Software GPS Receiver for High-Altitude Spacecraft

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Solution Overview

Problem

Conventional GPS receivers are inadequate for high-altitude spacecraft applications due to their inability to effectively acquire and track weak GPS signals, which are sparse and weakened by the Earth's presence, leading to long acquisition times and inefficiencies.

Innovation Solution

A software-based GPS receiver system that utilizes coherent integration, diurnal thermal modeling, precision orbit propagation, and a special Kalman filter to enhance signal tracking, allowing for longer coherent integration and efficient navigation data updating, thereby enabling effective operation at high altitudes like GEO or HEO.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If conventional GPS receivers are used for high-altitude spacecraft, then hardware complexity is reduced, but signal acquisition capability deteriorates due to weak and sparse GPS signals at high altitudes

Engineering Contradiction:

Improvehardware complexityVSAvoidsignal acquisition capability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the fundamental operating parameters of the GPS receiver by implementing software-based signal processing with extended integration times (up to 4 seconds or more) and advanced correlation algorithms. This allows the system to accumulate signal energy from weak high-altitude GPS signals over longer periods, transforming the approach from hardware-oriented rapid acquisition to software-oriented sensitive detection

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces traditional hardware-based signal processing components with software implementations running on general-purpose processors. This substitution enables flexible adaptation to weak signal conditions through algorithmic improvements rather than hardware modifications, allowing coherent integration and advanced correlation techniques to be applied software-based signal processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If conventional signal acquisition methods are used, then processing speed is maintained, but acquisition time increases significantly for weak high-altitude signals

Engineering Contradiction:

Improveprocessing speedVSAvoidsignal acquisition time

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The patent implements coherent integration that continuously accumulates signal energy over extended periods (4 seconds or more) without interruption. This continuous integration process allows the receiver to build up sufficient signal-to-noise ratio from weak high-altitude GPS signals, maintaining processing efficiency while dramatically reducing acquisition time through cumulative signal detection

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent performs preliminary orbit propagation and signal parameter prediction before actual signal acquisition. By pre-calculating expected signal characteristics based on spacecraft orbit data, the system can focus processing resources on the most likely signal parameters, reducing the search space and accelerating acquisition of weak signals

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If software-based processing is implemented, then adaptability to signal changes is improved, but computational requirements increase

Engineering Contradiction:

Improvesignal processing adaptabilityVSAvoidcomputational energy consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent divides the signal processing task into distinct segments: coherent integration over extended periods, followed by correlation processing, and then acquisition decision-making. This segmentation allows the system to perform computationally intensive integration first, then use the accumulated signal energy to facilitate faster, less computationally demanding correlation and detection stages

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial integration approaches where the system performs coherent integration for a predetermined period, then evaluates whether sufficient signal energy has been accumulated. If the signal is sufficiently strong after partial integration, the system can terminate processing early, avoiding the full computational cost of extended integration while maintaining adaptability to varying signal conditions

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentEP2558885B1Software global navigation satellite systems receiver for high-altitude spacecraft applications

Publication Date: 2016.07.20 THE BOEING CO

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AI summary

A system that provides GPS-based navigation and orbit determination capabilities for high-altitude spacecraft. The system uses an existing spacecraft processor and an easy-to-space-qualify minimum-hardware front end to minimize the need for new space-qualified hardware. The system also uses coherent integration to acquire and track the very weak GPS signals at high altitudes. The system also uses diurnal thermal modeling of a spacecraft clock and precision orbit propagation to enable longer coherent integration, a special Kalman filter to allow weak signal tracking by integrated operation of orbit determination and GPS signal tracking, and a segment-by-segment, post-processing, delayed-time approach to allow a low-speed spacecraft processor to provide the software GPS capability.