Aerospace and Electronic Systems Magazine April 2017 - 41
image on a new display device (called a RamTech, connected to a
Vax 780 computer). No one on staff could figure it out, but I did it
in a week: I was a hero! Later as a graduate student at Stanford,
we needed speed to process large data sets, so I learned how to
program a double-buffered-input fixed-point arithmetic accelerator that came with our Data General computer. The accelerator had sat idle because no one was confident enough to invest
the time in learning how to use it. After mastering it, I was able
to process data in a previously impossible fashion-synoptically
and at fine resolution-giving us a new view of (in that case)
Saturn's rings. I would carry that same approach to computation
and synoptic assessments into my work at JPL.
Riccardo: I am curious to know if working with radars was an
interest already at the beginning of your studies and how it influenced your university career.
A new view of the world, with
radar eyes, captivated me.
Paul: In my junior year, a researcher from the Jet Propulsion Laboratory came to the University of Pennsylvania to talk
about a mission called Seasat [Seafaring Satellite], the world's
first civilian synthetic aperture radar satellite. This talk showed
a new view of the world, with radar eyes, and further captivated
me. I asked after the talk if there were any summer opportunities
for students, and after a short telephone interview, I was hired to
work on Seasat image analysis for the summer.
That summer in California at JPL was so wonderful that I
was determined to stay in California. I applied to only Californiabased PhD programs and was accepted at Stanford University to
do research on a JPL mission-Voyager observations of Saturn's
rings. From this point onward in my career, radio wave propagation, scattering, and scientific interpretation of microwave-based
data sets would be the focus. Eventually I returned to JPL, in
1992, and pursued a career in synthetic aperture radar science
Riccardo: I understand that before getting involved in radar
developments, you studied wave propagation in plasmas and, in
particular, the dynamics and observations of Saturn's rings. Can
you tell something about it?
Paul: The observations from Voyager were microwave radio occultation data, which is a form of bistatic CW radar. Voyager was navigated to pass behind Saturn's rings with respect
to Earth. As Voyager went behind the rings, the telemetry was
turned off, so only a continuous wave signal at X-band and Sband were transmitted, with the antenna pointing back at Earth.
Note the power of the transmitter was only in the tens of watts, so
to observe the signal, it needed to be highly coherent, and the antennas on Earth to receive it had to be very large. The variations
in the amplitude and phase of the received signals then provided
information about the size and density of particles in Saturn's
rings. My research involved resolution reconstruction using inverse Fresnel filtering, which is very similar to synthetic aperture
radar processing, and interpretation of the dozens of ring particle
Younger days in Japan: Paul Rosen (right) with Isamu Nagano, professor of electrical engineering at Kanazawa University, Kanazawa,
Japan. Professor Nagano later became vice president for research and
international affairs at the university until his retirement in 2012. This
photo shows a visit to a cleanroom facility in February 1991. During his
2 years at Kanazawa University, Paul accompanied Professor Nagano
on visits to many companies and space agency facilities to give lectures
and advocate for placement of Kanazawa University students.
dynamical features discovered in these data. I was able to discover and interpret some new physical phenomena-resonance
waves in the rings excited by gravitational interactions with the
moons of Saturn-and these led to well-cited publications in the
literature. It was the beginning of my career path of working on
radar systems and science as inseparable aspects of the problem.
Riccardo: Following your PhD at Stanford University, you
spent some time in Japan, at the Kanazawa University. How was
Paul: I spent 2 years in Japan with my wife and 4-monthold daughter. It was in Japan that I studied wave propagation in
plasmas. My sponsor at Kanazawa University, Professor Isamu
Nagano, was a wonderful man and a brilliant designer of magnetometers and electric field measurement instruments (Figure 2).
He was part of a team led out of Kyoto University that has electromagnetic instrumentation on Japan's Akebono satellite to
study low-frequency wave propagation in the plasmasphere.
My work focused on applying analytic signal techniques to
analyzing the electric and magnetic field measurements in the
plasma, which included estimating plasma properties as a function of position on orbit. To be honest, my research in plasmas
did not lead to great discoveries; however, I continued to work
and publish on Saturn's rings with a colleague who had moved to
the University of Tokyo, and I made a number of lifelong friends
and colleagues in Japan. I had the good fortune to tour many
companies in many cities in Japan with my host, who was responsible for placing university seniors at companies upon their
graduation. This allowed me to understand Japanese industry,
culture, customs, and people. While I did not pursue research
in plasmas further, these 2 years were very important in establishing contacts for the research I was to begin at JPL and also
learning how to work and succeed in the international space research community.
IEEE A&E SYSTEMS MAGAZINE