International Space Station and Ham Radio Slow Scan TV Transmission
1 January 2022
Not all dreams can be achieved, as a small child I wanted to be a astronaught, honestly, I still would love to go to space. So I find myself intrigued with any and all things related to space exploration. So for a geek like the the idea of interacting with Astronaughts is very compelling. Enter the ARISS (Amateur Radio on the International Space Station) program for geeky thrills.
Many of the Astronaughts on the ISS have earned their amateur radio licenses so that they can speak with school children around the world to encourage STEM and space carrers. Some of the astronaughts will occasionally use their recreational time to speak to any hams that are listening for their signal.
But over the last few years one of the most popular things they setup is setting up Slow Scan TV transmissions that occure over the space of several days. During that period they will repeatedly transmit a SSTV slide show that repeats several times. Since the ISS's polar orbital pattern covers the earths surface multiple times over the course of a day it's possible for stations all over the world to decode the messages. They use a format called PD120, and pause for two minutes between images. Each pass over a particular part of the earth will generally last sometime between eight minute and twelve minutes. Which means a lucky station can get two to four images each pass.
The space station is about two hundred and twenty miles from the earths surface, which means that the roughly 25 watt signal can be heard with a small antenna.
So this Christmas I learned that there was a SSTV event commemorating the moon race. I decided it was time to receive some SSTV from the space station. I setup my SDR with a 1/4 Wave antenna and recorded three days of passes. Here are the decoded results that were recognizable.
Hopefully for the next event I'll be able to get the complete series, and with a lot of luck, noise free copies!
