Impact of satellite glints on the transient science on ZTF scale

TL;DR

Satellite glints from orbiting debris significantly contaminate ground-based astronomical observations by producing false transient signals, and this study develops detection methods to quantify and mitigate their impact on surveys like ZTF and LSST.

Contribution

The paper introduces a routine for detecting satellite glints in single exposures and applies it to ZTF data, revealing their prevalence and characteristics across various orbits.

Findings

73,000 glint events detected in ZTF images

Glints pollute 3.6% of ZTF images between 2019-2021

Glint flashes have durations of 0.1 to 10^{-3} seconds with brightness increases of 2-14 magnitudes

Abstract

Thousands of active artificial objects are orbiting around Earth along with much more non-operational ones -- derelict satellites or rocket bodies, collision debris, or spacecraft payloads, significant part of them being uncatalogued. They all impact observations of the sky by ground-based telescopes by producing a large number of streaks polluting the images, as well as generating false alerts hindering the search for new astrophysical transients. While the former threat for astronomy is widely discussed nowadays in regard of rapidly growing satellite mega-constellations, the latter one -- false transients -- still lacks attention on the similar level. In this work we assess the impact of satellite glints -- rapid flashes produced by reflections of a sunlight from flat surfaces of rotating satellites -- on current and future deep sky surveys such as the ones conducted by the Zwicky Transient Facility (ZTF) and the Vera Rubin Observatory Legacy Survey of Space and Time (LSST). For that, we propose a simple routine that detects, in a single exposure, a series of repeated flashes along the trajectories of otherwise invisible satellites, and describe its implementation in FINK alert broker. Application of the routine to ZTF alert stream revealed about 73,000 individual events polluting 3.6\% of all ZTF science images between November 2019 and December 2021 and linked to more than 300 different glinting satellites on all kinds of orbits, from low-Earth up to geostationary ones. The timescales of individual flashes are as short as $0.1$--$10^{-3}$ seconds, with instant brightness of 4--14 magnitudes, peak amplitudes of at least 2--4 magnitudes, and generally complex temporal patterns of flashing activity. We expect LSST to see much more such satellite glints of even larger amplitudes due to its better sensitivity.