Spacecraft Payload Steering for High Inclination Orbits
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Solution Overview
Problem
Spacecraft in highly inclined elliptical orbits face challenges in maintaining optimal payload orientation due to complex motion of the optimal target across the Earth's surface and with respect to the spacecraft, leading to suboptimal communication and broadcast services, especially at high latitudes where elevation angles are small and prone to blockages.
Innovation Solution
The use of polynomial and Fourier series functions parameterized by an onboard orbit propagator processor to actively steer the payload orientation towards the optimal target coordinates, accounting for orbital drift and perturbations, allowing continuous alignment of the antenna pattern with the target, even when the orbit's inclination and eccentricity change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a satellite is disposed in an HIEO to enable higher elevation angles, then the elevation angle to users is improved, but the spacecraft has substantial motion with respect to users causing complex payload orientation requirements
Solution Approach 1:
The patent applies dynamics by making the payload orientation adaptive rather than fixed. The spacecraft bus actively steers the payload antenna boresight to track a moving optimal target point on the Earth's surface, with orientation angles (yaw, pitch, roll) continuously adjusted based on real-time spacecraft position and target coordinates. This dynamic adaptation resolves the contradiction by enabling high elevation angles while managing the complexity through automated tracking algorithms.
Solution Approach 2:
The patent implements feedback through the continuous computation of optimal target coordinates based on spacecraft position, and the subsequent adjustment of payload orientation to track this moving target. The system monitors spacecraft location, calculates the optimal ground target point that maximizes elevation angle, and feeds this information back to the attitude control system to adjust antenna pointing. This closed-loop feedback mechanism resolves the orientation complexity by providing a systematic method to adapt to the changing geometry of HIEO.
2Measurement precision
If polynomial and Fourier series functions are used to steer payload orientation, then continuous alignment with optimal target is achieved, but computational complexity increases
Solution Approach 1:
The patent applies parameter changes by using polynomial and Fourier series functions to model the relationship between spacecraft position and optimal target coordinates. These mathematical functions transform the complex orbital mechanics calculations into manageable parameter relationships, allowing the system to compute yaw, pitch, and roll angles as functions of orbital parameters. This approach achieves precise payload alignment while reducing computational complexity through analytical solutions rather than iterative numerical methods.
Solution Approach 2:
The patent introduces mathematical functions (polynomials and Fourier series) as intermediaries between the spacecraft orbital position and the payload orientation commands. These functions serve as mediators that translate complex orbital dynamics into simplified steering angle calculations. By using these intermediary mathematical models, the system achieves precise alignment without directly computing the full complexity of orbital mechanics in real-time.
3Adaptability or versatility
If the optimal target coordinates move across the Earth's surface, then service coverage is improved, but maintaining payload orientation becomes more difficult
Solution Approach 1:
The patent applies preliminary action by pre-computing the optimal target coordinates and orientation angles using polynomial and Fourier series functions before executing the steering maneuvers. The system calculates the desired payload orientation in advance based on predicted spacecraft position and target coordinates, allowing the attitude control system to follow a predetermined steering profile. This preliminary calculation approach simplifies real-time operation by replacing complex on-the-fly computations with pre-derived steering commands.
Data Source
AI summary
Spacecraft payload orientation steering is provided for an orbiting spacecraft in motion along an orbit track around a celestial body, the orbit track having a nominal inclination with respect to an equatorial orbit, a substantial eccentricity, and a drift angle with respect to the nominal inclination. Coordinates of an optimal payload target location as a function of a spacecraft position along the orbit track are determined, the target location being on the surface of the celestial body and having a substantial motion with respect to the surface and with respect to a spacecraft nadir. A payload of the spacecraft is substantially aligned with the determined coordinates by steering the satellite body to correct for at least one of the inclination drift angle, and the eccentricity, thereby adjusting the spacecraft orientation as a function of the spacecraft position along the orbit track.