Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations over the epicenter region or its conjugate point. Theoretically speaking, due to some electromagnetic coupling effect, electromagnetic emissions from the earthquake preparation zone could propagate from the lithosphere to the atmosphere, and could reach the ionosphere, even up to the inner magnetosphere. This paper introduces the electric field detector (EFD) onboard the ZhangHeng‐1 satellite (ZH‐1). The EFD is designed to measure electric field fluctuations within the broad frequency range of DC to 3.5 MHz, divided into 4 channels: ULF (DC–16 Hz), ELF (6 Hz–2.2 kHz), VLF (1.8 kHz–20 kHz) and HF (18 kHz–3.5 MHz). The sampling rates of the channels are 125 Hz, 5 kHz, 50 kHz and 10 MHz, respectively. The EFD includes 4 spherical probes mounted on a over 4.5 m boom and an electronic box inside the satellite module. The resolution of the EFD is 1 μV·m‐1·Hz‐1/2 at frequencies from DC to 16 Hz, and the sensitivity is 0.1 μV·m‐1·Hz‐1/2 at frequencies from 6 Hz to 2.2 kHz, 0.05 μV·m‐1·Hz‐1/2 in the band 1.8 kHz to 20 kHz, and 0.1μV·m‐1·Hz‐1/2 from 20 kHz to 3.5 MHz. The dynamic range from DC to 20 kHz is over 120 dB, and over 96 dB from 20 kHz to 3.5 MHz. The EFD has two observation modes: survey mode and burst mode. The survey mode concentrates primarily on electric field power density values; the burst mode provides high sampling rate waveform data. The detailed configuration of the EFD onboard the ZH‐1 is also introduced in this paper. During the six months’ orbit test phase, the EFD recorded a number of natural electromagnetic emissions. Preliminary analysis of these data suggests that the EFD performs well onboard the ZH‐1 and is meeting the requirements of the scientific objectives of ZH‐1.

In this perspective, we outline that a space borne gravitational wave detector network combining LISA and Taiji can be used to measure the Hubble constant with an uncertainty less than 0.5% in ten years, compared with the network of the ground based gravitational wave detectors which can measure the Hubble constant within a 2% uncertainty in the next five years by the standard siren method. Taiji is a Chinese space borne gravitational wave detection mission planned for launch in the early 2030 s. The pilot satellite mission Taiji-1 has been launched in August 2019 to verify the feasibility of Taiji. The results of a few technologies tested on Taiji-1 are presented in this paper.

The quasiperiodic (QP) waves accompanied by simultaneous energetic electron precipitations in the high-latitude ionosphere were recorded by the sun-synchronous circular orbit China Seismo-Electromagnetic Satellite (CSES). The new features of QP waves observed by CSES are the well-pronounced rising-tone structures and very short repetition periods, which are not ofen reported by previous studies. The repetition period of QP waves varies from~1 to over 20 s, with wave spectral properties displaying dynamic structures and clear cutoff frequencies. The majority of QP waves appear at geomagnetic latitudes from~50°to 65°, and L shell from~3.5 to 4, mostly inside the plasmapause. The QP waves obliquely propagate towards decreasing L shell directions with right-handed polarization, with wave normal angles varying from~30°to 50°. Out of the 68 events examined, 19 of them show synchronous variations of ultralow frequency (ULF) magnetic field pulsations in certain portions of the wave event. The energetic electrons predominately precipitate in a double-peak pattern (~400 to 550 keV and~700 to 800 keV). No clear periodic precipitating fluxes were found. The estimated time interval of energetic electrons driving free energy to modulate the whistler-mode waves varies from 0.04 to 30°s, which is roughly consistent with the observed repetition periods (10 to over 20 s). For the fast repetition period (~1 to 2s) QP wave, it is likely caused by the bouncing of the extremely/very low frequency (ELF/VLF) whistler-mode wave packets from the conjugate ionosphere.

The aim of this work is to validate the China Seismo-Electromagnetic Satellite 01 (CSES-01) Electric Field Detector (EFD) measurements through the analysis of the instrument response to various inputs: (a) geomagnetic field variations, (b) plasma density depletions, and (c) electromagnetic signals from natural and artificial sources such as Schumann resonance and VLF (Very Low Frequency) antennas. The knowledge of the geomagnetic induced electric field vs×B (where vs is the satellite speed and B and the local magnetic field), and the plasma variations effect, described by the Orbit Motion Limited (OML) theory, are key parameters to determine the expected theoretical values of the EFD sensors potentials data. Based on the CSES on-board measurements of plasma parameters and geomagnetic field, a direct quantitative validation is presented. In addition, the electromagnetic signals detection capability is checked but only qualitatively confirmed, since the ionospheric complexity does not allow an accurate theoretical computation of waves modulation. The quantitative comparison highlights the very good agreement between observed and theoretical potentials values during average condition. Conversely, in case of strong electric fields, the OML theory shows partial inability in reproducing the actual space plasma conditions resulting in a reduced theoretical values reliability. Finally, both natural and artificial electromagnetic signals are satisfactorily identified showing a reliable sensitivity in different frequency bands.