Philip Castro, Applied Optimization; Charles J. Wetterer, KBR; David Strong, Strong EO Imaging; Casey Schuetz-Christy, Mellennium Engineering and Integration LLC, an Axient Subsidiary; Francis Chun, U.S. Air Foce Academy
Keywords: Space Situational Awareness (SSA), Space Domain Awareness (SDA), Characterization, Spectroscopy
Abstract:
The SSA community has performed research in the past to suggest that resident space objects (RSOs) may have age related color changes. That is, they have increased flux in the bluer wavelengths or decreased flux in the redder wavelengths (blueing), or increased flux in the redder wavelengths or decreased flux in the bluer wavelengths (reddening) with age. The goal of our research is to investigate the color change of Geosynchronous Earth Orbit (GEO) satellites with age. Using the Falcon Telescope Network, we plan to observe groups of GEO satellites, under similar illumination conditions (longitudinal phase angles), that are considered identical (as closely as possible) but of differing ages (time on orbit) to look for a relationship of color change with age. We anticipate finding a color change with age for the groups of identical GEO satellites.
There is the general belief within the SSA community that RSOs redden with age (Abercromby et al., 2005), but the research of objects on orbit has not proven this to be the case (Pearce et al 2020 JSSE). (Pearce et al 2020 JSSE) showed that five Russian SL-12 rocket bodies showed the color change of blueing with age; their flux decreased in the longer (redder) wavelengths with age. Other research has shown mixed or inconclusive results. Part of this is due to the RSO sample being a mixture of RSO types (rocket bodies, debris, and GEO satellites) (Cardona et al 2016), and a mixture of solar panel technology on a common GEO bus type (Frith et al 2015). While the first group found blueing with age for rocket bodies of one group, the second group showed no relationship with age. (Schmitt 2020) found no color change with age for three bus types, but did for a fourth bus type, Loral, which showed a blueing with age.
We plan to observe groups of identical GEO satellites that were launched at different times outside of glint season to obtain spectroscopic measurements and hyperspectral signatures at similar illumination conditions. Observations outside of glint season are expected to be much less dynamic. By identical GEO satellites, we mean a common bus type, solar panels, contractor, operator, and equipment. The planned targets of this research leverage previous work in the area of age-related color change. The planned targets have as many attributes as a controlled variable as possible and only the age as a dependent variable, avoiding the risk of mixed RSO types and a mixture of technology. If a relation is found between aging and color change, we aim to quantify it.
Determining a color change with age will help to characterize GEO satellites. GEO satellites change their brightness throughout the night (timescales of minutes or hours) as the illumination conditions change relative to a ground-based observer. A GEO satellites signature may also change seasonally (timescales of weeks or months) as the angle of the Sun, satellite, and observer change. This is most noticeable during glint season. A color change with age would be another change for GEO satellites, on timescales of years, that needs to be understood and accounted for.
Date of Conference: September 19-22, 2023
Track: Satellite Characterization