Radiation Shielding Experiment Module (RSEM)

Radiation Shielding Coating developed by TakeMe2Space would help increase the lifespan of a CubeSat and enable satellite builders to use non-radiation-hardened electronic components in the circuits inside of the satellite – hence reducing the cost and time of development of the satellite.

Validation of Shielding in space

RSEM has been launched to space in the ISRO PSLV C-58 mission on 1st January 2024. Its in a circular orbit at 350 km altitude and 9.6° inclination. Data is downlinked via S-band communication with ground station. The data proves the effectiveness of each of 4, 50, 100 micron thick coating against radiation. The captured data shows the efficacy in the situation of a multiple C-class and X-class solar flares which took place with RSEM live in-orbit.

Design principles of RSEM

With the RSEM module, we are testing the effectiveness different thickness and different coating methods against high energy radiations. The coating is done on a 2mm thick Aluminium (AL 6061) - which the most common material today used for CubeSats.

The RSEM consists of 5 housings as shown in the image below. The design of RSEM enables us to test the effectiveness of various radiation-shield-coating (thickness & coating methods) with respect to ionising radiations experienced in LEO. While in orbit, RSEM would track the radiation dosage (TID) that passes through these radiation-shield-coatings and captured by the respective dosimeter.

Final RSEM assembly

The process of coating involved, coating one surface of anodised AL 6061 plates and fixing them into the dosimeter shells as shown in the diagram below. With respect to electronics - the data logger circuit is powered by a STM32 micro-controller which communites using RS485 protocol. Each dosimeter circuit also has a STM32 processor which monitors the TID (Total Ionisation Dose) using PWM (Pulse Width Modulation) and records an average value every 500 seconds.

Radiation Shielding Coating in RSEM

RSEM is designed to test various thickness of coating. We have been able to grow a non-porus thick coating of the material on top of Aluminium substrate. The following image shows an example of the inside surface of the Aluminium plate.

Integrity Tests of the RSEM

• Random & Sine vibration was performed on the RSEM to ensure it can survive the PSLV launch conditions. The following video is a live capture of the shock test along the z axis. We tested 5g, 10g, 20g, 30g, 40g and 50g. RSEM survived !

• RSEM cleared conductive emissivity (CE), conductive susceptibility (CS), radiated emissivity (RE) and radiated susceptibility (RS) tests at the EMI/EMC lab with MIL-E standards and space grade limits.

• RSEM was operated in 0.00001 mBar vaccum and thermal cycling between -25°C to 65°C. We observed no out-gassing and no flaking of coating. All sensors on the payload also worked as expected.

• To test the dosimeters inside the RSEM, we took the payload to a radiation lab and exposed it to controlled radiation. As shown in the picture below, two viles with pre-determined radioactive substance was kept close to the dosimeter housings. The test was run for 3 cycles to see the sensor captured data.

Electronics in RSEM

The electronics in RSEM was built using standard industrial-grade commercial components to prove their applicability in space.

• Power circuitry: RSEM is powered by a 32-28V source from POEM (the PS4 experimental stage of PSLV, by ISRO) which then is converted to the required 5v and 3v3 using galvanically isolated DC-DC converters, to ensure protection and low noise in the controller and communication section.

• Communication: RSEM uses a highly reliable RS485 communication IC on board from Texas Instruments with additional external transient protection which operates at 2Mbps to send data to the POEM platform when commanded.

• Controller: The microcontroller powering RSEM from the STM-U5 series was apt for this mission and met all the flexibility and reliability requirements including hardware ECC which is used to handle soft errors caused due to SEU (single-event upsets) conditions which are often seen in space due to solar flares.

• EMI/EMC Compatibility: A set of iterations were made to RSEM to ensure it passed a series of conductive and radiative emission and susceptibility tests with MIL grade (461G) specifications. To enable this a set of common mode filters from Wurth Electronics as well as industry standard design practices were utilised.

• Measuring TID (Total Ionising Dose): The RadSens v2 which is a compact dosimeter was used in the shielded and control chambers which measures radiation intensity in μR / h and average measurements every 500s of operation.

Looking for radiation sheilding for your Sat?

You can order the RadSield coating from TakeMe2Space. We can customise the thickness of the coating based on the orbital height and radiation dosage you want to prevent. Get in touch with us, and we are always up for a conversation about how we can help you increase lifespan of your satellite and reduce overall cost.