Aerts and her colleagues suggest Kepler should target an open star cluster called NGC 2244, which is rife with these stars and could be a strong test case for the method. Such a study would require Kepler’s undivided attention for six months straight to observe how the periods of stellar oscillations change over time. Still, other science could be done using the data collected, because Kepler’s large field of view would take in more than just the cluster.
“I do believe the proposed study would be a useful project,” says Ronald Gilliland, an astronomer at The Pennsylvania State University who has used Kepler data in the past to conduct asteroseismology studies. “If it could be carried out, obtaining six months of coverage at a level of 0.01 percent to 0.05 percent precision as in the white paper, then very useful and unique science would likely result from this.” But he says it is too soon to tell how precise Kepler’s new mode will be, and he has doubts that even massive-star asteroseismology will be possible. “We still do not know some very basic things about what the actual capability of the spacecraft will be. Tests are underway that should provide better insights about this within a couple of months.” Ultimately, he was less than sanguine. “I do not personally have much hope that Kepler can find important work to do in its new two-wheeled configuration.”
Even if the telescope does carry on with efforts to perform stellar physics, many Kepler scientists are loathe to abandon the observatory’s original raison d’être, and hope the observatory can continue studying planets, albeit in a modified fashion. “The proposers have argued a useful case,” planet hunter and Kepler science team member Sara Seager of the Massachusetts Institute of Technology says of the asteroseismology proposal. “[But] it's hard for me to be objective about non-exoplanet astronomy.” And adapting Kepler to a purpose it wasn’t designed for could present additional difficulties, such as the need to design a whole new infrastructure to convert raw data to usable scientific information, she adds. “One concern is what kind of pipeline has to be developed for a new project? And what if another wheel fails midway or just after development? Such risks and costs also need to be taken into account.”
In the end, it may be that none of the new proposals win out. The Kepler team must prove that the science possible with the two-wheeled instrument is valuable enough for a piece of the ever-shrinking NASA budget pie. If none of the proposals meet that high bar, the Kepler funding may be allocated to other, fully functioning missions. “We have to ask how valuable is the science per dollar,” Seager says. “Space telescopes are very expensive to operate, on the order of [at least] $10 million per year. So the question is: Is the science worth the cost?” The Kepler team plans to submit the best proposals to NASA for review later this year. Those deemed worth further study will be examined by an external committee next year, with a final decision expected next summer.