I always wanted to be an astronaut, although that was a stretch dream when it comes to reality.  I’m physically not made to take the amount of work-out that is needed to be one.  I am however am extremely passionate about what NASA stands for, what our great country has to offer for the future of Space development through innovation, genius and simply put, passion to go where no one has gone before.  I had once applied for a job at NASA to run their software and IT development – and was duly declined a job.  But, I’m proud of the fact that I was able to apply and then got a response back from them.  It was greatly appreciated.

When I first got into the APRS subject matter, I also started playing w/ the APRS w/ ISS subject matter.  And, as a natural progression to my APRS iDigi/iGate project (more on that page), I wanted to explore and extend this work into the ARISS. ARISS is an acronym for, “Amateur Radio on the International Space Station” project.  Onboard the ISS, is an APRS repeater under the alias of ‘ARISS’ that responds to APRS packets directed into the 145.825Mhz (2m). The packet is received and responded to by aliases such as RS0ISS, NA1SS, and so on.  More details can be found on this page which talks about “How to Contact ISS” both through voice (different frequency range) and packets (APRS on ISS 145.825MHz).

So, let’s suppose you have a radio that is packet enabled (it does not have to be APRS enabled – only so long as it is packet enabled), and you have a TNC (Terminal Node Controller) attached to it (or built into it); And, you’re ready to and WANT to send an APRS packet to ISS.

  • First, you will need to determine when exactly does the ISS pass-through your zone above the havens. You can find out exactly what date/time that pass-thru occurs very easily by visiting this page. Select “ISS” from the satellite drop down, punch in your current ground location/coordinates and ask for pass predictions.  The page will list down the pass prediction results for your coordinates.
  • Second, you will set up your radio by tuning it into the “145.825Mhz” frequency and set the mode to “Packet” mode.
  • Third, ready up your TNC; if you have an external TNC (like a Kantronics 3+ or a 9612+), hook it up to your radio (you will need to figure out from your radio and TNC manufacturer as to how to connect them both together so they can talk to each other seamlessly. I should have a few wiring diagrams here for your reading pleasure) and ensure that communication is working fine between the two.
  • Fourth, ready up your TNC and you PC;  connect your TNC and PC together w/ a COM connection – such as DB9 or USB, whatever makes you happy.
  • Fifth, set up the communication ready btwn your PC and the TNC; open a serial communication application / tool – such as PuTTy or HyperTerminal in Windows and open the TNC COM port from your PC.  This should establish a live communication btwn your PC and your TNC.
  • Now, your PC is connected to TNC, your TNC is connected to your radio, your radio is tuned into 145.825MHz, your radio is connected to a good exterior or super good internal antenna for 2M at high gain.
  • Your now set to go to next step
  • We now need to set up a simple setting in your TNC
    • In your PuTTy or HyperTerminal app, type the command that will allow to change the “UNPROTO” path.  This is done by typing in “UNPROTO CQ via ARISS”
    • what this command does is it tells your TNC to send all CQ targeted packet messages VIA the ARISS repeater in the ISS” (if you are new to TNC commands, you should read this great article on TNC commands by Larry Kenney -WB9LOZ )
    • Now your TNC knows to package up your ARISS packets to be routed to CQ (the virtual target end point) “via” the “ARISS” repeater alias on the ISS.
    • Next, change the TNC mode into “CONVERSE” mode.  CONVERSE == conversation mode; This can be done by typing in a “CONVERSE” and then hit Enter into the PuTTY or HyperTerminal prompt.  Your TNC is now in conversation mode.
  • Next, wait for the pass-prediction date/time (By now you would’ve guessed that it’s best that you get all the previous steps completed ahead of time to save all the adrenaline-rush when the time comes to see the action)
  • Now, wait, how would you know when the ISS pass-through.  Yes, you know the date/time.  But, wait, is there not a better way to visually see where ISS is in relation to my location ? ABSOLUTELY YES.
    • Go to this website and download this simply fantastic application written by W9KE Tom Doyle. Great, simple to use tool. I use this a lot.
    • Install and run this app, follow the set up video Tony’s site and you in the game
  • when the time’s right, send packets
    • when the ISS passes through your location (it sure will at some point, keep track of the pass thru predictions from Tom’s tool), in you TNC (while you’re in the CONVERSE mode, type in “=Hello from <your name>, <your location>” and hit enter.  By hitting enter, you are asking the TNC to package up the message and send it to the ISS’s repeater.  Remember, “UNPROTO CQ via ARISS” command.
    • now you should note that sending one packet by itself does NOT guarantee that the ISS station would receive it.  It has thus become customary for ARISS enthusiasts to go crazy and send multiple packets in bursts of time window in a hope that at least one of their packets gets received by the ISS.  You should use common courtesy to not flood the airwaves w/ your packets thereby “radio polluting the airwaves” and preventing others’ packets from reaching the ISS. You get the gist. Simple rule =  Be courteous.
    • When the ISS repeater receives your packet, it “repeats it back to the earth” sort of like a relay race, it hands off the received packet back to earth.  Then what happens ??
    • Then, an iGate on the earth, will receive that relayed packet and submits it to the APRS-IS server (an internet server) that keeps a log of ALL the APRS activity from all around the world.  Actually there are MANY APRS-IS (IS==internet servers) servers – they all act in unison like a “server farm”
    • Once your packet is successfully reported to the APRS-IS server, you should be able to track your packet and your callsign down at this website

So, that’s a long short summary of what APRS for ISS is all about.  My project on this subject matter, relates to the building of an iGate that receives relayed messages from the ISS and reports those into the APRS-IS servers. Such that, one’s ARISS packets are logged into the APRS-IS servers.

I’ll pause here. Too much typing on this subject for now.

Below you will find pictures of my ARISS APRS for ISS rig setup. Please kindly review and comment


Thanks, 73


2 Responses to ARISS – APRS with ISS

  • Do you operate DMR?
    if so,when.

    TNX de N2DCB

  • Hi George – I have been heads down the last few months traveling for work business. And, have been out of pocket for DMR activity/QSOs. However, my two repeaters Buck-Hill and Medina have good activity on several talkgroups. You should feel free to jump in on MNDMR or MNStatewide TGs anytime and make contacts. There are several of us always willing to connect and chat and would enjoy making your acquaintance. 73, N0AGI-Nagi

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