Re: TJM Starlink Darksat obs 2020 04 03 UTC

From: Anthony Mallama via Seesat-l <seesat-l_at_satobs.org>
Date: Sat, 4 Apr 2020 08:48:31 -0400
I entered Ted's data as input to the three brightness models I am
maintaining. The dimming of Darksat relative to the mean of other Starlink
satellites is as follows: flat-panel model, 2.2; phase-angle model, 1.7;
and distance-only model, 2.3. So, in general about +2 magnitudes of
dimming. (References for flat-panel model:
http://www.satobs.org/seesat/Mar-2020/0109.html and
https://arxiv.org/abs/2003.07805.)

The only other visual magnitude that I've located for DarkSat at its
operational altitude was recorded by Jay Respler (reference:
http://www.satobs.org/seesat/Mar-2020/0126.html). He commented in his
report for that observing session "STARLINK 1130 DARK is one of the
Brighter sats!". For the three models mentioned above DarkSat was indeed
brighter than the mean by 2.8, 2.9 and 3.1 magnitudes, respectively, or
about -3 magnitudes.

The brightness ratio between +2 and -3 magnitudes is 100. It seems likely
that Respler observed a strong Starlink flare. Other Starlink satellite
'flashes' have been reported by Brad Young (reference:
http://www.satobs.org/seesat/Mar-2020/0023.html). Brightness surges could
be due to Sun-glint from the flat-panel shaped bodies of these sats or from
their solar arrays.

One additional observation of DarkSat was reported by Tregloan-Reed et al.
(reference: https://arxiv.org/pdf/2003.07251.pdf). They recorded DarkSat
and a reference satellite (Starlink-1113) in the g' band-pass (475
nanometer) of the Sloan photometric system. DarkSat was found to be 55%
fainter than the reference when the observed brightness was adjusted for
the distance to each satellite. When my flat-panel model is taken into
account, DarkSat is found to be 61% fainter. Those percentages each
correspond to approximately one magnitude of dimming.

Tony Mallama
_______________________________________________
Seesat-l mailing list
http://mailman.satobs.org/mailman/listinfo/seesat-l
Received on Sat Apr 04 2020 - 07:49:31 UTC

This archive was generated by hypermail 2.3.0 : Sat Apr 04 2020 - 12:49:31 UTC