Solar Orbiter Radio and Plasma Waves – Time Domain Sampler: In-flight performance and first results

¹ Institute of Atmospheric Physics, Czech Academy of Sciences, Boční II/1401, 141 00 Prague, Czech Republic
e-mail: soucek@ufa.cas.cz
² Faculty of Mathematics and Physics, Charles University, V Holesovickach 2, 18000 Prague 8, Czech Republic
³ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
⁴ Space Sciences Laboratory, University of California, Berkeley, CA, USA
⁵ Physics Department, University of California, Berkeley, CA, USA
⁶ LPP, CNRS, Ecole Polytechnique, Sorbonne Université, Observatoire de Paris, Université Paris-Saclay, Palaiseau, Paris, France
⁷ Swedish Institute of Space Physics (IRF), Uppsala, Sweden
⁸ LPC2E, CNRS, 3A Avenue de la Recherche Scientifique, Orléans, France
⁹ Université d’Orléans, Orléans, France
¹⁰ CNES, 18 Avenue Edouard Belin, 31400 Toulouse, France
¹¹ Technische Universität Dresden, Würzburger Str. 35, 01187 Dresden, Germany
¹² Space Research Institute, Austrian Academy of Sciences, Graz, Austria
¹³ Astronomical Institute of the Czech Academy of Sciences, Prague, Czech Republic
¹⁴ Department of Space and Plasma Physics, School of Electrical Engineering and Computer Science, Royal Institute of Technology, Stockholm, Sweden
¹⁵ Radboud Radio Lab., Department of Astrophysics, Radboud University, Nijmegen, The Netherlands
¹⁶ Goddard Planetary Heliophysics Institute, University of Maryland, Baltimore County, Baltimore, MD 21250, USA
¹⁷ Heliospheric Physics Laboratory, Heliophysics Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received: 31 March 2021
Accepted: 14 June 2021

Abstract

Context. The Radio and Plasma Waves (RPW) instrument on board Solar Orbiter has been operating nearly continuously since the launch in February 2020. The Time Domain Sampler (TDS) receiver of the RPW instrument is dedicated to waveform measurements of plasma waves and dust impact signatures in an intermediate frequency range from 0.2 to 200 kHz.

Aims. This article presents the first data from the RPW-TDS receiver and discusses the in-flight performance of the instrument and, in particular, the on-board wave and dust detection algorithm. We present the TDS data products and its scientific operation. We demonstrate the content of the dataset on several examples. In particular, we study the distribution of solar Langmuir waves in the first year of observations and one Type III burst event.

Methods. The on-board detection algorithm is described in detail in this article and classifies the observed waveform snapshots, identifying plasma waves and dust impacts based on the ratio of their maximum amplitude to their median and on the spectral bandwidth. The algorithm allows TDS to downlink the most scientifically relevant waveforms and to perform an on-board statistical characterization of the processed data.

Results. The detection algorithm of TDS is shown to perform very well in its detection of plasma waves and dust impacts with a high accuracy. The initial analysis of statistical data returned by TDS shows that sporadic Langmuir waves that are not associated with Type III events are routinely observed in the inner heliosphere, with a clear increase in occurrence rate closer to the Sun. We also present an example of RPW observations during an encounter of the source region of a Type III burst, which exploits the on-board calculated histograms data.