Whats ALON and ALAT?
ALON and ALAT define the attitude, or the direction in which the centre (the “z-axis”) of AO-40 points. The spacecraft spins around this axis. As the 2.4GHz antenna is aligned along the z-axis of the spacecraft, the attitude also indicates the squint. Knowing the ALON/ALAT, the position of the spacecraft, and the location of the receiver, the squint can be calculated for any point in the orbit. Sometimes the terms BLON/BLAT are used – the “B” is short for the German word “Bahn”, for path. Imagine the spacecraft’s orbit as lying on a thin flat plate through the centre of the Earth. This is called the orbital plane. Essentially, the z-axis stays in a fixed direction relative to that plate (but not to the Earth), throughout the orbit, in much the same way as a spinning top always points upwards. ALAT is the number of degrees above or below that plane that the z-axis points (at perigee). (North is positive, usually visualised as “above” the plane). ALAT of zero is always desirable so that
