The Neutral Particle Detector on the Mars and Venus Express missions

The Neutral Particle Detector (NPD) is a new type of instrumentation for energetic neutral atom (ENA) diagnostics. This thesis deals with development of the NPD sensor designed as a part of the plasma and neutral particle packages ASPERA-3 and ASPERA-4 on board Mars Express and Venus Express, the European Space Agency (ESA) satellites to Mars and Venus, respectively. It describes how the NPD sensors were designed, developed, tested and calibrated. It also presents the first scientific results obtained with NPD during its operation at Mars.The NPD package consists of two identical detectors, NPD1 and NPD2. Each detector has a 9o x 90o intrinsic field-of-view divided into three sectors. The ENA detection principle is based on the surface interaction technique. NPD detects ENA differential fluxes within the energy range of 100 eV to 10 keV and is capable of resolving hydrogen and oxygen atoms by time-of-flight (TOF) measurements or pulse height analysis…


1 Energetic neutral atoms in space
1.1 Production mechanisms
1.1.1 Charge exchange
1.1.2 Back-scattering
1.1.3 Sputtering
1.2 Classification
1.3 ENAs at non-magnetized planets
1.3.1 ENA environment of Mars
1.3.2 ENA environment of Venus
2 Energetic neutral atoms detection
2.1 ENA imaging
2.2 Principle functions of ENA instruments
2.3 Deflection systems
2.4 UV rejection
2.5 ENA detection and analysis: Instrument examples
2.5.1 Foils
2.5.2 Surface interaction
2.5.3 High frequency shutters
3 The ASPERA-3 and ASPERA-4 experiments
3.1 Scientific objectives
3.1.1 ASPERA-3
3.1.2 ASPERA-4
3.2 Instrument overview
3.2.1 The Ion Mass Analyzer (IMA)
3.2.2 The Electron Spectrometer (ELS)
3.2.3 The Neutral Particle Imager (NPI)
3.2.4 The Digital Processing Unit (DPU) and the scanner
4 The Neutral Particle Detector (NPD)
4.1 The measurement technique
4.2 NPD mechanical design
4.2.1 Deflector
4.2.2 Start unit
4.2.3 Stop unit
4.2.4 Surfaces
4.3 Electronics
4.4 MCP assembly
4.5 Data formats
I4.6 Instrument level qualification
4.7 NPD response to high energy particles
5 The NPD calibrations
5.1 Introduction
5.1.1 Calibration facilities
5.1.2 Calibration setup
5.2 Theoretical principles
5.2.1 MCP characterization
5.2.2 Beam characterization
5.2.3 Geometrical Factor calculation
5.2.4 Efficiency
5.2.5 Energy resolution
5.2.6 Mass resolution
5.3 Measurement principles
5.3.1 MCP characterization
5.3.2 Angular response measurements
5.3.3 Efficiency
5.3.4 Energy resolution
5.3.5 Mass resolution
5.4 ASPERA-3 / NPD calibration results
5.4.1 Calibration objectives
5.4.2 MCP characterization
5.4.3 Efficiency measurements
5.4.4 Angular response
5.4.5 Geometrical factor
5.4.6 Energy resolution
5.4.7 Mass resolution
5.4.8 Heater and temperature sensor characterization
5.4.9 Dark noise
5.5 ASPERA-4 / NPD calibration results
5.5.1 Calibration objectives
5.5.2 MCP characterization
5.5.3 Efficiency measurements
5.5.4 Angular response
5.5.5 Geometrical factor
5.5.6 Energy resolution
5.5.7 Mass resolution
5.5.8 Heater and temperature sensor characterization
5.5.9 Dark noise
6 Scientific results. The NPD measurements at Mars
6.1 Subsolar ENA jet
6.1.1 Introduction
6.1.2 Observations
6.1.3 Discussion
6.1.4 Summary
6.2 Observations of the Martian subsolar ENA jet oscillations
6.2.1 Introduction
6.2.2 Observation geometry
6.2.3 ENA jet fluctuation observation
6.2.4 Statistics on the intensity variations
6.2.5 Discussion
6.2.6 Summary
6.3 Other results by the ASPERA-3 / NPD
6.3.1 Global response of Martian plasma environment to an interplanetary
structure: From ENA and plasma observations at Mars
6.3.2 The Hydrogen Exospheric Density Profile Measured with ASPERA-3 / NPD
6.3.3 Energetic Hydrogen and Oxygen Atoms Observed on the Nightside of Mars
6.3.4 First ENA observations at Mars: ENA emissions from the Martian up-per atmosphere
6.3.5 Direct Measurements of Energetic Neutral Hydrogen in the Interplan-etary Medium
6.3.6 Energetic Neutral Atoms from the Heliosheath
7 Summary and future prospects
A NPD data processing
A.1 In addition to the NPD operation modes
A.2 Log-compression algorithm
A.3 NPD data display
Glossary of Acronyms

Author: Grigoriev, Alexander

Source: Umea University

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