Re: [Orekit Developers] Status of the Android application -- 2

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

On Thu, Aug 11, 2011 at 11:01 PM, MAISONOBE Luc <luc.maisonobe@c-s.fr> wrote:
> Hi Alexis,

Hi,

> First of all, I'm sorry to be rather slow to answer these days, but I am on
> holidays and working in my house. Pascal is the backup mentor and can help
> you in most cases. I will try to be more responsive :-(

No problem :)

> I am still not able to install this version. My personal tablet keeps
> telling me « Orekit n'a pu être installé. Libérez de l'espace et réessayez.
> », despite I have only 206Mbytes used and 1.7GBytes available on the sdcard
> (and 6.6Gbytes available on an additional mounted sdcard). I have tried both
> versions from today (included the -2 one) and the version from two days ago.
> I think the problem lies in my tablet which still forec close most
> applications and ask for accounts reconfiguration at each reboot. I did not
> yet try to retrieve the syslog using adb.

Very strange :/

> By the way, I noticed you used the wrong logo for Orekit. The pink one was a
> variation suitable only for the forge theme. The proper logo is here:
> <https://www.orekit.org/forge/projects/orekit/repository/revisions/master/entry/src/site/resources/images/orekit-logo.png>
> (I can also send a scalable SVG version if you prefer).

Thanks, it will look better on a white background :)

> Concerning the other questions you asled earlier, I agree with everything
> Pascal said. I would stress out the fact TLE is really something weird. It
> is unfortunate it is so widely used as from a space flight dynamics points
> of view it has really many drawbacks. The reason why Pascal advised you to
> avoid extracting the orbit from TLE and put it in a Keplerian model is due
> to one of these drawbacks. This is probably out of scope, but as a summary
> the rationale is that TLE is not an orbit per se, it is a combination of an
> orbit *and* a propagation model, and the orbit part is filtered to work with
> the mathcing model and only with the matching model (it is a kind of what we
> call « mean orbit » with some specific high frequency parts removed, the
> removed parts being propagation model dependent). Using an orbit extracted
> from TLE with another propagation model (i.e. Kepler, Eckstein-Heschler,
> Brouwer, Lyddanne, numerical propagator, DSST, or anything else) does not
> work.

Ah ok.

I originally did this because of a sentence I've found on the old
static site saying "Even when no extrapolation in time is needed,
state information (position and velocity coordinates) can only be
computed threw the propagator. Untreated values like inclination,
RAAN, mean Motion, etc. can't be used by themselves without loosing
precision.", so I thought it meant that reusing the data computed
after an extrapolation to fill a KeplerianPropagator is OK, but
re-using it from the TLE object (directly by the getters) would be
wrong. But I understood wrong :/

> Concerning numerical keypad, I think the compromise to have numbers and not
> scientific notation is the least inconvenient one. Perhaps in the future we
> will have some default settings for huge values like attraction coefficient,
> so we may avoid entering it each time and simply select it from a list (you
> can have a look at the Constants class, which provides a few useful
> constants for our field, like several mu values and also Earth equatorial
> radius, flatness ...).

I was thinking of adding a "Settings" panel where you would set the
attraction coefficient (as well as the dataset path). By the way, if
you press "Menu" on the Orekit's home screen, there is a "Settings"
menu which shows an "Unimplemented" error :)

Alexis