Countdown to comet touchdown
Tomorrow (12 November 2014) Rosetta’s Philae lander is set to make history when it attempts the first ever soft landing on a comet.
Artist's impression of Philae, touching down on comet 67P. Credit: ESA.
On board the lander is the UK-led Ptolemy instrument which will perform on-the-spot analysis of the composition of the ices and organic material within comet 67P. After a decade-long journey chasing its target, Europe’s Rosetta became the first spacecraft to rendezvous with a comet. Since the rendezvous in August 2014, Rosetta, supported by scientists in the UK, has been mapping the comet’s surface; making important measurements of its gravity, mass and shape; assessing its gaseous, dust-laden atmosphere; and probing its plasma environment. Once Rosetta has released the Philae lander it will continue to follow the comet around the Sun and as it moves back out towards the orbit of Jupiter.
Comets are considered to be primitive building blocks of the Solar System and may have helped to ‘seed’ Earth with water, perhaps even the ingredients for life. But many fundamental questions about these enigmatic objects remain, and through a comprehensive, in situ study of the comet, Philae aims to unlock the secrets within.
Touchdown
Rosetta will release Philae at 08:35 GMT on 12 November at a distance of approximately 22.5 km from the centre of the comet. Landing will be about seven hours later at around 15:30 GMT.
With a one-way signal travel time between Rosetta and Earth on 12 November of 28 minutes 20 seconds, confirmation of separation will arrive on Earth ground stations at 09:03 GMT and of touchdown at around 16:00 GMT.
During the seven-hour descent, Philae will take images and conduct science experiments, sampling the dust, gas and plasma environment close to the comet. It will take a ‘farewell’ image of the Rosetta orbiter shortly after separation, along with a number of images as it approaches the comet surface. It is expected that the first images from this sequence will be received on Earth several hours after separation.
Once safely on the surface, Philae will take a panorama of its surroundings. Again, this is expected back on Earth several hours later.
The first sequence of surface science experiments will begin about an hour after touchdown and will last for 64 hours, constrained by the lander’s primary battery lifetime. Longer-term study of the comet by Philae will depend on for how long and how well the batteries are able to recharge, which in turn is related to the amount of dust that settles on its solar panels.
Landing day press conference at ESA
On landing day ESA will hold a press conference at the Rosetta Mission Operations Centre (ESOC) in Darmstadt.
Three control centres are involved in the landing: the Rosetta Mission Operations Centre at ESA’s Space Operations Centre (ESOC) in Darmstadt, Germany; the Lander Control Centre at DLR in Cologne, Germany; and the Lander Science Operations and Navigation Centre at CNES in Toulouse, France.
Live feed on ESA TV
The activities at each control centre will be closely linked and will be featured in a combined English-language ESA TV programme broadcast from ESOC, with live updates transmitted from all three control centres.
The Rosetta mission and the UK
With funding from the UK Space Agency and the Science and Technology Facilities Council (STFC), Rosetta is a mission with significant UK involvement from industry and science.
One of the main challenges for all the companies designing instruments for Rosetta has been to ensure the components remain intact for ten years, while the spacecraft makes its way to the comet, and then work perfectly when it gets there. Not an easy task!
Industry involvement
- Airbus Defence and Space, based in Stevenage, was the major subcontractor for the Rosetta platform
- e2v, based in Chelmsford, designed and supplied the high performance imaging devices used in the Navigation Camera, OSIRIS narrow field and wide field cameras and VITRIS-M instruments on the orbiter and ROLIS and CIVA instruments on the lander
- ABSL Space Products provided innovative batteries for the spacecraft and lander.
- These are smaller, lighter and much more reliable than the traditional nickel-cadmium batteries
- ERS Technology supported the development of many subsystems including the reactions wheels, solar array drive motors, Philae harpoon motors and developed the lubricant for the atomic force microscope on the Micro-Imaging Dust Analysis System (MIDAS)
- Technology created by CGI Group helped to explore some of the issues involved in such a long mission.
- The company was also involved in the development of the Rosetta on board software
- Moog provided tanks to store the helium used by the lander
- STFC’s RAL Space co-developed the Ptolemy instrument with the Open University and designed the thermal insulation for the GIADA and VIRTIS instruments as well as the Philae lander itself
- SciSys UK Ltd is responsible for the spacecraft Mission Control System development and maintenance. In recognition of this work on the Rosetta and the Beagle 2 missions, SciSys were awarded the title of “Innovator of the Year” by the UK Computing Awards for Excellence 2004
- Surrey Satellite Technology Limited (SSTL) designed a wheel that will stabilise the probe as it descends and lands on the comet
- Telespazio VEGA was involved in many aspects of the Rosetta mission, from the overall design of the spacecraft to the on-board software
Science involvement
UK scientists are involved in ten of the 21 experiments that Rosetta will carry out during its mission:
- The Open University in collaboration with STFC RAL Space designed and built the Ptolemy instrument on the lander and is contributing scientific expertise to the GIADA, MUPUS and SESAME instrument teams
- The University of Kent will be helping to analyse the results from the OSIRIS instrument and have been involved in observing Rosetta’s target comet from ground-based telescopes to aid mission planning
- Imperial College London and University College London’s Mullard Space Science Laboratory (MSSL) supply the team studying the comet’s plasma
- Scientists at Oxford University are part of the science team for VIRTIS
- Queen Mary College at the University of London will be investigating the results of the CONSERT instrument
- Researchers from Queen’s University Belfast are part of the team observing Rosetta’s target comet using ground-based telescopes