Michael I. Mishchenko (1959–2020): The Architect of Light Scattering
Michael Igorovich Mishchenko was a titan in the fields of radiative transfer and remote sensing. As a Senior Scientist at the NASA Goddard Institute for Space Studies (GISS), he revolutionized our understanding of how light interacts with non-spherical particles—ranging from interstellar dust to the aerosols in Earth’s atmosphere. His work provides the mathematical foundation for much of modern climate modeling and satellite observation.
1. Biography: From Crimea to NASA
Michael Mishchenko was born on March 1, 1959, in Simferopol, Crimea (then part of the Soviet Union). His academic pedigree was rooted in the rigorous Soviet school of theoretical physics. He attended the Moscow Institute of Physics and Technology (MIPT), graduating with honors in 1982. He later earned his PhD in Physics and Mathematics from the Main Astronomical Observatory in Kyiv in 1987.
Mishchenko’s early career was shaped by the influence of Victor Sobolev, a legendary figure in radiative transfer. In 1992, following the collapse of the Soviet Union, Mishchenko moved to the United States to join the NASA Goddard Institute for Space Studies (GISS) in New York City. He remained at GISS for the rest of his career, eventually becoming a naturalized U.S. citizen and one of NASA’s most cited and respected atmospheric scientists until his untimely passing on July 21, 2020.
2. Major Contributions: Beyond the Sphere
Before Mishchenko, most climate models and remote sensing algorithms relied on "Mie Theory," which assumes that particles (like water droplets or dust) are perfect spheres. However, nature is rarely spherical. Mishchenko’s career was dedicated to solving the "non-spherical problem."
The T-Matrix Method
While the T-matrix approach was originally proposed by Peter Waterman in the 1960s, Mishchenko transformed it from a theoretical curiosity into a practical powerhouse. He developed efficient, stable computer codes that allowed scientists to calculate light scattering by complex, non-spherical shapes (like ice crystals or soot aggregates) with unprecedented precision.
Coherent Backscattering
He provided the first rigorous theoretical explanation for the "opposition effect"—the sudden brightening of a celestial body (like the Moon or Saturn’s rings) when illuminated from directly behind the observer. He identified this as "coherent backscattering," a quantum interference effect in multiple-scattering media.
Aerosol Polarimetry
Mishchenko was a fierce advocate for using the polarization of light—not just its intensity—to study Earth’s atmosphere. He was the Project Scientist for the NASA Glory Mission, designed to measure the properties of aerosols using a polarimeter. Although the satellite was lost due to a launch vehicle failure in 2011, his theoretical work on polarimetry remains the gold standard for current missions like PACE.
3. Notable Publications
Mishchenko was a prolific author with over 300 peer-reviewed papers. His work is characterized by mathematical elegance and extreme physical rigor.
- Scattering, Absorption, and Emission of Light by Small Particles (2002): Co-authored with Larry Travis and Andrew Lacis, this Cambridge University Press book is considered the "bible" of the field, replacing older texts as the primary reference for researchers.
- Light Scattering by Nonspherical Particles: Theory, Measurements, and Applications (2000): A comprehensive volume that bridged the gap between theoretical physics and practical remote sensing.
- Capabilities and limitations of a narrow-band multi-angle photopolarimeter for retrieving properties of terrestrial atmospheric aerosols (1997): A seminal paper in Applied Optics that laid the groundwork for modern satellite aerosol retrieval.
4. Awards & Recognition
Mishchenko’s contributions earned him nearly every major accolade in his field:
- NASA Exceptional Scientific Achievement Medal (2003): For his development of the T-matrix method.
- Henry G. Houghton Award (2004): Awarded by the American Meteorological Society (AMS) for his work on non-spherical scattering.
- The JQSRT Waterman Award (2007): Recognizing his leadership in the light-scattering community.
- Asteroid 22686 Mishchenko: In 2010, the International Astronomical Union named a main-belt asteroid in his honor, recognizing his contributions to planetary science and radiative transfer.
- Fellowships: He was a Fellow of the American Physical Society (APS), the American Geophysical Union (AGU), and the Optical Society of America (OSA).
5. Impact & Legacy
The "Mishchenko Codes"—his publicly available T-matrix software—are perhaps his greatest legacy. They are used daily by thousands of researchers in fields as diverse as:
- Climate Science: Modeling how volcanic ash or wildfire smoke reflects sunlight.
- Biomedical Optics: Studying how light scatters through human tissue.
- Astronomy: Analyzing the composition of cometary dust and planetary regolith.
As the long-time Editor-in-Chief of the Journal of Quantitative Spectroscopy and Radiative Transfer (JQSRT), he maintained a standard of "uncompromising rigor," often personally mentoring young authors to ensure their mathematical proofs were sound.
6. Collaborations
Mishchenko was a central node in a global network of physicists. His most enduring partnership was with Larry Travis, with whom he worked at GISS for decades. He also collaborated extensively with Joop Hovenier (University of Amsterdam) on the fundamental symmetries of light scattering.
He was known for his "school" of thought, which emphasized that remote sensing must be treated as a branch of classical electrodynamics rather than a mere empirical exercise. This philosophy influenced a generation of scientists at NASA and beyond.
7. Lesser-Known Facts
A Passion for History
Mishchenko was an amateur historian of science. He wrote several deep-dive essays on the history of the concept of "photons" and the evolution of radiative transfer theory, often correcting historical misconceptions in his papers.
The "Mishchenko Standard"
He was known for his formidable—and sometimes intimidating—intellectual honesty. He famously had little patience for papers that used "simplified" physics where rigorous solutions were possible. To have a paper accepted by Mishchenko was considered a "badge of honor" in the optics community.
New York Intellectual
Despite his Soviet roots, he became a quintessential New Yorker, often seen walking near Columbia University, where he served as an adjunct professor, deeply engaged in the city's intellectual life.
Michael Mishchenko’s death in 2020 was a profound loss to the scientific community. He left behind a world that better understands the invisible particles filling our skies, viewed through the lens of the elegant mathematics he spent his life perfecting.