The Analyser of Space Plasmas and Energetic Atoms (ASPERA-4) for the Venus Express mission
Coates, A. J.; Kallio, E.; Fedorov, A.; Säles, T.; Barabash, S.; Lundin, R.; Holmström, M.; Gunell, H.; Brinkfeldt, K.; Andersson, H.; Yamauchi, M.; Grigoriev, A.; Sauvaud, J. -A.; Thocaven, J. -J.; Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Linder, D. R.; Kataria, D. O.; Kozyra, J.; Roelof, E.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp, N.; Woch, J.; Asamura, K.; Russell, C. T.; Zhang, T. L.; Szego, K.; Baumjohann, W.; Luhmann, J.; Mazelle, C.; McKenna-Lawlor, S.; Koskinen, Hannu E. J.; Riihela, P.; Brandt, P.; Scherrer, J.; Mura, M.; Milillo, M.
Sweden, France, Japan, Austria, United Kingdom, United States, Finland, Germany, Ireland, Italy, Hungary, Switzerland
Abstract
The general scientific objective of the ASPERA-4 (Analyser of Space Plasmas and Energetic Atoms) experiment is to study the solar wind-atmosphere interaction and characterise the plasma and neutral gas environment in the near-Venus space through energetic neutral atom (ENA) imaging and local charged particle measurements. The studies to be performed address the fundamental question: How strongly do the interplanetary plasma and electromagnetic fields affect the Venusian atmosphere? The ASPERA-4 instrument comprises four sensors; two ENA sensors, electron and ion spectrometers. The neutral particle imager (NPI) provides measurements of the integral ENA flux (0.1-60 keV) with no mass and energy resolution but relatively high angular resolution. The neutral particle detector (NPD) provides measurements of the ENA flux, resolving velocity (0.1-10 keV) and mass (H and O) with a coarse angular resolution. The electron spectrometer (ELS) is a standard top-hat electrostatic analyser in a very compact design. These three sensors are located on a scanning platform providing a 4π coverage. The instrument also contains an ion mass composition sensor, IMA (ion mass analyser). Mechanically, IMA is a separate unit electrically connected with the ASPERA-4 main unit. IMA provides ion measurements in the energy range 0.01-36 keV/ q for the main ion components H+, He++, He+, and the ion group with M/q20-80amu/q.