[amsat-bb] Re: sirius orbit name?

i8cvs domenico.i8cvs at tin.it
Fri Feb 22 19:51:58 PST 2008

----- Original Message -----
From: "Alan Sieg WB5RMG" <wb5rmg at somenet.net>
To: <amsat-bb at amsat.org>
Sent: Friday, February 22, 2008 6:23 AM
Subject: [amsat-bb] Re: sirius orbit name?
> The reference to the Molniya orbit could be to recall the orbit of
> AO-13...     slow high-altitude lingering Northern Hemisphere apogees,
> rotating ascending nodes about the globe to distribute coverage more
> evenly around the globe. Over the US, next over Europe, then over Asia.
> This was very popular at the time, and would likely be welcomed again.
> I would suspect that a 'tundra-inclined orbit', fixed over the US as the
> Sirius Radio Sats are, would not be as internationally well supported.
>    /;^)
> --
>   <- WB5RMG is Alan Sieg  *  http://wb5rmg.somenet.net ->

Hi Alan, WB5RMG

I agree with you because a "tundra-inclined orbit fixed over the US as the
Sirius Radio Sats are would not cover the whole globe in different times
of the day as did the "about" Molniya orbits of OSCAR-10, OSCAR-13
and AO40 having an orbit  inclination lower than 63.4 degrees.

By the way there is another very interest orbit suitable for the Amateur
Satellites  called "Apogee at Constant Time-of-Day Equatorial " or ACE



The ACE orbit developed by Andrew E. Turner and Kent M.Price of Ford
Aerospace was described in QEX magazine march 1989 and this article was
translated into italian and adapted with great details by my self  for Radio
Rivista 7/89

In my article I simulated the advantages to use the ACE orbit using the
following uptodated keplerian elements in AMSAT format that can be
filled by hand into any computer program following the specific software

For example using InstantTrack the epoch time listed belowe must be
introduced this way:  8 172.58333333

Satellite                   :  ACE
Epoch time              :  08172.58333333
Inclination               :  0.2 deg
RA of node              :  270.000  deg
Eccentricity             :  0.4873233583
Arg of perigee         :  90 deg
Mean anomaly         : 180 deg
Mean motion           :  5 rev/day
Decay rate                : 1.6e-07 rev/day^2
Epoch Rev               : 1
Beacon frequency    : 145.810 MHz

Additional celestial elements if needed :

S.M.A. semimajor axis   : 14454.26194 km
Anomalistic Period        : 288 min
Apogee                            : 15108 km
Perigee                            : 1028 km

If you run this keplerian elements  you will realise that the ACE orbit is
sun-synchronous and the acquisition of the satellite during day hours comes
at the same local time in any terrestrial area.

With a selected window of the launch epoch-time like in the above keplerian
elements the satellite is available for everybody at their favourable social

In addition only one satellite covers the whole terrestrial globe in 24
hours and the time of acquisition is the same in every place and for

For example the numbar of day hours that the satellite is in range is the
same for the East coast of USA and for Japan.

There are many advantages and of coarse disadvanges using an ACE orbit
and all of them are discussed into the above mentioned articles.

Enjoy !

73" de

i8CVS Domenico

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