MPPE / ENA Energetic Neutrals Analyzer

Transcription

1 MPPE / ENA Energetic Neutrals Analyzer M. Wieser, S. Barabash, P. Wurz K. Asamura Y. Saito and the MPPE/ENA team. Swedish Institute of Space Physics University of Bern ISAS/JAXA

2 ENA is a 2 nd generation instrument 2nd Generation ENA (BepiColombo, Mercury) 1st Generation CENA (Chandrayaan-1, Moon) Many lessons learnt at the Moon that are applicable for Mercury! 2

3 How it works (4) Velocity (mass) analysis & detection using a time of flight coincidence system. (1) Ion rejection and angular collimation

4 Calibration Calibrated at University of Bern Mefisto Calibrated using beams of neutral H, He, O (limited Ca) Beam energy 30eV eV Angular scanning through full FoV UV response

5 Calibration data examples Angular response Mass response Nominal FWHM = 25 x 9

6 ENA sensor performance

7 Science targets (I) ENA measures energetic neutral atoms which are generated by: particle precipitation onto Mercury surface generating sputtering and backscattering charge-exchange collisions between energetic ions and background cold neutrals in the magnetosphere Energy of ENA provides information about the generation process at the surface and the source population (plasma) precipitating into the Mercury surface. ENA measurement Energy < 100eV Heavy particles ENA origin: sputtering Energy: 0.1 1keV Hydrogen ENA origin: backscattering Energy: keV Hydrogen ENA origin: charge exchange Energy: keV Heavy particles ENA origin: charge exchange Objective Sputtering source of the exosphere Morphology and dynamics of the precipitation zones from the solar wind and magnetosphere Morphology and dynamics of the precipitation zones from the solar wind and magnetosphere Magnetospheric dynamics and structures Dynamics of planetary ions

8 Science targets (II) The backscattered and sputtered atoms from the Moon surface have been observed, although there are no ENA measurement at the Mercury so far. Backscattered neutral hydrogen of times the solar wind flux (Wieser et al., 2009) Sputtered oxygen flux of times the flux of backscattered hydrogen is detected at the Moon (Vorburger et al., 2014). [Wieser et al., 2009] [Futaana et al., 2012]

9 Basic observation geometry ENA has a fan shaped field of view oriented such that during one spin of MMO almost 4pi angular coverage is obtained.

10 Data products and modes of operation (I) (1) Mass accumulation mode (main science mode): 4 dimensional binned matrix with dimensions Sector x Spin-angle x Energy x Mass every 4 seconds or a multiple of 4 seconds. Maximum number of bins: n(sector) = 8 n(spin-angle) = 32 n(energy) = 8 n(mass) = 128 Number of bins are configurable and depends on telemetry availability. Maximum total number of bins < 8192; e.g. 7 x 16 x 8 x 4 bins.

11 Data products and modes of operation (II) (2) TOF mode (focus on high resolution time of flight data): 2 dimensional matrix with dimensions Energy x Time of flight every 4 seconds or a multiple of 4 seconds e.g. 8 x 1024 bins. (3) Counter mode (focus on system performance): 3 dimensional matrix with dimensions Spin-angle x Energy x Counters every 4 seconds or a multiple of 4 seconds

12 Observation plan (I)

13 Observation plan (II) ENA uses L-mode only. ENA can be ON continuously, except for the period when the instruments should be OFF (for example, survival for severe thermal condition near apohelion). On average, TLM budget seems to allow the following mode in case of continuous measurement: Energy: 8 steps Angular resolution: 16 x 7 bins (22.5deg x 25deg) Mass: 3-4 bins Time resolution: 32-64s The instrument is running with synchronizing to the spacecraft spin pulse. The highest time-resolution is 4s. High resolution mode (for time, mass,..) will be considered near periherm (good condition for sputtered and backscattered particles) and near apoherm (may be good for charge-exchange particles).

14 A quiclook example from SARA/Chandrayaan-1 Time

15 ENA FM