The ISS Is Beaming Down Images This Week � Here's How to Grab Them

Right now � literally this week � the International Space Station is transmitting slow-scan TV images on amateur radio frequencies. You can receive them with a handheld radio, a free phone app, and about ten minutes of setup. No license required to listen.

If you’ve ever wanted a reason to dust off that Baofeng or justify buying one, this is it.

What’s Happening

ARISS (Amateur Radio on the International Space Station) runs periodic SSTV events where the ISS transmits commemorative images on VHF and UHF frequencies. This April, there are two overlapping events:

  • Series 31 — April 10–14 on 437.550 MHz, Robot 36 mode
  • PD120 event — April 11–16 on 145.800 MHz FM, PD120 mode, callsign RS0ISS

The transmission cycle is roughly two minutes on, two minutes off. During a good overhead pass, you can catch one or two complete images.

What You Actually Need

The barrier to entry here is almost embarrassingly low:

A VHF/UHF radio. Any dual-band handheld works. A Baofeng UV-5R ($25), a Yaesu FT-65R, a Kenwood TH-D75 — whatever you’ve got. Even an RTL-SDR dongle with a simple antenna will do the job. Set it to FM, tune to 145.800 MHz (or 437.550 for the Robot 36 event), and make sure the squelch is open.

A decoding app. This is where the magic happens. On Android, grab Robot36 (free on Google Play and F-Droid). It supports Robot 36, PD120, and a dozen other SSTV modes. On iOS, SSTV Slow Scan TV works well. On a laptop, MMSSTV is the classic choice. Point your phone’s microphone at the radio speaker, and the app decodes the audio into an image in real time.

ISS pass times. You need to know when the station is overhead. Use Heavens-Above (heavens-above.com), the ISS Detector app, or N2YO.com. Look for passes with at least 20° maximum elevation — higher is better. An overhead pass (70°+) gives you roughly 10 minutes of window, which is enough for multiple image transmissions.

Step by Step

1. Check your pass times. Pull up your location on Heavens-Above and note the next few ISS passes. Evening and morning passes tend to work best since there’s less local interference.

2. Tune your radio. Set 145.800 MHz FM with squelch fully open. You’ll hear static until the ISS rises above your horizon.

3. Open your decoder. Launch Robot36 (or your app of choice) and hold the phone near the radio speaker. When the ISS comes into range, you’ll hear the distinctive warbling sound of SSTV data. The app starts decoding automatically.

4. Account for Doppler. The ISS moves at 17,500 mph, which shifts the frequency slightly. As it approaches, the signal will be a few kHz high; as it recedes, a few kHz low. On FM with a handheld, this usually isn’t a dealbreaker — the FM capture effect handles most of it. But if your image looks stretched or garbled, try stepping the frequency up or down by 5 kHz during the pass.

5. Save everything. Robot36 auto-saves decoded images to your Pictures folder. Even if the decode looks rough, keep it — partial images from space are still pretty cool. Also consider recording the raw audio as a backup so you can re-decode later with different software.

Tips from the Field

A rubber duck antenna can work for a strong overhead pass, but a simple quarter-wave ground plane antenna dramatically improves your chances. You can build one from a chassis-mount SO-239 connector and five pieces of wire for under $5. If you’re feeling ambitious, a handheld Yagi pointed at the ISS will pull in rock-solid signals even at low elevation angles.

Do a test run before the actual pass. Tune to 145.800 outside of an SSTV event — you might hear packet or voice from the ISS on a regular day, which confirms your setup works.

If you miss this event, ARISS runs several SSTV transmissions per year. But the April window is one of the longest, so it’s worth the effort now.

After the Images: What Next?

Catching SSTV images from the ISS is a gateway into satellite operating. Once you realize you can work stations 250 miles above your head with a handheld, the natural next step is making actual two-way contacts through amateur satellites — SO-50, RS-44, and the FM repeater birds are all workable with a modest setup.

When you start making satellite contacts, you’ll want a logbook that doesn’t fight you. Most satellite QSOs happen fast and involve details like grid squares, satellite name, and mode that traditional loggers handle awkwardly. I’ve been using Hamtrax for my satellite work because it handles all the fields without forcing me into a contest-style interface. The contacts go into the same logbook as my HF and POTA QSOs, which means I’m not juggling three different apps for three different activities.

Whether you decode one clean image or five partial ones, submit them to the ARISS SSTV Gallery (ariss.org) — you can earn a diploma for participating, which is a nice addition to the shack wall.

Clear skies and good passes this week. 73.

If you’re looking for a free logbook that handles everything from POTA to satellite QSOs, check out Hamtrax.

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