No abstract

The ESA-JAXA BepiColombo mission to Mercury will provide simultaneous measurements from two spacecraft, offering an unprecedented opportunity to investigate magnetospheric and exospheric particle dynamics at Mercury as well as their interactions with solar wind, solar radiation, and interplanetary dust. The particle instrument suite SERENA (Search for Exospheric Refilling and Emitted Natural Abundances) is flying in space on-board the BepiColombo Mercury Planetary Orbiter (MPO) and is the only instrument for ion and neutral particle detection aboard the MPO. It comprises four independent sensors: ELENA for neutral particle flow detection, Strofio for neutral gas detection, PICAM for planetary ions observations, and MIPA, mostly for solar wind ion measurements. SERENA is managed by a System Control Unit located inside the ELENA box. In the present paper the scientific goals of this suite are described, and then the four units are detailed, as well as their major features and calibration results. Finally, the SERENA operational activities are shown during the orbital path around Mercury, with also some reference to the activities planned during the long cruise phase.

[1] A 3-D, kinematic, solar wind model (Hakamada-Akasofu-Fry version 2 (HAFv.2)) is used to predict interplanetary shock arrivals at Venus, Earth, and Mars during a sequence of significant solar events that occurred in the interval 5-14 December 2006. Mars and Venus were on the opposite side of the Sun from Earth during this period. The shocks from the first two east limb events (5 and 6 December) were predicted to interact to form a single disturbance before reaching Earth and Venus. A single shock was indeed recorded at Earth only about 3 h earlier than had been predicted. The composite shock was predicted by HAFv.2 to arrive at Venus on 8 December at $0500 UT. Solar energetic particles (SEPs) were detected in Venus Express Analyzer of Space Plasmas and Energetic Atoms-4 data for some 3 d (from <0530 UT on 6 December), and an energetic storm particle (ESP) event signaled the arrival of a single shock wave at 0900 UT on 7 December. SEPs were correspondingly recorded at Mars. However, the eastern flank of the composite shock was predicted to decay to an MHD wave prior to reaching this location, and no shock signature was observed in the available data. The shocks generated in association with two flare events that occurred closer to the West Limb on 13 and 14 December were predicted by HAFv.2 to remain separate when they arrived at Earth but to combine thereafter before reaching Mars. Each was expected to decay to MHD waves before reaching Venus, which was at that time located behind the Sun. Separated shocks were observed to arrive at L1 (ACE) only 8 min earlier than and 5.3 h later than their predicted times. The western flank of the combined shocks was predicted to arrive at Mars early on 20 December 2006. An indication of the passage of this shock was provided by a signature of ion heating in Mars Express IMA (ion mass-resolving analyzer) data from <0424 UT on 20 December. The predictions of the HAFv.2 model for Earth were each well within the ±11 h. RMS error earlier found, on the basis of significant statistics, to apply at 1 AU during the rise and maximum phases of solar cycle 23. Overall, the model is demonstrated to be capable of predicting the effects produced by shocks and by the background solar wind at Venus, Earth, and Mars. It is suggested that the continuous presence of solar wind monitors (plasma and interplanetary magnetic field observations) at ''benchmark planets'' can constitute a necessary and valuable component of ongoing and future space weather programs for the validation of solar wind models such as HAFv.2.