Amsatoscar

AMSAT-OSCAR 10 has provided some surprisingly good activity tately. Stations from Kuwait to Borneo have been heard and worked by stateside hams. Unfortunately, we will have little or no use of the satellite until May. Since the ground control stations cannot change the satellite's orientation in space, its behavior due to things Jike precession and nodal regression can be predicted as is shown in Table 1.

These calculations were provided by Ross WB6GFJ, using a computer program developed by Jim G3RUH. The most important items in this chart are sun angle and percent illumination. Sun angle refers to the orientation of the satellite with respect to the sunJs radiation. Zero sun angle occurs when the sun's rays are perpendicular to the plane of the solar arrays on the spacecraft, giving 100 percent illumination. When the angle hits 90 degrees, we have virtually no illumination of the solar cells.

The other numbers on the chart, the Bahn coordinates, tell us when the satellite's antennas are pointed at the Earth. When the longitude is 180 degrees and the latitude is zero, A0-10 is aimed at the middle of the Earth when at its highest point or apogee. During the year, the latitude will move onfy slightly, but the longitude shows a continuous trend to smaller values. For us, this means that signals will be best early in each orbit. Later in each pass, the antennas will be aimed away from the Earth and communications will be very difficult or impossible.

f am assuming that the satellite will survive the period in late March and early April when the sun angle will be so bad that all active systems on the satellite most likely win power down and the batteries will be discharged. A0-10 has done well in this type of situation before, but there are no guarantees that things will be easy again. If you find the satellite active, keep your erp down to 100 Watts or less on the 70-cm uplink, avoid operation around perigee (possible eclipse peri-

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