Solar Orbiter

Thematic Group: PEPS
Scientific Leader of PAS: Philippe Louarn
Main OSU: Observatoire de Paris

Background / description

Solar Orbiter will explore the inner regions of the heliosphere.
This probe includes both in-situ solar wind sensors and solar imaging instruments. It will therefore be able to finely characterize the local environment and, simultaneously, to study the dynamics of coronal structures, in conjunction with NASA’s Solar Probe Plus.
Among the ten onboard instruments, the Solar Wind Analyser SWA instrument suite (PI: Christopher Owen, MSSL/UCL) is dedicated to the measurement of solar wind and its various components.

It brings together:
(1) a ‘Proton-Alfa’ sensor (PAS) that measures the main component of the solar wind,
(2) a ‘Heavy Ion Sensor’ (HIS),
(3) an ‘Electron Sensor’ (EAS).


The PAS/Solar Orbiter observation service mainly concerns the preparation and monitoring of operations throughout the mission, the programming of the different PAS modes and their optimization in relation to the scientific objectives. It also involves evaluating and quantifying the aging of the detectors and, if necessary, modifying instrument settings, recalculating and adapting the calibration matrices. The service includes the validation of PAS data, their formatting into physical measurements before distribution to the community.
This service will play an important role in the scientific animation of the SWA suite measurements in relation to the other Solar Orbiter instruments, Solar Probe Plus and supporting ground-based observations. The last part of the activity will concern outreach toward the general public.

Main tasks:
1. Calibration of the PAS instrument and optimization (use of the Spare model) – Optimization of HT controls
2. Commissioning and ‘technical’ analysis of the operation of the instruments. Flight calibration and cross-calibration. Follow-up of the evolution of the detectors and update of the calibration matrices.
3. Scientific evaluation of the ‘PAS’ cyclograms. Programming and monitoring of operations. Cyclogram optimization (‘burst’ modes) according to scientific objectives.
4 Validation and physical formatting of the data. Make available the data in exploitation and archiving centers (CDPP, Archive ESA).
5 Scientific animation. Links with other instruments and Solar Probe Plus. Ground observations. Space Weather aspects. Modeling.
6 Outreach. The Sun, its activity, its eruptions and their ‘terrestrial’ impacts. Instrumentation in extreme environments, its interest to promote engineering vocations. 

The service is planned for the entire duration of the mission, i.e. a minimum of 7 years after launch (in 2020). It will rely on IRAP’s scientific teams associated with Solar Orbiter (~ 9 researchers) which bring together specialists in plasma physics, heliospheric and solar physics.

April 15, 2020: Wake-up of the instrument.

Involvement of IRAP

The Proton-Alfa Sensor (PAS) has been developed under the scientific and technical responsibility of IRAP.
Co-PI: Philippe Louarn.
Project leader: Andrei Fedorov.


MSSL, INAF (Frascati), University of Prague, LPP, SWRI.