Although millimeter-wave astronomy had started two decades earlier, at the beginning of my career in the 1990s new ground-based telescopes were being placed at higher and drier sites to access new frequencies that would widen the range of molecules and physical conditions that could potentially be explored in the Universe. In between the telescope and the outer space there is the terrestrial atmosphere, with its own molecules, affecting the observations in a particularly dramatic way. The new telescopes, operating even at submillimeter wavelengths for the first time, needed an accurate atmospheric radiative transfer model, for both scheduling and calibration.
As a young Ph. D. student at Yebes Observatory in Spain, part of the Germany-France-Spain consortium called Institute de Radioastronomie Millimétrique (IRAM) that was operating an outstanding 30 meter telescope at Pico Veleta (Granada, Spain) and an interferometer at Plateau de Bure (France), I started working on the atmospheric radiative transfer models that were used for those telescopes. Some of the firsts papers that I read in my career were those by Prof. Hans Liebe describing his MPM model, outstanding pieces of literature that still are of basic reference today. It all started with those papers and, for more than 30 years now, I have been working on measuring the mm/submm atmospheric spectrum with state-of-the-art experiments in order to fine tune the atmospheric radiative transfer models used by the observatories, specially the Atacama Large Millimeter Array (ALMA) located at the 5000 m high Llano the Chajnantor in Chile which, with its 66 antennas, is the leading instrument in mm/submm astronomy.
In this lecture, I will present the exciting experiments in which I had the chance to take part over the years that contributed to make progress on our knowledge of the mm/submm atmospheric spectrum. They include the first ground-based measurements of the atmospheric Zeeman splitting in an isotopologue of molecular oxygen, carried out with a small (2.5 m) radiotelescope at Plateau de Bure (France) ; ground-based 200-1600 GHz measurements of the atmospheric spectrum from Mauna Kea (Hawai’i) ; and the recent and not completely published 157-752 GHz study of the atmospheric spectrum at kHz resolution from Llano de Chajnantor (Chile). The quality of the spectra obtained in this last experiment makes it, in my opinion, perfect to honor Prof. Hans Liebe, with whom it all started.
