Since the conception of the SatNOGS one of our design mantras was modularity, not only we believe that the SatNOGS stack should be able use a wide variety of components but also that components should be able to used in a wide variety of applications.
This Sunday May 1oth 2015 the SatNOGS team had the chance to test how versatile our SatNOGS rotator and control software was by tracking the Aeolus-2way High Altitude Balloon.
Tracking was made possible by receiving APRS data from the Aeolus-2way High Altitude Balloon and converting them using a specialized script as azimuth and elevation coordinates.
The balloon launched from the center of the Peloponisos peninsula of Greece in the city of Megalopolis at Plaka airstrip at around 11:10.
The SatNOGS team was positioned 35 km (~21.7 miles) West – NorthWest of the launch site on the Antenna park near the Ano Dolianna village of Mt Parnon. An inverter was used to power two laptops sever ham radio transceivers and our SatNOGS rotator and provide sufficient power for the team’s needs
The balloon began it’s descent at 34.660 meters and it’s payload was successfully retrieved.
We would like to congratulate and thank all parties involved in this high altitude balloon launch for the great team work and cooperation and especially the Aeolus team for their commitment.
Moving forward we would like to consolidate our communications with the broader community, especially around news for SatNOGS project. For this reason we setup a newsletter to keep everyone interested updated for our latest developments.
ESA’s Summer Of Code In Space (also known as SOCIS) is an open source development program specifically for students run by the European Space Agency Under this program. ESA funds students to write space-related code for open source projects during the northern hemisphere’s summer.
Having access to an awesome 3D printer is certainly crucial for the SatNOGS project but the SatNOGS hardware is much more than 3D printed parts. To push the development of the ground station forward the core development team decided to acquire an oscilloscope, a programmable power supply and a Vector Network Analyzer
Following our ideal of sharing resources with the community, sharing it with the local hackerspace, we decided to install our instruments to it’s lab and share them with anyone interested.
In the future we plan to include to our instruments among other things a frequency generator and a signal analyzer.
We consider having access to a complete electromechanical lab/workspace is crucial not only for SatNOGS but for any community driven open hardware initiative.
To cover our needs we communicated with AlephObject in order to purchase a LulzBot TAZ4 3D printer. LulzBot didn’t only provided us with a superb open hardware 3D printer as usual but also they donated it to the SatNOGS project!
We are really excited by their offer, and stay true to the spirit of sharing that characterizes our project from the very beginning we decided to share our new 3D printer with the awesome community of the local hackerspace of Athens Greece a physical space dedicated to open hardware and software hacking.
To celebrate the occasion members of our team and the local hackerspace gave a welcoming event, and our 3D printing expert showcased TAZ4 and it’s awesome capabilities. He gave a hands-on introduction in 3D printing in general, TAZ4 and PrintRun (the free -as in freedom- software controlling LulzBot). Members and visitors of the hackerspace had the chance to print their own stuff (from Rocktopus figures to OpenBCI electrodes).
10 days ago we deployed a SatNOGS v2 on top of hackerspace.gr in Athens, Greece. This is the first SatNOGS deployed on the field and we couldn’t help but thinking that this is a huge milestone and brings great pride to the team!
(obviously the front cap is closed at the finished deployment)
The deployment was pretty straightforward, with one UHF helical antenna (our VHF is still up for matching) and no SatNOGS client controlling it (still under development for connection to Network). We simply controlled it with gPredict and Gqrx. POE for powering it up and minimal weather shielding (just some silicone on and around the bolts of the box)
We were able to track and record many different satellite passes and we encountered some software issues with our arduino homing code (see our post on community forum for details) which we hotfixed.
Congratulations to the whole SatNOGS team for the first deployment!
After a nice code push, scheduling observation functionality is now complete in SatNOGS Network website. The website is now able to dynamically calculate and schedule observation windows given a satellite for all available Ground Stations. The functionality works like this:
The observer enters the New Observation page. After selecting a Satellite and associated Transponder desired, the observer selects the timeframe for the observation. The timeframe selection is constrained in the future with maximum width being 8 hours (this could change as we scale the Network). After hitting ‘Calculate Observation’ the system returns a proposed Timeline of the observation, that includes the Ground Stations to be used and their individual observational windows. For this calculation we use PyEphem library and input the Ground Station locations, Satellite TLE, and timeframe desired.
Once the proposed timeline is reviewed and/or modified the observer can schedule the observation by hitting ‘Schedule Observation’. This creates the Observation in our database as planned, together with its associated individual observations for the Stations.
The Stations, through the Client, query the Network API frequently for scheduled individual observations.They then execute them on time, and push back the recorded data to Network, for further analysis by the Observers (making them also publicly available!)
Optimization of the Scheduling functionality will be further pursued. Ideas like deduplication of overlapping (more than 50%) individual observations, and accounting for horizon constrains are already in the works, and will be evaluated (in terms of their efficiency) as the Network scales up.
We’ve been thinking for some time that there is no need to install two separate RTL-SDR dongles to cover both VHF and UHF. It increases power consumption on WR703N without actually having any benefit, as using two dongles simultaneously is limited by the CPU power and network bandwidth.
A diplexer would allow the connection of a single dongle on both antennas. After studying the theory behind filters, we decided to implement a pair of Chebyshev filters. This type of filter has very steep roll-off and the maximum ripple can be a design parameter.
The two filters, a high-pass to attenuate the VHF band and a low-pass to attenuate the UHF band, should be crossing at exactly 288MHz@-3dB. Attenuation on each band should be at least 50dB. We calculated that a 9-pole Chabyshev filter would match these requirements and started designing a prototype on Qucs. Qucs is an open source circuit simulator which helped us verify that our calculations are correct.
The LPF has a maximum insertion loss of 0.4dB in VHF. The attenuation in UHF is more that 60dB. Some ripple can be observed on the chart, but it should not affect reception of narrow band signals.
The HPF has a maximum insertion loss of 0.2 dB in UHF. The attenuation in VHF is more that 80dB.
Special care has been taken to ensure minimal cross-talk between the two filters. The bottom layer of the PCB is a complete ground plane and two copper shieldings have been solder on top of each filter.
Please note, that this diplexer can be used only for receiving. For transmission, a higher grade of components (high voltage caps, high current inductors) should be used.