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Refinement of MSX Attitude Using Infrared Astrometric Catalogs

Refinement of MSX Attitude Using Infrared Astrometric Catalogs. Sean J. Carey Boston College. MSX Celestial Group. Stephan Price (AFRL) : PI Michael Egan (AFRL) : Source extraction Image Construction Sean Carey (BC): Positional refinement Thomas Kuchar (BC) : Artifact mitigation

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Refinement of MSX Attitude Using Infrared Astrometric Catalogs

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  1. Refinement of MSX Attitude Using Infrared Astrometric Catalogs Sean J. Carey Boston College

  2. MSX Celestial Group • Stephan Price (AFRL) : PI • Michael Egan (AFRL) : Source extraction • Image Construction • Sean Carey (BC): Positional refinement • Thomas Kuchar (BC) : Artifact mitigation • Don Mizuno (BC) : Dark offset corrections

  3. Introduction • Statement of Problem • Description of DAF Errors & Artifacts • Solution • Fits to Astrometric Truth • Summary

  4. Statement of Problem • Program Requirements • Tenth of detector (1.8) Accuracy • Absolute Pointing • Needed for Image Registration, Super-resolution • Astrometry • Ring Laser Gyros and Star Tracker • APL Definitive Attitude File (DAF) • time evolution of the boresight pointing • typical errors 15-45, time varying

  5. MSX/IRAS Comparison Carina Nebula

  6. Description of DAF ErrorsJumps • Jumps in Star Tracker • ~3% of long scans • Register Bad Portion • Usually short segment • Use astrometric matches • Update DAF • Adjust boresight • Difference quaternions • Create • Apply

  7. Description of DAF ErrorsGaps • Data Dropouts • ~3% of DCEs • Recover radiometer data • Interpolate • Boresight position • Spacecraft position • Spacecraft velocity

  8. Description of DAF Errors Noise • High Frequency Noise • Amplitude up to 4 • 1/f noise for f > 1 Hz • Wiener (optimal) Filter • Remove in-scan trend • Fit noise model to PSD • Filter Boresight • In-scan • Cross-scan

  9. In-scan boresight filter Cross-scan similar 1-4 amplitude High noise segments Description of DAF ErrorsFilter Construction / Application

  10. Description of DAF ErrorsAttitude Adjustment • Point Source Association Criteria • Position Match • Simultaneous Flux Match • Two step Fitting Process • Fit to Astrometric Truth • MSX to MSX Registration (Global Refinement) • Iterate until convergence (2 iterations) • Cubic Splines • Least Squares Fit

  11. Astrometric Sources • MSX Astrometric Catalog (0.12-0.2 error) • ACRS • PPM • Fluxes: IRAS + models • Need Additional Sources for Sparse Regions • Refined MSX Sources -or where available - • 2MASS Positions (< 0.2 error) -and- • MSX Refined Fluxes

  12. Fit to Astrometric Truth

  13. Global Registration

  14. MSX - Astrometric 30 match window Global refinement (l) = 0.54 (b) = 0.61 MSX - MSX 30 match window Global refinement (l) = 1.53 (b) = 2.15 Pointing Improvement

  15. Pre-refinement Post-refinement Pointing Improvement Registration of Images

  16. Pointing Improvement Summary • MSX-Astrometric Match Uncertainty • In-scan (l) = 0.8 • Cross-scan (b) = 1.0 • MSX-2MASS Uncertainty • Independent Measure • In-scan (l) = 1.80 • Cross-scan (b) = 1.87

  17. Summary • Mission Requires < 1.8 Positional Accuracy • Boresight Positions Refined Through • Optimal Filtering • Comparison with Astrometric Truth • Global Registration (solution) • Met Program Requirement • Imaging • Version 2 of MSX PSC

  18. Description of DAF Errors • Jumps • Gaps • Noise • Attitude errors

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