The European Space Agency (ESA) has announced extension of its Rosetta comet mission until the end of September 2016. The decision was taken at a meeting of the Science Programme Committee.
ESA revealed that at the end of September 2016, the comet will be moving away from the Sun again and at that point Rosetta will no longer be receiving enough power to continue using its scientific instruments efficiently at which point the spacecraft will most likely be landed on the surface of Comet 67P/Churyumov-Gerasimenko.
Launched in 2004 and arrived at the comet in August 2014, the Rosetta has been studying the nucleus and its environment as the comet moves along its 6.5-year orbit closer to the Sun. Following a detailed survey of the surface of the comet, Rosetta deployed the lander, Philae, to the surface on November 12, 2014.
Philae continued its preliminary science experiments for about 57 hours at which point it went into hibernation for lack of enough sunlight due to its skewed landing position in a shadowed area that prevented the batteries from being charged fully for it to continue operating. However, the lander woke up again a few days back and has since contacted Rosetta on two occasions.
ESA had funded Rosetta’s nominal mission until the end of December 2015, but at a meeting today, ESA’s Science Programme Committee has given formal approval to continue the mission for an additional nine months. At that point, as the comet moves far away from the Sun again, there will no longer be enough solar power to run Rosetta’s set of scientific instrumentation efficiently.
Matt Taylor, ESA’s Rosetta Project Scientist is thrilled by the news and said that the extended mission will allow them to study decline in the comet’s activity as it moves away from the Sun again.
“By comparing detailed ‘before and after’ data, we’ll have a much better understanding of how comets evolve during their lifetimes.”
Comet 67P/Churyumov-Gerasimenko will be making its closest approach to the Sun on August 13. Continuing its study of the comet in the year following perihelion will give scientists a fuller picture of how a comet’s activity waxes and wanes along its orbit.
The extra observations collected by Rosetta will also provide additional context for complementary Earth-based observations of the comet. At present, the comet is close to the line-of-sight to the Sun, making ground-based observations difficult.
As the activity diminishes post-perihelion, it should be possible to move the orbiter much closer to the comet’s nucleus again, to make a detailed survey of changes in the comet’s properties during its brief ‘summer’.
In addition, there may be an opportunity to make a definitive visual identification of Philae. Although candidates have been seen in images acquired from a distance of 20 km, images taken from 10 km or less after perihelion could provide the most compelling confirmation.
During the extended mission, the team will use the experience gained in operating Rosetta in the challenging cometary environment to carry out some new and potentially slightly riskier investigations, including flights across the night-side of the comet to observe the plasma, dust, and gas interactions in this region, and to collect dust samples ejected close to the nucleus.
As the comet recedes from the Sun, the solar-powered spacecraft will no longer receive enough sunlight to operate efficiently and safely, equivalent to the situation in June 2011 when the spacecraft was put into hibernation for 31 months for the most distant leg of its journey out towards the orbit of Jupiter.
In addition, Rosetta and the comet will again be close to the Sun as seen from the Earth in October 2016, making operations difficult by then.
However, with Rosetta’s propellant largely depleted by that time, it makes little sense to place the spacecraft in hibernation again.
“This time, as we’re riding along next to the comet, the most logical way to end the mission is to set Rosetta down on the surface,” says Patrick Martin, Rosetta Mission Manager.
“But there is still a lot to do to confirm that this end-of-mission scenario is possible. We’ll first have to see what the status of the spacecraft is after perihelion and how well it is performing close to the comet, and later we will have to try and determine where on the surface we can have a touchdown.”
If this proposed scenario were played out, then the spacecraft would be commanded to spiral down to the comet over a period of about three months.
It is expected that science operations would continue throughout this period and be feasible up to very close to the end of mission, allowing Rosetta’s instruments to gather unique data at unprecedentedly close distances.
Once the orbiter lands on the surface, however, it is highly unlikely to be able to continue operations and relay data back to Earth, bringing to an end one of the most successful space exploration missions of all time.