The Distributed Ground Station Network

tracking CubeSats faster, anywhere and anytime for everybody!

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The Distributed Ground Station Network (DGSN) is a novel network concept of small ground-stations and connected via the internet for performing automatic scans for cubesats and other beacon signals. By correlating the received signal with the precise, GNSS synchronized reception times of at least 5 ground stations, it enables the positioning of the signal's origin. Thus a global tracking of small satellites becomes possible in this "reverse GPS" mode. It allows mission operators to position and track their small satellites faster after piggy-back commissioning, when the final orbit is yet undefined and could differ from the specified orbit. Furthermore it allows permanent communication in "data-dump" mode. In this mode, DGSN ground-stations relay the received data to the servers and thus to the operator.
Let's track everything, together!
PS: We're currently ground testing the prototype in Stuttgart "tracking" the TV-Tower

May we give you a quick overview?

Anything goes!

The "Anything Goes" hackaday prize challenge has a fitting slogan. It matches our effort to build a Distributed Ground Station Network for tracking satellites and especially tiny CubeSats. Providing CubeSat operators with information where their CubeSats are is really important, because in right after launch, they sometimes need to wait and "scan" for their CubeSats' signals. In this crucial phase, the satellite is on their own and can be to hot or too cold or running out of battery power. This happened before and resulted in loss of CubeSats making them literally space debris.

To support those missions, we sarted DGSN several years ago and constantly worked on the concept and first prototypes. We are now at a stage, where hardware needs to be built and deployed for first field tests. We now know, that DGSN will work. We still need to know, how good it will work under real conditions. Thus "Anythings goes" is a nice statement, but we want to know how good DGSN will "go". Let's find out and build it!

Update: Graph above
During the International Astronautical Congress 2016 (IAC) the PocketQube team by TU Delft showed a nice graph how long it usually takes for NORAD to release the Two-Line Elements (orbit data) of different small satellites with respect to their radar cross section. The essence is that it takes longer when they are smaller. It can be up to 14 days and that could already be too crucial for some missions. So it was great for us to have been presented the current status of DGSN at IAC to be in close contact with small sat operators. We will look forward to help and assist them during their various missions! (for the full IAC2016 paper, click here)

Citizen Science supports Space Operations!

Space for everyone! You can help space operations within a collaborative team. Telling where the satelite signal came from is only possible when 5 or more people's ground stations received it. So here is where the citizen science comes into play in several ways.:

The basic principle of tracking can only be achieved in a global team of "sat spotters". The more people setting up ground stations there are, the more often, the more precise and the longer the cube sat can be tracked. Community satelite spotting will provide additiona data to the space operator.

The product of it will be stored in an open data base and provided to the satelite operator as well as the community. We believe, that the community can use the data in creative ways and find results in the measurement data beyond the intended goal of tracking cubesats. We forsee that the community will use it for locating thunderstrikes, correlating the atmospheric conditions and and air mixtures by measuring the dampening of the signal on its way from the satellite to the ground station, using the GRAVES radar station in France for passive radar or something yet out of our imagination. People will do whatever they can and what is fun! We support this with DGSN.

We are starting it small, with only 5 of our own ground station and tracking everything that's flying ober Stuttgart. This is our challenge to show you how to do it. You can already be part building it. For the next stations, the community will take over and make it awesome!

Summarizing: YOU are important, because the more people are setting up nodes, the better we can track signals! See, the TW-tower tries to hide, but we all will find it! Be a node!

[Fig: first test with 8 stations]


Of course DGSN can do more than just track satellites and help small sat operators to find their sats earlier. With Software Defined Radio it is easy to track other signals. So tracking airplanes and provide thier tracks and ADSB signals (DGSN can track it and ADSB has the track in it anyway, so it is a redudancy check) to everyone. And also small a neighborhood help" can be done. We now have Freifunk (a free wifi-internet connaction initiative) attached to our Antenna Forrest, as...

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  • 1 × rtl-sdr dongle (modified)
  • 1 × antennas (currently for 2m and 70cm)
  • 1 × GPS device
  • 1 × PC or Micro-PC (Raspberry PI)

  • If you are on the International Astronautical Congress 2017 in Adelaide, meet us

    hornig09/14/2017 at 20:25 0 comments

    I always wanted to impact a into something :). Proof of concept for .

    After the IAC2017, we will upload the paper for you to read it also...

    More to come later.

  • How to decode Bell202 modem signal? APRS signals from the ISS at 4 stations

    hornig08/15/2017 at 17:24 0 comments

    Now, 4 DGSN stations receiving APRS from orbit by the ! Stations are now in Settrup (a lovely small village in Lower Saxony!), in Stuttgart, near Lake Constance and in Jena. Where should we put one next? If you have a suggestion, please tell me here >>

    My task is now that I still want to know the content of APRS the sent here! Would anyone please help me decode? :) I uploaded a Python Numpy NPY file here. It incuded the Signal Peak you see in the graph above from those 4 stations

    What I know is that APRS uses Bell202 coding with two frequencies of 1200 Hz and of 2200 Hz. Each represent either a 1 or 0. I just started to play with an FFT Kernel of 8K samples and I already found phases of those frequencies but so far I couldn't find the starting flag of the AX.25 frae 01111110.

    As far as I know, Bell202 was also used in old internet modems. So I guess that there are people on Hackaday who play around with old modems and solve those problems while sleeping. If so, please comment below.

    Until then, I will keep on playing with the 4 stations and trying to decode APRS signals.... :)

  • DGSN timing-board goes earth quakes: Tunnel-God-Detector for NASA Space Apps Challenge 2017

    hornig05/07/2017 at 11:06 0 comments

    Last weekend, I (Andreas) was part of the NASA Space Apps Challange 2017. It is the biggest global hackathon with more than 180 locations and more than 20,000 participants.

    The theme was "Earth Observation" and the participants worked to combine space data from NASA with their very own solution to create something incredible helping solve global problems. I was part of the Team "Tunnel God Detector" to detect and locate tremors to support emergency respond teams and thus saving people in danger.

    Why I write this is easy: I provided the time synchronization method of my Distributed Ground Station Network and we improved it for the Tunnel-God-Sensors a lot by just discussing it in crazy ways that are just possible during hackathons like these.

    I had so much fun and met awesome people! I want to say thank you to all of you. And I want to invite everyone to keep on working on the project even after SpaceApps. For that, it is on hackaday now >>

  • Space … the final frontier … for our spaceballoon

    hornig03/22/2017 at 16:47 0 comments

    Have you ever dreamt of going to space?! At least as a child you did.

    Unfortunately we didn’t quite make it to space ~100km quite yet – but at >22km we (our balloon that is) have been higher than at least 99.99% of you out there. Commercial airplanes fly at 8.5km to 10.7km to give you something graspable to compare it to.

    Ever since we saw the first footage of a camera attached to a weather balloon we became fascinated by the idea to take our own images. The visible curvature of our small sphere (speak: earth) floating through space captured was ever so inspiring. You don’t even need to spend a lot of money doing so.

    The project dubbed “spaceballoon” was accomplished by the team (andreashornig, exco, makefu) collaborating at our local hackerspace – the shack. On Saturday, 4.3.2017 we successfully launched it from the nearby Grillplatz Rotenberg on top of the Württemberg mountain.

    The launch was exciting – even more so because we had more than 10 people waiting for us on the hill we chose for takeoff.

    Here is a visualization attempt of the logged data: >>

    Nadka made an awesome video with the onboard footage and with some material that was taken by someone at the launch site.

    This is the flight path from one of the onboard android phones:

    The „hunt“ for the balloon was thrilling as we lost contact with our transmitter multiple times.
    Through interpolation and some luck picking up the signal again we were able to pickup the payload – even though the commercial tracker and the android phone didn’t tell us their location – or anything for that matter.

    We are also really happy that the last minute efforts of team Bremen bore fruits.

    As people are already telling us they also have plans (for a long time) to start a weather balloon of their own – here you can show your hands if you want to be the / a part of the next balloon project. You find a lot of needful things on our Github Repository.

    A big and unorganized spaceballoon photo album can be found here.

    Special thanks to Andreas ( for taking the initiative thus causing the project to finally happen and to exco ( for sourcing the necessary parts and hacking together the whole thing into the final product.
    For the lessons learned we wrote you the weather balloon guide.

    Reminder: writing it down makes it science – so document your projects.

    Find more on our twitter account for the spaceballoon.

  • Weltenraum is go! Shackspace plenum approves new radio/medialab room

    hornig10/20/2016 at 23:14 0 comments

    Finally, Stuttgart hackerspace shackspace will get a new room, den Weltenraum. It is a German play on words for "Worlds and Room" and also an old fashioned word for "Space". It fits perfectly because it is a room shared by different interest groups in shack that are interested in media (editing, videos, podcasting, music) as well as the ham radio operators and sdr fans. And the latter means us, the satellite space guys. Today was our weekly plenum and we finally have the go-ahead to put our ground station radio equipment there and connect the AntennaForest to the Weltenraum.

    The slides you can hardly see on the above photo are on GitHub.

    So we have a base of operations for all things radio now. The net weeks we will realize all the moebles you see on the image below and the network infrastructure to the AntennenWald. With this, we can connect our DGSN ground station antennas and also the FreiFunk-Stuttgart hardware. It will take some hard work setting everything up, but we put our crowdfunded money (and also a big chunk of our hackaday prize 2016 money) to very good use.

    Our plan is to have a comfortable "hacking" environment until december and then we don't need to sit on the rooftop net to the antennas, we will do that from Weltenraum and with company of other creative people around us. This fruitful cohacking will be of benefit for everybody. And this project will attract more people and grow. If you are around, we will give you a tour!

  • This is why we do it! Helping operators, helping missions, helping everyone!

    hornig10/09/2016 at 23:16 0 comments

    I (Andreas) had been the chance to attend the International Astronautical Congress 2016 (IAC) In Guadalajara, Mexico this September. It is the biggest space congress on Earth and I teased about it in the previous logs already. I am back home now and here is the promised longer version.

    Actually I attended two space congresses. I had been on the waiting list for the Space Generation Congress 2016 and was lucky enough to received a last minute slot. It is a youth congress in conjunction with the IAC to have "a voice from the youth perspective" in the space community that is meeting during the year and mainly during IAC. More then 150 people from mor than 60 countries gathered and discussed various topics in working groups. The result of these working group are presented as recommendations during the United Nations meeting of COPOUS (United Nations Committee on the Peaceful Uses of Outer Space). So what everyone is doing there is pretty amazing and I try to take part every year since I stumbled across thme by accident in 2011. So it was great to work with other space enthusiasts in our Telecommunications Working Group about how to make it easier for small sat operators to allocate needed frequencies from the ITU. I don't want to spoil too many details already while the reports of our and the other working groups are currently written. So I recommendto you to check their webpage in 1-2 months because they will openly publish it. But summarizing we had a consensus that the speed of development for a current cubesat is way shorter than than the typical frequency allocation process and all parties should be aware of this right from the begining.

    Of course I met old friends of mine and found new friends. This is why I like space. Everyone is working together for the betterment of everyone in one way.

    And then after SGC2016, the IAC2016 started. Guadalajara and Mexio as the host city and country did a marvelous job! It was a realy pleasure being there. I will directly jump to my personal highlight of the IAC, Elon Musk's plenary talk about his/SpaceX's Mars Mission. I won't go into details, because I linked to the full video here and you can see why I was so impressed. I really hope that he achieves everything he proposed there. Unfortunately I needed to leave his talk early because my own technical session and my paper presentation started right after his talk. I presented the current status of DGSN and what implications a highly distributed, internet connect grid can have. I don't really like the word Internet of Things, but I needed to give the talk a title and you can already find my slides (linked in github) in the previous log. I got great and honest feedback from Mr. Mattas (ITU) about why using Open-Source and also from other cubesat operators. This is why we decided to go for the Small Sat Operations technical session, because DGSN can have an impact with small sat operations. And we also learned, that we transmit with DGSN or any other ground station network on behalf of other missions is complicated and ITU emphasized to respect the rules. For us/DGSN it is okay, because in the current phase, we don't hink about doing that (yet).

    Related, the PocketQube team by TU Delft showed a nice graph how long it usually takes for NORAD to release the Two-Line Elements (orbit data) of different small satellites with respect to their radar cross section. The essence is that it takes longer when they are smaller. It can be up to 14 days and that could already be too crucial for some missions. So it was great for us to have been presented the current status of DGSN at IAC to be in close contact with small sat operators. We will look forward to help and assist them during their various missions! (for the full IAC2016 paper, click here).

    All in all we know, why we're working on DGSN, because we can help others and all benefit!

    This log will be updated....


    hornig10/02/2016 at 19:06 0 comments

    Hi all,

    I am just sitting at the Guadalajara Airoport and need to wait until I can board my flight to Mexco City (=> Paris => Stuttgart). The International Astronautical Congress 2016 was great and I will update this log as soon, as I will be home. But in the meantime the presentation is on Github now.

    And my personal highlight was Elon Musk's talk avout SpaceX's Mars mission. Unfortunately, I needed to leave earlier to go to my session. So I didn't had the chance to ask my "serious" question at the end. I like the kissing booth idea a lot! :)

    Soon more....

  • International Astronautical Congress 2016 in Guadalajara - Biggest Space Congress, Elon Musk's Mars plans, maaaany space presentation, Ant-Man and a touch of magic

    hornig09/25/2016 at 22:12 0 comments

    This will be a rather short update, because longer updates needs to wait until after I will have presented the current status of DGSN at the International Astronautical Congress 2016 in Guadalajara. IAC2016 will take place next week and I just got my badge and programme book (yes, book, it is 290 pages heavy).

    I will present our paper "New space operations in the internet of things era - anywhere, anytime, anything!" in Small Satellite Operations Session (B4.3) on Tuesday, 2016-09-27 14:45. So feel kindly invited to come if you are around!

    I will give another log afterwords and I intend to load the paper and presentationto github (if the IAF allows, or I will rewrite it ;) ). In the meantime you can get some impressions about IAC, the SpaceGenerationCongress and how awesome the city of Guadalaraja is on my twitter @andreashornig.

    As a huge Mars fan, my personal highlight will be SpaceX's Elon Musk's plenary about his plans for “Making Humans a Multiplanetary Species”. They will also stream it live in case you will miss it.

    IAC will start tomorrow, but today I met Ant-Man so I will look for the Pym Tec booth to check for their space progamme and I felt a touch of magic...

    Really excited!

    PS: there is Con Comics today at the expo, too. I hope their guests will be also there tomorrow! So cool! :)

  • How to use GRAVES radar in France to detect the ISS and metoerite showers

    hornig08/15/2016 at 19:58 0 comments

      If you want to track the ISS or just want to listen to "blips" generated by meteorites rushing through the atmosphere, then this short how to will show you how to use "passive radar's" reflexion on the ISS metal hull or the plasma tubes in the atmopshere created by the meteorites.

      1. your location should be in Europe (more great infos here)
      2. set your SDR# to GRAVES frequency of 143.05 MHz
      3. set the "Resolution" of the fft window to at least 52488 bins. That was our biggest mistake at first. We couldn't see the signal due to it's smaaaall bandwidth! But then we cranked up the resolution.
      4. GRAVES radar is always on (at least that is what we experienced), so you wait and check for signals.
      5. If you check GPREDICT for ISS contact times, you should see the faint relexion signal that is marked with 3) in the image below.

      We did this ourselves to learn if it is possible with our RTLSDR dongle and what settings we need for the Distributed Ground Station. And this is our result with our very own crappy code. You also see, we increased the amounts of bins...

      We are still not sure, what kind of blips we received there. So if you know, post in in the comments below! That would be awesome! We also asked ONERA. The should know, they operate GRAVES :).

      More images will be shown in the next log. Happy blips hunting so far!

  • Monitoring the 2m-band: One day of radio contacts by the International Space Station

    hornig08/13/2016 at 17:52 0 comments


    • how does a signal from the International Space Station look like? Like this!
    • how often does the ISS switch on the Slow Scan TV? At least not during our testing period.
    • what else did we learn? Only use a fixed gain when you have neighboring ham operators in close vicinity of your ground station. Saturation acvoidance!


    After monitoring the 70cm-band, we checked back the 2m-band. But not the NOAA satellites, this time we wanted to look for the biggest human-made construction in space so far:

    International Space Station, got you!

    As a fancy fact, the ISS is not only equiped with special dedicated communication hardware and channels to their mission control. But also there is amateur-radio (ham) equipement installed for redundancy/emergency reasons and also for outreach (check for more infos). And astronauts on board the ISS hold the official ham-operator's license for operating the equipement.

    HAMs in space aka astronauts' gobal radio

    Unfortunately, we didn't receive voice transmission, because this is mostly done to communicate to special events like school classes, space camps or else. The astronauts' busy schedules are only allowing this from time to time. It was not planned during our tests. The Slow Scan TV was also not active on 145.8 MHz. It is even active even less frequently, but if active it transmits images taken inside the ISS or other interesting footage. (you would have seen it in the video. top left window)

    Active packages everywhere

    BUT what is always active is the APRS system on 145.825 MHz. You can transmit your APRS packet from earth to the ISS system and it relays it back. And we received APRS packages during each pass. You can easily see it in the video above (top, right window). As you saw before in our other logs, you see the doppler effect on the transmittion. You see packages of several seconds being transmitted.

    How to receive the ISS?

    Reception was easy. We used the turnstile antenna on our RTLSDR dongle. That's about it. What was tricky for our location and perhaps most of your's as well are other amateur radio channels. We are looking for a rather weak signal from space. What we saw were really ppwerfull transmission on neighboring amateur-radio channels. So autogain was not an option this time due to the high dynamic range of signals in the received frequency band driving the levels to maximum. And during this autogain phases, weak signals like those of ISS were harder to monitor. What solved this was finding a fixed gain that offers anough head-room for pwerful signals and also not effecting the weaker signals. We applied the "you crank up gain as long as the noise floor is not being raised significantly". That worked and with 30dB gain we made the monitoring you see in the video.

    The ISS is pretty awesome! We keep on tracking you! :)

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sm3ulc wrote 09/27/2016 at 14:09 point

Why not start with basic recording of the raw IQ signals for sharing? Demanding special built receivers reduces number of possible participants by 99.99%. SatNOGS have been around for a while but haven't even reached that basic thing.

  Are you sure? yes | no

hornig wrote 09/27/2016 at 16:39 point

Ahoi, so is ThumbNet, FunCube, GENSO (not really), KIWISDR, you name it. We're not building an own receiver. RTLSDR serves pretty well right now and it's pretty affordable.

The part of IQ data sharing you need to explain to me, because I could think of so many things now. So instead of guessing, I ask back :).

  Are you sure? yes | no

Polard Jean Marie wrote 09/10/2016 at 13:56 point

Why do you listen Graves in NFM ? I use USB, set my rig at 143.049 anf have nice pings and doppler curves. I try to use also VOR to get pings but this is more difficult. Anyway a nice project . I follow you !

  Are you sure? yes | no

hornig wrote 09/25/2016 at 22:16 point

Hi Polard,

thanks for the nice words. I just needed to find out "better" settings for my own programme. I wasn't aware that the signal has such a small bandwidth, My fft windows was just 2^13 bits long and in the resulting fft I couldn't even see anything happen on that frequency. That I why I checked with sdr# and finally found it :).

This is what I wanted to share with you. It was waaayy to easy for me, so I didn't think of it as the first reason.

  Are you sure? yes | no

xof wrote 06/26/2016 at 06:17 point

Have a look at too.  They have a network of >500 stations worldwide, synchronized to the micro-second by GPS.  They localize lightning strikes using the time of arrival of VLF signals.  There is an extensive 'Projektbeschreibung' in (System Red)

  Are you sure? yes | no

hornig wrote 10/13/2016 at 18:17 point

Hi xof, yes, I have one of their kits. As far as I know they use a combination of direction (with their two segments antenna) and gps time correlation. The cool thing is that they can tune to lower frequencies then the rtlsdr can (below 30MHz) where the effects of the wideband pulse produced by the lightning is better detectable.
However "knacks" can be also heared on amateur radio bands when between you and the transmitter are lightnings. I didn't find a good "pattern" how such a rf signature looks like.

If you have such a signature, please tell me. That would be awesome to include :).

  Are you sure? yes | no

Nikos Roussos wrote 05/06/2016 at 10:36 point

You should definitely checkout SatNOGS. We won the Hackaday prize 2 years ago. It would be great to expand the scope of the ground stations to include "reverse GPS" functionality.

  Are you sure? yes | no

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