SatNOGS is a network of stations that report satellite telemetry to a central database.  I’m just getting started in this but here’s what I’ve done so far. The whole SatNOGS project is designed to let amateurs build up a simple satellite station that will report telemetry. The website contains info on antennas, rotators, software and other info needed to get going. In particular, the software runs on a Raspberry Pi, a low-priced computer running Linux, and an RTL-SDR USB radio. Since I already have a home satellite station I downloaded the software, loaded it onto an SD card and plopped it into a Pi. The whole system is configured to run remotely, so you have to SSH into the Pi from another computer to set it up, but that’s not too hard. You also have to set up an account on SatNOGS and get an API key that will link the computer to their system. Then you can set up station locations – I set them up for my home station and for the W2MMD clubhouse.

Once that’s done you can log into the SatNOGS dashboard and schedule passes that you’ll be monitoring (that’s right – you control your local computer from the SatNOGS website – it took a while for me to figure that out). Here’s how that looks:

The dashboard will list the upcoming passes for each satellite giving you the date and time and a radar plot of the pass.  In the picture above all 3 satellites have very low elevation passes, so they probably won’t be good candidates, but many passes may be overhead and work well.

I don’t have this set up at the W2MMD clubhouse yet because I need to order another Pi and a RTL-SDR radio. At home I’m running with my two M2 eggbeaters in the attic because my rotator controller has improbably quit working, and my results haven’t been too good. But I’m expecting the antennas at W2MMD will be great, and that we’ll be able to copy telemetry from lots of satellites. Stay tuned…

Also note that there’s a SDR package for the Pi called Gqrx – haven’t tried it yet but would be an easy, cheap station.

8/29/18 – Got the rotator working! Had lots of trouble identifying the USB port on the Pi that should be configured in the SatNOGs software.  Even if I had that working, we would still need to switch the rotator cable between the Pi and the PC for SatNOGS and regular operating. After a lot of trial and error I found that the PstRotator program can be commanded by the Hamlib rotctld component of SatNOGS! This took a lot of configuring but basically it involved:

• Setting up the rotator in SatNOGS to talk to the 192.168.50.21:4533 port
• Turning on Hamlib in PstRotator and leaving it set to the default port and
• Opening port 4533 in the Windows firewall

That works, and lets the Pi control the rotator thru a network connection rather than needing to change the cables! Very cool. We can now use the great antenna system at W2MMD for telemetry reporting on all sorts of satellites. I’m eager to see how well that works.

8/31/18 – Looks like everything works. The Pi will command the rotators thru the PstRotator interface. Gotta be sure that there aren’t conflicting signals going to the rotator from different sources; for example from SatNOGS, a remote operator and a console operator. I swapped out the rtl-sdr for an Airspy but haven’t had a chance to compare them – the Airspy is about 5x as costly so it should perform better.

11/4/18 – Lots of operators all over the world are using out SatNOGS station for observations – we have more than 1600 observations in a little more than 2 months. SatNOGS records the audio picked up from our SDR receiver and dumps it into a database from which it can be analyzed. It stores the data in a .OGG compressed lossless format. So how can you listen to that audio and decode it yourself? The easiest answer that I’ve found is to use the free version of Audacity, a sound editing program. Download the .OGG from the satellite pass that you want to decode and open that file in Audacity. Then set the output path to a virtual audio cable that you’ve connected to the input of the program that you want to use for decoding.  In the example below I’ve downloaded the audio from a NO-84 pass and want to decode the PSK data using Fl-digi. So I set Fldigi’s input to VAC Line 4, which is also Audacity’s output (because Audacity isn’t directed to a speaker you won’t hear the output). You can see the audio signals (vertical bars) in Audacity, and when playing thru that part of the audio track Fldigi will decode the PSK being fed into VAC Line 4. This works with all sorts of digital signals – CW and PSK with Fldigi, SSTV with MMTV, NOAA weather fax with Wx2Img, etc. So you don’t need to actually be present to decide satellite audio – you can set up SatNOGs to do it and then download and decode it later. I don’t think this is as accurate as doing a live recording in the W2MMD station using SDR Console and creating an IQ recording, but it’s a pretty good substitute when you can’t actually be at the console during a pass.