The Italian Space Agency (ASI) and China National Space Administration (CNSA) agreed on an Italian participation in the Chinese CSES (Chinese Seismo-Electromagnetic Satellite) mission aimed to monitor and study electromagnetic and particle phenomena correlated to Space Weather events, magneto/iono/litosphere coupling mechanisms, and the general physics of the terrestrial ionosphere.

The first CSES satellite (CSES-01) was successfully launched on Feb 2, 2018 from the Jiuquan Satellite Launch Center by means of a Long March 2D orbital carrier rocket, reaching a circular sun-synchronous orbit (descending node: 14:00 PM, local time) at a ~500-km altitude and ~98° inclination, with an expected lifespan of 5 years.

A second satellite (CSES-02) is under development and scheduled for launch in early 2024, with an expected lifespan of 6 years to guarantee CSES operativity over time.

CSES-02 activities on the Italian side include:

- INAF-IAPS: development, testing and calibration of an Electric Field Detector (EFD-02);

- INFN: development, testing and calibration of a High Energy Particle Detector (HEPD-02);

- INAF-IAPS: enabling Chinese personnel (scientists and engineers) to access any development phase of EFD-02 models;

- INAF-IAPS: enabling Chinese personnel to access SWIPS Facility and ancillary labs for calibration of Langmuir probes and Plasma Analyzer scheduled to fly on board CSES-02.

INFN is the leading institution, and it coordinates its Divisions and Laboratories of Bologna, Frascati (LNF), Naples, Rome Tor Vergata, and Trento (TIFPA), in collaboration with INAF-IAPS in Rome, University of Rome Tor Vergata, University of Trento, and University of Naples 'Federico II'. 

CSES-02 activities are the natural continuation of the operationally and scientifically successful Limadou Project. The design, development, testing, and shipment of the HEPD-02 particle detector and EFD-02 electric field detector constitute their core. In addition, an extensive test program at the INAF-IAPS Plasma Chamber is scheduled for EFD-02 models, as well as for other instruments developed by the Chinese counterpart, which contribute to form an integrated, synergic 9-payload measuring suite mirroring the one still operating on board CSES-01.

Key parameters measured by CSES instruments are:

- electromagnetic fields;

- electric-field and magnetic-field intensity;

- ionospheric and plasma parameters;

- ionic energy and density;

- electronic density and temperature;

- plasma composition;

- total electron content (TEC);

- ionic drift velocity;

- energetic particles;

- electron and proton flux/pitch angle.

Like CSES-01, CSES-02 relies on a CAST2000 platform (DFH Satellite Co. Ltd China, supported by China National Space Agency [CNSA], China Earthquake Administration [CEA], China Aerospace Science and technology Corporation [CASC], Institute of Crustal Dynamics [ICD], and others). Its orbital plane is planned to be the same as CSES-01's, even though including a 180° phase shift in order to optimize revisit time (5 days to 2.5 days) and improve spatial resolution (5° to 2.5°).

EFD-02 Electric Field Detector @INAF-IAPS

Upon the development phases of the CSES-01/EFD-01 detector (by the Lanzhou Institute of Physics, LIP), a fertile collaboration with the Italian Limadou team would go on in order to identify major criticalities stemming from the DEMETER/ICE instrument's legacy. The collaboration involved INFN, INAF-IAPS and LIP personnel across various testing and calibration sessions, resulting in a successful fix of a subset of such criticalities. Tight time deadlines prevented the development team from implementing a complete restyling of the instrument before launch. Yet, the Limadou team was able to advance its science/tech activities and propose a fully updated version of the electric field detector to the Chinese counterpart.

INAF-IAPS is currently in charge of the full development and testing of the EFD-02 detector, which is scheduled to fly on board the CSES-02 satellite. EFD-02 includes four identical Electric Field Probes (EFPs) placed at the end of 4.5-m-long booms, designed to return the three components of the local electric field via a 'Double Probe' technique, i.e., starting from measurements of potential difference between couples of electrodes. This instrument will allow the measurement of the electric field across the DC/ULF, ELF, VLF, and HF frequency bands along three axes (not simultaneosly over the HF band) with a sensitivity of the uV/m order (which represents the current state-of-the-art sensitivity to observable ionospheric oscillations). 

Each EFP carries a voltage adapter at high input impedance as the core of any sensor’s front-end electronics (FEE). The FEE, which is designed to minimize noise, also provides the bias current that enables changes in the working point along the characteristic I-V curve and subsequent optimization of sensitivity to variations in the floating potential. One key novel feature of EFD-02 sensors is self-adaptive bias-current injection, which will enable the detector to remarkably span 6 orders of magnitude across the plasma density range (10E12 to 10E6 m-3) averting saturation.

EFD-02 observations - paired to magnetic field data - will be key to the entire mission, since able to monitor the e.m. wave environment along the orbit. Low-frequency measurements will enable the fine investigation of plasma structures modulated by solar perturbations transiting across the interplanetary medium, that is, the effct of solar forcing on plasma currents embedded in the ionospheric system. Mid frequencies will return information about the ionospheric dynamics, possibly in correspondence with particle precipitation from the radiation belts, and with special focus on acoustic gravity waves (AGWs) generated by seismo-induced lithospheric phenomena. Finally, high-frequency data are expected to give insight into plasma neutrality violations induced by either solar forcing or litho/ionospheric coupling.