08/13/2014 at 13:36 •
Despite the fact that NEMA 17 stepper motors were considered our best choice, at the time of our first design some old NEMA 14, spare parts from an old Rep-Rap, where available so we stuck with them. Last week, we received our new motors and did some tests. The first test was to find the optimal torque without overheating the (also new) drivers. Although we have some results, tests will be continued and we will come up with some numbers probably by next week.
Additionally we are working on the new rotator design. We placed the motors on top. This way we managed to decrease the profile of the design a bit and also now the device is a lot more serviceable. Now you don't need to remove everything if you want to access the motors or the worm gear. We are also trying different designs in order to improve the connection between the stepper shaft and the worm gear.
08/18/2014 at 12:56 •
For v0.2 of our ground station we have been working on consolidation of our electronics trying to minimize size and upgrade the components. Combined with the current minimized approach for the gear assemblies, this will enable us to deliver a smaller more rigid and reliable ground station.
The electronics that needed to be fitted in are the following:
* An Arduino. We selected Pico for the size advantage
* Two stepper drivers. We are using Pololu compatible A4983 based stepper drivers.
Agis (our electronics expert) designed an integrated board to fit everything in. Here is the result:
And the schematic:
We are printing the PCB as we speak and will be posting a new log with the construction and testing.
08/18/2014 at 17:47 •
SatNOGS as a project has been concieved as many Satellite Ground Station implementations (like the v0.1 which is ready) coupled together under a global Network that would enable anyone to utilize SatNOGS as a single platform for observations.
The UX idea is simple. An observer/astronomer/maker/hacker accesses our global Network via a web interface. Then she provides details about the observation that she would like to schedule like, which satellite, which band, what timeframe, which encoding etc. Then, having all the info , the system calculates the possible observation windows, on the available Ground Stations connected to the Network for the given timeframe (taking into account any tool, location and time constrains). Once the observer confirms the proposed "observation job" then it gets sent as a job to each Ground Station (GS) job queue to be executed when it has to.
GSs are gathering observations, decoding/recording them and sending them back to the Network, making them available to the observer (and the world!).
Here is a glimpse into the initial DB Schema of the Network (not all attributes are populated in the tables)
The general design of the Network part of SatNOGS constitutes a typical many-to-many scheduling problem (many observers to many ground stations) Interestingly enough projects have been developed for observations planning and scheduling on satellites like Hubble (HST) Projects like SPIKE  and ASPEN . Those are examples of many-to-one scheduling system s and we have been looking around for implementations that would be similar to our proposed one. Unfortunately we haven't found anything closely related, thus we are building the Network part from scratch.
Given the expertise of our software people, we are building the application part on Django (python), and relying on rest APIs for communication with our ground stations. The first iteration of the network will be focused on a client-pull approach (versus a server-push) to eliminate any network restrictions.
Our challenges towards the global network are interesting. Given the data-heavy approach of the network (imagine all observations from all stations stored and indexed) we expect data storage to be a serious challenge. We are evaluating deep-storage as an approach to this, and we welcome any feedback or ideas around that.
08/20/2014 at 15:37 •
SatNOGS is focused on TX operations for Low Earth Orbit (LEO) satellites. Most satellites in those orbits transmit signals in relatively low power (compared to GSO satellites). 100mW to 2W is a typical range for LEO. Given that power output and our RX assembly (yagi + dvb dongle for reception) a Low Noise Amplifier can really improve our RX capabilities.
We decided that LNA would be an integral part of our RX assembly early on, but we could not easily find something that would meet our requirements (bands, noise figure, cost, size etc). After browsing and researching a lot of different options out there, we stumbled upon LNA4ALL.
LNA4ALL  is a great project by 9A4QV. The amplifier is built around Mini-Circuits PSA4-5043+ E-PHEMT Ultra Low noise MMIC amplifier operating from 50 MHz to 4 GHz. Small SOT-343 package combine low noise and high IP3 performance with internal match to 50 ohms. With 20 Euros as a pricetag, this was the LNA we were looking for.
We are using our 5V output from the regulator we have inside SatNOGS as VCC for the LNA (required a tiny bit of modification) and the LNA is connected in line between our RX dongle and the antenna (using SMA connectors)
Initial tests are showing great improvement in our reception (tested against a variety of bands, encoding and satellites) making this LNA an irreplaceable part of our project.
Proper shielding and housing should be in place, so we designed  and 3d printed quickly a housing for this LNA. Some grounded aluminum tape makes up for a shield.
More tests will follow, and we are designing new antennas and evaluating their matching.
09/18/2014 at 14:35 •
As outlined in project description and previous logs, a central part of our projects is what we call "SatNOGS Network". SatNOGS Network is a web application running on a server that takes care of discovery of ground stations, registering of users, scheduling and job-detailing of observation as well as data collection and analysis once an observation is done.
After 3 straight weeks of python/django hacking and almost 100 commits, we are proud to have a working prototype of the SatNOGS Network.
The model of the application is now polished and able to handle all basic operations for Stations, Users, Observations, Satellites, Transponders, Antennas and Data.
Next in line in terms of functionality implementation is the ability to plan observations based on user provided info (satellite, transponder etc) using SGP4 in python, and also a detailed view of Observation (with data and timeline).
The main page features a map with all ground stations, details about a featured ground station and latest completed and scheduled observations.
The code can be found (follow and contribute too!) here: https://github.com/satnogs/satnogs-network
A live development version of the website with demo data [WARNING ;)] can be found here: https://dev.satnogs.org/
09/20/2014 at 13:31 •
It was time for us to test out the designs for our PCB that would take care of the motor control.
In a true hackerspace fashion instead of ordering the PCB we decided to built the capacity to produce our own (much needed moving forward). We could not settle for a simple single-side capability with no solder mask, so we shot for a typical side-project extravaganza :) What we ended up with was a double side capable UV exposer controlled for timing and after many tests the expertise to apply solder mask for uber cool finishing for our diy PCBs.
Back to SatNOGS specific PCBs the design was slightly changed from v1. We changed the capacitor, rerouted for optimal setup the board and thanks to [n0p] comments we added breakouts for unused Arduino pins (you never know what you will need!).
Production went smoothly and the PCB test showed that everything was in place correctly!
Having the finished v1.1 motor control PCB ready we thought that we could tidy up our power circuits too. That called for a PSU PCB tailored to our needs. Agis, our team electronics expert, quickly designed a PSU PCB based around a Voltage Regulator capable of having an input of 12V DC and an output of again 12V DC plus 5V DC stable through USB Type A too.
Production once again was smooth and we ended up with our PSU PCB. Pics below are from a slightly modified version with a cap (both designs can be found in our repo).
Detailed designs and Gerber files can be found in our Github repo
Next steps for our electronics will be to focus on the auto-homing circuits (using the handy breakouts!). A separate log on that will follow!
09/22/2014 at 12:52 •
During our quest for reliable Satellite transponder data we came into a sad realization. There is nowhere out there such a thing as a complete transponder database for operational satellites.
Having this information is crucial for SatNOGS operations on multiple levels. Observation scheduling, observation job details and mainly ground station operations.
It was obvious that we needed to build a DB of all transponders of operational satellites, and in a true community and open data fashion it needed to be open, crowd-sourced and not necessarily SatNOGS specific.
What we ended up with as a solution is SatNOGS DB . A separate crowd-sourced suggestions app build around transponder data for satellites. The source of truth about transponder data still lives under SatNOGS network (our main observation and scheduling website)(see previous posts) and SatNOGS DB would expose all these data and enable users around the world to provide suggestions about transponders for satellites.
Technically, the stack we are using is really interesting, thanks to our hipster-friendly software expert Nemo. In an effort to make this app as abstract, white-labeled and not SatNOGS specific as possible, no relational specific-schema database is used on the backend. We are using CouchDB  as our backend (with the appropriate hooks to SatNOGS Network) and a combination of PouchDB  and AngularJS  as our client-side front-end. This provides the ultimate flexible and responsive platform for best UX and re-usability. All suggestions are stored in blobs and once they land (moderated and approved) back to SatNOGS Network they become part of our SatNOGS Network database.
We will be pushing the site live this week (after re-factoring the code) and kickstarting the data with sources we could find around the net. (A post will follow)
Furthermore, by solving our data issue, we are providing the world (and especially ham and amateur satellite communities) with an open, accessible, crowd-sourced database for Satellite Transponder data. (yeah open data!)
09/22/2014 at 14:36 •
Working towards v2 of the Ground Station Gear Assembly, the SatNOGS hardware team has experimented with various gear designs. All of them where designed and 3D printed from scratch focusing on ease of reproduction and excellent mechanical operation and properties.
The new gear assembly (which is almost identical for both Azimuth and Altitude) sports a much thinner and compact design, driven by a much more powerful NEMA 17 Stepper motor.
Failing was part of the process. As you can see in the pics above, 3D printing a worm gear can be a monster of its own. After careful calibration and fine-tuning (layer heights, cooling, leveling, infill settings etc) on our 3D printer we were able to consistently reproduce worm and matching gears. We even experimented with acetone abs curing, which (based on the results we are seeing) we believe should be the default for our gears moving forward.
v2 of Ground Station is around the corner, and we will be posting later this week with full documentation, designs and instructions on how to build. Till then, back to gear-craze!
09/24/2014 at 20:41 •
Stepper motor and axis movement should be accelerated, decelerated and smooth. This is important for a variety of reasons including less strain on the axis and the gears, plus inertia compensation.
Agis with Manthos spend some time looking into some options and finally agreed to implement acceleration resulting to smooth tracking using an Arduino Library and amending it a bit. The results is pure awesomeness for our tracker:
This code and implementation goes straight in our v2 design. Code can be found in our repository.
09/24/2014 at 21:48 •
The time we've all been waiting for, has come. We are proud to release v2 of SatNOGS Ground Station (Tracking Box) with many upgrades and fixes from the previous version. Notably:
- Redesigned Axis Gear Assemblies. They are now smaller, more robust and reliable based around a much more powerful NEMA 17 Stepper Motor. The two assemblies are now structurally connected, making the whole assembly much more rigid. Also we redesigned the Worm Gear for improved printability on 3D printers.
- Integrated electronics. We designed and built a new PCB to house all electronics (Arduino, and Stepper Drivers) along with an additional PCB as a PSU for voltage regulation and neater cable management. (see previous log)
- Reworked stepper driving code, featuring a much cleaner code, acceleration and deceleration in movement, stop functions and early opto-homing support. (see previous log)
Tripod and On-board computer (TP-Link) stayed the same, with developments on them coming down the road.
A detailed Bill of Materials is available here.
We have also compiled a detailed construction guide, with step by step instructions on how to assemble the Ground Station Tracking box for both Mechanical and Electronics components.
Development does not stop with v2, and we are already working on the homing/zeroing code that will enable the homing parts we included in v2 to function. Moreover based on more testing we are applying to v2 and feedback from the community, we expect minor fixes to be released soon.
We can't wait to see v2 out there, built by others, so get started and/or provide feedback!