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System-Level Jitter Prediction Using Hexapod Reacting Balance and Frequency Analysis

This paper presents an analytical technique for characterizing system-level jitter for spacecraft by utilizing Hexapod Reaction Balance and Frequency Domain Analysis. The study aims to predict and mitigate disturbances in spacecrafts to ensure stable pointing. The Hexapod device accurately records dynamic force and torque responses, which are then analyzed in the frequency domain to determine system stability. The research showcases the application of this approach in historical experiments and launches, demonstrating its effectiveness in predicting payload jitter and ensuring agility in small satellite systems. The study concludes with the potential for combining Hexapod data and frequency response analysis to enhance spacecraft pointing stability.

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System-Level Jitter Prediction Using Hexapod Reacting Balance and Frequency Analysis

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  1. “Spacecraft Jitter Prediction using 6-DOF Disturbance Measurements” Bryce Carpenter Oliver Martin Jason Hinkle Sierra Nevada Corporation Space Systems Group IEEE Aerospace Conference March 2009

  2. Problem Statement Challenges Demand for Small Satellites • Flexibility • Lower Cost • Rapid Development • Increased Agility • … • Power availability • Smaller aperture • Decreased • pointing stability • … Beijing-1 Launch Oct. 2005 4-meter resolution, 24-kilometer swath agriculture, city planning, hydrology, 2008 Olympics, …

  3. Paper Contribution • Presentation Overview An analytical technique for system-level jitter characterization prior to system integration 1. Hexapod Reaction Balance 3. Structural Response Analysis 2. Frequency Domain Analysis 4. System-Level Jitter Prediction

  4. Historical Background 2005 – 2007 Distributed Sensing Experiment (DSE) Missile Defense Agency (MDA) February 2008 Trailblazer Operationally Responsive Space (ORS) August 2, 2008 Falcon 1, Flight 3 launches from Omelek Island in Kwajalein Atoll SpaceX

  5. Hexapod Reaction Balance • Measurement device for accurately recording a wide range of dynamic force and torque responses Steel Flexures Force Transducers Kinematic Transformation

  6. Previous Hexapod Uses

  7. Frequency Domain Analysis • Convert time-series to frequency domain using Discrete Fourier Transform:

  8. +Y Torque Waterfall Plot

  9. Power Spectral Density • Convert DFT to PSD:

  10. Structural Frequency Response Analysis • Conduct frequency response analysis in NASTRAN to determine camera motion due to RW disturbance Comm Deck Avionics Deck Payload Bay 28,339 Nodes 33,895 Elements

  11. System Jitter Prediction Reaction Wheel Disturbance Predicted Payload Jitter Flexible Body Response

  12. Payload Jitter Results

  13. Conclusion • SNC has developed the Hexapod to accurately measure high frequency forces and torques • Analysis of Hexapod data can be combined with a FEM frequency response analysis to determine system pointing stability

  14. Acknowledgments This material is based upon work supported by the U.S. Army Space and Missile Defense Command under Contract No. HQ0006-04-D-0002.”

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