OFFICE OF PREPUBLICATION AND SECURITY REVIEW 027 For Open Publication Department of Defense Jan 23, 2025 All-domain Anomaly Resolution Office (AARO) CLEARED An AARO Information Paper Correlations of Starlink1 Satellite Flaring with UAP Observations December 2024 Introduction With the advent of satellite communication mega-constellations including the SpaceX Starlink, Eutelsat OneWeb, Amazon Kuiper, and Chinese G60 constellations, there are currently thousands of artificial satellites in Low Earth Orbit (LEO)2 and tens of thousands more planned for launch over the next decade [1]. Satellite flaring is an optical phenomenon which occurs when sunlight reflects off a satellite's surfaces, such as antennas or solar panels. This paper discusses specular and diffuse reflection of sunlight from man-made satellites and how these effects can be misinterpreted as unidentified anomalous phenomena (UAP). It also provides a method for observers to determine whether observations may be attributable to satellite flaring. Background Using reflected sunlight from man-made satellites to observe and track their movement goes back to the earliest days of space exploration [2]. As noted above, several companies develop and launch mega-constellations, providing internet access to most of the globe. Currently, there are nearly 10,000 artificial satellites in LEO and this number is expected to grow several-fold over the next decade [1]. Figure 1 illustrates the location of Starlink satellites in orbit as of December 2, 2024, at 11:00 AM Eastern Standard Time. As of the end of November 2024, there were over 6,700 Starlink satellites in orbit. Figure 2 illustrates the concepts of diffuse and specular reflections, which describe how light bounces off objects. Figure 3 shows how sunlight reflected in these two ways is directed toward an observer on the surface of the Earth. As seen in the left side of Figure 2, diffuse reflection occurs when light reflects from a rough or irregular surface. Light impinging upon a rough surface reflects in many directions, which spreads the light over a large range of angles from the reflecting surface, as illustrated by the gray colored "light cone” in the Figure 3(a). From a single observation point, this cone of light can be visible for up to several minutes as the satellite moves in its orbit across the sky. Additionally, the intensity of reflected light significantly decreases the further away the observer is from the reflecting surface. At the Earth’s surface, the intensity of diffusely reflected light from a satellite in LEO will typically have diminished to the point that the brightness is 1 Any reference to a non-federal entity is for informational purposes only and does not constitute an express or implied endorsement of any commercial service, from AARO, the Department of Defense, or the Executive Branch. This report focuses on Starlink satellites, but its principles are applicable for any analogous satellite constellation. 2 Altitude for Low Earth Orbit (LEO) ranges from 300km to 2,000km. All-Domain Anomaly Resolution Office Chief of Staff, AARO 1 Authority: FY24 NDAA, now codified at 44 U.S.C. 2107 Page determined to be Unclassified Date: 2/14/2025 Reviewed by Chief of Staff, AARO Released in Full: X IAW FY24 NDAA, Section 1841(a)(1)(C) Case Number: 330UAP000027 Date: 2/14/2025