Modify gps-sdr-sim to point antennas away from Earth's nadir

Question

I'm currently trying to simulate the performance of a a custom PNT satellite constellation I have designed in software. I have parsed the satellite ephemeris data into RINEX Navigation file format and fed it successfully into gps-sdr-sim. However, I now need to modify gps-sdr-sim to somehow "point" the "GPS" antennas away/outwards from Earth since the purpose of the PNT constellation is to service Cislunar users.

I've only found the following line of code which suggests the receiver (based on Earth) uses the elevation angle in the sky/above horizon to calculate the appropriate gain based on the antenna pattern.

ibs = (int)((90.0-rho.azel[1]*R2D)/5.0); // covert elevation to boresight
ant_gain = ant_pat[ibs];

There's also this checkSatVisibility function that just simply checks if it's above the horizon (elvMask = 0).

int checkSatVisibility(ephem_t eph, gpstime_t g, double *xyz, double elvMask, double *azel)
{
    double llh[3],neu[3];
    double pos[3],vel[3],clk[3],los[3];
    double tmat[3][3];

    if (eph.vflg != 1)
        return (-1); // Invalid

    xyz2llh(xyz,llh);
    ltcmat(llh, tmat);

    satpos(eph, g, pos, vel, clk);
    subVect(los, pos, xyz);
    ecef2neu(los, tmat, neu);
    neu2azel(azel, neu);

    if (azel[1]*R2D > elvMask)
        return (1); // Visible
    // else
    return (0); // Invisible
}

I'm thinking I can modify this to be TRUE if and only if the satellite is not hidden in the two below cases (Top and Side):

Modify gps-sdr-sim to point antennas away from Earth's nadir

0 Answers0