Spacecraft Attitude Control for Blur-Free Imaging and Laser Downlink
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Solution Overview
Problem
Existing spacecraft imaging systems face challenges in acquiring sharp and precise images while maintaining high resolution and reducing complexity, particularly when using laser transmission modules, due to motion blur and increased electronic complexity.
Innovation Solution
A spacecraft system with a fixed field of view and laser line of sight, using a sensor array and laser transmission module integrated in the focal plane of the observation instrument, controls attitude to maintain a stationary optical or laser line of sight on a setpoint, allowing for image acquisition and transmission without blurring and reducing overall complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the spacecraft uses a laser transmission module to transfer data rapidly to the ground, then the productivity of data transfer is improved, but the device complexity increases
Solution Approach 1:
The patent combines the laser transmission module with the observation instrument by locating both in the same focal plane. This merging allows the spacecraft to use shared optical components and control systems, enabling rapid laser data transfer while reducing overall device complexity through component consolidation
Solution Approach 2:
The optical system serves multiple functions: it supports both the observation instrument for image acquisition and the laser transmission module for rapid data transfer. This multi-functionality allows the spacecraft to achieve high productivity in both imaging and data communication without proportionally increasing complexity
2Manufacturing precision
If the spacecraft reduces acquisition time to limit motion blur, then the manufacturing precision of images is improved, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The spacecraft employs periodic attitude adjustments to maintain the optical line of sight stationary on the ground during acquisition. This periodic stabilization allows for longer exposure times without motion blur, improving image sharpness while maintaining adequate signal-to-noise ratio through controlled, repeated positioning corrections
Solution Approach 2:
The patent uses TDI (Time Delay and Integration) technology which creates multiple copies of the image signal across successive detector rows. These copies are integrated together, effectively accumulating signal over time while maintaining sharpness by compensating for spacecraft motion, thus improving signal-to-noise ratio without sacrificing image precision
3Area of stationary object
If the spacecraft operates in pushbroom mode to observe terrestrial areas beyond field of view length, then the area of observation is improved, but the device complexity increases due to TDI configurations
Solution Approach 1:
The patent merges the laser transmission module with the pushbroom observation system in the same focal plane. This integration allows the spacecraft to extend observation area using pushbroom mode while avoiding separate complex electronic systems for laser communication, reducing overall device complexity through shared hardware and control architecture
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 high-quality image acquisition with improved signal-to-noise ratio and reduced complexity by simplifying equipment and control, enabling efficient image transfer via laser link during a moving orbit.
Implementation Method 1
a laser transmission module associated with a laser line of sight that is fixed in the spacecraft frame of reference, said laser transmission module being located in the focal plane or in a secondary focal plane of the optics or in an intermediate focal plane of part of the optics
Data Source
AI summary
A method for acquiring images by a spacecraft is disclosed having an observation instrument and a laser transmission module, the method including a phase of acquiring an image of the surface of the Earth and a phase of transmitting images using the laser transmission module, and during each acquisition phase and each transmission phase, the attitude control includes: a pointing modification step during which the attitude of the spacecraft is modified so as to orient the satellite towards a predetermined setpoint, a pointing immobilization step during which the attitude of the spacecraft is controlled for a time interval referred to as an immobilization period so as to keep the spacecraft oriented towards the setpoint.