Author: Nikoletta Triantafyllopoulou

Gr-leo: A GNU Radio open-source space channel simulator

In order to understand what gr-leo is and why it is considered to be a powerful, open-source simulation tool, let us first take a look at why it is necessary. Gr-leo is here to fill a gap and to ensure that the quality of communication between a satellite and the ground station is not impaired in any way.

The case

For the success of a satellite mission, there are many conditions that should be taken into consideration. Telecommunication between Earth and a satellite plays a vital role in that success. However, the quality of the telecommunication can be majorly affected by a number of parameters. These can impact and reduce the quality of transmission between Earth and a Satellite. Some of these parameters are: the relative motion of the orbiting satellite, the operating frequencies, the antenna set-up and of course the atmospheric phenomena. In order for the parameters to be predicted, the system should undergo extensive testing under realistic channel conditions and not in a lab environment as that would not be realistic enough.

The solution

Gr-leo is an open-source, simulation tool that facilitates the testing of all these parameters under realistic channel conditions. It allows for the continuous testing of a system’s development, debugging and evaluation. This way the channel conditions are simulated to be realistic enough and indicative of the failures which might affect telecommunication.

The Build-up

Gr-leo is built with the implementation of a GNU Radio module. An Out-of-the-Tree module is a GNU Radio component that no longer lives under the GNU Radio source tree. This means that one can use the basic GNU radio blocks and reconfigure them so as to extend their functionality as they deem necessary. The new blocks created are also available to the community and can be combined with the existing blocks. This is the case with gr-leo. It adheres to the programming notion of blocks as it is found on GNU Radio, but there are new blocks created to suit the project’s needs. GNU Radio provides the community with a vast range of signal processing and channel estimation blocks. However, these can not extensively cater to the needs of a space telecommunication channel. This is why in order to build gr-leo new processing blocks were configured; with each block simulating a different component found in the space channel communication.

A more detailed look into gr-leo

Gr-leo is an open-source, space channel simulator; a tool created to facilitate the simulation of the Earth-Satellite system operation and to explore the possible failures that may occur in space channel telecommunication.

At the core of gr-leo is the channel model definition. The channel model definitions link the different components making up the Earth-Space communication system with a single GNU Radio block. The blocks are synchronous. Their functionality is to pass the signal from the input port to the worker function, alongside a pointer to the output buffer for the duration of satellite observation. A channel model block accepts a list of required parameters that need to be taken into consideration during the channel simulation. Gr-leo is efficient and versatile not only because it creates the appropriate realistic conditions for testing but also because it explores a wide range of parameters in great detail.

Below is an example of a UPSAT flowgraph combining gr-leo and the UPSAT transmitter. Both are included in the gr-satnogs module.

UPSAT gr-leo flowgraph
UPSAT Transmitter

By using the gr-leo module with the GNU Radio Companion integrated blocks we succeed in:

  • Defining a satellite and describing its orbit by providing a valid TLE.
  • Defining a tracker by specifying its coordinates, the operating frequencies, the antenna type and an observation time-frame.
  • Defining the communication channel model and specifying the desired attenuation types which need to be simulated.

Once these parameters are specified, the channel model block attenuates the input signal according to the defined channel model and the orbit of the satellite described by the TLE.

Takeaway

Gr-leo is an open-source space channel simulator developed as a subactivity of SDR Makerspace. It is created to facilitate testing (under realistic conditions) of all those different parameters affecting the quality of transmission between a ground station and an orbiting satellite. Built on the GNU Radio’s programming blocks it adheres to the open-source principles. It extends the use and functionalities of the basic GNU blocks in order to be able to serve the needs and the purposes of a space telecommunication channel. gr-leo is open-source and the blocks created are available to be used by the GNU Radio community. Contrary to other telecommunication channel simulation projects which are proprietary and provided under expensive licenses, gr-leo is open-source, available for everyone in the GNU Radio community to use and it is a powerful and efficient simulator.

If this sounds interesting to you and you wish to find out more you can take a look at the public repo, the wiki and the documentation pages! Feel free to join our community to share your thoughts and ideas!

LSF Project onboarding and the Libre Space Manifesto

Libre Space Foundation is an organization dedicated to creating open-source, space technologies. Often we come across a project that wishes to join us, or we are approached by exciting initiatives to assist them in their endeavors. However, joining LSF as a project is a process that must meet specific criteria and particular requirements. In this article, we wish to clarify a project’s eligibility to join LSF while at the same time, we elaborate on the pillars of the Libre Space Manifesto and the philosophy governing Libre Space Foundation. This article is not about the management, the organization or the development process alone. It is about the principles fueling our approach. It is about how and why we do things differently.

Repeating the title

Joining the Libre Space Foundation

For us, the Manifesto is found at the core of our operations and processes. Thus, all projects and all project decisions must adhere to the Libre Space Manifesto. The projects must abide by the Manifesto principles starting with the primary principle that Space should be open and available to all humanity. All the projects that join us are devoted to Space being available to all and open for everyone to explore. All projects we onboard work towards creating opportunities for learning, exploring innovative ideas and bringing Space closer to the public (such as LSTN offering public library communities the chance to build and engage with space technology).

For the principles of the Libre Space Manifesto to materialize, there are four pillars to which all our practices adhere.

  • Open-source, copyleft license.

Based on the Libre Space Manifesto, the projects joining LSF must have an open-source, copyleft license for anything developed and released within the project. For those not familiar with the term, a copyleft licensing scheme is a process that allows people to freely distribute copies of a certain work or even modified versions of it. Provided that the same rights will be preserved in derivative works created later down the line.

It should be noted that we strive to use open-source tools and applications, and it is imperative for the projects onboarded to adhere to the open-source methodology at every step of the workflow. In practice, we develop and use open-source tools and software, we modify them, explore their potential, and then we give back to the open-source community by distributing our work under an open-source, copyleft license.

The significance of this approach is that new types of software, features, projects and initiatives are created under an open-source license which enables their use by everyone who needs them. This approach delivers free solutions and tools and it guarantees that new ideas can continue to explore new potentials, fuel solutions and features for other individuals to enjoy.

  • Open Data (available to everyone in the community or to anyone who is interested).

According to the Libre Space Manifesto, all findings, all data should be available to everyone. Open data has always been in the core of our operations. The SatNOGS network, our global network of satellite ground stations, is a collaborative, world-wide community which receives satellite data. The observations made are stored online in the SatNOGS Database and are available for everyone to see and use. SatNOGS Database is a machine-readable data resource. The Open data approach we have at LSF has helped many projects, teams, universities to study Space and satellites in much detail. It has facilitated and helped other projects too. Polaris, par example, uses telemetry data that is received by the SatNOGS network of satellite ground stations.

  • Following Open Development processes.

At LSF, true to our beliefs, we use open development processes for our projects. We use Gitlab for organizing, managing, developing our projects and for the teams and team members to communicate efficiently. Since our collaborators, contributors and team members come from all over the world, Open Development processes are the best way to include everyone in the development process. This way we achieve a natural flow of conversations and contributions as the team members work towards accomplishing a common goal (or towards working on completing a project).

Every contribution, every idea and every discussion benefits not only an individual but the whole team, the whole project and often the contributions made are beneficial for other projects too. This, of course, is one of the advantages of open-source and open development.

Sequentially, under an open development process, documentation of the code is open for the public to view and detailed to allow for a better understanding of how a project works. New members can be introduced to the complexities of a project faster, and a greater audience of collaborators can contribute more easily. Code is tested in a collaborative way focusing on high-quality but often achieving fast progress, too. The team members can review the code, offering feedback, flagging problems early on, suggesting solutions and resolving issues. Quite often, this discursive approach to a project and the exchanging of ideas leads to the emergence of new and innovative projects and useful tools.

Open development processes is a common practice for us; an approach taking place on all channels of communication: on Gitlab, on the LSF Riot Channels and our Community Forums too. Consequently, this takes us to the next significant pillar of the Libre Space Manifesto.

  • Open Governance (with transparency and direct communication) for all projects.

As mentioned above, we try to use tools in our projects which are open-source. We use Matrix/Riot for all communications concerning the projects. We have a buzzing, collaborative and constructive community where individuals contribute. They share their worries, their problems, their achievements and their ideas. As project discussions and interactions are held in public, they become accessible to everyone, and everyone can join. This, in fact, has a catalytic impact on the way the community manages itself while working as a whole. The projects govern themselves, delegating responsibilities and asking for assistance or advice always having the project’s best interest at heart. Though different projects have different maturity levels and thus different governance paradigms, yet they too follow the general open governance principles. These include unrestricted participation, open and clear communications and decision making processes, and accountability for project roles.

Being part of the Libre Space Foundation

Once a project is given the green light to join LSF, then it receives the support and the tools necessary for project development, operations, legal guidance and even marketing, branding and communications. LSF guides the project through to success and completion. If your project meets all the necessary requirements and provided it adheres to the Libre Space Manifesto principles, LSF will give you all the assistance, guidance and tools to see it through.

If the way we do things sounds fascinating to you and you wish to join us, feel free to check out the Libre Space Manifesto! Don’t hesitate to show your support by signing up and sharing it with your friends and network!

Google Summer of Code 2020: Announcing the two projects we will be mentoring

For the second year in a row, Libre Space Foundation was selected as a mentor organisation for the Google Summer of Code initiative. The application period has closed and the results are in, and so it is with great excitement that we announce the two projects we will be mentoring over the next few months.

The Projects

The first project titled “Deep learning for Cubesat Behavior Segmentation with Collection of Contextual Information” will be working on the Polaris codebase. The project aims at supporting spacecraft operators by predicting the behaviour of their satellites and linking it to various data sources. There is a data challenge in collecting and sometimes in converting into time series. This data collection phase will allow for better information when understanding and estimating the behaviour of a spacecraft. External sources of data, namely, orbit propagation, solar and magnetic events, and various elements of space weather, will be some of the external sources providing the data needed. The machine learning approach employed for Polaris will transform these data sources into learning features so that a spacecraft’s behaviour is not only predicted but also explained by the “machine”. Deep learning means that the project is exploring the usage of different neural network architectures of several layers. The project is undertaken in close collaboration with the amazing team of the Polaris project.

The second project that Libre Space Foundation will be mentoring is a “Python Module for RF Collisions”. This project’s goal is to tackle an issue that troubles satellite observers quite frequently. With the number of deployed satellites in constant increase, it is often that satellites transmit with the same or near frequencies. This overlapping of frequencies interferes with the results of the observations and affects their accuracy. Thus, the project we will be mentoring aims at dealing with this exact issue. By building a Python module that will allow the ground station operators to specify the time and the location this interference occurs. This project is closely related and linked to SatNOGS and it will be used by the SatNOGS network as an internal or an external tool to let the observers know which other satellites are expected to be found in the results of their observations.

Google Summer of Code is an annual program offering university students the opportunity to work on open-source projects during their summer break while earning a stipend! Libre Space Foundation is devoted to working on open-source space technologies and you can find out more about our Principles regarding open-source and space in our Manifesto.

This year’s Google Summer of Code application period has been indeed a groundbreaking one as the initiative received 8,902 applications submitted by 6,626 students from 121 countries. These applications were reviewed by 199 mentoring organizations. Eventually, 1,199 students from 66 countries were selected. We are thrilled to be part of this grand initiative. But we are also excited and looking forward to working with our students over the next few months. Congratulations to everyone and welcome aboard!

The QUBIK Project: The progress so far

Libre Space Foundation is devoted to the vision of open-source technologies in space, and for this, we often join forces with researchers, individuals, and teams who share this vision with us. One exciting project we have taken up is the QUBIK Project.

QUBIK-1 Flight-ready
QUBIK-1 flight-ready

A few words about the Project

Our love for space has brought us in collaboration with Firefly Aerospace and the DREAM payloads program. This is a global competition to host academic and educational payloads as rideshare participants on the inaugural flight of the Firefly Alpha launch vehicle. For this project, we have been working together with FOSSA Systems and AMSAT EA. We have developed two PocketQube satellites, QUBIK-1 and QUBIK-2, and PICOBUS, a PocketQube deployer.

GENESIS N, FOSSASAT-1B, GENESIS L, PICOBUS-2, PICOBUS-1, FOSSASAT-2
From top left clock-wise: GENESIS N, FOSSASAT-1B, GENESIS L, QUBIK-2, QUBIK-1, FOSSASAT-2
PICOBUS deployer with satellites integrated
PICOBUS deployer with satellites integrated

The satellites are expected to have a short lifespan of up to 3 weeks of orbit. Regardless of how short-lived they will be, though, they are built to perform a range of communications experiments. While those experiments will be taking place, the SatNOGS network of ground stations will be receiving signals from these satellites. By exploiting Doppler Variations, the network of ground stations will perform orbit determination and satellite identification as early as possible. This will utilize the benefits and the capabilities of the SatNOGS network to the fullest and demonstrate the Space Situational Awareness aspect of it.

How the Project has been progressing for the last few months

On the 12th of December 2019, the thermal vacuum test for the PICOBUS took place at Instituto Nacional de Técnica Aeroespacial, and on the 16th of the same month, the vibration test was conducted at the NanoSat Lab of the Polytechnic University of Catalunya. A few months later, on the 8th of February 2020, our team working at Hackerspace.gr completed the assembly of the PICOBUS and QUBIK-1 and QUBIK-2. The next day marked the bake out day for the project at the Institute of Electronic Structure and Laser. Lastly, on the 12th of February 2020, at the NanoSat Lab, the vibration acceptance campaign took place for PICOBUS, and so did the Protoflight campaign for QUBIK-1 and QUBIK-2. At this point in the process, the software is being developed so that the project will be able to facilitate all the experiments that need to be carried out.

Qualification model of PICOBUS deployer getting ready for Thermal-Vacuum testing
Qualification model of PICOBUS deployer getting ready for Thermal-Vacuum testing
Qualification model of PICOBUS deployer just out of the Thermal-Vacuum chamber
Qualification model of PICOBUS deployer just out of the Thermal-Vacuum chamber
Flight model of PICOBUS deployer during vibration testing
Flight model of PICOBUS deployer during vibration testing
Deployment test of dummy mass satellites from PICOBUS deployer

QUBIK-1, QUBIK-2, and the PICOBUS deployer form an exciting project for which we have worked hard, and we have collaborated with inspiring teams. As the development draws to completion we are excited to see what this project will achieve.

If you find this project exciting too and you wish to find out more about Qubik you can follow the open-source repositories of the project.