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First observations: your day 5 output is identical to your input. Also, your xyz-dots are on the order of 1 au/d, which doesn't seem right. Regards

Firstly, for planetary modules, true and barycentric positions are relative to the barycenter of the solar system, even though they don't report EPHEM_PARENTBARY. So you should be able to create a satisfactory elliptical orbit for the Pluto-Charon system barycenter relative to the SSB. I'm not...

I've done more investigating about "ephemeris time" and how is defined for Spice and Horizons, and found that the correct conversion between ephemeris time and UTC is: ET = UTC + DELTA_T_A + DELTA_AT (relativistic correction not included) where DELTA_T_A is equal to 32.184 and DELTA_AT is...

Here's what I'm thinking: Let's say you make an ephemeris, where you define time as the number of seconds from Jan 1 2000, 0h UTC. This would be a natural place to fix the zero point of time in your ephemeris. Now, let's say you are creating this ephemeris in 1996. You would not know exactly...

I think that leap seconds may be the cause of the discrepency. Ephemeris time and UTC do not stay in sync over time. UTC is corrected from time to time by adding a leap second. Leap seconds were added Dec 31 2005, Dec 31 1998, June 30 1997, etc. I'm figuring Orbiter does not account for these...

Two Bowling balls made of lead will orbit perfectly in an empty universe, but I don't live in an empty universe. Regards

Actually, getting two very small objects to orbit each other is not possible in low Earth orbit due to the tidal force of the earth. One of your two objects is going to be slightly further away from the earth, and experience a slightly less pull toward Earth. The net effect is that the two...

I've done some more testing and I have an interesting result. In order to directly compare the positions given by the new Spice module with the default Orbiter positions, I created a Sol.cfg with two Earths, the second Earth having it's position calculated with the Spice module and spice kernel...

As far as I can tell, the group that makes the spice kernals distributed through NAIF (de421, nep068, etc.) is the same group that runs Horizons (the Solar System Dynamics group at JPL). It looks to me that they use these spice files to do the calculations that you get from Horizons. Regards

I've already started testing this, and so far it looks very good! I looked specifically at Triton, since I wrote the dll for it in the current Orbiter version, and this SPICE module appears to give a more accurate and up-to-date position for Triton than my dll. This is not really un-expected...

For a start, I would like to see the gondola put into one of the giant NASA vacuum chambers to test the overall life support systems at altitudes of 150,000 ft. I also have concern about the landing. Balloon landings are not very predictable.. Regards.

Sorry, orbital mechanics and fractal geometry have nothing in common. Regards

Looking good, but it's "MARINES", not "MARINE". Regards

Many people flew the shuttle prior to John Glenn's mission. No one (so far) has come close to a successful manned 150,000 ft. balloon flight. Regards

Here's the best shot I could find. Regards

One problem I see with this plan (among many): Isn't Don Piccard about 80 years old? Regards

You'll need some more info like your latitude and longitude, your heading, the date and time. Knowing all that, you should be able to calculate your global orientation. Regards

Ireland is definitely a country, but Northern Ireland is in a different category. Some may consider it its own country, but ultimate governance is in the hands of the UK parliament, so that makes it somewhat less of a "country" than Ireland, and could rightly be considered part of the UK rather...

The CAPCOMS for Apollo 11 were Duke, McCandless, Garriot, and Evans (for the landed part of the mission). There is a transcript of the audio for Apollo 11 from the landing through return to orbit which identifies who is speaking here: http://history.nasa.gov/alsj/a11/a11.html Regards

The transform should be this: X_M50 = X_Orbiter Y_M50 = cos(theta) * Z_Orbiter - sin(theta) * Y_Orbiter Z_M50 = cos(theta) * Y_Orbiter + sin(theta) * Z_Orbiter where theta is the obliquity of the Earth's axis, 23.4458878 degrees. If you want to be completely accurate, you would also need...