[Orekit Developers] [SOCIS 2011 | Android] Status of the test application

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

Hi,

As I said in my previous message, I'm working on a text-mode test
application just to see if I ask the correct parameters and to see if
I correctly understood how Orekit works. The idea is to make it manage
everything asked for the final Android application with all the
settings which will be asked in Android application.

Thanks to all the people in the Orekit team, there is a forge for the
SOCIS 2011 project, available here :
https://www.orekit.org/forge/projects/socis-2011 so you can get the
source code using git.

You can build the test application as a typical Eclipse project (you
may need to change the absolute paths to orekit and common-math jars).
If you want a runnable JAR snapshot, I can give you one, just ask me
:) The test application should do the tasks asked in the original
SOCIS idea on the Orekit's wiki, such as orbit conversion, visibility
test from a ground station and impulse maneuver computation (revision
d8816904).

* Orbit conversion : I don't currently convert from other kind of
orbits to TLE as I didn't found any way to do this in the Orekit API
(maybe I haven't searched enough), but conversion to TLE should work.
I have a little problem here, when I convert to an other orbit type
and back, I always get different values. For instance (using the
values in the VisibilityCheck tutorial) :

cartesian parameters: {P(-6142438.668, 3492467.56, -25767.2568),
V(505.8479685, 942.7809215, 7435.922231)}
=> keplerian parameters: {a: 7069220.386682823; e:
4.7773560605573003E-4; i: 98.18525099174988; pa: 13.741061002484;
raan: 150.34825333049; v: -13.952151446377911;}
=> cartesian parameters: {P(6678075.265811305, -2061220.4235367593,
1058183.5469654775), V(-811.5757877856272, -5310.96037055833,
-5246.935091790779)}

--

cartesian parameters: {P(-6142438.668, 3492467.56, -25767.2568),
V(505.8479685, 942.7809215, 7435.922231)}
=> circular parameters: {a: 7069220.386682823, ex:
4.640624024164525E-4, ey: 1.1347861453554246E-4, i: 98.18525099174988,
raan: 150.34825333049, alphaV: -0.2110904438939327;}
=> cartesian parameters: {P(6675791.679616528, -2060515.583546613,
1057821.6981928425), V(-809.9979252320031, -5313.349791618699,
-5248.435897099367)}

--

cartesian parameters: {P(-6142438.668, 3492467.56, -25767.2568),
V(505.8479685, 942.7809215, 7435.922231)}
=> equinoctial parameters: {a: 7069220.386682823; ex:
-4.5943365025280937E-4; ey: 1.3096576006275438E-4; hx:
-1.00299611012708; hy: 0.5709798956859086; lv: 150.1371628865961;}
=> cartesian parameters: {P(6154945.399984764, -3340147.482146172,
989070.1001473623), V(399.397286380678, -1444.6395330257305,
-7354.513659130439)}

I hope it's correct, but that seems strange. Maybe all the conversion
thing I did is wrong, but I reviewed the code multiple times and I
don't know what could cause that (except when I'm saying that the
toString() attribute outputs TRUE position angle type, but that's what
I understood in the Orekit API documentation).

* Visibility test from a ground station : It's basically a copy/paste
of the code present in tutorial/, with prompting the values from the
command-line instead of using only predefined constants.

* Impulse maneuver : I don't know if it's what is requested, but I've
handled this by asking a start date & maneuver length (in sec),
stopping the simulation at initial_date + start_date + maneuver_time
and showing the current orbit parameters just after the simulation
stopped.

As I don't know how to find data to test it, I may did some mistakes I
didn't noticed but I hope this app works :) I may also be wrong in
understanding how this works, just tell me so I can fix this :)

Ask me if you have any idea, if you think that I ask one parameter
which is useless (or if you want one more), or anything :)

Have a nice day

Alexis