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try here: http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/orbit/ISS/SVPOST.html

On reading .nio files: There isn't much documentation publically available on the format of .nio files, so I started snooping around with a hex editor to decode the format for myself. What I found out: The data at the beginning of the file contains text information about the file such...

I do know how to extract ephemeris data from .nio files, but I hadn't realized that some of those files had more coverage than .bsp data. Thanks for that info. It turns out that .nio files contain exactly the same data contained in .bsp files where they overlap and derive from the same...

Thanks for the feedback and suggestion. What I am planning on doing is to compute two sets of osculating elements for the orbit based on the state vectors at the beginning and end of the covered interval and use these to compute the ephemeris outside the interval. This will insure that there...

By my calculation, a 48 km difference in the calculation of the position of the solar system barycenter can be entirely accounted for by differences in the masses used for the giant planets and the Sun. Jupiter alone moves the solar system barycenter by about 750,000 km from the center of the...

I've made significant progress in using the ephemerides created by JPL for making ephemeris modules for Orbiter. What prompted this was my dissatisfaction with the results I was getting from a module I was creating for Nereid when compared to data retrieved from the JPL Horizons ephemeris...

Recent SpaceX news says they are looking into the possibility of flying the first and second stages back to earth (and soft landing) under their own power. Can this be simulated with this add-on, and if so, has anyone tried it? Regards

George Washington was the number one criminal in the colonial US while he led a war against Britain. Once independence was won, he becomes the greatest hero in the independent US. I don't think library late fees are going to change that. Regards

How are you reading the velocity in Orbiter? I get an apoapsis velocity of 2280 when I run a simulation. Regards

Not all lunar orbits are unstable. A few orbital inclinations give stable orbits. http://science.nasa.gov/headlines/y2006/06nov_loworbit.htm Regards

I disagree with this entirely (actually quite amusing): Inevitable global catastrophes (climate change, nuclear war, a huge meteorite fall) will result in quick Earth's civilization degradation or complete vanishing the way dinosaurs have extinct. The Humanity will be obliterated. So that's why...

I agree with about 50% of the arguement, but this part seems to be a bit fanciful: Inevitable global catastrophes (climate change, nuclear war, a huge meteorite fall) will result in quick Earth's civilization degradation or complete vanishing the way dinosaurs have extinct. The Humanity will...

I sincerely hope that no one is taking these rantings seriously. Regards

Orbiter's ephemeris for Earth and Mars gives an accuracy of a few hundred km. for the distance between the two. Consider it "checked out" . Same for Earth-Moon. Reason: extensive comparison of Orbiter positions with JPL Horizons data on positions of Earth, Mars, and Moon. Regards

The period of the Earth's rotation is basically unpredictable at the 0.001 sec level from year to year, and has historically changed by 0.001 to 0.005 sec from year to year in recent times. Since Orbiter's model assumes that this value is fixed, it comes down to what time-frame do you want to...

I think we have a consensus on what calculations need to be changed in the latest beta release, namely equation 7 should be what jarmonik posted in post #39: theta = SidRotOffset+2*PI*86400*d/SidRotPeriod+cos(Obliquity)*(LAN-L_rel). This is also backward compatable with pre-precession...

I've been working on my own program that simultaneously computes IAU and Orbiter models, so that I can independently validate the models that are being put forward. I think it is working correctly now, and so I've put in tblaxland's Orbiter models for Mars, Phobos, and Deimos, and can report...

On further review, the number I gave for PrecessionPeriod (-63188250) was not derived from IAU data, but is the best published result (period = 173,000 years). So, your number would be more consistent with the IAU data, since your assumption about the precession being about the orbit normal is...

I agree that since Tp >> Ts for all known bodies, that jarmonik's equation 7 (post 39) should be used. Also, I tested it in the case of an Orbiter precession model for Triton, which has a very large angle between all three planes (ref, rel, ecliptic), and was able to create an Orbiter model...

It's even a bit more complicated than that. Leap seconds have only been in use since 1972, when UTC was "synchronized" with atomic time (TIA) (the second was made to be the same length for both systems). From 1961 to 1972, UTC was corrected (both in offset and rate) on average every few months...