A dataset provided by the European Space Agency

Name EFW electric field double probe instrument
Mission Cluster
URL https://csa.esac.esa.int/csa-web/#search
DOI https://doi.org/10.5270/esa-rp1zebe
Abstract The EFW (Electric Field and Wave) instrument consists of four spherical probes deployed orthogonally on wire booms in the spin plane of each spacecraft. The potential differences between opposing probes, separated by 88 m tip-to-tip, are measured to provide electric field measurements in two directions, thus providing the full electric field vector in the spin plane of the spacecraft. Additionally, the potential differences between each of the probes and the spacecraft are measured, providing an estimate of the spacecraft potential relative to the plasma, which can be used as a proxy for the ambient electron density. In normal mode telemetry the electric field is sampled at 25 samples/s and low-passed filtered at 10 Hz, and in burst mode the electric field is sampled at 450 samples/s and low-pass filtered at 180 Hz. For both modes, the spacecraft potential is sampled at 5 samples/s. For short time intervals, the potential difference between the individual probes and the spacecraft can be sampled at rates up to 9000 samples/s and stored in an internal memory, which can be used to perform inter-probe interferometry to determine phase speeds. Potential differences for the two probe pairs can be sampled at rates up to 18000 samples/s. The output analogue signals from the preamplifiers connected to the spherical probes are also provided to the wave instruments (STAFF, WHISPER and WBD) for analysis of high frequency wave phenomena.
Description EFW scientific datasets for Cluster-1 (similar for all other Cluster spacecraft)

Spacecraft Potential
Dataset ID Dataset content
C1_CP_EFW_L2_P Spacecraft potential (0.2 sec resolution)
C1_CP_EFW_L3_P Spacecraft potential (4 sec resolution)

2D Electric Field measurements
Dataset ID Dataset content
C1_CP_EFW_L2_E 2D Electric field in ISR2, spacecraft frame, full resolution
C1_CP_EFW_L3_E 2D Electric field in ISR2, spacecraft frame, 4 sec resolution

3D Electric Field (assuming E.B=0)
Dataset ID Dataset content
C1_CP_EFW_L2_E3D_GSE 3D Electric field in GSE (E.B=0) (full resolution)
C1_CP_EFW_L3_E3D_GSE 3D Electric field in GSE (E.B=0) (4 sec resolution)
C1_CP_EFW_L2_E3D_INERT 3D Electric field in ISR2 (E.B=0) (full resolution)
C1_CP_EFW_L3_E3D_INERT 3D Electric field in ISR2 (E.B=0) (4 sec resolution)

ExB drift velocity
Dataset ID Dataset content
C1_CP_EFW_L2_V3D_GSE ExB drift velocity in GSE (full resolution)
C1_CP_EFW_L3_V3D_GSE ExB drift velocity in GSE (4 sec resolution)
C1_CP_EFW_L2_V3D_INERT ExB drift velocity in ISR2 (full resolution)
C1_CP_EFW_L3_V3D_INERT ExB drift velocity in ISR2 (4 sec resolution)

Internal burst mode
Dataset ID Dataset content
C1_CP_EFW_L2_PB Spacecraft potential (internal burst)
C1_CP_EFW_L2_EB 2D Electric field in ISR2, spacecraft frame, internal burst
C1_CP_EFW_L2_BB ExB drift velocity in ISR2, internal burst
Publication Gustafsson, G., et al., First results of electric field and density observations by Cluster EFW based on initial months of operation, Ann. Geophys., 19, 1219, 2001; https://doi.org/10.5194/angeo-19-1219-2001
Gustafsson, G., et al., The Electric Field and Wave Experiment for the Cluster Mission, Space Sci. Rev., 79, 137-156, 1997; https://doi.org/10.1007/978-94-011-5666-0_6
Temporal Coverage 2001-02-01 - current
Mission Description Cluster is the first constellation of four scientific spacecraft to study the Earth-Sun connection in three dimensions. Cluster offers unique opportunities to investigate physical processes in near-Earth space. Those processes are essential to study and understand the effects of the Sun on the vast Earth’s environment that is a highly varying system both in time and space. The four Cluster spacecraft in a polar orbit are unique in their ability to obtain a three-dimensional picture of medium and large-scale plasma structures. The varying Cluster spacecraft formation from 3 km to a few tens of thousands kilometres along the orbit enables multi-point local measurements of different regions at different scales that cannot be done with any other space mission.

Escoubet, C.P., et al., The Cluster mission, Ann. Geophys., 19, 1197, 2001; https://doi.org/10.5194/angeo-19-1197-2001
Escoubet, C.P, et al., Cluster - Science and Mission Overview, Space Sci. Rev., 79, 11-32, 1997; https://doi.org/10.1023/A:1004923124586
Creator Contact Mats André, Principal Investigator, Swedish Institute of Space Physics/IRF, Uppsala, Sweden, mats.andre@irfu.se
Publisher And Registrant European Space Agency
Credit Guidelines When publishing any works related to this experiment, please cite the experiment DOI found herein and the Cluster mission DOI (where appropriate).