A paper published at ApJ

A paper published at ApJ

Created
December 10, 2025
Tags
PaperComputer VisionAstronomy
Updated
December 10, 2025

We are pleased to announce that our paper “Second-timescale Glints from Satellites and Space Debris Detected with Tomo-e Gozen” has been accepted to the Astrophysical Journal (ApJ).

Masaomi Tanaka*, Ichiro Takahashi, Naoki Yoshida, Naonori Ueda, Akisato Kimura, Kazuma Mitsuda, Hirofumi Noda, Shigeyuki Sako, Noriaki Arima, Mitsuru Kokubo, Tomoki Morokuma, Yuu Niino, Nozomu Tominaga, Kenzo Kinugasa, Naoto Kobayashi, Sohei Kondo, Yuki Mori, Ryou Ohsawa, Hidenori Takahashi, Satoshi Takita, “Second-timescale Glints from Satellites and Space Debris Detected with Tomo-e Gozen,” the Astrophysical Journal (ApJ), 2025.
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A search for second-timescale optical transients is one of the frontiers of time-domain astronomy. However, it has been pointed out that reflections of sunlight from Earth-orbiting objects can also produce second-timescale “glints.”

Tomo-e Gozen Facility,

We conducted wide-field observations at 2 frames per second using Tomo-e Gozen on the 1.05 m Kiso Schmidt telescope.

(Top) Survey footprints of our observations in the equatorial coordinate. The color represents the total exposure time for each part of the sky. (Bottom) Distribution of the detected glints. The blue points show all the glints, while the orange points show those associated with cataloged objects. Note that the coordinates of the glints are given as viewed from the Kiso observatory.
(Top) Survey footprints of our observations in the equatorial coordinate. The color represents the total exposure time for each part of the sky. (Bottom) Distribution of the detected glints. The blue points show all the glints, while the orange points show those associated with cataloged objects. Note that the coordinates of the glints are given as viewed from the Kiso observatory.
Magnitude distribution of he detected glints (blue). Gray line shows the magnitudes of the glints detected in images deeper than 16.5 mag, which is used for the event rate estimate. The magnitude distribution of the glints associated with cataloged objects in shown with orange line.
Magnitude distribution of he detected glints (blue). Gray line shows the magnitudes of the glints detected in images deeper than 16.5 mag, which is used for the event rate estimate. The magnitude distribution of the glints associated with cataloged objects in shown with orange line.

We identified 1554 point-source glints that appeared in only one frame (0.5 s). Their brightness ranges from 11 to 16 mag, with fainter glints being more numerous. These glints are likely caused by satellites and space debris in high-altitude orbits such as the geosynchronous Earth orbit or highly elliptical orbits. Many glints brighter than 14 mag are associated with known satellites or debris with large apogees (>30,000 km).

In contrast, most fainter glints are not associated with cataloged objects and may be due to debris with sizes of 0.3–1 m. The event rate of second-timescale glints is estimated to be 4.7 ± 0.2 deg−2\rm{deg}^{-2} hr−1\rm{hr}^{-1} (average) and 9.0 ± 0.3 deg−2\rm{deg}^{-2} hr−1\rm{hr}^{-1} (near the equator) at 15.5 mag.

Our results demonstrate that high-altitude debris can represent a significant foreground in searches for second-timescale optical transients. They also imply that deep surveys such as Rubin/LSST will detect many of these glints in single-exposure images.

The press release (in Japanese) regarding this paper can be found at https://www.tohoku.ac.jp/japanese/2025/11/press20251126-03-space.html , and more details of this paper can be checked at https://doi.org/10.3847/1538-4357/ae0f99 .