ESA has announced the date upon which mission operators will crash the Rosetta spacecraft into the surface of the comet 67P/Churyumov–Gerasimenko. Unlike its now-sleeping companion, the Philae lander, there is no hope that once the spacecraft touches down on the surface of 67P, the science team will be able to re-establish contact with the legendary probe.
After arriving in orbit around 67P in August 2014, Rosetta and Philae have, and continue to provide ground-breaking insights regarding the enigmatic nature of wandering comets. It has been a mission of impressive feats and intense periods of nervous anticipation.
ESA was not slow to pull on the heartstrings, releasing cartoon after cartoon that succeeded in anthropomorphizing the remote explorers. The combination of a well-executed public awareness campaign coupled with the ambitious nature of the endeavour succeeded in capturing the public's attention in a way that few unmanned missions have managed before.
Unfortunately, as with all great things, Rosetta's mission must come to an end. The spacecraft is currently riding 67P out towards the orbit of Jupiter. At its furthest point, the probe will be some 850 million km (553 million miles) distant from the Sun. At this range, Rosetta will lack the bandwidth to transmit scientific data, and will be unable to gather enough precious starlight to power its systems. Returning the spacecraft to a state of hibernation is not an option, as the probe's heaters would almost certainly fail, preventing it from ever awakening.
Instead of risking this almost certain anaemic demise, the Rosetta team have elected to have Rosetta go out in a blaze of glory, by sending to probe to join Philae on the surface of 67P, with a preliminary date set for the 30th of September. According to Rosetta's handlers, the spacecraft's descent is likely to be far more challenging than that faced by Philae in November 2014.
The danger for Rosetta is not the force of landing, but rather the influence of the comet during the final six weeks prior to the collision. During this period, the probe will be more susceptible to the gravitational influence of the irregularly shaped comet. This could lead to deviations in Rosetta's trajectory – a significant problem for a spacecraft traversing a tight, eccentric orbit around an unpredictable comet. To keep Rosetta safe, mission operators will be forced to upload course corrections on a more regular basis.
The team is set to begin tweaking Rosetta's trajectory starting in August, with a final course correction scheduled for 12 hours before impact. If all goes well, Rosetta will touch down on 67P at a mere 50 cm per second – roughly half the speed at which Philae first collided with the comet. On the way down, Rosetta will be firing on all cylinders, collecting as much high-res imagery and scientific data as possible, before ending its 12-year journey in space by coming to rest on the surface of the comet it had spent its life documenting.
"We're trying to squeeze as many observations in as possible before we run out of solar power," comments Matt Taylor, ESA Rosetta project scientist. "30 September will mark the end of spacecraft operations, but the beginning of the phase where the full focus of the teams will be on science. That is what the Rosetta mission was launched for and we have years of work ahead of us, thoroughly analysing its data."