Ryan Kovacs, US Air Force Academy; Julie Simms, US Air Force Academy; Benjamin Roth, US Air Force Academy; Francis Chun, US Air Force Academy; Scott Donnell, US Air Force Academy; Timothy Giblin, US Air Force Academy
https://doi.org/10.64861/IYDL4085
Keywords: spectroscopy, spectra, spectrograph, satellite characterizations, unresolved
Abstract:
The use of transmission gratings to obtain the spectrum of an artificial satellite has been demonstrated and used by the Center for Space Situational Awareness Research (CSSAR) in the Department of Physics and Meteorology at the U.S. Air Force Academy (USAFA). Tippets et al. [2015] reported on the calibration of transmission gratings using emission lines of known stellar sources such as a Wolf-Rayet star. This enabled the determination of the pixel-to-wavelength conversion for a given telescope and camera system. In addition, Tippets et al. [2015] reported on the use of solar analog stars to remove the sun’s spectra from the satellite’s spectra. Dunsmore et al. [2016] presented spectral data of several operational communication satellites in geostationary orbit. The satellites’ reflectance spectra resemble a blackbody-like curve both before and after the glint. However, at the time of the glint the spectra show a shift towards blue, providing clear evidence that the solar panels were the source of the glints. These earlier studies used a transmission grating with a density of 100-grooves-per-millimeter, mounted on a 16-inch, f/8.2, Ritchey-Chrétien telescope, resulting in a spectral resolution of 103 25,000, three orders of magnitude higher than the transmission gratings. The use of the high-resolution Whoppshel spectrometer represents a significant leap in satellite characterization by potentially identifying fine-structure material features that are typically unresolved or misinterpreted as noise in low-resolution slitless spectroscopy systems. Reyes and Cone show that common spacecraft materials (including silicone paints and solar cells) produce distinct reflectance spectra, supporting reflectance spectroscopy as a practical method for material discrimination in space-object characterization [Reyes and Cone, 2018]. Calibration efforts are ongoing as an undergraduate physics capstone project with the goal of obtaining high-resolution spectra of several communication satellites in geostationary orbit. We report on the instrument set up of the Whoppshel, its characteristics and performance on the one-meter telescope, its calibration using stellar sources of different spectral types, and preliminary analysis from a data collection on a geostationary satellite. This high-resolution approach may reveal subtle spectral signatures that, once identified, can inform more accurate data reduction and interpretation models for existing low-resolution space domain awareness. By comparing high-resolution Whoppshel spectra against low-resolution transmission grating data, this study identifies the relative advantages of each for satellite characterizations. A key objective is to determine if high-resolution benchmarks can reveal previously unnoticed features in low-resolution sets, thereby improving the implementation and interpretation of lower-cost more efficient spectral sensors.
Date of Conference: September 15-18, 2026
Track: Satellite Characterization