# Search results

1. ### Solar radiation pressure rotation matrix

In my propagator, I’m currently using a SPICE library function to rotate the SRP Sun-satellite acceleration vector to the ECI frame, but I’m not totally sure that the result is correct. Since my skill in building rotation matrices is poor, I'd like to ask if someone can help me.
2. ### Integrating the satellite position

If I integrate the orbital speed (magnitude of the velocity vector) of a satellite as a function of time, I get the distance traveled. If I integrate the satellite position as a function of time, what do I get? Is there any physical meaning of that number?
3. ### J4 - J5 perturbations

In my simulation, I’m currently using J2 + J3 perturbations (Fx, Fy, Fz) as depicted on this page: https://en.wikipedia.org/wiki/Geopotential_model#The_deviations_of_Earth%27s_gravitational_field_from_that_of_a_homogeneous_sphere but I would also add J4 and possibly J5 too. Unfortunately, I...
4. ### Updates PSLV-C39/IRNSS-1H reentry prediction

Probably this will be the worst reentry prediction ever made (excluding the ISRO’s prediction), but I’m pretty confident that the following trajectories are fairly accurate (for a 570-day prediction): The earliest date is what is called “outlier”, because it has nothing to do with the others...
5. ### Lagrange points calculations

I wrote an MFD that displays the distance of the ship from the 5 Lagrange points. I used the formulas found at the link https://en.wikipedia.org/wiki/Lagrangian_point#Mathematical_details rewritten for the 3D space. Now I would improve the calculations but it’s not clear to me what happens in a...
6. ### Tiangong-1 strange orbit

I simulated with Orbiter the Tiangong-1 reentry. The result fairly agrees with a standalone specially crafted simulation. Since the radius vector and the orbital speed seem to have a “strange” shape, I created the attached graph to better understand how the orbit is changing. I used 133 TLEs...
7. ### Updates Tiangong 1 reentry

I wrote a program to calculate the Tiangong 1 reentry date. Starting from a TLE, my prog propagate the initial state down to an altitude of 20 km. The simulation uses the NRLMSISE-00 atmospheric model considering the observed and predicted solar activity and geomagnetic levels. As can be seen...
8. ### API Question Sol file name

Is there any function or method to get the name of the sol file loaded in the simulation? For example, with the default distribution I should get "Sol.cfg".
9. ### General Question HasElements = FALSE

OrbiterConfig.pdf page 7: "If TRUE, the initial position/velocity is calculated from the provided set of orbital elements, otherwise from an explicit position/velocity pair (ignored if module supports position/velocity calculation)"; please, could somebody tell me how to write an explicit...
10. ### Problem Out of memory

After few minutes of flight, the "Virtual size" allocated by Orbiter 2016 (I use Sysinternals Process Explorer) goes beyond 4 GB and Orbiter crashes (I have 16 GB SDRAM and Win7 64 bit). My installation: Orbiter 2016 + D3D9Client2016-R1 + OrbiterSound40_20121120 (nothing else). I activated all...
11. ### Wind and oapiGetWindVector

I downloaded Orbiter Beta r.14 and I read in "API_Reference.pdf" the warning: "Local wind velocities are not currently implemented.". Does that mean that the new edition of Orbiter won't support the local wind? The function oapiGetWindVector is very good because it allows to query the wind...
12. ### .dll Question clbkPreStep doesn't get called

It seems that opcPreStep() doesn't get called from a dll for an atmosphere module. Then I tried with oapi::Module::clbkPreStep(), but it's the same; this is the code: class MODU : public oapi::Module { public: MODU(HINSTANCE hDLL); void clbkPreStep(double simt, double simdt, double mjd); }...
13. ### SDK Question How to calculate Sun elevation

I need to calculate the Sun elevation as seen from any point on Mars surface (the input is lat, lon on Mars and the output is the Sun elevation). I'm trying to use oapiGlobalToLocal() and oapiGetPlanetObliquityMatrix(), but I don't get any useful result. Please, could somebody help me?
14. ### How to calculate Ls

Ls is the solar longitude as well explained here. I calculate Ls using library functions or algorithms like this, but I'd like to know a "general" procedure valid for any celestial body. I can calculate the position and the velocity of the body (and hence I can calculate any orbital element)...
15. ### .dll Question How to load an Orbiter module from a standalone program

When I want to use an Orbiter DLL written by me from a standalone program, I don't have any problem, but when I try to use an Orbiter DLL which comes with the standard distribution (celbody or atmospheric DLL), I get the error code #126 (module not found) for LoadLibrary. Please, could somebody...
16. ### Waiting for JPL's Horizons update (New Horizons C/A)

In the JPL's Horizons site, for the New Horizons (ID= -98) I see the note: "Final trajectory update here prior to Pluto flyby. Reconstructions available later, after the encounter.". Then I thought to use a good integrator to estimate the closest approach distance. Since in the site I also...
17. ### API Question CELBODY2::GetParent()

I need to know the parent body of a celestial body. I call CELBODY2::GetParent() from inside CELBODY2::clbkInit(FILEHANDLE cfg), but I always get a NULL pointer. Please, could somebody help me?
18. ### SDK Question CELBODY2 flags

Suppose that I want to write a CELBODY2 DLL to tell Orbiter where Deimos is. The only working way I found is: 1) DLL1 calculates Deimos position wrt Mars; 2) DLL2 calculates Mars position wrt Sun; 3) DLL3 calculates Sun position wrt Solar System Barycenter. All the 3 DLLs return the flags...
19. ### Project Looking for bodies for my PlutoSys

I've finally wrote an efficient implementation to simulate the motion of Pluto and its 5 moons. I'd like to publish it because afaik it's the only accurate simulation for Pluto system, so far. I only wrote the DLLs and I need the textures and the meshes for the bodies. I found the very...
20. ### SDK Question oapiGetGlobalPos frame

In the file "API_Reference.pdf" I read that oapiGetGlobalPos "Returns the position of an object in the global reference frame" and that the global reference frame "is the heliocentric ecliptic system at ecliptic and equinox of J2000", but I get {-493478083; 18642718; -806901763} for the Sun...