Rosetta. The end of the mission.
After more than 12 years in space, and two years following comet 67P/Churyumov–Gerasimenko as they orbited the Sun, Rosetta mission concluded on September 30, 2016 with the spacecraft descending onto the comet in a region hosting several ancient pits.
Rosetta
was a European Space Agency (ESA) mission with contributions from its member states
and NASA. Rosetta’s Philae lander was provided by a consortium
led by DLR, MPS, CNES and ASI. Since launch in 2004, Rosetta was in its sixth orbit
around the Sun. Its nearly 8 billion-kilometre journey
included three Earth flybys and one at Mars, and two asteroid
encounters. The craft endured 31 months in deep-space
hibernation on the most distant leg of its journey, before
waking up in January 2014 and finally arriving at the comet in
August 2014. After becoming the first spacecraft to orbit a
comet, and the first to deploy a lander, Philae, in November
2014, Rosetta continued to monitor the comet’s evolution
during their closest approach to the Sun and beyond.
The decision to end the mission was predicated on the
fact that the comet was heading out beyond the orbit of
Jupiter, and there would be little power to operate the
spacecraft. The date selected for the end of mission was
immediately before entering superior solar conjunction, when
the Sun is close to the line-of-sight between Earth and
Rosetta, meaning communications with the craft would have
become increasingly more difficult.
The spacecraft began a 19 kilometers descent with a 208-second thruster burn executed on September 19, 2016, at approximately 20:50 UTC. During the descent,
Rosetta studied the comet’s gas, dust, and plasma environment
very close to the surface and took numerous high-resolution
images. Rosetta was targeting a point within a 700 x 500 metre ellipse, between two pits in the Ma’at region, on the comet's
smaller lobe. Reconstruction of the final descent trajectory
showed that the spacecraft touched down at 10:39:34 UTC at the
comet, 26 seconds earlier than the target time, and only 33
metres away from the target, some 720 million km from Earth.
Rosetta’s signal disappeared from screens at ESA’s mission
control at 11:19:37 UT. The touchdown site was subsequently
named Sais after a town in Egypt where the Rosetta Stone, for
which the mission was named, is thought to have been
originally located.
No large dust particles were collected during the
descent. The final image, reconstructed after Rosetta’s
landing, was taken with the OSIRIS wide-angle camera at an
altitude of about 20 metres above the impact point and had a scale
of 2 mm/pixel. Prior to that, much of the imaging campaign
during the descent focused on the 130 metre-wide pit named
Deir el-Medina. The camera succeeded in capturing detailed
images of the inside of the pit and its walls. These images
will be used to help understand the comet’s subsurface and
thus its geological history.
Right before impact, one of Rosetta’s star trackers
generated an event reporting a ‘Large Object’ in the field of
view: this was the local comet ‘horizon’. Upon touchdown, the
signal coming from Rosetta was lost, and mission operators
believe that this was most likely caused by the high gain
antenna immediately off-pointing from Earth at impact. No
further telemetry was received subsequently, indicating that
the planned safe mode and subsequent shut down of the
spacecraft likely occurred successfully.
However, Rosetta's usefulness does not entirely come to an end. Safely preserved beneath the spacecraft's thermal blankets is the Rosetta Disk, the modern equivalent of the original Rosetta Stone. Micro-etched on this 7.5 cm nickel disk are 1000 different languages, a comprehensive cultural archive gathered by the San Francisco-based Long Now Foundation. Each page of text, which is miniaturized and etched onto the disk as an image, requires only a microscope to be read. Such simplicity guards against the threat of changing technologies, which could make a digital disk unreadable by computers in the future.
Image compilation: ESA–D. C. Jimeno and M. P. Ayucar. CC BY-SA 4.0
References:
ESA: Mission complete:
Rosetta’s
journey ends in daring descent to comet. 30
September 2016
Pablo Muñoz et al. Rosetta
navigation during the end of mission phase
[PDF]. Symposium on Space, 2017
© 2025, Andrew Mirecki
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