Brightness variation period of the USA 144 decoy (1999-028C), 21 May 2017

From: Marco Langbroek via Seesat-l <seesat-l_at_satobs.org>
Date: Thu, 25 May 2017 16:29:15 +0200
On 24-5-2017 Alain Figer wrote, in response to my observational report:

> Hi Marco,
> 
> You wrote :
> 
>> Obtained a long datastring (a few thousand points spanning several minutes) 
>> on the USA 144 decoy in order to analyse its brightness behaviour.
> 
> I measured its photometric period on 23 May 2017 at 42.9s. 


I have now completed the analysis. The resulting curve can be seen in this blog
post:

https://sattrackcam.blogspot.nl/2017/05/updating-changing-tumble-period-of-usa.html

Fitting a sinusoid to 2838 photometric point measurements obtained over a 7m
55.5s timespan, spanning pre- and post culmination, I get a peak-to-peak period
of 43.528 +- 0.005 seconds (21 May 2017, 22:17:51 to 22:25:46 UT).

This is close to but slightly different from Alain's 42.9 s figure above,
perhaps the result of foreshortening effects.

The brightness varied between mag +7.2 (R band) and invisible (= fainter than
mag +9.4).

The photometry was done with TANGRA on a video obatined with a WATEC 902H and
Samyang 1.4/85 mm lens.

- Marco


-----
Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.
e-mail: sattrackcam_at_langbroek.org

Cospar 4353 (Leiden):     52.15412 N, 4.49081 E (WGS84), +0 m ASL
Cospar 4355 (Cronesteyn): 52.13878 N, 4.49937 E (WGS84), -2 m ASL
Station (b)log: http://sattrackcam.blogspot.com
Twitter: _at_Marco_Langbroek
-----
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Received on Thu May 25 2017 - 09:30:03 UTC

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