[Orekit Developers] SOCIS 2011

[Alexis ROBERT <alexis.robert@gmail.com>]

Hi,

First of all thanks a lot for selecting me! I'm very happy to program
on Orekit during my summer! :)

I know I could have sent a little "hello" message as SOCIS organizers
advertised as soon as the announcement came out, but I preferred to
wait until I have something to discuss instead of sending an
uninteresting plain hello mail :)

By the way, it seems that this mailing list has not a lot of traffic,
and I hope nobody will not be annoyed but the mails about the SOCIS
progression and hire a professional killer to make me quiet which is
something I may find unpleasant. I've heard that some people opened a
blog for their GSoC but that may not be as interactive as a
mailing-list, so just tell me what do you prefer :) (or if you have
other ideas)

About source code management, I've seen you use git, and I was
planning to open a temporary project on Gitorious, which enables to
have multiple repositories so that I can have test repositories
without disturbing Orekit's forge, and we could simply push the final
repository on the Orekit forge when the progress is sufficient. Is it
ok for you ? :)

As I wrote in my proposal (available here :
https://www.orekit.org/wws/arc/orekit-developers/2011-07/msg00005.html
), I'm currently starting with understanding the computations and
making them in J2SE (because making the GUI layout without
understanding what's required and how to do that is pretty certain to
lead to errors), and I have some questions (the most part is just to
see if I understood correctly -- if it's ok, I will post the J2SE app
just to see if it's ok for you and if it's what you want the Android
app to do).

About computing visibility from a ground station (I figured out that
ground station visibility was in the tutorial/ folder, thanks for
that! :) ) :

* If I understood correctly the required parameters for the final user
would be only initial date, position, velocity (in the EM2000 frame),
station coordinate (in terrestrial frame), maxCheck (for the event
detector) and elevation (which triggers the event), is that right ?
* In the example, a Keplerian propagator is used, with the "(could be
more elaborate)" mention in comments. Would you like something else ?
* Will the elevation check sufficient out of the tutorial usage ? (I
really don't know about this question, just asking to be sure :) )
* I've seen there is not explicit code for managing earth rotation, is
it taken into account implicitly by saying that the Earth body is in
the terrestrial frame ? If it's taken into account implicitly,
shouldn't we add an other date  to specify the coordinates on earth
(or initial earth position) ?

About orbit conversion :

If I understood correctly, it's just for instance something like that :

  KeplerianOrbit ko = // init code
  CircularOrbit co = new CircularOrbit(ko);

am I right ?

About impulse maneuver :

* If I understood correctly, the way to manage maneuver, is to use a
Numerical Propagator and to select some forces like Gravity and an
Impulse Maneuver force. As the impulse maneuver requires a trigger
event, is it simply start date and end date of the maneuver ?
* If I understood correctly again, the parameters available for the
final user would be initial date, initial position & velocity of the
body (in the EM2000 frame), start time for the maneuver, end time for
the maneuver and the velocity delta, am I right ?

Thank you again, and have a nice day :)

Alexis Robert