620 days remaining, roughly 21 months, quite a significant amount of time. Considering the mission duration of 3906 days, this is only the last 16% of a 10 year long journey through interplanetary space. The climax is the critical landing phase of only a few hours duration, in which the planning, development and operational efforts of more than 15 years of hard work will have to face reality. 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 Philae mission, a.k.a. Rosetta Lander, launched in March 2004. An international consortium provided for the necessary funding and support to realize the Philae mission and the team at DLR in Cologne is responsible for most operational, engineering and management tasks. The team at DLR/MUSC is working closely together with CNES, responsible for science planning and navigation, and the science community and subsystem providers, which, all together, form the Philae project team.
Cruising piggy-back on Rosetta ever since launch, Philae is well protected from the harsh space environment and enjoys the luxury of travelling without using any of its on-board resources, but, nevertheless, had the opportunity to be involved in 3 Earth swing-by’s, a Mars swing-by and two asteroid fly-by’s. 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, starting November 2014. In addition, numerous spacecraft check-outs and characterizations were performed during the seven year long cruise phase, keeping not only the hardware, but also the ground teams in shape.
Prior to the grand finale, however, both Philae and Rosetta went into a three year long hibernation phase in 2011, with the entire spacecraft switched off, placed into spin stabilization and without any contact with the Earth until January 2014. In these three years, Rosetta has gone further into deep space 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 took it right through the asteroid belt. In January 2014, the hibernation phase will come to and end as Rosetta, all by itself, will wake up, stop spinning, return to a 3-axis stabilized attitude, and take up contact with Earth. Until this point nothing can be done from the ground to help Rosetta!
Upon wake-up the ultimate challenge that Rosetta and Philae have to face together is to chase, catch and conquer an opponent, which isn’t playing by the rules. Smaller and more hostile than initially planned, the comet, a.k.a. Churyumov-Gerasimenko (67P – CG), is ‘out of spec’. Philae was initially designed for a much more massive comet. However, due to a launcher problem the launch was postponed and a new comet had to be found. 67P is much smaller than the ‘in spec’ comet and, although some last minute technical modifications were introduced, the already challenging landing has become even more challenging. The current scientific observations and predictions also indicate that the comet will be much more active than assumed during the development phase. Although it is exactly this property that makes comets scientifically so interesting, the operations team would prefer to deal with this activity only after a successful landing.
You can see that all the right ingredients are in place that make this mission an extraordinary blend of engineering skill, spot on planning and risk mitigation.