Satellite Drag Flap Atmospheric Density Measurement
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Solution Overview
Problem
Current methods for accurately estimating atmospheric density in low Earth orbit (LEO) are hindered by the need for high-precision, expensive instrumentation and ground-based systems, which increase complexity and cost, and are unable to provide real-time, high-resolution measurements.
Innovation Solution
A satellite, SPATULA, is designed to measure atmospheric density by deploying a drag flap that subjects the satellite to a significant external torque, allowing for in-situ estimation using commercially available sensors and processing, thereby reducing costs and system complexity while enabling real-time data acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional high-precision instrumentation and ground-based systems are used to estimate atmospheric density, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the atmospheric density measurement capability from complex ground-based tracking systems and conventional satellite instrumentation, implementing it instead through the satellite's native attitude control system. By utilizing the reaction wheel's angular momentum measurements and the drag flap's aerodynamic torque, the system obtains density estimates without requiring specialized high-precision sensors or ground infrastructure.
Solution Approach 2:
The satellite's attitude control system serves dual purposes: maintaining orbital attitude and measuring atmospheric density. The reaction wheel, already necessary for attitude control, provides angular momentum data that, when combined with drag torque measurements from the deployable flap, enables self-contained atmospheric density estimation without external ground-based systems.
2Measurement precision
If conventional high-precision instrumentation is used to estimate atmospheric density, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent makes the attitude control system multi-functional by having it perform both attitude maintenance and atmospheric density measurement. The reaction wheel serves dual purposes: controlling satellite orientation and providing angular momentum data for density calculations. This eliminates the need for separate expensive measurement instruments.
Solution Approach 2:
The patent employs commercially available, low-cost sensors and standard reaction wheels instead of expensive specialized instrumentation. The drag flap uses simple deployable structures with commercially available materials, achieving accurate density measurements through clever use of basic components rather than high-cost specialized equipment.
3Measurement precision
If conventional ground-based systems are used to estimate atmospheric density, then measurement precision is improved, but the system requires ground infrastructure increasing device complexity
Solution Approach 1:
The patent removes the dependency on ground-based tracking systems by extracting the measurement capability entirely to the satellite platform. The atmospheric density is measured in-situ using the satellite's own sensors and actuators, eliminating the need for external ground infrastructure while maintaining measurement accuracy.
Solution Approach 2:
The satellite becomes self-sufficient for atmospheric density measurement by using its own attitude control system and onboard sensors. The reaction wheel and drag flap combination enables the satellite to measure density independently without requiring ground-based tracking or processing infrastructure.
4Measurement precision
If conventional approaches are used to estimate atmospheric density, then accuracy is improved, but real-time measurement capability is reduced
Solution Approach 1:
The patent enables continuous real-time atmospheric density measurement by continuously monitoring the reaction wheel's angular momentum and the drag flap's aerodynamic torque during orbital operations. The attitude control system continuously adjusts to maintain orientation while simultaneously providing a continuous stream of density data at the orbital measurement bandwidth.
Solution Approach 2:
The system uses feedback from the reaction wheel's angular momentum measurements and drag torque data to continuously update atmospheric density estimates in real-time. The attitude control system's continuous adjustment based on these measurements provides ongoing density information at the full orbital measurement rate.
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
The SPATULA satellite achieves accurate and real-time atmospheric density estimates with a root mean square error ranging from 1×10−13 kg/m3 to 2×10−12 kg/m3 and a bandwidth of 0.03 min−1 to 1 min−1, comparable to conventional approaches but with a smaller, cheaper design.
Implementation Method 1
a drag flap coupled to the bus where the drag flap is configured to deploy during an orbit to subject the satellite to a drag torque about a first axis passing through the bus of the satellite
Implementation Method 2
The bus may include a reaction wheel to measure a reaction wheel angular velocity output
Implementation Method 3
a gyroscope to measure a gyroscope output
Implementation Method 4
a star tracker to measure a star tracker output
Implementation Method 5
a global position system (GPS) receiver to measure a position and a velocity of the satellite
Data Source
AI summary
A satellite in orbit around a planetary body includes a bus and a drag flap coupled to the bus. The drag flap is used to increase the drag torque applied to the satellite. The bus may house sensors and actuators, such as a star tracker, a gyroscope, a reaction wheel, and a global position system (GPS) receiver to monitor the attitude of the satellite in response to the applied drag torque. The measurements from the sensors and actuators may be used to determine the drag torque applied to the satellite. An estimate of the atmospheric density may be then be determined based on the drag torque. Compared to conventional approaches, the satellite and methods described herein estimates the atmospheric density at comparable, if not better, resolution and bandwidth. The atmospheric density estimates may also be acquired in real-time using a cheaper, lighter, and smaller satellite.