Re: [Orekit Users] how to calculate iss passes

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

appdeveloper80@gmail.com a écrit :

> Hi,

Hi Matteo,

> I'm trying to calculate iss passes over Rome and I start from propagation
> tutorial and I write this code
> (https://gist.github.com/anonymous/fb939c0df8e6a72282eb27cc76840ac9).
> But if I compare the rise and set date with the Heavens Above prevision
> (http://heavens-above.com/PassSummary.aspx?satid=25544&lat=41.9028&lng=12.4964&loc=Roma&alt=53&tz=CET)
> I don't find a match:
>
> My code finds:
>
> Visibility on station1 begins at 2017-02-23T14:06:33.974
> Visibility on station1 ends at 2017-02-23T14:12:28.528
>
> Heavens Above calculates:
>
> 23 Feb	-	12:48:03	10°	NNW	12:50:12	16°	N
> 12:52:20	10°	NE	daylight
> 23 Feb	-	14:24:14	10°	NW	14:27:21	37°	NNE
> 14:30:26	10°	E	daylight
> 23 Feb	-	16:00:50	10°	WNW	16:03:44	29°	SW
> 16:06:36	10°	SSE	daylight
>
> Note that Heavens Above times are in CET timezone.
>
> Can you help me where my error is?

From a quick check, I see two things.

First is that you created a Keplerian orbit from mean orbital elements and
propagated them as if they were osculating elements. You will get tens or
perhaps hundreds of kilometer differences after some propagation time.
As Heavens Above used TLE, you should use TLE too for propagation, so you
use the same semantic on parameters and the same model.

Second, when copying the mean anomaly (131.4349), it seems you forgot to
convert from degrees to radians.

Hope thi_s helps,
Luc

> Thanks,
>
> Matteo