K9XN

Want to try something cool with stuff that you most likely already have?  Downloading images from the ISS space station is so much fun and really easy to do with a handheld receiver and a smartphone!

The international space station is manned by Astronauts and Cosmonauts that are licensed Amateur Radio Operators.  On-board the ISS is a small VHF/UHF amateur radio station used to talk to children during school events and other Amateur Radio Operators.

Every so often the crew of the ISS will transmit images from a computer that they have connected to the VHF/UHF transceiver using a mode called Slow Scan Television or SSTV. SSTV is a long popular mode used by ham radio operators on HF frequencies to send still images.  However this mode is also used on VHF/UHF frequencies as well and is easy to decode using a smartphone with a free app.

 

What you need:

1.  A handheld receiver that can tune into the 144 MHz -2 meter Amateur Radio band.  A 2m HT works great!
2.  An android smartphone or tablet.
3.  The “Heavens Above” satellite tracking app (or similar app to track the ISS and or other satellites.  You can open the following link on your Android device to download the app:  https://play.google.com/store/apps/details?id=com.heavens_above.viewer
4.  “Robot36” or similar SSTV decoding app.  You can open the following link on your Android device to download the app:  https://play.google.com/store/apps/details?id=xdsopl.robot36

*This can also be done with an Apple iPhone or iPad as well with apps available from the Apple App Store, so look for equivalent apps if you have an Apple device.

 

Finding out when the ISS is transmitting imagery:

You can find out what the current status is of the Amateur Radio Station on the ISS by visiting this site:  http://www.ariss.org/current-status-of-iss-stations.html

They also announce activities about ARISS (Amateur Radio on the International Space Station) on the ISS fan site:  https://www.issfanclub.com/

The AMSAT website is also very informative and will post news on ISS radio transmissions:  https://www.amsat.org/amateur-radio-on-the-iss/

 

Tracking the ISS in orbit:

Once you find out when they are transmitting images, you will need to know when and where the ISS will be over your geographic area to receive the images.  You can track the ISS online using a PC by visiting NASA’s “Spot The Station” website:  https://spotthestation.nasa.gov/home.cfm

But it is far better to have a real-time tracking app installed on your Android device like Heavens Above:

 One of the best things about the Heavens Above app is that every time you start the app the “Keplerian” elements are automatically updated.  Keplerian elements are the numbers that define a satellite’s orbit.  So these “Keplerian” elements are also known as Orbital Elements.

Obviously to update the elements the app will need access to the internet.  Either via cellular connection or Wi-Fi.

Once Heavens Above is started you will see several choices.  “ISS” is listed as the 3rd option down.

Click it to open a menu that will show the dates and times for various passes of the ISS.

 

 

 

Since the app is made by a European developer please note that the dates are in YEAR-MONTH-DAY format.  The times are in your local time zone based on the time set of your device.

Click on one of the passes at a reasonable time in the future that you are available to be present for the pass.

There are many “glancing” passes where as the ISS will not be directly overhead, but will be on the edge of your horizon.  It is possible to decode the images from such a pass, but the pass will not last as long and their also could be large buildings in your way that will degrade the signal.

An overhead pass would look like this:

 

This image is an example of a more or less direct overhead pass and will give me the best opportunity to receive the images of the ISS.  As you can see the ISS will start to appear at about 230 degrees (Southwest) and then fly overhead with a bearing of about 56 degrees (Northwest).

The information at the bottom of this screen will show you exactly when you will start to be in range of the ISS for the reception of the signal:

Exit Shadow: This shows you the AOS (acquisition of signal) time.  The time that the ISS starts to be within your range.

Max Elevation:  This shows you the time where the ISS will be at it’s highest elevation point in its orbit.

Below 5 degrees:  This shows you the time where the ISS will be starting to be out of range from you (flying away over the horizon).

Sets:  This shows you the time at which the ISS will leaving your area and will be out of range.  Also known as LOS (loss of signal) time.

The ISS travels at 17,150 miles-per-hour or about 4.76 miles per second, so it is really traveling fast!  It has to in order to stay in a stable orbit and not come down into our atmosphere.  This means that generally on an optimum overhead pass you have approximately 15-18 minutes where the ISS will be in range to receive its signals.

The ISS orbits the earth approximately every 92 minutes, so you will have another opportunity in 92 minutes to receive the signal again, but with a less optimized path overhead, meaning that you will have less time that the ISS is within signal range.

 

Setting your handheld receiver up to receive the ISS signals:

The transmission of the SSTV images is done using FM (Frequency modulation), so you can receive the images using a standard FM Handie Talkie (HT) or scanning receiver.

Program the frequency of 145.800 MHz into your receiver, and then adjust your squelch setting to wide open (you want to hear static).  You can adjust the volume a bit so that it is not super loud.

 

Using your smartphone and HT to receive the SSTV Images:

In general is is a good idea to choose a location to receive the images that has a clear path to the horizon. Large buildings or other structures will block the signal from reaching your radio receiver properly.  I like to go to an open field or top of a parking garage, but a residential neighborhood would be OK as long as there is no large buildings or houses blocking your path directly to the satellite for the pass.

On your smartphone, open the Robot36 app,  and place the smartphone within close proximity of your HT speaker.  As soon as the satellite comes within range you will start to hear some high pitched tones.  Adjust the volume and closeness of the smartphone or tablet to get the best image.

You may also have to move the handheld radio around a bit in your hand orienting the long sides of your antenna toward the position of the satellite in the sky. Try moving the radio about to get clear tones with minimal static keeping the smartphone close to the speaker of the radio.

In the photo you will see that the radio is under the smartphone and the antenna instead of being straight vertical is orientated with its long side toward the ISS in the sky.

I needed to move the radio around a bit as the ISS passed overhead keeping the smartphone’s microphone within close enough proximity to pickup the audio from the radio.

You should start to receive an image in the Robot36 screen.  If you have clear loud tones and are not receiving an image, be sure to set the receive mode to AUTO MODE receive from the menu (the 3 dots in the upper right bit of the display).

You should start to receive the image line by line.

This image is one that I received on April 13, 2018 from a ISS pass and shows a retrospective of Salyut 6 Cosmonauts .  Salyut 6 was a Russian space station that was in orbit from 1977 to 1982.

Here is another great image received that is part of the Salyut 6 retrospective:

To save the images you can click on the little disk icon on the Robot36 app.  The ‘X’ icon will clear the display so be careful that you don’t inadvertently hit that button.

 

Conclusion:

Receiving these images has been a lot of fun, but does require a bit of practice to get the best and cleanest images.  The green lines are a result of noise or weak signal beacuse of the orientation of the radio’s antenna, but the above images are pretty darn good.

The ISS crew does transmit these SSTV images fairly regularly to promote the space station and respective space agencies.  So next time they are transmitting get outside and receive these images directly yourself!  This would be an excellent family activity as kids would love to know that they are receiving signals directly to their phone from the International Space Station!

Other setups using directional antennas, SDR receivers and laptop computers can yield better results, but require more setup time before AOS (acquisition of signal) and can be cumbersome compared to an HT and a smartphone.

I hope you enjoyed this blog post.  Satellites operations have been a new interest for me over the past year, and I have had a blast talking on a few amateur radio satellites and receiving images from the ISS and weather satellites.  If you are interested in Amateur Radio satellites AMSAT is a great resource:  https://www.amsat.org/

73! de Nick N9SJA