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The main objectives of CALYPSO are to calibrate in-flight the Hot Ion Analyzer (HIA) onboard the Cluster satellites and to conduct studies aiming at HIA data quality improvement. Cluster is a key 'cornerstone' mission of the European Space Agency's Horizon 2000 Programme. Consisting of four identical satellites that make correlated measurements in space, it is the first ever scientific mission that allows to study phenomena in three dimensions and that makes possible the distinction between spatial and temporal variations. The mission started its operational phase in February 2001 and is currently extended till the end of 2016. The results from CALYPSO have a direct impact on data accuracy provided by one of its instruments.

The HIA instrument is part of the Cluster Ion Spectrometry (CIS) experiment, having the objective to measure the three-dimensional velocity distributions of ions. Due to a variety of factors (e.g. exposure to radiation, detector fatigue and aging, adjustments in operating parameters), the HIA detection efficiency changes over time, prompting for continuous in-flight calibration.

Cluster orbit (in red) and the key magnetosphere regions encountered. In winter (left picture), Cluster orbit has the apogee in the magnetotail. The spacecraft configuration is shown (not at scale), with C1, C2, C3 and C4 designating the four satellites. The key regions of the cusp and plasma sheet are encountered. In summer (right picture), the Cluster orbit has the apogee in the solar wind, the key regions visited by the satellites being the cusp, magnetopause, bow-shock and solar wind. Credit to http://sci.esa.int/ .

The activities planed by CALYPSO have a major relevance for the Cluster Active Archive (CAA) program of ESA, that aims at preserving the properly calibrated, high-resolution instrument data provided by the four Cluster spacecraft. In addition, the proposed activities fill an important need in the magnetospheric science community: by increasing HIA data quality and by extending the instrument calibrated data set, the project will provide opportunities for new or more conclusive scientific research. Moreover, it will bring a better understanding of particle detectors performance in space as a function of time, which would be useful in preparation of future experiments.

The project team is formed by Dr. Adrian Blagau (Principal Investigator), Dr. Octav Marghitu (deputy-PI), Dr. Dragos Constantinescu, Dr. Andreea-Maria Julea, Dr. Ciobanu Mircea, Dr. Horia Comisel, Vlad Constantinescu and Costel Bunescu

The project is carried out at the Space Plasma and Magnetometry Group from the Institute of Space Sciences (GPSM/ISS), Bucharest - Magurele.

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