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Fifth European Conference on Space Debris

30 March - 2 April 2009
Darmstadt, Germany

Photometric Studies of Orbital Debris at GEO

Patrick Seitzer (Dept of Astronomy University of Michigan)
Kira Abercromby (CalPoly)
Heather Rodriguez-Cowardin (ESCG/JS)
Ed Barker (NASA/JSC)
Gary Foreman (Univ. of Michigan)
Matt Horstman (ESCG/ERC)

Paper Presented at the 5th European Space Debris Conference,
Darmstadt Germany, March 30 - April 2 2009


  • Review of NASA Optical GEO Debris program.
  • Results from optical photometry of faint GEO debris.
    • Astronomical filters BVRI
    • Comparison with lab based measurements of selected surfaces
    • What is optically faint debris made of?

Cerro Tololo Inter-American Observatory, Chile

Michigan Orbital DEbris Survey Telescope


0.6-m aperture Schmidt.
1.3 x 1.3 deg field of view.
Survey with CCD in TDI mode.

MODEST Survey sequence

Brightness Distribution - one 7 night run

Examples of Detections

CTIO 0.9-m telescope

  • Follow-up in real-time (< 30 min)
  • 0.22 deg field of view
  • Objects handed over from MODEST assuming circular orbit
  • Track object at object’s rate
  • Success rate of reacquisition greater than 90%.
  • Establish 6 parameter orbit and multi-color photometry for all objects fainter than R = 14.5

Magnitude versus Eccentricity

Optical Photometry

  • Goal - orbits and photometry of complete sample of faint debris.
  • Selected on basis of brightness and angular motion.
  • All observations with CTIO 0.9-m while tracking object.
  • Astronomical filters - BVRI.
  • Sequence of 5 exposures in each of R-B-V-I-R
  • Some objects show little brightness variation in all filters, some objects a lot of variation in all filters.

Stable Object - 4 sequences

Highly Variable Object - 3 sequences

Colors for Stable Objects

Colors for Highly Variable Objects

Comparison with NASA/JSC Lab Measurements
Heather Rodriguez-Cowardin

Sample Intact MLI in NASA/JSC Lab

Rotated by robot in lab - work of H. Rodriguez-Cowardin

How measure true colors of tumbling object like this?
Can not observe in different filters sequentially!

In Progress - Synchronized Observations

0.9-m - master - B filterMODEST - sync - R filter

Both telescopes track same object - exposure start and duration synchronized to < 50 milliseconds

Photometry of GEO Debris

  • Sample well selected on basis of brightness and angular motion.
    • Probably biased towards low eccentricity objects.
  • Stable objects show a small locus of colors in color-color diagram.
  • Consistent with lab measurements of mylar, but redder.
    • But lab measured in atmosphere, not vacuum!
    • No space weathering effects in lab!
  • Work underway to measure true colors of tumbling debris.

Размещено 4 июня 2009

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