Bonnie Buratti on Cassini, CRAF, and M3
Bonnie Buratti is a Principal Scientist at the Jet Propulsion Laboratory and the Manager of the Asteroids, Comets and Satellites Group. Bonnie has been an active researcher at JPL since she received her Ph.D. in 1983, working on CRAF, Cassini, New Horizons, and the Moon Mineralogy Mapper on Chandraayan-1. I sat down with Bonnie at JPL last August to learn about M3; we also talked about the experience of working on other missions or instruments that don’t ultimately fly and how a person or group recovers after such a setback. Bonnie has a strong publication record and an impressive history of service; her latest paper appeared in the April issue of Icarus.
B.J. Buratti, J.M. Bauer, M.D. Hicks, J.A. Mosher, G. Filacchione, T. Momary, K.H. Baines, R.H. Brown, R.N. Clark and P.D. Nicholson. “Cassini spectra and photometry 0.25-5.1 microm of the small inner satellites of Saturn.” Icarus, Volume 206, Issue 2, p. 524-536, April 2010.
The nominal tour of the Cassini mission enabled the first spectra and solar phase curves of the small inner satellites of Saturn. We present spectra from the Visual Infrared Mapping Spectrometer (VIMS) and the Imaging Science Subsystem (ISS) that span the 0.25-5.1 μm spectral range. The composition of Atlas, Pandora, Janus, Epimetheus, Calypso, and Telesto is primarily water ice, with a small amount (˜5%) of contaminant, which most likely consists of hydrocarbons. The optical properties of the “shepherd” satellites and the coorbitals are tied to the A-ring, while those of the Tethys Lagrangians are tied to the E-ring of Saturn. The color of the satellites becomes progressively bluer with distance from Saturn, presumably from the increased influence of the E-ring; Telesto is as blue as Enceladus. Janus and Epimetheus have very similar spectra, although the latter appears to have a thicker coating of ring material. For at least four of the satellites, we find evidence for the spectral line at 0.68 μm that Vilas et al. attributed to hydrated iron minerals on Iapetus and Hyperion. However, it is difficult to produce a spectral mixing model that includes this component. We find no evidence for CO2 on any of the small satellites. There was a sufficient excursion in solar phase angle to create solar phase curves for Janus and Telesto. They bear a close similarity to the solar phase curves of the medium-sized inner icy satellites. Preliminary spectral modeling suggests that the contaminant on these bodies is not the same as the exogenously placed low-albedo material on Iapetus, but is rather a native material. The lack of CO2 on the small inner satellites also suggests that their low-albedo material is distinct from that on Iapetus, Phoebe, and Hyperion.
1. What first drew you to the field of space science?
I always liked to build things, experiment, and explore. As a child I always wanted to know how things worked, and I was hungry for knowledge about the cosmos. Space is pretty much the exploration of everything, so it seemed to be the best field for someone who wanted to explore. The wonder never stops.
2. Tell me a little bit about CRAF.
CRAF, the comet rendezvous asteroid flyby mission, was [to be] the first close look at a comet. As you know, the U.S did not send a mission to Comet Halley during its apparition in 1986. That was kind of a disappointment to American scientists. But then, it was followed by the selection of what we would now call a flagship mission. They didn’t call it that back then, but the Comet Rendezvous Asteroid Flyby (CRAF) was supposed to be a double to Cassini – basically to be a parallel path, we’d create two spacecraft. It got selected. I was selected for the imaging team, which was just great. Joe Veverka was the team leader and it was kind of tooling along and it got cut. . . It was kind of silly because it was really the economy of scale where you get not two for the price of one, but maybe two for the price of one and a half where you had this Mariner Mark spacecraft that was being built at JPL, and everything — everybody was selected, all the science had been through peer review.
3. When you’re a scientist funded to work on these kinds of missions, and all of a sudden, something is canceled, do you immediately have to go out and find something else to do?
Usually, you have a lot of irons in the fire. You have a lot of sources of funding. This is one reason why you have to keep a lot of sources of funding, because if something dries up, then you have something you do. JPL does tend to rise to the occasion, though, of finding funding when something gets cancelled.
4. On M3, as on most missions, the science team is pulled together from across the country. Was there anything in particular that Carle did to bring the team together before observations?
She did a lot. We did have telecons every other week. Now, it’s every week now that we have data. She had team meetings about three times a year, three to four times a year. Of course, the team is hand picked. It’s people that she knows she can work with, that play well with others. Everybody had a role. Everybody had things to do. So, it was fairly disciplined, quite frankly, the team in keeping on track and on message. And of course, she’s a very dynamic leader. She’s very good. As in any team, issues arise. People get upset because maybe they weren’t assigned the thing they wanted to do. And she comes in right away and deals with those things openly and in the beginning.
5. Now, you’ve worked on big missions, little missions, everything in between. In your experience, as a Co-I on these missions, what makes for a good PI?
I think making sure that everybody on the team has a role and that everyone has a piece of the pie. You have to make sure that everyone has something that they can do that they feel valuable. I think, sometimes, a lot of the conflicts I’ve seen on teams, it’s over turf or they’re competing on different projects. So, I think it’s important to have that out in the open, and then maybe have two people that sub projects or different parts of the same project and just make sure that everybody’s able to get credit for some part of the work, because as scientists, we do have to do that in order to keep on top. We have to first author publications and all that sort of thing.
There are always going to be scientific disagreements. I mean, that’s what drives science. It’s okay to be wrong as long as it’s not fraudulent or based on fudging the data– as long as it’s an honest idea that’s out there. So, I think it’s okay — you have to realize that it’s okay for two team members to have different opinions about a piece of data. I mean, that’s what propels them and other people to go and look and then eventually get to the truth. So, conflict is good in science, that kind of friendly [conflict], as long as it doesn’t get personal.
6. Aside from science, what else is important to you?
My family is very important to me. My three grown sons and my spouse are the main focus of my life. To live responsibly and with compassion, to be a good citizen of the world is important to me, as it should be to everyone. I also have a lot of mundane hobbies like reading, hiking, cooking, and gardening.
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