SSTV on the LEOs

The low orbit satellites offer a special challenge to the SSTV operator. FO-20 and FO-29 are great satellites for the serious SSTVer. A typical satellite pass will last 10 to 15 minutes at the most. If you don't have your act together beforehand, the pass will be over before you ever get started!

Scottie 1 mode lasts about 2 minutes, and Scottie 2 mode lasts about 1 minute. Robot 36 only lasts a half minute. Scottie DX lasts about 4 minutes. Due to doppler effects on the LEOs, the top few seconds of a picture are often lost while trying to find the sync frequency. Robot 36 is so short that the few seconds taken to find the sync pulse may result in almost half the picture lost. If only a single transmission for the pass is being considered, Scottie DX is an option, but seldomly results in a great picture because either the satellite rolls, the pass ends, or some lid has to send a CW CQ on frequency or a malicious QRMer has to whistle in the middle of the picture. Scottie 1 mode has produced many good pictures for me, but overall, I think Scottie 2 is the best bet. The picture will loose a little resolution, but there will be no multipath, and the extraneous effects are less likely to happen. If you and your SSTV contact really have your act together you may each be able to get in two pictures, but this is very rare.

Since the LEOs have a small footprint, you must select a pass that covers both stations. I live in Colorado. If I want to exchange SSTV pictures with someone in New Jersy over a LEO, then I look for a pass where the satellite passes over the midwest somewhere, giving both of us a good view angle to the satellite, and about 12 minutes to get our SSTV transmissions completed. The next pass will be about 1000 miles west, so it would be the one for me to schedule an SSTV contact with the West coast. Some tracking programs allow you to enter the locations of both of you, and then they will modify the time limits so both of you are in the footprint. Because the time is short, and the doppler effects high, you every piece of automation available.

You must have a completely automatic tracking system and your SSTV station must be completely automatic in going from Voice to SSTV and back, or you will forget something in the rush.