I.R.I.S. - CubeSat

The I.R.I.S. (Intelligent Relay for Infrared Signals) project introduces a scaled-down 4U CubeSat payload designed for educational demonstration purposes, showcasing the potential of optical communication technology. Drawing inspiration from NASA's TBIRD program, our project leverages Commercial Off-The-Shelf (COTS) components to achieve a formidable data transmission rate of 6.6GB/second. Unlike traditional CubeSats, our model will not enter orbit but serves as a testament to the feasibility of high-speed communication in space on a reduced scale. This paper outlines the architecture, components, and testing results, offering insights into the challenges and innovations of employing cost-effective solutions for advanced space communication.
The project team is composed by me and Emile Bailey.

Differences from TBIRD

NASA's Architecture

Our Architecture

●  Compact Design for Efficiency:
Our CubeSat is meticulously crafted in a 4U configuration, weighing under 2 kg, embodying a balance between compactness and efficiency.
●  Versatile Communication System:
Leveraging a bi-static optical sub-assembly, our communication system excels with separate apertures for downlink (6.6 Gbps) and uplink (2 Kbps) transmissions. This careful balancing of data rates considers both mission requirements and hardware constraints.
● Integrated FPGA Communication Hub:
The core of our communication prowess lies within the Xilinx Artix 7 FPGA board. Seamlessly integrated, it hosts two SFP+ connectors for optical transceivers, offering a centralized and robust communication solution.
● Efficient Data Storage:
Embracing a pragmatic approach, our CubeSat relies on a 64GB SD Card for data storage—a compact yet reliable solution ensuring streamlined data management throughout the mission.
● Innovative Transceiver Technology:
Departing from conventional methods, our CubeSat integrates a GTP transceiver within the FPGA. This unique approach to amplification sets us apart from projects relying on EDFA technology.
● Custom ARQ Protocol for Reliability:
In the realm of data transmission, we implement a custom Automatic Repeat Request (ARQ) protocol. This bespoke approach ensures error-free communication, even at lower data rates, showcasing our commitment to reliable transmissions.
● Strategic Weight Considerations:
Adhering to stringent weight constraints, our CubeSat is not just compact but also optimized for efficient thermal radiation. This design choice enhances thermal management, ensuring optimal performance.
● Multifunctional Uplink Signal:
Beyond its primary role in communication, our uplink signal serves a dual purpose—acting as both a communication channel and a beacon for spatial tracking. This multifunctional use demonstrates the versatility ingrained in our project.

Compute Unit

Main Board

Power Unit

CubeSat Chassis

Optical Unit

Optical Coupler

IRIS CubeSat Aspect

Optical Unit Section Analysis

The Optical Unit is composed by an aluminium external body (7000 series), as well as an internal PLA composite black body. Both TX and RX lenses are made by JGS1 Quartz, it is an excellent optical material in the range of 185 - 2500nm wavelengths.

● Transmitter Section: This section is composed by a trasmission barrel that houses an aluminium fiber collimator and a 30mm Focus lens. The distance between the collimator lens and the focus lens has been carefully determined based on the wavelength of the infrared light, as well as their focal length.

● Receiver Section: This section is composed by a reception barrel that houses an quadrant photodiode and a 30mm Focus lens. The distance between the photodiode and the focus lens has been carefully determined based on the wavelength of the infrared light, as well as it's focal length.

Test Phase Results

We made it! I.R.I.S. has successfully achieved a downlink speed of 5 Gb/s. Below are the test phase results that demonstrate the performance and integrity of our optical communication system.

● ILA Scan: The eye diagram displayed in this image represents the signal integrity analysis performed during the test phase. The diagram shows an open eye pattern with 34,304 open area sections and an open unit interval (UI) of 57.58%. This indicates a high-quality signal with minimal bit error rate (BER), essential for achieving our target downlink speed. The results confirm that I.R.I.S. system can reliably transmit data over optical links with pretty good performance metrics.

Eye Diagram Scan

● ILA Scan: This screenshot captures the real-time data analysis conducted during the test phase of the I.R.I.S. project. The Integrated Logic Analyzer (ILA) is utilized to monitor and debug the high-speed data transmission. Various signal probes, showing the successful handling of data packets and control signals. This setup was crucial for ensuring the integrity and accuracy of the data transmission.

Integrated Logic Analyzer Scan

Project Status

  1. Research Phase
  2. Conception Phase
  3. Developement Phase
  4. Test Phase
  5. Project Completed

Note : On the Test Phase, we successfully demonstrated downlink capabilities up to 5Gb/s.
As we're moving forward to a bigger and more complex project, we decided to stop the developement of this device.
We learned so much from this adventure, and I'm definetely going to use the skills acquired to make next projects even more successful!