According to NASA, the ailing Kepler Space Telescope is officially beyond repair, and is hereby relieved of its planet-hunting duties. But the Agency isn't giving up entirely. The question now turns to how the prolific spacecraft might be put to new use, and NASA is open to suggestions.
Above: An artist's depiction of Kepler 62f, announced in April to be one of the most Earth-like planets the telescope had discovered to date.
NASA's enormously successful telescope had been orbiting the Sun a little over four years when the second of its four gyroscopic reaction wheels – which keep the spacecraft's optics pointed at star systems found in a small patch of the Milky Way – gave up the ghost back in May. Unfortunately, the probe requires three operational reaction wheels to keep its gaze locked onto systems thought to harbor planets in the so-called "goldilocks" zone – the "just right" orbital distance at which a planet is neither too hot nor too cold for the persistence of liquid water and, by extension, life. Attempts to jolt either of the telescope's wheels back into operational order have been unsuccessful.
The Kepler mission on the whole, however, has been an unprecedented success. "At the beginning of our mission, no one knew if Earth-size planets were abundant in the galaxy. If they were rare, we might be alone," said William Borucki, Kepler science principal investigator in a statement. "Now at the completion of Kepler observations, the data holds the answer to the question that inspired the mission: Are Earths in the habitable zone of stars like our sun common or rare?"
The $600-million mission managed to confirm the presence of 135 planets beyond our solar system in its brief run, and upwards of 3,500 candidate planets still in need of further review. Fortunately, all that data has been collected; what it requires now is some good sifting. According to John Grunsfeld, associate administrator for NASA's Science Mission Directorate:
Kepler has made extraordinary discoveries in finding exoplanets including several super-Earths in the habitable zone. Knowing that Kepler has successfully collected all the data from its prime mission, I am confident that more amazing discoveries are on the horizon.
In other words: the spirit of Kepler's original directive will carry on in the analysis of data the telescope has already collected. But what of new science? What of new data?
The aims of their original mission now outside the realm of possibility, Kepler scientists are now asking for community input on alternative scientific targets for the erstwhile planet-hunter. The agency has issued a call for white papers, and included the following description of the telescopes potential:
Kepler’s exquisite photometric precision during the nominal mission was due to its ability to finely point at one position on the sky. Additionally, Kepler continued this pointing for weeks to months generating long-term light curves. The two wheel mission will not be able to point as well or for as long a time period, but the pointing capability may be sufficient to enable alternative science investigations.
How long and how well will Kepler be able to point where we need it? It's not entirely clear. NASA notes that Ball Aerospace has done some preliminary tests on what the telescope can be expected to achieve with 2/4 wheels and "minimal thrusters," though the agency emphasizes that these assessments have yet to say definitively, what the spacecraft can be expected to do.
That being said, the agency has provided the following as a potential timeline:
Expected Schedule
At this time, the expected plan and schedule leading to a repurposed Kepler mission is as follows:
2 Aug 2013 – Release of call for white papers
3 Sept 2013 – Due date for submission of white papers
1 Nov 2013 – End of review period for white papers, report submitted to NASA HQ
1 Feb 2014 – Senior Review proposal for repurposed Kepler submitted to NASA HQ
Spring 2014 – Decision for funding for repurposed Kepler spacecraft
Summer 2014 – Begin new science program(s)
A new, repurposed mission by this time next year? Yes, please.
More info on the Kepler kibosh, and the decision to move forward in a new, as-yet-determined direction, over at NASA.