Re: Starlink-7 'train' seen

From: Richard Cole via Seesat-l <seesat-l_at_satobs.org>
Date: Fri, 5 Jun 2020 05:47:10 +0000
The Starlink-7 orbit is currently all-Sun, so the altitude of Sun at the 
spacecraft is only varying by a few degrees, 0+/-14deg. If the panels 
are actively tracking the Sun at all (which they probably don't need to 
given the small range), while keeping in low-drag mode, the panel is 
near local vertical at all times.

For Marco's observation (max alt of 83 at az 155, I think), and if 
panels were Sun-tracking, there would have been a reasonable glancing 
angle of panel to see, ~22 degrees, given the local Sun altitude at the 
time. The fact he saw them faint suggests they are not fully 
Sun-tracking at this time.

If they were adopting one elevation angle only, say +5deg, around the 
orbit, then visibility from northern latitudes would be poor if the 
spacecraft were near zenith.

The attitude control mode of the panels in very early operations (i.e. 
in safe mode) has not been understood, though it might be expected to be 
simpler than whatever is used later while getting sufficient power to 
work in safe mode. Perhaps they are programmed to use one panel 
elevation only in safe-mode? The one in use at the moment is +5, or 
perhaps just zero?

regards

Richard Cole


On 04/06/2020 23:13, Marco Langbroek via Seesat-l wrote:
> 
> 
> 
> Observed the Starlink-7 'train' from yesterday's launch from Leiden, the
> Netherlands, through clearings in the cloud cover, near 22:44 UT (4 Jun). This
> was a zenith pass, and they were faint: visible in binoculars, but not naked eye.
> 
> Video had, alas, a field of clouds in the FOV as they were passing.
> 
> So it really is becoming a pattern: high elevation passes are not good for the
> brightnes sof these satelllites, passes lower in the south are more favourable.
> Counter-intuitive, but true for these flat satellites!
> 
> - Marco
> 
> 
> -----
> Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.
> e-mail: sattrackcam_at_langbroek.org
> 
> Station (b)log: http://sattrackcam.blogspot.com
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> Twitter:        _at_Marco_Langbroek
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Received on Fri Jun 05 2020 - 00:48:05 UTC

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