PI Perspective: William Borucki
Eight years passed from John F. Kennedy’s 1961 speech about men on the moon to the first small step onto lunar dust. William Borucki’s dream of launching a spacecraft to observe distant stars for evidence of planets hospitable to life took three times longer to realize.
Borucki, of NASA’s Ames Research Center, is the progenitor and scientific principal investigator of NASA’s $600-million Kepler mission. The spacecraft launched on March 7, 2009 and has since started it search for planets around other stars. While Kepler will find planets of all kinds – it has already spotted “lots of Jupiters,” Borucki said – Kepler’s uniqueness is in its ability to find Earth-sized rocky orbs orbiting in habitable zones, in which water can be a liquid and support biology as we know it.
Ball Aerospace & Technologies Corp. built the Kepler spacecraft and its sole instrument, a telescope with a 1.4-meter primary mirror feeding light from a 100-square-degree patch of space (roughly the area covered by one’s open hand at arm’s length) into a 95-megapixel photometer. The detector is capable of keeping tabs on more than 100,000 stars as far away as 3,000 light years, looking for dips in brightness as subtle as the shadows of individual gnats flying across burning headlights. The gnat known as Earth blocks 0.0084 percent of the sun’s light, for example.
Kepler is about many things. Most profoundly, it seeks to answer a question of deep scientific, even philosophical, implications: Are we alone? But coming to fruition, Kepler also represents an extraordinary example of the fruits of persistence.
Borucki published his first paper on detecting extrasolar planets in 1984. By the late 1980s, he was working with the National Bureau of Standards (now known as NIST) on developing photomultipliers capable of detecting planets crossing the faces of distant suns. But CCD technology seemed more promising, and Borucki knew of Ball Aerospace’s expertise in applying this digital “film” to scientific problems. Ball also happened to employ an expert in the occultation photometry of stars.
“We had a manufacturer who was noted for good instrumentation. We had a scientist on their staff who had done this kind of work. We had an expert on CCDs, the detectors of choice,” Borucki recalled. “And it came together that we were able to work as a team to build this instrument and get NASA to fund it.”
Eventually. The team gelled in 1992, proposing FRESIP, for Frequency of Earth-Size Inner Planets. NASA, skeptical that such detectors existed, rejected the proposal.
In 1994, the FRESIP team tried again, this time for NASA’s first Discovery Program round. The costs worried NASA.
In 1996, the mission’s name changed to Kepler at the suggestion of science-team member Carl Sagan and others, NASA agreed that the costs were in line. But agency officials argued that automated photometry of tens of thousands of stars was impossible. The science team built its own telescope in an old dome at Lick Observatory and, using a 9-megapixel digital camera, showed they could monitor the brightness of 10,000 stars.
The Kepler team proposed again in 1998. This time, NASA selection officials questioned whether such sensitive photometry could be done amid all the on-orbit noise. A million-dollar NASA Ames test bed later, Borucki’s team put such fears to rest, too.
Ball Aerospace had supported Borucki’s mission throughout, spending hundreds of thousands of dollars each proposal round. Finally, in 2000, Kepler made it to the finals, and in 2001 was chosen as the 10th Discovery mission.
The mission’s functional simplicity – Borucki has described the spacecraft as “a camcorder in space” – belies its technological difficulty. Scientific breakthroughs of the sort Kepler was aiming to deliver demand path-breaking engineering. In Borucki’s experience as an experimentalist at NASA Ames, that meant an iterative process of designing, building, testing, then redesigning, rebuilding and restesting “until it did what you wanted,” Borucki said.
Ball Aerospace, on the other hand, followed the classic NASA five-phase, linear approach, where the idea is to design it right the first time, build, test, launch and operate the spacecraft. NASA Discovery budgets are crafted accordingly. On Kepler, as external factors and engineering surprises familiar to major space-science missions mounted, budgets became squeezed and project managers were forced to make hard choices.
Certain tests – in particular those relating to catching and fixing sources of noise in dozens of channels of Kepler’s electronics – had to be sacrificed with the understanding that the science team would develop mathematical models to correct the issue post-launch, Borucki said. Minimizing noise is central Kepler’s ability to detect gnatlike habitable-zone planets.
The ongoing modeling effort placed unexpected demands on the science operations budget, Borucki said. It was an ongoing challenge because it was always, ‘Well, there’s not enough funds to do that,’ or ‘We don’t have the schedule to do that.’”
In other cases, such cooperation worked well, such as when Ball telecom engineers found they could support higher telemetry rates than initially thought.
“They said, ‘We can handle a lot more data than you are thinking about. Will that help you?’ And of course the answer was, ‘Sure, it helps a lot,’” Borucki said. “So they found ways of improving the mission over what we had proposed. So there was a balance, and we used that to our advantage.”
To aspiring principle investigators, Borucki’s advice is to come up with science compelling enough to win long-term support from the science community, NASA officials and industrial partners. Then, he said, “Be persistent. Because a lot of this is just working at each of these problems in a very persistent fashion. There’s usually a solution. You just have to work very hard at finding it and getting it all to work.”