Re: [Orekit Users] HEE or GSE Frames?

[MAISONOBE Luc <luc.maisonobe@c-s.fr>]

Hi Simon,

"Spörri Simon (s)" <simon.spoerri@students.fhnw.ch> a écrit :

> Hi Luc,
>
> thanks a lot! i'll try setting up an HEE transform from ICRF and GSE  
> from GCRF. However, as of which release is the ICRF available? IMHO  
> it is not available before 6.0-Snapshot, and there i do have  
> building problems due to the missing commons-math 3.2 Snapshot.

Yes, you will have to use this version. Another reason for this is  
that the TransformProvider interface was added last year only.

> Afaik you're also involved in the commons-math development... Do i  
> have to build the current commons-math Trunk as 3.2-Snapshot to get  
> this working?

Yes, the current Orekit snapshot depends on some features available  
only in Apache Commons Math 3.2. So for the few days to come, you'll  
have to build it by yourself.

Note, however, that we are really close to release Apache Commons Math  
3.2 officially. I expect to start the release process near the end of  
this week. Once Apache Commons Math will be officially released, we  
will also release Orekit 6.0 afterwards.

> I could also derive my transformations from the  
> SolarSystemBarycenters Frame, but I think this is (still?) EME2000  
> based?

Yes. I'll fix ICRF probably today, though.

best regards,
Luc

> Cheers,
> Simon
>
>
> From: MAISONOBE Luc <luc.maisonobe@c-s.fr<mailto:luc.maisonobe@c-s.fr>>
> Reply-To: <orekit-users@orekit.org<mailto:orekit-users@orekit.org>>
> Date: Wed, 27 Mar 2013 10:26:36 +0100
> To: <orekit-users@orekit.org<mailto:orekit-users@orekit.org>>
> Subject: Re: [Orekit Users] HEE or GSE Frames?
>
> simon.spoerri@students.fhnw.ch<mailto:simon.spoerri@students.fhnw.ch> a  
> écrit :
>
> Dear all,
>
> Hi Simon,
>
>
> I am developing a webbased visualization tool of in-situ data gathered by
> various satellites. Now fyi i am not very proficient in astronometry or
> astrophysics... Nevertheless I'd like to use orekit to consolidate
> coordinates
> from different coordinate systems provided by the data sources which
> use mostly
> HEE (Heliocentric Earth Ecliptic) or GSE (Geocentric Solar Ecliptic)
> coordinates. Now i was wondering if there already are some helper classes or
> predefined transforms that could be used for transformations to ICRF or GCRF
> respectively from the aforementioned coordinate systems
>
> Unfortunately, these coordinates systems are not supported (yet) by Orekit.
>
> The only global solar system frame we have is ICRF, located at solar
> system barycenter, and I even think it's orientation is slightly wrong
> (the famous 18 mas offset between GCRF and EME2000 striked again ...).
>
> By the way, could someone confirm me that GCRF and ICRF should be
> aligned? If so, I'll fix our ICRF.
>
> Implementing a new frame is mainly a matter of implementing the
> TransformProvider interface which only declares one method:
> getTransform(AbsoluteDate date) between the new frame and one existing
> frame chosen as its parent. All the rest (inserting the frame in the
> tree, providing cache and thread safety, combining transforms) is
> already done by the rest of the framework.
>
> Considering Heliocentric Earth Ecliptic, I would select ICRF as its
> parent frame so there are no translations (both centered at solar
> system barycenter). In order to compute the rotation, we need the
> Earth motion, which is already available in Orekit using JPL
> ephemerides (see the package bodies). So the first direction , from
> solar system barycenter to Earth is easy to get in ICRF. The second
> direction (normal to the ecliptic) can be computed at each time using
> the cross product of position and velocity, but this would provide an
> instantaneaous ecliptic. I don't know if the precise definition of
> this frame use an instantaneous value or some mean value. If a mean
> value is used, then there is probably a simple model for it, perhaps
> even a fixed direction.
>
> Considering Geocentric Solar Ecliptic, it seems to me it could be
> defined either by a similar process as HEE but starting from GCRF
> instead of ICRF (and reversing the X direction, of course), or defined
> starting from HEE and performing a translation towards Earth and a 180
> degrees rotation.
>
> hope this helps,
> Luc
>
>
>
> help is very appreciated!
>
> cheers,
> Simon
>
>
>
>
>
> ----------------------------------------------------------------
> This message was sent using IMP, the Internet Messaging Program.



----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.