A Summary of Five Years of Michigan Orbital Debris Survey Telescope (MODEST) Data
- Paper number
IAC-08.A6.1.3
- Author
Dr. Kira Abercromby, ESCG/Jacobs Sverdrup, United States
- Coauthor
Dr. Patrick Seitzer, University of Michigan, United States
- Coauthor
Dr. Mark J. Matney, National Aeronautics and Space Administration (NASA), United States
- Coauthor
Dr. Ed Barker, NASA Johnson Space Center, United States
- Coauthor
Ms. Heather Rodriguez, National Aeronautics and Space Administration (NASA)/Johnson Space Center, United States
- Year
2008
- Abstract
The acquisition of optical survey data of human-made objects in the geosynchronous orbit (GEO) commenced in January 2002. The data are acquired at the Michigan Orbital Debris Survey Telescope (MODEST), located at Cerro Tololo Inter-American Observatory near La Serena, Chile. Currently, 151 nights of data have been collected and compiled into a database of optical observations of correlated (CT) and uncorrelated (UCT) targets. Acquisition is performed near the anti-solar point using a sidereal track of the telescope and a counter-sidereal drift scan of the charged-couple device and 5-second exposures. A detection is counted if the object is seen in at least four frames, however, most GEO objects are seen in eight frames equating to observational time arc of approximately five minutes. The orbital arc is short and an assumed circular orbit is necessary to obtain orbital elements for the detected object. When assessing all objects, the mean orbital estimation bias is 34 degs, 0.14 degs, and 0.04 degs for right ascension of ascending node (RAAN), inclination, and mean motion, respectively. However, it is well known that RAAN is ill-defined when the inclination is close to zero so the mean bias improves to 3 degs if only observed inclinations greater than 1 degs are considered. By assuming a diffuse Lambertian phase function, an albedo of 0.2, a standard distance of 36,000 km, and a 0º phase angle, the observed broad-R magnitudes are used to determine an absolute magnitude and size. The size ranges for the MODEST data are as small as 30 cm for a CT and 20 cm for a UCT. As a function of absolute magnitude, the distribution of objects is bi-modal. The first maximum is near a broad-R magnitude of 14.5 corresponding to a size of 95 cm. The second maximum is dominated by UCTs where the faint end reflects the sensitivity roll-off of the system. Using a probability-of-detection where all objects are weighted based on where the telescope looked and then plotted in angular momentum space, two distinct clumps of UCTs are seen. One of the clumps is near the inclination and RAAN where fragments from the Titan 3C-4 transtage break-up that occurred on 21 February 1992 would be expected. The other clump may be from the Ekran 2 breakup that occurred on 23 June 1978. All of the data from the 5-year MODEST data collection period and a close inspection of the equinoctial seasons will be discussed herein.
- Abstract document
- Manuscript document
IAC-08.A6.1.3.pdf (🔒 authorized access only).
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