Optimizing Communication: A Ground Station Subsystem for CANSAT Operations

In this article we will be discussing about:-

• What is a CANSAT?
• How important is a ground station?
• What role does a Software Engineering student play in a CANSAT team?
• What are the main objectives considered during development of the ground station?
• How to design the system architecture?
• A real time CANSAT ground station.

What is CANSAT?

Lets start with the big question what is meant by a CANSAT? Why is it so important?

CANSAT are miniature satellites designed and developed mostly by students to improve their understanding on how a real-life satellites work and how to develop them. These are mostly designed in the form of a cylindrical structure under less than a 100 cm height.

CANSAT is really important because they are a beautiful conjugation of software and hardware development. Students who work on CANSAT projects get hands on knowledge on both software (programming) and hardware(electronics) technologies.

How important is a ground station?

Ground station for any satellite (both actual and CANSATs) is really important as it the vital link between the satellite and earth. The ground station acts as a data center for all the data being captured and transmitted by our satellite. Through this ground station we will be able to monitor our on board subsystems.

In a CANSAT the ground station allows us to retrieve and analyze the data captured by the sensors on board. Any failure in telemetry can be easily observed through the ground station and potentially fixed if the problem originates from our ground station or software (not a hardware failure within the CANSAT’s communication module).

What role does a Software Engineering student play in a CANSAT team?

To quote the great J. Robert Oppenheimer“Theory can only get you so far” Similarly Electronics can get you so far

We need a software application (ground station) for data monitoring and analysis and code to be written into the on board micro controller. That’s where a software engineer who is well versed with those concepts is really helpful.

Though these things can be done by a student from any department but a software engineer brings a certain level finesse to the on board code because with the current rise in AI chat-bots and code generators anybody can write a code, but it takes experience and a strong foundation in software engineering principles to write highly optimized code for resource-constrained systems like CANSATs. Optimized code ensures efficient data transmission and overall mission success.

What are the main objectives considered during development of the ground station?

Just like while developing any software application we must have our objectives clear before hand. When it comes to a CANSAT’s ground station the following are the objectives that are need to be kept in mind while developing:-

• Scalability :- The application should be just restricted to the number of parameters processed by that system. Even if there are new parameters added to our current system our software should be in a state where it can handle such data as well.
• Throughput :- The amount of time data that can be processed by our system in a given amount of time. In satellite systems the time for processing is very little as the data is dynamic and is transmitted at very short intervals. So the complete throughput of the ground station should be high.
• Reliability :- The ground station software is a crucial part of any satellite system. It should have proper backup plans without any data losses.
• Efficiency :- The ground station software should be designed for overall efficiency in its operation.

How to design the system architecture?

There are several steps involved to in designing your system architecture for the ground steps :-

• Selecting communication module :- In general situations the choice of the communication module is completely based on our preference but in certain competitions the communication module is specified by the organizers in such cases we can’t do anything. But in other cases try selecting a communication module which is omnidirectional, which gives the least amount of garbage values when there isn’t an LOS (Line Of Sight). The following are the most used communication modules in any CANSAT:-

• Selecting language of choice :- Selecting the programming language is really crucial while designing any software architecture. Based on the requirements and your expertise choose a programming language that is most suitable and has a lot of developer support. Based on that language choose proper frameworks and libraries for the system development. For example if you are proficient in Python use the Django is a very reliable framework that can help in developing scalable full stack applications.
• Selecting type of Database :- Choice of a database is important in any software system architecture but in a ground station it plays a very crucial role. There are three major features that need to be considered while choosing a database — data volume, throughput and easy to integrate. There are several databases that have all the above mentioned features like MYSQL, SQLite, PostgreSQL, MongoDb,etc, so choose a database that can be easily integrated into your system.
• Data Flow :- Draw a proper flow chart describing your data flow from your CANSAT to the software’s front-end. This helps in understanding — data transmission, preprocessing and visualization in a clear way.

Based on the above system architecture we can decide the tech stack based on which we will be building our application. While its common to use different programming languages for the front-end and back-end but my personal suggestion is try sticking onto one programming language it will be really easy to debug when the entire system is built using one language. This reduces the complexity of integration and promotes better code cohesion. Though we can still use different programming languages but while integrating the front-end and back-end be a bit extra careful.

A real time CANSAT ground station.

This ground station was developed for the CANSAT India student competition by IN-SPACe, ASI and ISRO.

The mission objectives were clear that we will be transmitting data packets consisting of 16 values using Xbee S2C pro at every 2 second interval. So to develop a system for this requirements we first designed the system architecture. As our team consisted of members that were proficient in Typescript and Python we designed our architecture using them. As the Xbee module transmits data we can print those values onto the serial monitor of our arduino IDE. We made sure that the values transmitted were in a proper string format as it would be easy to preprocess that data and push it into the database.

We wrote a python script that was used to read data from the serial monitor and publish the data into our database.

We utilized pythons libraries like:-

• serial- for reading the serial monitor values.
• firebase_admin- for publishing data into firebase and fetch data from firebase based on necessity

The firebase was a really good choice of database as it was easy to implement and throughput was really wonderful.

And once the data was in the database it was a piece of cake to call it on to our front-end built using NEXT JS. The entire application was built considering the level of scalability based on that the tech stack was mainly selected.

The images of the application are displayed below:-

To conclude, these were the techniques and procedures used by me while developing a ground station for a CANSAT. It’s important to remember that everyone has their own approach and method of development based on their preference and expertise.