Introduction

Deploying commercial-off-the-shelf (COTS) hardware like Intel Loihi 2 processors in space requires rigorous radiation assurance. A critical reference for this effort is the emerging body of standards for “New Space” radiation reporting, exemplified by industry reports from 2022 (“Rad-tolerance-report-2022”).

Unlike traditional GEO missions requiring >100 krad tolerance, LEO missions at 550 km face a more nuanced environment. This article breaks down the reporting standards ArkSpace uses to qualify its neuromorphic payload.

The LEO Radiation Environment

Low Earth Orbit (LEO) is protected by Earth’s magnetosphere but still exposes electronics to three primary threats:

1. Trapped Protons: Concentrated in the South Atlantic Anomaly (SAA).
2. Galactic Cosmic Rays (GCR): High-energy heavy ions that penetrate shielding.
3. Solar Particle Events: Sporadic bursts of protons and ions.

For a 5-year mission at 550 km, the baseline requirement is 50 krad (Si) Total Ionizing Dose (TID).

Reporting Standards: What Matters?

When evaluating a “Rad-Tolerance Report,” we look for specific test methodologies:

1. Total Ionizing Dose (TID)

Reports must specify the dose rate. “Low Dose Rate Sensitivity” (LDRS) is critical for bipolar devices, though less relevant for the CMOS logic used in neuromorphic chips. We look for testing data up to 50 krad with functional verification at intermediate steps (10, 20, 30 krad).

2. Single Event Effects (SEE)

This is the “instant killer” for COTS electronics. Reports must characterize:

• Single Event Latchup (SEL): The threshold Linear Energy Transfer (LET) must exceed 75 MeV·cm²/mg. If a device latches below this, it is generally unsafe for space.
• Single Event Upset (SEU): The cross-section (probability) of bit flips. For neuromorphic processors, we need to know if bit flips affect the neuron state (transient error) or the routing table (critical failure).

3. Proton vs. Heavy Ion Testing

A 2022-era report typically emphasizes proton testing for LEO missions (due to the SAA dominant spectrum) versus heavy ion testing which is more critical for deep space. For ArkSpace, proton testing results are the primary filter for component selection.

The “New Space” Approach

Traditional “Rad-Hard” parts are expensive and generations behind in performance. The trend highlighted in 2022 reports is “Rad-Tolerant by Design”:

• Using standard COTS parts (like ARM processors or FPGAs).
• Applying system-level mitigation (Watchdog timers, Triple Modular Redundancy).
• Accepting a non-zero error rate but ensuring the system can recover.

This philosophy underpins the ArkSpace architecture: we don’t expect the Loihi 2 chip to be immune to radiation. We expect the system to detect errors (via redundant voting) and reset the chip if necessary.

Conclusion

The “Rad-tolerance-report-2022” represents a shift in how the industry validates hardware. It moves away from absolute immunity toward characterized resilience. For the Exocortex Constellation, verifying our neuromorphic payload against these reporting standards is the final gate before orbital demonstration.

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Official Sources

1. Radiation Environment: NASA Space Radiation Analysis Group (SRAG), AP-8/AE-8 Models.
2. Testing Standards: ESCC Basic Specification No. 22900, “Total Dose Steady-State Irradiation Test Method.”
3. ArkSpace Hardware Spec: arkspace-core/docs/hardware/snn-payload.md
4. Reference Report: “Rad-tolerance-report-2022” (Internal Reference/Industry Baseline).