SERENA (Search for Exospheric Refilling and Emitted Natural Abundances Experiment)

The SERENA instrument suite (Search for Exospheric Refilling and Emitted Natural Abundances) will study in-situ the composition, the vertical structure and the source of the deposit processes of the exosphere of Mercury.

The SERENA instrument suite (Search for Exospheric Refilling and Emitted Natural Abundances) is composed of the following instruments:

ELENA (Emitted Low-Energy Neutral Atoms): detection of neutral particles

MIPA (Miniature Ion Precipitation analyzer): measure of magnetospheric and solar ions fluxes

PICAM (Planetary Ion Camera): imaging mass spectrometer for planetary origin ions

STROFIO (Start From A Rotating Field Mass Spectrometer) : thermal and low energy neutral particles spectrometer.

The SERENA consortium is led by the Principal Investigator S. Orsini from IFSI, Rome, Italy.

BepiColombo MPO Planetary Ion Camera (PICAM)

PICAM is one of the four sensors belonging to the SERENA instrument suite. (http://lxtosh.ifsi.rm.cnr.it/SZ/BCserena/). Since MPS is only involved in the PICAM sensor we describe details of that sensor only.

PICAM Scientific Objectives

One of the major questions to be investigated by the BepiColombo mission is the role and efficiency of the surface of Mercury as a source of exospheric neutrals and magnetospheric ions.

By measuring ions at relatively low energies, i.e. from thermals up to a few keV, PICAM will offer the possibility to get information on the soil composition, on the rate of neutral escape from the surface, on the efficiency of the various source locations as well as on the physical processes that act to eject the neutrals from the surface. The main objectives of PICAM are listed as follows:

Processes by which Neutrals are Ejected from the Surface of Mercury
Large-Scale Chemical Composition of the Hermean Soil
Amount of Atoms Ejected from the Surface of Mercury and to Measure the Flux of Planetary Ions Returning to the Surface
Existence of an Ionosphere and the Convection of Plasma in the Hermean Environment
Structure of the Hermean Magnetosphere and its Interactions with the Solar Wind
Characteristics of the Solar Wind Flow Near the Planet

Technical Data

The PICAM (Planetary Ion CAMera) ion mass spectrometer operates as an all-sky camera for charged particles allowing the determination of the velocity distribution and mass spectrum for ions over a full 2π field of view (FOV), from thermal up to ~3 keV energies and in a mass range extending up to ~132 amu (Xenon). An instantaneous 2π FOV coupled with this mass range and a mass resolution better than ~100 result in a superior performance.

Energy range	1 eV - 3 keV
Energy resolution ΔE/E	10-50% (controllable)
Viewing angle	2.17 π
Angular resolution	6 – 10 deg (controllable)
Mass resolution m/Δm	>100
Optimal temporal resolution	10 sec
Geometric factor G	0.021 cm2 ster
Instrument total mass	1343g
Power consumption	3.1-7.0 W
Data rate	0.5-3.0 kbit/s

Electronic block diagram

Instrument Operation

Since launch of Bepi Colombo in October 2018 the SERENA instruments were operated and tested successfully. The first scientific measurements with the insruments were successfully obtained during the spacecraft's Earth flyby in April 2020 in the region of the Earth's magnetosphere. The next science measurements with the instruments are planned for Bepi Colombo's Venus flybys on 15 October 2020 and 11 August 2021.

Further information about the SERENA experiment can be found in:

Orsini, S. et al., SERENA: A suite of four instruments (ELENA, STROFIO, PICAM and MIPA) on board BepiColombo-MPO for particle detection in the Hermean environment, Planetary and Space Science, 58, 166-181, 2010

Orsini, S. et al., SERENA: particle instrument suite for Sun-Mercury interaction on board BepiColombo, Space Science Reviews, 2020, submitted