Space for the day

Dennis Overbye has an article in The New York Times about new work for a satellite:

The little spacecraft that could may still have some life left in it.
Hearts were broken around the lonely cosmos in the spring when a critical wheel on NASA’s Kepler spacecraft (photo) got stuck, leaving its telescope unable to point precisely enough to continue prospecting for Earth-like planets in a starry patch of the Milky Way. But Kepler’s managers say they have a plan that could keep it hunting for these exoplanets for three or four more years.
“K2: the story begins,” Steve Howell, Kepler’s deputy project scientist, told a recent gathering of astronomers at NASA’s Ames Research Center, borrowing the name of the world’s second-highest mountain to herald the proposed mission.
In its four years of monitoring the brightness of each of 160,000 stars in one patch of sky, Kepler identified 3,500 possible exoplanets by seeing stars dim when planets crossed in front of them. It also enabled the first rough estimate of the abundance of habitable planets in the Milky Way: about one in five sunlike stars have potentially habitable Earth-size planets, meaning billions of chances for the existence of ET. Not to mention how it revolutionized the understanding of the internal structures of the stars themselves through the practice of “astroseisemology”.
But the little spacecraft was only beginning to zero in on planets with orbits analogous to our own, Earth-size worlds that take a year to orbit suns similar to our own, candidates for Earth 2.0, in the vernacular. K2 would no longer train Kepler on only one set of stars. Instead, it would skip around the sky, monitoring the stars in one spot continuously for up to eighty days.
Over such an interval, Kepler could not detect any planets with orbital periods more than a few weeks. But it could detect planets with habitable orbits around the smaller, dimmer stars known as red dwarfs. For such stars, the temperate orbital regions, or Goldilocks zones— where the surface temperatures on a planet are mild enough for liquid water— are closer and thus have shorter orbital periods.
“There are niches where we can deliver small planets,” said Dr. Howell, noting that K2 would cover five to ten times as much of the sky as the original Kepler survey, and could discover hundreds of planets around the red dwarfs.
Kepler was launched in March of 2009 after a decades-long battle by its originator and prime scientist, William Borucki of NASA’s Ames Research Center in Mountain View, California, to show that planets could be detected this way.
Its original field of view, 160,000 stars on the border of the constellations Cygnus and Lyra in the thick of the Milky Way, was chosen to a provide as large a sample as possible of sunlike stars for a cosmic census of exoplanets. To do this, Kepler had to be able to point precisely and stably enough to keep all these stars on the same pixels of its camera for four years.
The loss of a second reaction wheel— Kepler was launched with four— left the spacecraft prone to rolling about its telescope’s line of sight, especially when its solar panels, which wrap halfway around the telescope like a cape, are unevenly illuminated by sunlight.
That, unfortunately, is the case when Kepler points at Cygnus. Light exerts pressure, which is why comets have tails. “The sun, unfortunately, continues to shine,” said Charles Sobeck, deputy project manager of Kepler, and the uneven solar illumination makes the spacecraft roll and unable to keep stars on the right pixels. Through all of this, the telescope and detector remained unscathed, making it a valuable astronomical resource already in space. In response to a call for ideas about how to make use of Kepler, astronomers submitted more than forty white papers.
The solution was a neat bit of rocket science. Tests have shown sunlight can be used to stabilize Kepler. The key is to keep it pointed in directions that leave its solar panels evenly illuminated. “When it’s stable, it’s really stable,” Sobeck said.As a result, Kepler’s planet hunting will now be limited to fields of stars that lie along a circle known as the ecliptic— the path traversed by the Sun through the zodiac.
Sobeck said giving up the original field of view was a big hurdle. “After four years, that was emotionally difficult.”
The reward will be variety, as well as a new lease on life. Part of the sun’s path goes right across the center of the galaxy, in the constellation Sagittarius, and other parts, away from the Milky Way, cross outside galaxies, where Kepler could record the rise and fall of supernova explosions that have proved critical to understanding cosmic history. Other fields of opportunity include stormy regions strewn with clouds of gas and dust where new stars and presumably new planets are being born, so Kepler, if the plan goes through, will be able to study stars and planets in a variety of environments.
For now, however, K2 is only a proposal, still being tested. The idea has to pass muster with NASA’s astrophysics division and then survive a review at NASA, in a sort of bake-off with other needy projects.
The final decision on Kepler’s fate will come next spring. Regardless of the answer, the Kepler team will go on. The scientists have three more years of work to analyze the data that has already been obtained, including the whole last year of the spacecraft’s observations, which Borucki characterized in a news conference as “the most valuable data we have.”
Sobeck is hopeful for more. “Nobody wants to turn off a spacecraft in orbit,” he said.

Rico says hey, we paid for it and put it up there, we oughta get something out of it...