Multi-needle Langmuir Probe for Ionospheric Electron Density
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Solution Overview
Problem
Existing Langmuir probe methods for measuring ionospheric electron density suffer from low accuracy and limited resolution due to uncertainties in determining spacecraft potential and electron temperature, particularly when using spherical fixed-bias probes, and require time-consuming voltage sweeps.
Innovation Solution
A multi-needle Langmuir probe system with cylindrical probes biased to different potentials allows for simultaneous measurement of electron density without needing to know the electron temperature or spacecraft potential, using the difference in collected currents and voltages to calculate the platform potential, which is independent of exact electron temperature values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spherical fixed-bias Langmuir probe is used to measure electron density, then the measurement process is simplified, but the accuracy of electron density determination deteriorates due to dependence on electron temperature and spacecraft potential uncertainties
Solution Approach 1:
The single probe measurement is segmented into multiple probes (at least two) biased at different potentials. Each probe measures current at a specific bias voltage, and by comparing measurements across multiple probes operating in the electron saturation region, the system eliminates dependence on spacecraft potential and electron temperature uncertainties, thereby resolving the accuracy problem while maintaining operational simplicity
Solution Approach 2:
The invention changes the bias voltage parameter across multiple probes to different values (at least two different biases in the electron saturation region). This parameter variation allows the system to measure current at different potentials and use the differences to calculate electron density independently of spacecraft potential and electron temperature, thus improving measurement precision
2Loss of information
If a voltage-sweep mode is used with Langmuir probe to obtain current-voltage characteristics, then plasma parameters can be extracted, but the measurement time increases and temporal resolution is limited
Solution Approach 1:
Multiple probes are pre-biased at different voltages before measurement begins, with each probe already positioned in the electron saturation region. This preliminary configuration eliminates the need for time-consuming voltage sweeps, as all necessary measurements can be taken simultaneously at the pre-set bias points, thereby reducing measurement time while still obtaining sufficient plasma parameter information
Solution Approach 2:
The system maintains continuous measurement capability by having multiple probes simultaneously operating at different bias voltages. This continuous parallel measurement approach replaces the sequential voltage-sweep method, allowing plasma parameters to be extracted without interrupting the measurement flow, thus improving temporal resolution
3Productivity
If multi-needle Langmuir probe with multiple fixed biases is used to determine absolute electron density, then time resolution and spatial resolution are improved, but device complexity increases
Solution Approach 1:
The probe system is segmented into multiple needle probes (at least two), each independently biased at a different voltage in the electron saturation region. This segmentation enables simultaneous measurements at multiple potentials, achieving high time and spatial resolution while keeping each individual probe element simple in structure
Solution Approach 2:
The multi-needle probe system performs multiple functions simultaneously: each probe measures current at a different bias voltage, enabling both electron density determination and spacecraft potential measurement. This multi-functionality is achieved through a relatively simple extension of the basic probe structure, minimizing the increase in device complexity
4Loss of information
If swept Langmuir probe is used for ionospheric electron density measurement, then plasma parameters can be extracted, but measurement accuracy deteriorates due to uncertainties in spacecraft potential and electron temperature determination
Solution Approach 1:
The invention changes the bias voltage parameter to at least two different values in the electron saturation region across multiple probes. By measuring current at these different biases and using the differences, the system eliminates the need to know spacecraft potential and electron temperature, thereby improving electron density measurement accuracy while still extracting plasma parameters
Solution Approach 2:
The multiple probes biased at different voltages act as intermediaries that measure current at various potentials. These intermediate measurements serve as mediators to eliminate the direct dependence on uncertain parameters (spacecraft potential and electron temperature), allowing accurate electron density determination through the relationship between current differences and voltage differences
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides high-time and high-spatial resolution electron density measurements, is immune to payload charging effects, and allows for real-time determination of platform potential, enabling accurate operation of other spacecraft devices and potential control.
Implementation Method 1
The basic principle of the Langmuir probe is to expose a conductor to the plasma, bias it relative to some reference potential (the platform potential) and measure the collected current
Implementation Method 2
A body in a plasma (having a plasma potential Vp) will experience a current as it is hit by the electrons and ions of the plasma
Implementation Method 3
Potentials well above the spacecraft potential can be used to ensure that the probes are operating in the saturation region where absolute electron density measurements can be taken
Data Source
AI summary
A method of determining payload potential may include the steps of receiving data on a first bias voltage and a resulting first collected current of a first needle of a multi-needle Langmuir probe, receiving data on a second bias voltage and a resulting second collected current of a second needle of the multi-needle Langmuir probe, assigning a value for the electron temperature in which the multi-needle Langmuir probe was operating, and using the current and voltage data, the assigned electron temperature value and Langmuir probe theory to calculate the platform potential of the multi-needle Langmuir probe.