A. Milillo, S. Orsini and A. Mura (INAF/Institute of Space Astrophysics and Planetology) And the SERENA Team

SERENA - HEWG meeting, Rome, May, 2013 Hermean environment (from Milillo et al., SSR, 2005)

SERENA - HEWG meeting, Rome, May, 2013 SERENA Search for Exospheric Refilling and Emitted Natural Abundances NPA: ELENA investigates the Hermean escaping neutral gas (strongly linked to its surface), and the processes responsible of such a population. STROFIO investigates the exospheric gas composition. IS: PICAM investigates the exo-ionosphere extension and composition. MIPA investigates the plasma precipitation toward the surface of Mercury.

SERENA vs Hermean environment SERENA - HEWG meeting, Rome, May, 2013

1.Chemical and elemental composition of the exosphere 2.Neutral gas density asymmetries 3.Exo-ionosphere composition 4.Exo-ionosphere spatial and energy distribution 5.Plasma precipitation rate 6.Surface emission rate and release processes 7.Particle loss rate from Mercury’s environment Remote sensing of the surface composition Magnetosphere structure and dynamics Planetary response to SW variations ENA imaging applications for comparative solar- planetary relationship) Heavy ion sputtering products Primary scientific objectives of SERENA. Support to other Bepi experiments. Challenging goals. SERENA scientific objectives SERENA - HEWG meeting, Rome, May, 2013

ELENA is a Time-of-Flight neutral atom detector which provides direction and velocity of neutral particles at energy >10 eV. ELENA SERENA - HEWG meeting, Rome, May, 2013

ELENA Scientific Operations SERENA-ELENA will detect released particles from the surface of the planet ( Orsini et al ) providing angular distribution and ToF spectra.

ELENA surface scanning SERENA - HEWG meeting, Rome, May, 2013 This measurement correlated with the observation of ion flux to the surface seen by MPO/SERENA-MIPA will provide the surface efficiency in particle releasing via ion sputtering and back-scattering The s/c motion will allow a mapping of released particles from the surface of the planet (Orsini et al. 2008).

Signal simulation for different sources BackscatteringCharge exchangeIon sputtering SERENA - HEWG meeting, Rome, May, 2013

We have simulated the ELENA coverage of surface ion interaction by using different precipitation referenced models and cases: Kallio et al., 2003: Hybrid model Mura et al., 2005: Luhman model Massetti et al., 2007: Toffoletto- Hill model ELENA estimated outcomes

South IMF case Extreme event case Parker IMF case Kallio et al.

Precipitation derived after Schleicher et al Observations Mura et al. South IMF case

IMF (-20, 0, -5) aphelion Massetti et al. IMF (-20, 0, -5) perihelion Extreme case IMF (-45, 16, -20) Nsw 120 cm -3

Mura et al., 2005 Mura et al., 2008 Kallio et al., 2003 Massetti et al., 2007 SERENA - HEWG meeting, Rome, May, 2013 Estimated ENA distributions

ELENA coverage for a whole Mercury season with 1.a hypothetical uniform flux 2.uniform flux inside cusp projection

SERENA - HEWG meeting, Rome, May, 2013 ELENA LT Coverage: Summer Autumn

SERENA - HEWG meeting, Rome, May, 2013 ELENA LT Coverage: Winter Spring

SERENA - HEWG meeting, Rome, May, 2013 ELENA Geographic Coverage: Summer Autumn

SERENA - HEWG meeting, Rome, May, 2013 ELENA Geographic Coverage: Winter Spring

2. uniform flux inside cusp projection ELENA LT Coverage: Summer Autumn

ELENA Coverage: Winter Spring

ELENA Geographic Coverage: Summer Autumn

ELENA Geographic Coverage: Winter Spring

SERENA-PDR, Rome, 2-3 December, 2008 Global charge-exchange ENA imaging from two vantage points MMO-ENA MPO-ELENA MPO close to the apoherm in the nightside

Summary of ELENA primary objectives SERENA - HEWG meeting, Rome, May, 2013

STROFIO is a novel mass spectrograph that determines particle mass-per-charge (m/q) by a time-of-flight (ToF) technique. STROFIO concept SERENA - HEWG meeting, Rome, May, 2013

STROFIO measures the in-situ neutral particles with low energies (exospheric particles) with good mass resolution. For details see Desai presentation…. Spectrum of H 2, He, Ne, N 2, Ar, O 2, CO 2 STROFIO Scientific Operations

Summary of STROFIO primary objectives SERENA - HEWG meeting, Rome, May, 2013

MIPA (Miniature Ion Precipitation Analyser) is a simple ion mass analyser optimised to provide monitoring of the precipitating ions and to measure the main groups of ions present in the magnetosphere. To obtain a full measurement, a scanning in energy and in angle will be operated within a duty cycle less than 1 minute. MIPA scientific operations SERENA - HEWG meeting, Rome, May, 2013

2pi coverage total coverage sample pixel (1 of 24) Field of view of one MIPA pixel

SERENA - HEWG meeting, Rome, May, 2013 MIPA Scientific Operations

SERENA - HEWG meeting, Rome, May, 2013 PA distribution low-latitudesPA distribution high-latitudes precipitating (PA 90°) Example: IMF (–20, 0, –5) nT at aphelion SW inside the Mercury’s Magnetosphere

Summary of MIPA primary objectives SERENA - HEWG meeting, Rome, May, 2013

PICAM is optimized to measure low energy ions. Its main objective is to detect and characterize the exo-ionosphere and thereby complete the analysis of the composition of ions released from the surface/exosphere and ionized in the Hermean environment. To obtain a full measurement, a scanning in energy will be operated within a duty cycle about 1 minute PICAM concept SERENA - HEWG meeting, Rome, May, 2013

PICAM pixel SERENA - HEWG meeting, Rome, May, 2013 PICAM was illuminated by an N 2 + ion beam at 1 keV, coming from 50° elevation from the top right azimuth.

SERENA - HEWG meeting, Rome, May, 2013 PICAM mass analysis PICAM mass resolution is M/ΔM > 50 Simulations: M=39 and 40 AMU.

SERENA - HEWG meeting, Rome, May, 2013 Na + density distribution (in Log 10 of Na + /cm 3 at TAA=150° in the equatorial plane) for average and idealysed solar wind conditions. Exo-ionosphere characterization

Summary of PICAM primary objectives SERENA - HEWG meeting, Rome, May, 2013

SERENA operations vs phase

SERENA-HEWG meeting, Santa Fe, May, 2008 SERENA objectives 1 and 2: STROFIO SERENA objectives 3 and 4: PICAM SERENA objective 5: MIPA SERENA objective 6: ELENA, MIPA and STROFIO SERENA objective 7: ELENA Winter and Summer dayside SERENA objectives

SERENA-HEWG meeting, Santa Fe, May, 2008 SERENA objectives 1 and 2: STROFIO SERENA objectives 3 and 4: PICAM SERENA objective 6: STROFIO SERENA objective 7: ELENA and PICAM Winter nightside SERENA objectives

SERENA-HEWG meeting, Santa Fe, May, 2008 SERENA objectives 1 and 2: STROFIO SERENA objectives 3 and 4: PICAM SERENA objective 6d: STROFIO Summer nightside SERENA objectives In the light of new MESSENGER results, plasma precipitation and ion sputtering can efficiently occur also in the night side, hence in the learning phase also ELENA should be operated

SERENA-HEWG meeting, Santa Fe, May, 2008 SERENA objectives 1 and 2: STROFIO SERENA objectives 3 and 4: PICAM SERENA objective 5: MIPA SERENA objective 6: ELENA, MIPA and STROFIO SERENA objective 7: ELENA and PICAM at periherm Autumn and Spring SERENA objectives

MPO Orbit phases A LB C LD EB ED

45 SERENA timeline SERENA timeline has been developed and discussed within the team and ESA (SERENA TL meeting, Sept. 2011). “Late” and “Early” B and D phases are introduced.

SERENA - HEWG meeting, Rome, May, 2013 Thank you

SERENA - HEWG meeting, Rome, May, 2013 Energetic Neutrals Planetary Surface EXOSPHERE INTERPLANETARY SPACE Solar wind Low-Energy Neutrals Magnetospheric Ions Energetic Neutrals MPO/SERENA MPO/PHEBUSMMO/MPPEMPO/MIXS MPO/SimbioSys MAGNETOSPHERE MPO/SIXS MPO/SERENA MPO/MERTISMMO/MSASI Electromagetic fields MPO/MAG MMO/MGF MMO/MDMMMO/PWI

SERENA-HEWG meeting, Santa Fe, May, 2008 Dayside coordinated measurements 1 MPPE SERENA SIXS MGF MAG PWI Joint measurements of MPPE-MEA and MIA, MGF and PWI, on the MMO spacecraft and SIXS, SERENA-MIPA and PICAM and MAG on the MPO spacecraft, will confirm plasma penetration inside the magnetosphere.

SERENA-HEWG meeting, Santa Fe, May, 2008 Exospheric coordinated measurements MSASI PHEBUS The exospheric configuration and composition will be measured by MPO/PHEBUS, and MMO/MSASI and MPO/SERENA-STROFIO in terms of column density, composition and profile variations. STROFIO, in particular, will be the only instrument able to determine the night side exospheric composition. SERENA

SERENA-HEWG meeting, Santa Fe, May, 2008 Dayside coordinated measurements 2 SERENA MIXS PHEBUS Together with plasma penetration measurements described above, other dedicated instruments will observe the response of the planet in term of radiation and particles release. MIXS will observe the X-Ray emission of planetary aurorae while SERENA-ELENA will monitor the emission of neutral atoms. SERENA-STROFIO and PHEBUS and MSASI will observe the exospheric response of Mercury in terms of column density, composition and profile variations. MSASI

SERENA - HEWG meeting, Rome, May, 2013 Scientific requirements of SERENA- other MPO instruments joint investigations

SERENA - HEWG meeting, Rome, May, 2013 Scientific requirements of SERENA- other MPO instruments joint investigations (2)

SERENA - HEWG meeting, Rome, May, 2013 Remote sensing the surface properties from exospheric measurements Due to the strong link between the exosphere and the surface it is possible by measuring neutrals and ions at relatively low altitudes to obtain information regarding the composition of the regolith upper surface. However, some release processes are non-stoichiometric and involve only selected species. Eventually, to be able to successfully infer a source composition from exospheric measurements, it is really important to know the mechanism of ejection and the properties of the particular surface.

SERENA - HEWG meeting, Rome, May, 2013 Surface signature in the environment nearby the surface: MPO/SERENA Planetary Surface MPO/PHEBUSMPO/MIXS EXOSPHERE MPO/SimbioSys MMO/MSASI MPO/MERTIS The surface elemental abundances mapped by MIXS, the surface mineralogy mapped by MERTIS and the surface cratering mapped by SIMBIO-SYS will allow released exospheric atoms to be related to the surface constituents. MMO/MDM

The ion flux arrival angle and energy are analysed by an electrostatic deflector. The ions exiting the energy analyzer are post accelerated up to 1 keV energy by a voltage applied to a ToF cell. Inside the cell, ions hit START and STOP surfaces producing secondary electrons recorded by two ceramic channel electron multipliers giving respective timing, hence the ion velocity and, in combination with known energy, the mass. MIPA concept SERENA - HEWG meeting, Rome, May, 2013

Field of view of one MIPA pixel SERENA - HEWG meeting, Rome, May, 2013 SimulatedMeasured

SERENA - HEWG meeting, Rome, May, 2013 Energy resolution

Ions enter through an annular slit. After reflection on an ellipsoidal ion mirror the 90° polar angle distribution is folded into a polar angular range. Here the ions pass a modulated wire gate which defines discrete packets of ions for analysis of the time-of- flight. Particles pass through a narrow, toroidal analyzer and are reflected by a planar mirror. After they enter the TOF and imaging section, until they impact on the MCP. PICAM concept SERENA - HEWG meeting, Rome, May, 2013 The PICAM ion optics is based on the principle of a modified pinhole camera. The sensor is symmetric along the Z-axis and its FOV is a hemisphere centred along this axis.

SERENA Search for Exospheric Refilling and Emitted Natural Abundances Neutral and Ionized Particle Detectors for Hermean Environment Investigations S. Orsini (PI), S. Livi (CoPI-STROFIO), K. Torkar (CoPI-PICAM), S. Barabash (CoPI-MIPA) A. Milillo (PI Dep., Sci. Coord.), P. Wurz (Sci. Coord.), A. Olivieri (ASI PM), E. Kallio (SGS), and the SERENA TEAM ELENA: Emitted Low Energy Neutral Atoms Neutral particle emission form Mercury’s surface STROFIO: Exososphere Mass Spectrometer Exospheric density and composition PICAM: Planetary Ion CAMera Planetary ions composition and distribution MIPA:Miniature Ion Precipitation Analyzer Solar wind ion precipitation INDUSTRY: OHB-CGS (Milano) & AMDL (Roma)