Dual Star Trackers for Stereoscopic Spacecraft Range Determination
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Solution Overview
Problem
Existing star tracker systems for space vehicles lack accurate and efficient methods for determining range during rendezvous and proximity operations, particularly in rideshare-capable vehicles with limited space and mass constraints.
Innovation Solution
Employing a pair of star trackers positioned at different locations on the space vehicle to capture stereoscopic images of a space object and stars, combined with global navigation satellite system data, to calculate a precise range using focal length and angular offset, and utilizing a Kalman filter and machine learning algorithms for enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single star tracker is used for range determination, then the device complexity is low, but the measurement precision of range is insufficient
Solution Approach 1:
The patent transitions from a single star tracker (2D imaging) to a stereoscopic pair of star trackers (3D spatial measurement). By positioning two star trackers at different locations on the space vehicle, the system creates a baseline separation that enables triangulation-based range determination, adding a third dimension to the measurement capability and significantly improving range accuracy.
Solution Approach 2:
The patent introduces common reference stars as an intermediary element that both star trackers image. These reference stars serve as a shared reference frame, allowing the system to compute angular offsets and perform relative positioning calculations. The reference stars mediate between the two star trackers and the final range determination, enabling accurate measurements despite the added system complexity.
2Measurement precision
If stereoscopic imaging with two star trackers is implemented, then range determination accuracy improves, but the device complexity and mass increase
Solution Approach 1:
The star trackers in the patent serve multiple functions: they perform traditional attitude determination by imaging stars, and simultaneously perform range determination by imaging both reference stars and the space object. This multi-functionality eliminates the need for separate ranging instruments, reducing overall system mass despite using two star trackers instead of one.
Solution Approach 2:
The star trackers utilize their own imaging capability and existing focal length specifications to perform range determination without requiring additional dedicated ranging hardware. The system serves its own ranging needs using the inherent properties of the star trackers themselves, avoiding the mass penalty of adding specialized equipment.
3Reliability
If multiple estimation methods are combined with filtering algorithms, then the reliability of range determination improves, but the computational complexity increases
Solution Approach 1:
The patent implements a feedback mechanism through the Kalman filter, which continuously processes measurements from both star trackers and updates the range estimate. The filter uses the angular offset measurements and incorporates process noise and measurement noise models to provide optimal estimates. This feedback loop continuously refines the range determination, improving reliability through iterative correction of estimates based on new measurements and previous state information.
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
Provides accurate and reliable range determination for rendezvous and proximity operations, enabling precise maneuvering of space vehicles around other objects, and allowing for dynamic algorithm testing via a massless payload interface.
Implementation Method 1
a first star tracker disposed at a first location on or near the space vehicle, the first star tracker configured to obtain first images of a space object and stars; a second star tracker disposed at a second location on or near the space vehicle, at a distance D from the first location, the second star tracker configured to obtain second images of the space object and the stars and the first images and the second images being stereoscopic images
Data Source
AI summary
A space vehicle system includes a first star tracker disposed at a first location on or near the space vehicle, the first star tracker configured to obtain first images of a space object and stars and a second star tracker disposed at a second location on or near the space vehicle, at a distance D from the first location. The second star tracker is configured to obtain second images of the space object and the stars and the first images and the second images being stereoscopic images. The system also includes a processor configured to determine an estimate of a range from the space vehicle to the space object based on the first images and the second images.