Fifth European Conference on Space Debris
30 March - 2 April 2009
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
- 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
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 filter||MODEST - 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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