T minus 377 days!
377 days remain, just over one year– quite a significant amount of time. Considering that the duration of the mission up to landing is 3906 days, this is merely the final10 percent of a 10-year-long journey through interplanetary space.
The climax will be the critical landing phase, which will only last a few hours, and during which the planning, development and operational efforts of more than 15 years of hard work will be put to the test. It is this reality that the Operations Team at DLR/MUSC in Cologne is facing together with their national and international partners.
The pioneering and challenging space mission I am referring to is the Rosetta mission, with the Philae lander, launched in March 2004. An international consortium provided the necessary funding and support to realise the Philae Lander, important part of the Rosetta mission, and the team at DLR in Cologne is responsible for most of the operational, engineering and management tasks. The team at DLR/MUSC is working closely with CNES, responsible for science planning and navigation, as well as the scientific community and subsystem providers that, together, make up the Philae project team, and of course with ESA, responsible for the Rosetta mission.
Preparations for landing in T minus 377 days: Philae in the DLR Landing and Mobility Test Facility (LAMA). Image: DLR (CC-BY 3.0)
Cruising piggy-back on Rosetta since the launch, Philae is well protected from the harsh space environment and enjoys the luxury of travelling without using any of its on-board resources. Together with Rosetta, it has had the opportunity to be involved in three Earth swing-bys, a Mars swing-by and two asteroid fly-bys. Philae’s scientific instruments, which were designed for deciphering the structure, composition, environment and general characteristics of the comet, had the opportunity to participate in these exciting events as a warm-up for the finale, which starts in 2014 after Rosetta wakes up from hibernation. In addition, numerous spacecraft checkouts and characterisations were performed during the seven-year cruise phase, prior to the three-year hibernation phase, keeping not only the hardware, but also the ground teams in shape.
Prior to the grand finale, however, both Philae and Rosetta were put into a three-year hibernation phase in 2011 – the entire spacecraft was switched off, and placed into spin stabilisation without any contact to Earth until January 2014. During these three years, Rosetta has continued to travel into deep space further than any solar powered spacecraft ever before, reaching a maximum distance of 5.29 Astronomical Units from the Sun, which is close to Jupiter’s orbit and through the asteroid belt. In January 2014, the hibernation phase will come to an end as Rosetta, all by itself, will wake up, stop spinning, return to a three-axis stabilised attitude, and resume contact with Earth. Until then, nothing can be done from the ground to help Rosetta!
DLR engineers prepare for the first ever landing on a comet using a model faithful to the lander. Image: DLR (CC-BY 3.0)
Upon wake-up, the ultimate challenge that Rosetta and Philae will face together is to chase, catch and conquer an opponent that does not play by the rules. Larger and more hostile than initially thought, comet 67P Churyumov-Gerasimenko is 'out of spec'. Philae was initially designed for a much less massive comet. However, due to a launcher problem the launch was postponed and a new comet had to be found. 67P is much larger than the 'in spec' comet and, although some last minute technical modifications were introduced, the already complicated landing has become even more challenging. Current scientific observations and predictions also indicate that the comet will be more active than was assumed during the development phase. Although it is exactly this property that makes comets so scientifically interesting, the operations team would prefer to deal with this activity only after a successful landing.
Philae lander (centre) on board the ESA Rosetta spacecraft
All the ingredients that make this mission an extraordinary blend of engineering skill, accurate planning, risk mitigation and science are in place. The Rosetta mission will further our understanding of comets, the origin of the Solar System and the formation of life on Earth.