# [amsat-bb] Re: G3RUH plan 13 algorithm help

Gus gus at 8p6sm.net
Fri Jan 24 04:33:53 PST 2014

```Yes, but one thing I've never quite understood was how to convert RAAN
into Longitude.  All the neat explanations on non-earthly frames of
reference and vernal equinoxes stop short of explaining how to start
with RAAN (in a set of elements) and compute forward in time from the
epoch to get the longitude of the ascending node of the current orbit.
Anyone with a link to an online resource that can help make this clear?

On 01/24/2014 05:38 AM, David Johnson wrote:
> HI,
>
> Right Ascention of the Ascending node.
>
> The point in the orbit at which it crosses the equator going northbound.
>
> Here 's a good example:
>
> http://www.pe0sat.vgnet.nl/satellite/
>
> 73
>
> Dave, G4DPZ
>
> On 24/01/14 08:59, Lizeth Norman wrote:
>> *HI all,Found this at this
>> page:http://www.amsat.org/amsat/articles/g3ruh/111.html
>> <http://www.amsat.org/amsat/articles/g3ruh/111.html>Orbit Plane:* Fixed
>> (almost) with respect to the stars, in orientation defined by argument of
>> perigee, inclination and RAAN.
>> Origin: Earth's centre.
>> X: Directed towards perigee
>> Y: 90 degrees from perigee round the orbit in direction of satellite's
>> motion
>> Z: Perpendicular to orbit plane
>> I think I understand most of the math in the algorithm. In the above
>> context, what does RAAN mean?
>> Sorry for being obtuse!
>> Norm n3ykf
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>

--
Gus 8P6SM
The Easternmost Isle
```