OTV-4 X37B located and orbital elements

From: Greg Roberts via Seesat-l <seesat-l_at_satobs.org>
Date: Wed, 27 May 2015 20:21:35 +0200
When visible passes were due to start over Southern Africa on the
25th May 2015 I realized that my chances of seeing it were minimal
due to almost continuous cloud during my winter season for the next
two-three months so I posted predictions for several of the cities
in South Africa on my FACEBOOK page using the search elements
provided by Ted Molczan and hoped that some people, especially in
the amateur astronomical community, would respond and join in the fun.

To cut a long story the appeal did pay off and late today Ted was able
to issue an accurate orbit which has been confirmed by observations
just made ,and still to be measured and reported.

The story begins with Deon van Rooyen , who lives in Krugersdorp, close
to and west of Johannesburg, who secured two images of a possible
satellite on the 25th May running quite a bit early on Teds search
orbit.  On the 26th Hannes Pieterse,  who lives in Bloemfontein , secured
an almost accidental image - he refers to it as a "shot in the dark"
when he recorded a satellite trail as he was setting up his equipment
early to look for the satellite and deciding what exposure to use. Luckily
he recorded the satellite just as it started entering the earths shadow.
A few seconds later and we might still be looking for it!

With this new information Ted was able to determine the orbit given below.

IOD report:
40651 15 025A   0098 G 20150525165115000 27 25 0857566+201583 17 S
40651 15 025A   0098 G 20150525165128000 27 25 0931879+165172 17 S
40651 15 025A   0098 G 20150525165136000 27 25 0955831+141313 17 S
40651 15 025A   0099 G 20150526170439000 27 15 0725027-031439 17 S

OTV 4                                                    312 X 325 km
1 40651U 15025A   15146.67143856  .00012365  00000-0  50000-4 0 05
2 40651  37.9580 299.6157 0009895 251.1044 108.8670 15.85136336 08
Arc 20150525.7-0526.71 WRMS resid 0.052 totl 0.012 xtrk

Eccentricity and rate of decay remain guesses.

These elements were confirmed to be virtually "spot-on" as I was able to
secure fourteen images on tonight's pass through a reasonably cloudy sky
and will measure and post tomorrow.

As yet I have not received any other reports but expect some to come in
over the space of the next hour or so.

My thanks go to Deon and Hannes  -  and to the other observers who got
negative results for one or other reason.  This is the first time any of 
have done any "serious" satellite observing and maybe the sense of
achievement,  and excitement of the chase,  might encourage them to do
some more :-))

Thanks also to Ted Molzcan  and Cees Bassa  who put a lot of work into
deriving orbits that fitted the data provided.  Without their input this
report would not be possible.

I think I should also mention that Teds pre-launch elements for
LIGHTSAIL were virtually "spot on" as I received radio transmissions
from it a few hours after launch on the 20th May 2015.

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Received on Wed May 27 2015 - 13:22:26 UTC

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