Wednesday, 25 March 2020

SpaceX's Starlink Darksat is, indeed, darker

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The image above is a composit of stacked frames from four video sequences shot in the evening of March 22. Apart from a stray Chinese rocket booster that happened to cross the field, it shows four Starlink satellites from the 2020-001 launch: Starlink-1114 (2020-001P), Starlink-1030 (2020-001N), Starlink-1084 (2020-001B) and Starlink-1098 (2020-001D). These satellites are currently at their intended operational altitude.

Starlink 1030 is also known as DARKSAT
- it is the Starlink satellite that has been given an experimental coating to reduce its brightness.

As can be seen in the video stack, the coating indeed seems to reduce the brightness. The effect is also very apparent in the photographic imagery below, comparing Darksat to two other operational altitude Starlink satellites in the same orbital plane, Starlink-1114 and Starlink-1084 that both passed within 5 minutes of Darksat. The two regular Starlink satellites are well visible, but Starlink-1030 Darksat is very faint in the image:

click to enlarge
The video images were taken with a WATEC 902H and Canon FD 1.8/50 mm lens at 25 fps. The photographic images were taken with a Canon EOS 80D + EF 2.5/50 mm lens at 1000 ISO, 10 seconds exposure.

It is difficult to attach reliable magnitudes to the video and photographic imagery, but I'd say the magnitude difference between Darksat and the others is probably in the order of 1 to 2 magnitudes. Given their shape, the brightness which Darksat and other Starlink satellites can attain will probably be  highly depending on the viewing angle (as well as of course the phase angle at time of observation), i.e. which part of the satellite you are looking at.

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