NASA
An artist's conception shows NASA's Kepler space telescope observing a planetary transit.
By Alan Boyle, Science Editor, NBC News
NASA is getting plenty of advice?? and sympathy?? as it assesses whether its Kepler planet-hunting telescope can be revived after the failure of its reaction-control system. The reactions from scientists and engineers range from repair tips to an Audenesque elegy. Here's a sampling:
How to fix Kepler
The reason why the $600 million Kepler spacecraft can no longer search for planetary transits is that two of its four gyroscopic reaction wheels can no longer spin. Mission managers say Kepler needs at least three of those wheels in working order to hold its position still enough to stare at alien stars.
The most recent part to fail is known as reaction wheel 4. The mission's deputy project manager, Charlie Sobeck, told reporters that the Kepler team could try putting some reverse torque on that wheel in hopes of freeing it up.
Two other possibilities were raised by Scott Hubbard, who headed NASA's Ames Research Center during the development of the Kepler mission and is now a consulting professor of aeronautics and astronautics at Stanford University.
One option would be to try turning on reaction wheel 2, which failed last July. "It was putting metal on metal, and the friction was interfering with its operation, so you could see if the lubricant that is in there, having sat quietly, has redistributed itself, and maybe it will work," Hubbard said in a Stanford Q&A.
"The other scheme, and this has never been tried, involves using thrusters and the solar pressure exerted on the solar panels to try and act as a third reaction wheel and provide additional pointing stability," he said. The mission's principal investigator, Ames' Bill Borucki, said on Wednesday the thrusters couldn't hold the spacecraft stable enough for planet-hunting. Nevertheless, it might be one of the options under consideration.
For the time being, Kepler has been put into a holding pattern that should minimize its thruster fuel consumption and give the Kepler team several months to weigh all the options, the costs and the potential scientific benefits.
The problems facing the Kepler planet-hunting probe are reviewed in NASA's weekly video roundup.
Going beyond Kepler
Even if the Kepler spacecraft can't be revived, Borucki says that only half of the data collected so far have been fully analyzed. He estimates it'll take another two years or so to complete the analysis.
Meanwhile, NASA has just given the go-ahead its next planet-hunting satellite: the Transiting Exoplanet Survey Satellite, or TESS. That $200 million project would put a telescope array in space in 2017 to perform an all-sky survey, looking for exoplanets in orbit around the nearest and brightest stars. That strategy is markedly different from the one used by Kepler, which stared at a relatively small patch of sky straddling the constellations Cygnus and Vega.
This October, the European Space Agency plans to launch a space probe called Gaia to conduct a census of more than a billion stars in the Milky Way. Gaia could detect thousands of distant planetary systems, and measure their orbits and masses using a technique known as astrometry.
ESA is working on another planet hunter called the Characterizing Exoplanets Satellite, or CHEOPS, which is due for launch in 2017. CHEOPS would conduct high-resolution transit observations of stars that have already been found to host planets.?
The $8.8 billion James Webb Space Telescope, which NASA bills as the successor to the Hubble Space Telescope, could conceivably analyze the atmospheres of alien planets. It's currently due for launch in 2018.
Paying tribute to Kepler
NASA's associate administrator for science, John Grunsfeld, said it's too early to consider Kepler "down and out." But many astronomers fear that Kepler's planet-hunting days are finished.
"I think 'The mission is not over' means 'the mission is over,'" Caltech's Mike Brown said in a Twitter update on Wednesday. "Might be other things it can do. But, kids, I think the mission is over."
Alan Boss, an astrophysicist at the Carnegie Institution for Science who's part of the Kepler team,?was similarly downbeat. In an email sent to AAAS MemberCentral, he called this week's setback a "disaster":
"I am afraid that the loss of this second reaction wheel effectively means the partial loss of Kepler's main science goal: determining the frequency of Earth-sized planets orbiting their stars at distances such that liquid water could occur on the planets' surfaces.?Kepler has taken an outstandingly impressive four years of data, but we still need another three or so years of outstandingly impressive data to be certain of the frequency of Earth-size planets. Right now we have enough data to make an intelligent extrapolation about what that number is, but that is not the same as actually determining that number. Kepler was planned to do that for us. There is no other mission in sight that can reproduce for us what Kepler was in the process of doing. The upcoming?(2017) NASA TESS Mission?will help to push the exoplanet field forward, but it is not designed to find Earthlike planets around sunlike stars, like Kepler was."
"This is one of the saddest days in my life. A crippled Kepler may be able to do other things, but it cannot do the one thing it was designed to do."
Another Kepler team member, Geoff Marcy of the University of California at Berkeley, told KQED that he felt dizzy and teary-eyed over the spacecraft's situation. "It?s a loss for our species," he said. "That sounds dramatic, but we pride ourselves as a species of exploration, seeking answers beyond the horizon, answers about our place in the universe. And Kepler was answering those questions."
Marcy went so far as to tweak W.H. Auden's poem "Funeral Blues" to pay tribute to Kepler. Here's the astronomer's elegy to a spacecraft:
Stop all the clocks, cut off the Internet,
Prevent the dog from barking with a juicy bone,
Silence the pianos and with muffled drum
Bring out the coffin, let the mourners come.Let jet airplanes circle at night overhead
Sky-writing over Cygnus: Kepler is dead.
Put crepe bows round the white necks of doves,
Let the traffic officers wear black cotton gloves.Kepler was my North, my South, my East and West,
My working week, no weekend rest,
My noon, my midnight, my talks, my song;
I thought Kepler would last forever: I was wrong.The stars are still wanted now; let's honor every one,
Pack up the moon and dismantle the sun,
Pour away the ocean and sweep up the woods;
For nothing will ever be this good.With thanks to W.H.Auden.
For a video rendition of "Funeral Blues," check out this clip from "Four Weddings and a Funeral."
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.
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