def _reception_coord(x_t, y_t, z_t, vx, vy, vz, travel_time):
    """ Calculates satellite coordinates at signal reception time
    Input:
        satellite coordinates at transmission time (x_t, y_t, z_t) [m]
        satellite velocity in ECEF frame [m/s]
        signal travel time calculated from pseudorange [s]
    Output:
        satellite coordinates at signal reception time
    """
    x_r = x_t-vx*travel_time
    y_r = y_t-vy*travel_time
    z_r = z_t-vz*travel_time
    return x_r, y_r, z_r