Ground-Based Orbital Tracking With Chopper-Modulated Signal Detection
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Solution Overview
Problem
Accurate tracking of small, dim orbital debris is challenging due to low signal return and high background noise, especially during the short sunlit time window before eclipse, which degrades the signal-to-noise ratio (SNR) and introduces angular errors from factors like thermal changes and atmospheric deflection.
Innovation Solution
A ground-based telescope system with a detector tracks the orbital object while integrating its signal to improve SNR, uses celestial background objects for angular correction, and employs high frame rates or a rotating chopper wheel to mitigate streaking, combined with data processing techniques like shift-and-add and image correlation to determine accurate orbital parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the telescope tracks the orbital object to improve SNR, then the signal integration is enhanced, but the celestial background streaking increases due to high angular rates
Solution Approach 1:
The patent applies periodic action by using a rotating chopper wheel that modulates the incoming light at a known frequency. This creates a periodic signal that can be distinguished from the streaking background, allowing the orbital object's position to be measured accurately even during high-speed tracking when background objects would otherwise appear as continuous streaks.
Solution Approach 2:
The chopper wheel acts as an intermediary device between the telescope and the orbital object. It introduces a controlled modulation to the light path, creating a reference signal that helps separate the orbital object's position information from the streaking background, effectively mediating the measurement problem.
2Speed
If the telescope slews at high angular rates to track low altitude objects, then the tracking speed is improved, but the background celestial objects streak across the detector
Solution Approach 1:
The rotating chopper wheel imposes a periodic modulation on the light signal at a frequency that is distinct from the streaking pattern caused by high-speed tracking. This allows the system to distinguish between the orbital object's motion and the background streaking, maintaining angular location determination accuracy even at high tracking speeds.
Solution Approach 2:
The system uses the known rotation frequency of the chopper wheel as feedback to distinguish the orbital object's position from the streaking background. By referencing the periodic modulation, the system can accurately determine angular locations even during rapid slewing operations.
3Measurement precision
If the integration time is increased to improve SNR, then the signal accumulation is enhanced, but the sky background noise increases
Solution Approach 1:
The chopper wheel creates a periodic signal that allows the system to distinguish the orbital object's light from the sky background noise. By modulating the signal at a known frequency, the system can filter out background noise while maintaining the object's signal, improving SNR without requiring excessively long integration times that would amplify sky noise.
Solution Approach 2:
The chopper wheel serves as an intermediary that separates the orbital object's signal from the sky background noise. The periodic modulation it introduces creates a distinctive signal pattern that can be isolated from the noise, allowing improved SNR while minimizing the harmful effect of sky background noise.
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 system achieves precise tracking of small debris by enhancing SNR and reducing angular errors, enabling accurate determination of orbital parameters and collision prediction.
Implementation Method 1
The orbital object is sunlit, yet the sun is below the horizon. To track small orbital debris, which has a low signal return, the telescope is slewed to track the dim orbital object, allowing integration of the signal to obtain adequate signal-to-noise ratio (SNR).
Implementation Method 2
An alternative way to ameliorate the streaking is to use a rotating chopper wheel, which applies a modulation to the transmitted intensity on the image. The chopped streak then changes from a continuous line to an intensity modulated line, for example a series of dots at regular or irregular spacing.
Implementation Method 3
The system may also include range measurements, using the same telescope with a laser or a separate ranging system.
Data Source
AI summary
The present disclosure achieves accurate tracking of sunlit orbital objects, including small, dim orbital debris, using a ground-based telescope and detector which tracks the orbital object. The angular position of the orbital object relative to background celestial objects is accurately determined over a trajectory, allowing accurate determination of the orbit parameters.