Re: [Orekit Developers] [esasocis2012] report of 1 week (android dev)

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

Nigi Fabio <nigifabio@gmail.com> a écrit :

> hi all,

Hi Fabio,

> in the first week my completed todo list is:
> study the code
> make same little bug fixing

Could you detail what bug you fixed?

> add latest version of library embedded to code
> fix same warning and little problem on code
> updated android lib to 4.1 support (in progress)
>
> todo for next week (please comment add or remove thing i really appreciate)
>
> improve visual experience to 4.1 and retrocompatibility (and
> tablet/orientation mode)

Good.

> remove same minor warning on interface
>
>
> i ask again there is same functionality that you need over this?

The functions I would like to have are for example close encounter  
detection with two orbits. This can be done with one propagator for  
the first object, one dediczated event detector registered within the  
first object propagator. The event detector would have a reference to  
an analytical propagator for the second object and would monitor the  
dot product of relative velocity direction with respect to relative  
position direction. When this dot product is positive, the distance  
between the two objects increases with time. When this dot product is  
negative, the distance decreases. When the dot product is zero (i.e.  
when an event is triggered, the objets are at a local maximum or  
minimum distance (maximum if the dot product crosses zero from  
positive values to negative values, i.e. when the "increasing" boolean  
indicator is false), minimum otherwise.

So with this setup, when we launch the first propagator, at each event  
function check the event handler will compute its g function, which  
will ask the second propagator to provide position/velocity at the  
current date, from which relative values and dot product are computed.  
The propagator and event detection framework will detect the zero  
crossings and will call the "eventOccurred" method. You can put some  
code in this method to log the event and display it on the  
application, with event date, current distance, and indication if it  
is a maximum or minimum distance. It would be nive to also be able to  
filter some values. For example we may not be interested by maximum  
distances but only by minimum distances, and in fact even only by  
minimum distances that are below some safety threshold (this is a  
classical need for debris collision risks).

> there is samething in the old great app that is annoying when you use it?

Managing orbits and displaying their value could be improved. For now,  
they are displayed by a simple call to toString() if I remember well,  
and this is difficult to read.

best regards,
Luc

> thanks,
> Fabio
>
> --
> Fabio Nigi



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