In-orbit results of the Coupled Dark State Magnetometer aboard the China Seismo-Electromagnetic Satellite

Abstract

Abstract. The China Seismo-Electromagnetic Satellite (CSES) was launched in February 2018 into a polar, sun-synchronous, low Earth orbit. It provides the first demonstration of the Coupled Dark State Magnetometer (CDSM) measurement principle in space. The CDSM is an optical scalar magnetometer based on the coherent population trapping (CPT) effect and measures the scalar field with the lowest absolute error aboard CSES. Therefore, it serves as the reference instrument for the measurements done by the fluxgate sensors within the High Precision Magnetometer instrument package. In this paper several correction steps are discussed in order to improve the accuracy of the CDSM data. This includes the extraction of valid 1 Hz data, the application of the sensor heading characteristic, the handling of discontinuities, which occur when switching between the CPT resonance superpositions, and the removal of fluxgate and satellite interferences. The in-orbit performance is compared to the Absolute Scalar Magnetometer aboard the Swarm satellite Bravo via the CHAOS magnetic field model. Additionally, an uncertainty of the magnetic field measurement is derived from unexpected parametric changes of the CDSM in orbit in combination with performance measurements on the ground.

CSES High Precision Magnetometer Data Products and Example Study of an Intense Geomagnetic Storm

“…(2018, 2019), and Pollinger et al. (2020). Here, we only provide a general description of the method presently used (note, indeed, that the method is likely to be improved throughout the mission lifetime).…”

“…For the magnetic field measurement, the instruments thus selects one of the two CPT resonance superpositions N = 2 or N = 3 depending on the angle provided by the fluxgate sensors (Pollinger et al., 2018). In the equatorial region the CPT resonance superposition N = 3 is used while toward the poles the CPT resonance superposition N = 2 is applicable (Pollinger et al., 2020). To better understand the structure of the FGM and CDSM data set, an illustrative example is given in Figure 3.…”

“…The processing involves a calibration model of pre-flight calibration parameters and additional parameters determined during the in-flight calibration process. These parameters, as well as the calibration model and main results, have been described in Cheng et al (2018, and Pollinger et al (2020). Here, we only provide a general description of the method presently used (note, indeed, that the method is likely to be improved throughout the mission lifetime).…”

Satellite Measured Ionospheric Magnetic Field Variations over Natural Hazards Sites

“…The HPM data processing pipeline includes corrections, interference mitigation, synchronisation, and calibration steps for the nominally sampled 60 Hz FGM vectors and 30 Hz CDSM values [3]. The science data cover the latitude range from −65 deg to +65 deg with a temporal resolution of 1 s. The CDSM instrument is a scalar magnetometer based on two-photon spectroscopy and has a noise level of ∼50 pT/sqrt(Hz) at 1 Hz, an accuracy of 0.19 nT (1σ), and a total magnetic field measurement range from 10 3 -10 5 nT [4]. The HPM instruments are parallel aligned, from the satellite surface outwards in the layout FGM1-FGM2-CDSM, and mounted along a 4.7 m nadir pointing boom in order to minimise the spacecraft magnetic disturbances.…”

“…The HPM instruments are parallel aligned, from the satellite surface outwards in the layout FGM1-FGM2-CDSM, and mounted along a 4.7 m nadir pointing boom in order to minimise the spacecraft magnetic disturbances. In-orbit results with a performance analysis have been reported by [5], the CSES data description, and data service are detailed in [6].…”