Observation by Nick James: Starlink glint geometry
Uploaded by
Nick James
Observer
Nick James
Observed
2023 Jan 09 - 19:36
Uploaded
2023 Jan 11 - 22:26
Objects
Spacecraft
Equipment
Exposure
10s max stacks
Location
Chelmsford, UK
Target name
Starlink
Title
Starlink glint geometry
About this image
This timelapse from my UK004G meteor camera shows an interesting phenomenon related to the way that the Starlink satellites are orientated in space. In operation the each of the satellites is effectively a thin tile with a its large, flat face pointing downwards towards the centre of the Earth. This face is designed to be shiny in order to minimise scattered light and reduce the visible magnitude of the spacecraft. This works most of the time but it is possible to get a glint from this shiny, flat surface when the geometry is right.
From the satellite's point of view the glint happens when the Sun and the observer are on opposite limbs of the Earth. For a satellite at 550km altitude and an Earth radius of 6,378 km the angle between the Sun and the observer in these circumstances is around 44 degrees and the slant range is around 2,700 km. In this example the satellites are at an altitude of 13 deg and the Sun is 31 deg below the horizon in the same direction as the satellites. In the evening the centre of the glint region moves downwards and to the north as the Sun gets further below the horizon.
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