[amsat-bb] A pass from the past

Bryan Green bryan at kl7cn.net
Wed Apr 1 23:25:04 UTC 2015

Hi, David!

I do gave the data as E-mailed to me each week from AMSAT via ARRL. I have an archive. 

When I tried as you suggested, neither Orbitron nor predict showed the time I observed -- they both have it coming over at about 05:34Z. They appeared to use current keps. 

Sent from my iPhone

> On Apr 1, 2015, at 15:50, David G0MRF <g0mrf at aol.com> wrote:
> If I understand you correctly, you need to predict where the satellite was a couple of months ago.
> To do that you need a set of keps from a date close to the one you are looking to predict.
> At present AO-73 shifts about 4 minutes over a period of 1 month, so you need to be within 1 week to get reasonable accuracy.
> I believe Celestrak or possibly the AMSAT archive may have this data.....but it's not very often used.
> Regards
> David
> -----Original Message-----
> From: Bryan Green <bryan at kl7cn.net>
> To: AMSAT-BB <amsat-bb at amsat.org>
> Sent: Wed, 1 Apr 2015 22:24
> Subject: [amsat-bb] A pass from the past
> Hello, all!
> Long story short:
> I have handwritten notes and a recording
> from a past AO-73 pass.
> My notes are dated that the pass was from 05:18Z -
> 05:31Z on 2015-01-29.
> My recording indicates that the start was at 05:19Z on
> 2015-01-29. (I have the clock on the MP3 device set to UTC).
> I have a
> spreadsheet of every pass I've tracked since the beginning of the year, and I'm
> going back to update the AOS, Max, and LOS azimuths, since I didn't start
> recording those until February.
> Here's what I did:
> Fed the AMSAT TLE file
> from 2015-01-30 into Orbitron.
> It predicts AO-73 AOS at 05:32Z, and LOS at
> 05:39Z
> Got the old-school predict program, fed it the same file, and got
> exactly the same results.
> How can I best simulate an orbit prediction from
> the past?
> I have SatPC32 but I don't understand how to use it to get a pass
> prediction.
> Thanks in advance for the help!
> -- bag
> Bryan
> KL7CN/W6
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