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Mode Schedule explanation



Hello again,

I sent an email last night suggesting a schedule string for AO-27:

>> 000o196J242o
>> 
>> Where '0' is zero, 'o' is lower case 'oh' for "transponder off", 'J' is
>> when the Mode J transponder is ON.

Someone questioned what it all meant:

>With all that said, I am disappointed to report that I haven't the
>slightest idea what "000o196J242o" means, other than at 000 (whatever
>that is) the transponder is "o"ff, at 196 (whatever that is), the
>transponder is available in Mode "J", and at 242 the transponder is
>off again.

As a very quick explanation, the "196" above refers to the point in time
when the satellite has completed 196/255th (~77%) of one revolution of an
orbit.  The reference point is 0/255, which is at perigee (closest approach
to the earth).

The relationship between where perigee occurs, and where the satellite
exits from eclipse, is constantly changing, which is why this schedule
string is only good for a few days...  but entering the string every few
days is easier than wasting time chasing the satellite when it's switched off!

Just about every piece of amateur satellite tracking software should have a
means of entering the schedule, as Phase-based schedules were very
important for AO-10 and AO-13.  (Are there any other operational satellites
which run a Phase (MA *255/360) or TEPR-based schedule?)

So, it should be as simple as working out how to enter the schedule into
your favourite tracking program, and then you'll see when the satellite
will be on or off.


73 Chris vk6kch



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