ISS SSTV Transmissions Scheduled for December 6th through 8th

From December 6th to December 8th, the International Space Station will be transmitting images to Earth via Amateur frequencies and SSTV (Slow Scan Television).

Now, even though this uses the Amateur radio service, anyone can participate. It’s very easy to listen in to these broadcasts. You don’t even need a special license. It’s a great project to do with kids or learn about radio science and space.

All mentioned resources and references will be listed at the bottom of the article.


What you need:

  • Receiver
  • Antenna
  • Tablet/phone/laptop
  • Satellite tracking software (heavily recommended)
  • Audio Recorder (recommended)

The great news is that all of this can be had for under $50.

For a receiver, an SDR dongle kit works perfectly. SDR dongle kits can be purchased off of Amazon for around $20 to $30. SDRs, or software defined radios, are wide band receivers that typically, in the case of low-end models, receive frequencies from 100MHz to 2.4 GHz. A benefit of using SDRs is the water fall display, which shows a graphic of activity happening within a frequency range. This will allow for easier fine tuning to counteract the Doppler effect. A common example of the Doppler effect is the change in pitch of a speeding car as it passes you.

dopplerfrequenz

An example of the Doppler effect. As the car moves, the pink waves at the front of it compress. (Source: Charly Whisky)

An antenna can be homemade. Some antenna design can be constructed for less than $4 dollars. Typically, the antenna will be of a directional yagi style.

SDR dongles can be connected to phones, tablets and computers. Software can be used to utilize the SDR dongle. There are lots of programs, both free and paid, for this purpose. Although the paid programs include some more advanced features, the free programs are ample for beginners.

Satellite tracking software is heavily recommended unless you know how to calculate a satellite’s orbit. There are tons of free programs that will do this. All you have to do is provide a location and select a satellite (ISS, in this case). It will give information like location, distance, speed, the time at which the satellite will pass over you, and where on the horizon the satellite will be. This way, you know when and where to point your antenna and start listening.

An audio recorder is recommended to record the digital transmission. It is easier to record the audio of the data transmission, then to later decrypt it from home. The signals will sounds like a series of metallic or digitals sounds that your computer, with the appropriate software, can understand. This is usually done through direct digital processing.

Capturing image transmissions is a very rewarding experience that requires some patience. Don’t expect to get it on the first shot. Luckily, the ISS completes an orbit every 90 minutes. So, for a 3 day period, there will be plenty of opportunities to collect image transmissions from the ISS.

Before you go chasing the ISS, you should know about picking out a site to capture the signals. This isn’t something that can easily done from indoors, unless you have an external antenna with a remote rotor on it. You’re going to need to find a place with a clear shot of the horizon. An open field would be best. It doesn’t have to be perfect, but a clean horizon from where the passover is going to happen is preferable. Ensure that there are no metallic structures in the way.

Additionally, you’re going to need to know what frequencies to listen to. The frequency you are going to use is called the downlink frequency. This is what the receiver picks up. The uplink frequency is the transmitted frequency. Transmitting is only allowed if you are properly licensed by the FCC or your country’s variant of the FCC. Also, it’s generally bad practice to transmit during an event like this because you would potentially be causing unwanted interference.


Resources:

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Categories: News, Science

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