30 March - 2 April 2009
ESA/ESOC
Darmstadt, Germany

• Acquire First Experience with Reflection Spectroscopy at the OGS
  • Spectrograph at OGS never used for “fast moving” targets
    • Experiment
• Get First Spectra of Space Debris at High Altitudes
  • Ultimate goal are spectra of high area-to-mass ratio GEO-like objects
  • material
  • Start with bright, known objects
    • Use known surface material for calibrationd
  • Try fainter debris

• Reflection spectroscopy
  • quantitative comparison of the measured spectrum with the spectrum of the illuminating source
  • careful calibration of extinction
• Tracking
  • first acquisition of satellites/debris
  • often outside field of view of 13 arcm(combination of mount model and ephemeris errors)
  • autoguiding not possible for satellites/debris objects
    • most objects remain in 5”-slit for < 4 minutes
• Faint Objects
  • Very low signal-to-noise
  • observations have experimental character and are very time consuming

• Low resolution spectrograph
• The OGS ESA spectrograph uses “grisms” as dispersive elements

Filters needed to separate second order spectra

• Available grisms
  
  • lowest dispersion selected (“GrismBB):
  • best S/N for given magnitude and integration time
  • wavelength: 450 -950 nm
  • dispersion: 0.4 nm/pixels

  Selection of Objects

  • Four types
    • minor planets (results to be compared with published data)
    • large intact GEO objects (catalogue objects)
    • bright GEO debris objects
    • bright high AMR GEO objects
  • Selection criteria
    • orbit quality
    • availability of manufacturer data on surface materials
    • brightness
    • visibility constraints (phase angle, Earth shadow, Milky Way, etc.
    • …

  Observed Objects (Feb 2009)

  

  2nd Order Spectra

  Extinction

  Air mass 1.02 1.13 1.4 1.94

  Extinction coefficients

  Response Function

  Solar analog: Implicit response function Solar spectrum MSG-2 raw   Normalize Spectrum raw/solar analogue(extinction!)

  Phase Angle Dependence

  Meteosat MSG 2 at different phase angles: 38° 60° 88°

  Spectrum as a Fingerprint?

  Object S92005 GTO debris Magnitude 14 AMR 0.02 two nights Assumptions: attitude? same phase angle Features: slope modulation shape peaks

  Solar Cells?

  Minor Planets vs. Debris

  Debris: S92005 GEO E08211A GEO Planets: Nausikaa Pomona Influence of space environment on debris => „reddening“ ?

  Conclusion

  • It works!
  • First spectra of space debris in GEO and GTO
  • Spectra of the same object are consistent
  • Debris show different characteristics
  • The features might be used to identify objects
  • Observations seem to confirm the „reddening“ effect
  • Still a long way until we can identify the materials of the high area-to mass objects
  Размещено 6 мая 2009
  Все представленные материалы размещены с согласия авторов докладов

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