// check if ephemeris is available for usSVID
    GPSSATELLITES GpsSatellites;
    GpsGetSatellites(&GpsSatellites);
        // sat struct  is channel based so find SVID
    for (int i = 0; i < NUM_OF_CHANNELS; i++)
    {
        if (GpsSatellites.gsSatellite[i].usID == usSvid)
        {
            if(GpsSatellites.gsSatellite[i].fEphemerisAvailable != GPS_TRUE)
            {
                fEphemerisAvailable = GPS_TRUE;
                                SirfPollEphemeris(usSvid);
                break;
            }
        }
    }