I have a question about Orbiter 2016 and I hope this is the appropriate place to ask it.
Does Orbiter 2016 accurately model the Earth as an oblate spheroid and if yes, is the atmosphere modeled to fit the spheroid? I am asking about the shape here, not the gravitational model.
While working on the Virtual AGC for NASSP we have noticed that multiple programs have trouble with the spherical Earth in Orbiter 2010. For example, the program 22 of the AGC is used to track a landmark on Earth. As an input the program wants geocentric latitude, longitude and altitude above the Fischer ellipsoid. The AGC then calculates the position vector of the landmark from these inputs. For a landmark on the Earth, we kind of have to trick the AGC to make it work. The longitude is fine, but latitude and altitude have to be adjusted so the AGC finds the correct position of the landmark on the spherical Earth. In NASSP we have set the radius of the spherical Earth to the radius at Cape Canaveral.
Similarly the entry interface is defined as 400k ft altitude above the Earth. Again, the spherical vs. ellipsoid Earth is relevant in some calculations the AGC does. The AGC actually has a program to calculate midcourse corrections itself. For low latitudes at entry interface, where the radius difference is more pronounced, the maneuvers the AGC is calculating become increasingly inaccurate.
I have set a Delta Glider at different points on the Earth on oceans and the radius always seemed to be identical. So if despite the awesome terrain models in Orbiter 2016 the average shape of the Earth is still not an oblate spheroid, consider this a feature request. :thumbup:
I've been thinking about this, as part part of figuring out how the shuttle launched to a 28.45º orbit from a pad at 28.6º, and found that the pad is at 28.6º geodetic latitude, and at 28.45º geocentric latitude.
Thus, launching east produces a 28.45º orbit... but I get a 28.6º :uhh: (just tested it with DG). So I also think the Earth is "too spherical".