Andrew Coates on the Plasma Environments of the Planets

Special Topic of Planetary Exploration Interview, November 2011

Andrew J. Coates

Photo credit: UCL/MSSL.

The work of Professor Andrew J. Coates ranks at #2 by papers and #6 by cites in our Special Topics analysis on Planetary Exploration, based on 160 papers published over the past decade and cited a total of 2,343 times. Two of these papers appear among the most-cited papers over the past two years. In  Essential Science IndicatorsSM from Thomson Reuters, Coates has several Highly Cited Papers in the fields of Space Science and Geosciences.

Coates is Professor of Physics and Head of Planetary Science at the Mullard Space Science Laboratory (MSSL), University College London. He is also Deputy Director of UCL's MSSL, located in Surrey. He is also a Fellow of the Royal Astronomical Society and a Member of both the American Geophysical Union and European Geophysical Union.


SW: Please tell us about your educational background and research experiences.

My first degree (B.Sc.) was at the University of Manchester Institute of Science and Technology in physics, then I did an M.Sc. and D.Phil. in plasma physics at the University of Oxford. My D.Phil. work was on the boundaries of plasmas and ion rarefaction waves—most of the work was experimental using a Langmuir probe in the basement lab in Oxford's Engineering Science building. If I wanted to change something with the experiment I'd have to wait until the next day when we had a vacuum again.

As an undergraduate I was lucky enough to go to CERN as a summer student which interested me in big science, and the interest in plasmas came from fusion originally, but by the end of my D.Phil., I thought that commercial fusion was 30 years away—maybe it still is! Now, with planetary exploration, we have to get the instrument right years in advance and the only way to change something with the experiment means another mission!

SW: What first drew you to planetary research? Is there a specific area within this field on which you focus, or do you maintain a wide variety of interests?

I've always been interested in space and the planets—perhaps influenced by my father taking me outside and showing me Sputnik going over as a baby! The moon landings, and the Voyager outer planet explorations, were also very inspirational. But during my D.Phil. in Oxford I went to a talk, the Halley lecture, by Professor Boyd, the then director of MSSL-UCL. It was about an upcoming European space mission to the famous Halley's comet which the lab had just become involved in. I thought wow! Can we really do planetary exploration in Europe? And what a target, a world-famous comet with a plasma and dust tail, and plasma unconstrained by vacuum chambers.

By a fluke I saw a postdoc job advertised at MSSL-UCL, applied, and got it, and ended up managing instruments to go on AMPTE (artificial comet) and Giotto as well. It was dream job for me, and with the chance to do science analyzing data too. I'm still giving invited talks about my Giotto work, partially with Rosetta in view.

Andrew J. Coates

Andrew J. Coates
Andrew J. Coates in the lab (top), and in the calibration chamber (bottom).

My specialty is the plasma interaction with unmagnetized objects, such as comets, Titan, Enceladus, Venus, and Mars, planetary magnetospheres, and planetary exploration. Through my career I've been lucky to work on many of the planetary and magnetospheric missions with plasma instruments on board. One of these was Cassini, which I've been fortunate to have been involved with since our instrument proposal in 1989, selection, getting the money, design, build, test, test, and test, calibrate launch, arrival at Saturn, the prime mission to 2008, equinox mission to 2010—and it's still working well during the current "solstice" mission (North polar summer on Saturn) with a spectacular end of mission in 2017.

I've also been fortunate to work on many other missions, the early days of Cluster (until Cassini took over), and more recently Mars Express and Venus Express as well. We also developed an interest in planetary surfaces, and we led the stereo camera team in the ill-fated Beagle 2. I'm currently Principal Investigator for the PanCam instrument on the ExoMars rover which will be a very exciting mission to Mars in 2018—recently this has become a joint mission studied with NASA, ExoMars-C.

SW: You're lead investigator on the Cassini CAPS electron spectrometer. What, would you say, is the ultimate hope or goal of this investigation? How does it fit in to the larger Cassini mission?

We designed the electron spectrometer to explore Saturn's plasma environment—in particular electrons between 0.6 and 28,000 eV. The energy range includes a "gap" in previous observations by Voyager, between 6 and 20 keV. The idea of CAPS was to explore all aspects of Saturn's magnetosphere—including structure, dynamics, interaction with moons and rings. Data from the ELS instrument, and from its partner instruments in CAPS—the Ion Mass Spectrometer and Ion Beam Spectrometer—have been key to the exploration of Saturn's plasma environment. Several hundred papers have used CAPS and ELS data.

ELS data in particular have contributed to a number of unexpected discoveries, such as the ring atmosphere and ionosphere, heavy negative ions at Titan, water cluster ions at Enceladus, and Rhea's atmosphere. The ultimate goal is to provide as good data as possible to help characterize the most complex magnetosphere in the solar system.

SW: Your most-cited original article in our analysis is the February 2005 Science paper, "Composition and dynamics of plasma in Saturn's magnetosphere," (Young DT, et al., 307: 1262-6). Would you tell us a bit about this paper—your expectations going in, your findings, where this work has gone since this publication?

Dave Young, the CAPS PI, led this paper. It was the first paper to describe CAPS data from all three sensors following Saturn orbit insertion. It described data from the first orbit of Saturn, and its aim was to provide the first plasma description from this cut through the magnetosphere.

"…sending robotic probes to explore and find out about our place in the Universe is one of our most important and inspiring endeavors."

The composition measurements showed that Saturn's magnetosphere is dominated by water group ions—coming, we know now, from a number of sources including Enceladus and the rings. The electron data showed two components of electrons—hot and cold—in the inner magnetosphere, as well as frequent dispersed "injection" events. A number of boundaries also showed up in the magnetosphere. One particularly interesting comparison was with the corotation speeds of protons and heavy ions. As well as the ion spectra, which one would expect to follow this trend, unexpectedly the electrons did too.

Several of these first observations have been followed up, particularly the "injections" which are partly due to interchange between cool, dense plasma from the inner magnetosphere and hotter, rarer plasma from the outer magnetosphere.

In addition we've been able to study a number of completely unexpected aspects of Saturn's environment, particularly during close flybys of Titan, Enceladus, the rings, Rhea, and other moons, as mentioned above.

SW: You're also involved with investigations on Mars and Venus. What would you say are the most important things we've learned about these planets so far and why?

I was asked to join the ASPERA-3 (Mars Express) and 4 (Venus Express) teams, to assist with the calibration of the electron spectrometer from that instrument and also with sensor blackening to cut down unwanted solar photoelectrons inside the analyzers, similar to the one we had developed for Cluster and Cassini. For the Venus instrument we also performed simulations to understand and calibrate the instrument response, and provided a radiation shield.

Page: < 1 | 2 >


   |   BACK TO TOP