NASA outlines ingenious plan to resurrect the Kepler planet hunter

[Fal]

NASA outlines ingenious plan to resurrect the Kepler planet hunter
ArsTechnica.com
By John Timmer



Back in August, NASA formally threw in the towel on attempts to get its Kepler planet-hunting probe working again. With the probe down to just two fine-pointing devices, there was just no way to keep the telescope consistently pointed at the right field of stars. Apart from the pointing issue, however, the remaining hardware was all fine, so NASA said it would consider proposals for alternate uses of the probe. Now, the agency has announced that it has settled on one proposal and will consider putting it into its 2014 budget.

The failed hardware is called a reaction wheel, and its job is to exert a small force that can turn the telescope over time. At least three of these wheels are required to keep the telescope staring at a specific spot long enough to gather useful data. The new proposal would effectively turn the probe's solar panels into a third reaction wheel—though an extremely limited one.

As photons are absorbed and emitted, they generate a small force on the object doing the absorbing (it's the same force that causes some asteroids to spin). Kepler is powered by solar panels that are arranged symmetrically across the probe's long axis. If the probe can be oriented so that the sunlight strikes these panels evenly, the photons will exert a constant and symmetric force against the probe. Kepler's two remaining reaction wheels can then push against that force and keep the telescope gazing steadily at one point in the sky, just as it was designed to do.

There's one problem, though: as Kepler swings through its orbit, the Sun itself will eventually end up between Kepler and its point of focus. Shortly after that point in its orbit, the Sun's light will start striking the opposite side of the probe, where it has no solar panels. So, four times during the orbit, the probe will be completely reoriented and stare at a different part of the sky, each for quarter of a year (Kepler is trailing the Earth on its trip around the Sun).

The approach is already in the process of being tested. If it works, Kepler will lose some sensitivity—some planets will have orbital periods that ensure they're either never spotted by Kepler or will only be caught once over several years. But close-in planets and those with roughly year-long orbits should be spotted just fine. With four distinct areas of the sky observed, Kepler's "K2" mission (as it's being called) will also give us a broader perspective on the distribution of planets in our galaxy.


http://arstechnica.com/science/2013/11/nasa-outlines-ingenious-plan-to-resurrect-the-kepler-planet-hunter/


Using photons to turn an entire satellite.  The utter frictionless-ness of space is so hard to comprehend as someone who doesn't work in the field.

[Geo]

It's a smart solution.

[Buster's Uncle]

NASA's Ailing Kepler Spacecraft Could Hunt Alien Planets Once More with New Mission
SPACE.com
By Mike Wall, Senior Writer  59 minutes ago



This image by NASA's Kepler spacecraft shows the telescope's full field of view taken in a new demonstration mode



NASA's hobbled Kepler space telescope may be able to detect alien planets again, thanks to some creative troubleshooting.

Kepler's original planet hunt ended this past May when the second of its four orientation-maintaining reaction wheels failed, robbing the spacecraft of its ultraprecise pointing ability. But mission team members may have found a way to restore much of this lost capacity, suggesting that  a proposed new mission called K2 could be doable for Kepler.

Engineers with the Kepler mission and Ball Aerospace, which built the telescope, have oriented the spacecraft such that it's nearly parallel to its path around the sun. In this position, the pressure exerted by sunlight is spread evenly across Kepler's surfaces, minimizing drift.

This strategy is returning some promising results, mission officials say. During a 30-minute pointing test in late October, for example, Kepler captured an image of a distant star field that was within 5 percent of the image quality achieved during Kepler's original mission.

"This 'second light' image provides a successful first step in a process that may yet result in new observations and continued discoveries from the Kepler space telescope," Charlie Sobeck, Kepler deputy project manager at NASA's Ames Research Center in Moffett Field, Calif., said in a statement.

The Kepler team is currently conducting tests to see if the spacecraft can maintain such pointing stability over periods of days and weeks — a necessity for discovering exoplanets.



This conception illustration depicts how solar pressure can be used to balance NASA's Kepler spacecraft


Kepler launched in March 2009 on a mission to determine how frequently Earth-like planets occur around the Milky Way galaxy. The spacecraft finds exoplanets via the "transit method," noting the telltale brightness dips caused when an alien world crosses the face of, or transits, its host star from the instrument's perspective.

Kepler has been remarkably successful, spotting more than 3,500 planet candidates to date. Just 167 of them have been confirmed so far by follow-up observations, but mission scientists think 90 percent or so will end up being the real deal.

Researchers are still sifting through the mountains of data Kepler returned during its four years of science operations. Kepler team members have expressed confidence that they'll find Earth analogs in these databases, allowing the mission's primary goal to be achieved.

The proposed K2 mission would continue Kepler's exoplanet hunt, albeit in a modified fashion. K2 would also gather data about supernova explosions, star formation and solar-system bodies such as asteroids and comets, among other things, team members have said.

The Kepler team has officially presented the K2 mission concept to NASA Headquarters, which is expected to decide by the end of the year if the idea progresses to a vetting stage called "senior review." The ultimate fate of K2, and the Kepler spacecraft, will likely be known by the middle of next year, Kepler officials have said.


http://news.yahoo.com/nasas-ailing-kepler-spacecraft-could-hunt-alien-planets-172329156.html