meet both the scientific objectives and the challenges imposed by a deep-space mission. These challenges include long turnaround times for signals (up to 100 minutes), low bit rates for data (8 bps), low power availability (it is the first spacecraft ever to fly with solar power generators beyond 3.1 AU from the Sun) and very precise navigation during planetary swing-bys (Rosetta made use of gravity-assist manoeuvres with Mars and Earth to achieve its final orbit around the Sun).

ESOC must cope with the long mission duration and the related problems in scheduling expertise and experienced FCT personnel, while minimising overall cost. The central element of the Rosetta ground segment, the Mission Control System, is based on SCOS-2000.

The Rosetta Science Operations Centre (SOC) will produce detailed scientific mission planning requests, which are submitted to the MOC in the form of operation requests. The SOC will make pre-processed scientific data and the scientific data archive available to the scientific community.

A Rosetta Lander Ground Segment (RLGS) will control the Philae lander, in particular before and after completion of the landing and relay phase. These will be coordinated through the Lander Control Center at the German Aerospace Research Centre (DLR), Cologne, Germany, and the scientific control centre of CNES, France's space agency, in Toulouse.

The platform and payload

The Rosetta orbiter - spacecraft design

Rosetta is a large aluminium box, 2.8 x 2.1 x 2.0 metres in size. The scientific instruments are mounted on the 'top' of the box (the Payload Support Module) while the subsystems are on the 'base' (Bus Support Module).

On one side of the orbiter is a 2.2m-diameter communications dish antenna – the steerable high-gain antenna; the lander is attached to the opposite face. Two enormous solar panels extend from the other sides. These 'wings', each 32 square metres in area, have a total span of about 32m tip-to-tip. Each comprises five panels, and both may be rotated through +/-180° to track the Sun in every attitude assumed by the spacecraft.

Orbiter instruments

In order to investigate the comet nucleus and the gas and dust ejected from the nucleus as the comet approaches the Sun, Rosetta carries a suite of eleven instruments on-board the orbiter; the lander, Philae, is equipped with a further ten instruments to perform surface measurements.

The orbiter instruments combine remote sensing techniques, such as cameras and radio science measurements, with direct sensing systems such as dust and particle analysers. The instruments are provided by collaborative efforts between scientific institutes in ESA member states and the USA. Principal investigators in several European countries and America lead the nationally funded science teams.

Rosetta’s Philae lander on comet nucleus

The ~100-kg Philae lander will be the first spacecraft ever to make a soft landing on the surface of a comet nucleus. The lander is provided by a European consortium under the leadership of the German Aerospace Centre (DLR); other members include ESA, CNES and institutes from Austria, Finland, France, Hungary, Ireland, Italy and the UK. The Philae Lander Control Centre is located at the DLR facility in Cologne, Germany.

The lander structure consists of a baseplate and an instrument platform made in a polygonal sandwich construction, all made of carbon fibre. Some of the instruments and subsystems are beneath a hood that is covered with solar cells.

The lander experiments will study the composition and structure of Comet 67P/Churyumov-Gerasimenko's nucleus.