In this timelapse video a passing satellite is captured while orbiting the Earth, tumbling around it self and flashing in the sky. Many satellites do not have a constant brightness, they give off flashes which are often at regular times. As described by the Satellite Observers ( this flashing behavior is caused by the rotation of the satellite around its rotation axis. The satellite's metallic surfaces act as mirrors for the sun. Measuring the period between flashes give an approximation for the satellite's rotation period.
In this starry night of La Palma, Canary Islands, stars rise over the famous Isaac Newton Telescope in the observatory complex located on the top of the island. The V-shaped star configuration in this telephoto view is the head of constellation Taurus, the Bull, known as the Hyades star cluster. The bright star is Aldebaran, the Bull's eye.

Based on the imaging time and camera information the satellite is identified by Ted Molczan of It is the Glonass navigation satellite Cosmos 2364 (98077A / 25593). The satellite's angular velocity was ~0.01 deg/second. The satellite altitude was 19148 km and 23631 km from the observer as it was captured near the horizon. Its orbital period is 675.73 minutes. The flashes probably are specular reflections from the solar array, caused by rotation of the satellite, which probably no longer operates.

The timelapse is a 42-minute sequence starting around 1:30 UT, 2011 August 31. Each frame is 15 second exposure (+ 1s for intervals) and the video is 24 frames per second.

All rights reserved by Babak Tafreshi ( of The World at Night (TWAN) program.

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