After WWII he studied natural sciences at the University of Oslo (UiO) and received his undergraduate degree in astronomy 1950. He then worked as research assistant at the Institute of Theoretical Astrophysics, UiO, for three intervals in the 1950s, interspersed by fellowships at, respectively, Institut d'Astrophysique in Paris, CalTech, in Pasadena, California, High Altitude Observatory in Boulder, Colorado and the Cavendish Laboratory in the UK at the British radio-astronomer Sir Martin Ryle. He earned a doctorate in astrophysics at the University in Oslo in 1960 with a dissertation on An Investigation of the Temperature Conditions in Prominence with a Special Study of the Excitation of Helium.
From 1959-61, Tandberg-Hanssen was a professor at the University in Oslo. He then traveled back to the High Altitude Observatory, Boulder, Colorado, where he was employed until 1974, when he was employed at the Space Science Laboratory at NASA's Marshall Space Flight Center (MSFC) in Alabama. There, he was first Senior Research Scientist, later Deputy Director and then Director from 1987 to his retirement from NASA in 1993. Since 1993, Tandberg-Hanssen had a part-time post as professor of physics at the University of Alabama. During his tenure at MSFC, he built up a substantial, internationally based group of solar physicists; he was the Principal Investigator with instruments aboard two NASA spacecraft, the Apollo Telescope Mount and the Solar Maximum Mission, which carried out sweeping new studies of the Sun.
Tandberg-Hanssen has published more than a hundred scientific papers, mostly in solar physics, and several books, including Solar Activity (1967), Solar Prominence (1974), The Physics of Solar Flares (1988) and The Nature of Solar Prominence (1995). In particular, his book about the solar prominences (Solar Prominence) has become an international standard work within the discipline of solar physics. Tandberg-Hanssen became a member of the Norwegian Academy of Science and Letters in 1982.
Einar Tandberg-Hanssen was vice-president 1979-82 and president 1982-85 of Commission 10 of the International Astronomical Union (IAU) and president of the Federation of Astronomical and Geophysical Data Analysis Services (ISCU) 1990-1994. He has also received the NASA Exceptional Service Medal.
Tandberg-Hanssen's residence as a research fellow at the Institut d'Astrophysique in Paris in the 1950s laid the foundation for a lifelong interest in France and French culture. His great interest in and knowledge of French mediaeval churches, as well as the Norwegian stave churches, is reflected in two books, Letters to My Daughters (2004) and The Joy of Travel: More Letters to My Daughters (2007) which is at once a review, tourist guide and history book, shaped like a letter home to his two daughters from his many travels in Norway and France.
Dr. Tandberg-Hanssen’s Solar Physics Memoir paper, entitled Solar Prominences - An Intriguing Phenomenon was recently published and can be downloaded. The article starts with an autobiographical account, where the author relates how his several study-trips abroad gradually led him to the study of solar physics in general, and prominences particularly.