ALON stands for Attitude-LONgitude, therefore the longitudinal-statement (Longitude) of the flight-attitude. That reference is the semi-major-axis, that perigee, most near-earth point of the orbit, Earth's center and apogee (most distant orbit point) connects. Reference point is the apogee and the counting- direction goes in the same direction as the satellite move in its orbit. ALON indicates with values from 0 to 359 how the +Z-axis stands in reference by the semi-major-axis. ALON = 0 means for example that the antennas in the apogee show in direction Eearth, with ALON = 180 they point in the perigee to the Earth?s center. Values between 0 and 180 declare that the +Z-axis show to Earth on the way from the apogee to the perigee, and with values between 180 and 359 before the apogee.