A Space-Based Instrument Suite to Characterize Small Scale Plasma Turbulence in the F Region IonosphereL. Habash Krause1, C. L. Enloe1, and F. A. Herrero2

(1) United Stated Sir Force Academy, Department of Physics(2) NASA Goddard Space Flight Center

Presentation Overview

Motivation: Support Ionospheric Radio Science ResearchPlasma Local Anomalous Noise Environment (PLANE) SensorFlat Plasma Spectrometer (FLAPS) SensorFalconSAT-3 MissionFLAPSPLANE

Experiment MotivationUnstable plasma within the Earths low latitude ionosphere results in irregularities in refractive indexScintillations occur when radio waves pass through a turbulent ionosphere, reducing signal qualityScintillations disrupt signals important for communications/navigation systems.

Power in the noise approaches that of the signal for both VHF comm and L-band nav signals, especially in low latitudesPlasma bubbles most frequently observed near the magnetic equatorExperiment Motivation

Plasma depletions tend to form in the bottomside ionosphere, and if they upwell into the topside, they are called plasma bubbles. Initial onset due to Rayleigh Taylor InstabilityNon-Linear Development: Model Results (Hysell et al.)Linear Development: Schematic (e.g., Chen) Realistic description more complicated due to non-linear and kinetic effects. Results from non-linear fluid treatment provide insight into bubble development the effects of plasma density gradient and collisions with the neutral atmosphereInstability Mechanisms

Influence of kinetic effects on small scale structure (Winske)Instability MechanismsInertial Ion Length (c/wpi)g Simulations have shown that the Rayleigh Taylor Instability results in smaller-scale structures when plasma is treated as a massless electron/kinetic ion hybrid when compared to its fluid counterpart.

In situ measurements of ionospheric plasma spectra, differential in energy, provides information on the role of Non-Maxwellian plasma distributions on plasma bubble instigation/evolution.

In Situ Measurement of Ionospheric Plasma Turbulence: ChallengesSpacecraft-plasma interactions may perturb the environment local to the spacecraftAn accurate in situ measurement of the ambient environment cannot be made by a probe that disrupts the plasma in its vicinity.Quiescent?Turbulent?Spacecraft-induced turbulence can affect the plasma environment in the ram and wake.Space-borne plasma instrumentscan only see the local environmentof the spacecraft.

Plasma Local Anomalous Noise Environment (PLANE)Objective: To identify/characterizeturbulence in the plasma environmentoriginating in the frame of reference ofthe spacecraft distinct from global variations.Description: The PLANE instrumentwill use a pair of planar retardingpotential analyzers, linked by a feedbackloop, to distinguish ambient ions fromthose co-moving with the spacecraft.

Plasma Local Anomalous Noise Environment (PLANE)Mass- the mass of the RPA assembly: 0.2 kg.PIB Mass- the mass of the PIB is 0.2 kg.1.5 W Average power +5 V Nominal operating voltageDiscrete analog and digital I/ORequires S/C management of operation.

Flat Plasma Spectrometer (FLAPS)Advances in miniaturization technology have enabled significantly smaller plasma spectrometersFLAPS measures charged particle distributions differential in energy and angle. Initial concept shown here.FLAPS final configuration has five sensor heads, each with a unique look direction

SIMION Trajectory SimulationsParallel Plate Analyzer and Analyzer Constant: Analyzer constant varies as (L/D)2. The analyzer constant P = 25 for the L/D = 10 shown here.

f0.50000*1.33330.550000.982630.600000.750000.650000.580540.700000.449200.750000.342860.800000.253970.850000.177860.900000.111460.950000.052668

FLAPS SIMION Model ResultsSIMION model runs used to investigate theoretical expression for plate factor for different plate geometriesPlate factor P quantifies the ratio of charged particle voltage to plate voltage, related to plate geometry as:P= 6Equation for P assumes uniform electric fieldAt P=6, O+ passes through at 0.1825V. Theoretical voltage is 0.1667 V

FLAPS Description5 Ion SpectrometersMass: ~ 400 gSize: 9 cm 9 cm 7 cm Mounting bracket: 10.5 cm outer edgeInternal microcontroller, EPROM, FPGA TLM Connection

Physical Parameters (including electronics)Ion Spectra, differential in energy and angle0.05 eV 16 eV, 4% DE/E5 discrete angles (1 FOV each element)Key Characteristics:Assess relationship between non-thermalized plasma and small scale plasma bubblesPrimary Objective

The energy distribution at the peak of the angular distribution is simulated here for a realistic upper atmosphere.Log Plot Major and Minor ConstituentsLinear Plot O, N2k (eV)k (eV)Simulated Response

FalconSAT-3 Mission OverviewMass: ~ 100 lb (~50 kg)Size: 0.46 m (18 in) cubePayloads:Flat Plasma Spectrometer (FLAPS)Plasma Local Anomalous Noise Environment (PLANE)Micro Propulsion Attitude Control System (MPACS)Orbit:Altitude: 560 kmInclination: 35 degLaunch Vehicle: EELV/ESPADelivery: 3Q CY2006Launch: 4Q CY2006Operations: USAFA Ground Station

Questions?

Back-up Slides

FLAPS Energy SelectorSIMION 7.0 used to model charged particle trajectories in FLAPS energy selectorModeling Objectives:Verify instrument conceptUnderstand instrument response before functional testingDetermine transparency of instrumentVerify theoretical expression for plate factor

What are the optics on this? John from Amptek is curious about it. What are the materials?What are the optics on this? John from Amptek is curious about it. What are the materials?What are the optics on this? John from Amptek is curious about it. What are the materials?