[amsat-bb] Tracking EO 79

Wouter Weggelaar wouterweg at gmail.com
Mon Nov 14 19:14:41 UTC 2016

Hi Steve,

Spot on. Is is indeed a set of timers running off the eclipse
detection, and this will indeed make the on time drift.
We have not decided yet how to handle the drift, and we are still
characterizing the behavior of the transponder and its effect on the
power budget.

We are looking for longer term trends, as the utilization of the
transponder varies quite a lot in the short term. If we are power
positive enough, we may for instance lengthen the activation period.

But we also need to still do things like getting housekeeping and
whole orbit data down, and detumble the satellite periodically.

We will see how this develops over time!

Wouter PA3WEG

On Mon, Nov 14, 2016 at 4:07 PM, Greene, Stephan A
<stephan.a.greene at vencore.com> wrote:
> Yes, AO-27 used a similar technique ("TEPR") beginning not long after
> launch and for similar reasons - a computationally easy (for the
> satellite) way to control the transmitter (time after exiting eclipse)
> to ensure a positive power budget.  Although the link to the original
> page on amsat.org explaining it is broken,  a copy was posted here:
> http://www.om3ktr.sk/druzice/teprstates.html    The diagram assumes the
> satellite orbit is counter-clockwise and the "on" times are for
> descending node (North to South) passes.  Re-order the segments for
> ascending node (South the North).  The AO-27 command team later replaced
> "TEPR" with "TOPR", using an algorithm based on when the satellite is
> over the desired latitude band - easier for humans to understand, more
> calculating on the satellite.  (Guessing this occurred in late
> 1996-early 1997 based on amsat-bb email archives)
> The EO-79 control ops will have to adjust the timer settings in the
> satellite's software periodically to keep the transponder's "on" time
> roughly over the same latitude range.  Otherwise, as was experienced
> with AO-27, the band of latitudes where the transponder is on will
> "drift" seasonally.  It will move South approaching the Northern
> hemisphere winter solstice next month, and move North until the summer
> solstice.
> 73 Steve KS1G
> -----Original Message-----
> From: Greg D [mailto:ko6th.greg at gmail.com]
> Sent: Saturday, November 12, 2016 2:41 PM
> To: Amsat BB
> Subject: Re: [amsat-bb] Tracking EO 79
> Didn't AO-27 do something very similar?  There was an application for it
> that did the calculations.  I forget who the author was; perhaps it (the
> program, not the author) could be modified for EO-79?
> Greg  KO6TH
> Paul Stoetzer wrote:
>> It's basically calibrated for mid-northern latitudes now, so we should
>> hear it on daytime NA passes.
>> It wouldn't be difficult to write a script to calculate on and off
> times.
>> 73,
>> Paul, XE3/N8HM (currently in Progreso, Yucatán, Mexico)
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