Designing for Space: Mitigating Radiation Risks with Targeted Testing

Next-generation sensor systems rely heavily on high-performance electronics. At IST, our experienced team of engineers and technicians combines broad domain knowledge with practical expertise to solve our customers’ toughest problems. That’s why we were honored to be awarded a contract to develop the electronics module for a cutting-edge sensor package on board a satellite in low-earth orbit (LEO). The space environment poses a number of challenges that take the design requirements to the next level.

Rocket launches subject payloads to vibrational loads that can rip components from the PCB. Once in space, the high vacuum means that standard electrolytic capacitors will burst, and heat flows need to be carefully managed. But possibly the greatest challenge of all is radiation. Outside of the protection of earth’s atmosphere and magnetic field, subatomic particles and ions fly around near the speed of light. These particles can wreak havoc on unprotected semiconductor components. There are two broad categories that describe the effects of radiation on electronics:

1. Dose Effects: traditionally quantified in units of Gray or rad, Total Ionizing Dose (TID) is accumulated over time in the form of mechanical displacements in the semiconductor crystal lattice. When a particle travels through a material, it has a chance of striking a nucleus directly, which can transfer kinetic energy sufficiently to displace the atom into a new position. As these displacements accumulate, the performance of the device can degrade up to the point of total failure. The figure 1 below represents the defect clusters which can take place in the semiconductor lattice as explained above.

2. Single Event Effects (SEE): SEEs can happen at any time and can take many forms. Particularly in the regions surrounding the junction between semiconductor layers, an unexpected transfer of energy from an incident particle will have electrical effects that can present in many ways, including:

• Bit-flips in memory devices or serial interfaces that corrupt data or firmware
• Transient local spikes in voltage that upset precision analog references or provide spurious signals
• Latch-up, a self‑sustaining short‑circuit path that can permanently destroy a device.

Several techniques exist to harden electronic assemblies against radiation. Meticulous system design is a must, and robust software can go a long way in preventing loss of function or data corruption. Shielding assemblies using high-density materials can attenuate particle energy to a certain extent. Ultimately, the resilience of the system depends on the radiation tolerance of the individual components themselves.  ‘Rad-hard’ chips are generally ruggedized against radiation at the level of the silicon itself and are subjected to rigorous testing throughout the manufacturing process. The result is that prices can range from 10-50 times that of Commercial Off the Shelf (COTS) alternatives, and lead times can range from months to years. The aggressive schedule and budget associated with this mission limits our ability to rely on this first line of defense for every component. Instead, we employ a “careful COTS” strategy: select parts with a previous history of space flight or radiation testing and conduct testing of our own where no history exists.

Effective testing starts with an accurate radiation environment model– how many particles will we see over the course of the mission and at what energy? Orbital altitude and inclination will dictate both the ambient spectrum of radiation, and whether we pass through the South Atlantic Anomaly and polar regions, where the earth’s magnetic field concentrates particles with particularly high flux. These parameters can be integrated into overall mission radiation spectra using tools such as SPENVIS developed by the European Space Agency. With J. Ziegler’s SRIM, particle interactions with shielding materials, chip packaging, and the semiconductor themselves can also be modeled.

With models in hand, it’s time to take our hardware ‘under the beam.’  The K150 Cyclotron at Texas A&M’s Cyclotron Institute is a particle accelerator capable of precisely hurling protons at a target in open air. The accelerator takes up an entire building in the middle of campus, surrounded by several feet of concrete to keep the radiation contained. Starting at the ion source, electrons are ripped from hydrogen atoms, forming a plasma of protons. These are accelerated through a long network of electromagnetic guides, lenses, and sensors, culminating in the Target Chamber, where the Device Under Test (DUT) can experience a full year’s worth of space radiation in the span of a few minutes. The DUT is mounted to a 4-axis stage so that particular components can be targeted by the beam, and cables are run to the control room 50 feet away for data collection.

IST took 4 COTS devices / PCBAs and 1 custom PCBA to the Cyclotron to test against our mission’s radiation environment:

Table 1: List of electronic development boards undergoing testing

Each device was subjected to 2-3 regimes of particle fluence and energy. These parameters were carefully chosen with reference to our models, simulating the mission particle spectra with appropriate factors of safety. For full coverage of all components on the PCBAs, several individual setups were required, totaling 28 exposures of about 10 minutes each. During each test, inputs and outputs were recorded for later processing. Real‑time telemetry let us pause a run, annotate data, and inspect any anomaly before resuming.

Test results were broadly successful! We highlight here the Koheron CTL101 low-noise laser controller. This COTS PCBA offers precise control over the wavelength and power output of a narrow-linewidth laser diode. For the success of the mission, it is critical that the laser controller remain fully operational over the mission life, with minimal transient events due to space radiation. The many sensitive analog circuits on this assembly made it of particular concern.

Fortunately, the monitored signals under the beam remained close to baseline values, with trends well within the ranges expected under normal operating conditions, figure 4. No transient events were observed, and the controller is now undergoing continued evaluation on our development bench.

With our hardware qualified to the required levels, we can proceed to system integration with increased confidence in a mission success. This round of testing is an excellent example of the diverse challenges that we at IST take on. Rather than viewing radiation testing as a final checkbox, we approached it as a design tool—one that helps us refine our architecture, validate our assumptions, and deliver more robust systems. As we advance toward final integration and flight readiness, we’re excited to carry this momentum forward into the next phase of mission development!