Amoruso, L; Owen, CJ; Fortunato, V; De Marco, R; Bruno, R; Salatti, M; Abbattista, C; (2018) Solar wind analyzer - The solar orbiter milestone towards on-board intelligent decision making systems. In: (Proceedings) 69th International Astronautical Congress (IAC). (pp. A7, 3). The International Astronautical Federation (IAF): Bremen, Germany.

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Abstract

The most important challenge underpinning the transition to next generation of space missions design is the discrepancy between the dramatic increases in observation rate and the marginal increase in downlink capacity, enforcing the shift from the traditional “acquire-compress-transmit” paradigm to highly efficient intelligent on-board processing of observations, minimizing downlink requirements while respecting the limitations in power and bandwidth resources. Solar Orbiter (SO), an ESA/NASA mission, is a milestone both in the purely technological and scientific sphere. SO is designed to study the connection between the Sun and the heliosphere, with particular interest to open issues such as the sources of solar wind streams and turbulence, the heliospheric variability, the origin of energetic particles and the solar dynamo. The selected science payload is required to support making the link between in-situ and remote sensing observations, and is composed of ten instruments or suites of instruments including spectrometers, imagers, wave and particle instruments – many the result of large international consortia. In particular, the plasma suite Solar Wind Analyzer (SWA) comprises: Proton-Alpha Sensor (PAS), Electron Analyzer System (EAS), Heavy Ion Sensor (HIS) together with the Data Processing Unit (DPU), and will provide high-resolution 3D velocity distribution function of ions and electrons, together with ion composition, necessary to infer the thermal state of solar wind and its source regions, identify structures such as shocks, CME's and other transients, and determine the link between particle dynamics and waves. SO will explore new distance and latitude regions that remain unexplored, even accounting for existing Helios and upcoming Parker Solar Probe observations. The technical challenges include heavy constraints such as the limited bandwidth available to SWA for downlink, so that the whole set of raw particle data collected cannot be transmitted back to ground. Data processing is thus used to evaluate concise scientific properties of the solar wind, particularly the moments of the particle velocity distribution functions (VDF), such that it is then acceptable to transmit the full VDF data only at low frequencies. Then processing is re-adopted on these distributions to meet the required (lossless) compression rates (2-8). Another step towards the aforementioned paradigm shift is represented by the SWA Book-Keeping Algorithm (BKA), which has been designed to ensure that the individual sensors remain within the allocated telemetry rate on an orbit-averaged basis. The philosophy of the SWA book-keeping scheme has since been applied to all instruments with ESOC’s Operations Team introducing the concept of Operations Telemetry Corridors (OTC) to finely tune the rate of telemetry generation by the instruments.

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