Spacecraft Navigation Orbit Planning for Distant-Target Observability
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Solution Overview
Problem
Existing relative navigation systems using optical sensors for distant objects in space suffer from unobservable linear dynamics, leading to large estimation errors in relative position and velocity that depend on initial conditions, and require observation near the boundary between shade and sunlight regions, which is impractical for short-time estimation.
Innovation Solution
A navigation orbit calculation device that calculates an observable region and navigation orbit to ensure the observation start point is farther from the target than the end point, avoiding backlighted regions and using maneuvers to control the spacecraft's orbit, thereby reducing estimation errors without relying on boundary surface observations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If observation is performed near the boundary surface between shade and sunlight regions, then estimation accuracy of relative position and velocity can be improved, but observation time increases and the method becomes impractical for short-time estimation
Solution Approach 1:
The navigation orbit is designed in advance to ensure the spacecraft passes through the observable region at the optimal position (farther from target at start, closer at end). This preliminary orbital design eliminates the need for time-consuming boundary surface observations while maintaining high estimation accuracy through the predetermined geometric relationship.
2Ease of operation
If the spacecraft remains at a constant distance from the target, then the observation setup is simple, but estimation errors cannot be reduced below certain values due to lack of observability in linear dynamics
Solution Approach 1:
The invention introduces dynamic orbital movement where the spacecraft's distance to the target changes systematically during observation (farther at start, closer at end). This dynamic geometric relationship provides the necessary observability to reduce estimation errors while maintaining operational simplicity through automated orbit calculation.
3Adaptability or versatility
If Angles-Only Navigation is used for distant targets, then the system can operate at long range, but the navigation lacks observability when relative movement follows linear dynamics
Solution Approach 1:
The invention adds a temporal dimension to the observation geometry by designing the spacecraft to move along an orbit where its distance to the target changes over time. This transforms the static Angles-Only Navigation into a dynamic system with improved observability, allowing distant target operation while maintaining reliability through the time-varying geometric relationship.
Data Source
AI summary
A navigation orbit calculation device includes an observable region calculator and a navigation orbit calculator. The observable region calculator calculates an observable range observable by a sensor mounted on a spacecraft. The navigation orbit calculator calculates a navigation orbit that includes an observation start point included in the observable range calculated by the observable region calculator and an observation end point included in the observable range. A distance between the observation start point and an approaching target to be observed by the sensor is greater than a distance between the observation end point and the approaching target.