Help & Methodology Reference
The Space RHA Parts Radiation Advisor is a web-based screening tool that helps engineers assess the radiation susceptibility of electronic components for space missions. By combining a part number lookup with mission environment parameters and contextual usage questions, the tool produces a comprehensive risk assessment covering total ionizing dose (TID), displacement damage dose (DDD), and single event effects (SEE) — all within a single browser-based interface requiring no software installation.
The tool is designed for early-phase design trades, parts screening, and educational purposes. It draws on compiled test data from the Radiation Effects Data Workshop (REDW) spanning 1992–2025, providing statistical context for how devices of each type have historically performed under radiation exposure. The assessment is organized into five output sections: TID Assessment, Displacement Damage Assessment, Single Event Effects Risks, Derating & Mitigation Rules, and Design Tips.
Electronic components in space are exposed to a complex radiation environment consisting of trapped protons and electrons in the Van Allen belts, galactic cosmic rays (GCR), and solar particle events (SPE). These particles interact with semiconductor materials through several distinct mechanisms, each producing different types of damage. Understanding these mechanisms is essential for interpreting the assessment outputs.
TID is the cumulative energy deposited in a material by ionizing radiation, measured in rads (typically rad(Si) for silicon devices). Ionizing radiation — primarily trapped electrons and protons — generates electron-hole pairs in oxide layers. While electrons are quickly swept out, holes become trapped at the Si/SiO2 interface and in the bulk oxide, producing threshold voltage shifts, increased leakage currents, and timing degradation. TID effects are cumulative and generally irreversible, progressing over the mission lifetime. Typical space missions accumulate doses ranging from a few krad (LEO/ISS) to tens or hundreds of krad (GEO, MEO, or long-duration missions) behind 100 mil (2.54 mm) aluminum shielding [9, 10].
Displacement damage occurs when energetic particles (primarily protons and neutrons) collide with lattice atoms, displacing them from their equilibrium positions and creating vacancy-interstitial pairs (Frenkel defects) and defect clusters. These defects introduce energy levels within the semiconductor bandgap, acting as generation-recombination centers, trapping centers, and compensation centers. The resulting effects include reduced minority carrier lifetime, reduced carrier mobility, increased dark current in photodetectors, and decreased current transfer ratio (CTR) in optocouplers. Displacement damage is quantified by non-ionizing energy loss (NIEL), typically expressed as equivalent 1 MeV neutron fluence or 10 MeV proton fluence [10, 11].
SEE are caused by the passage of a single energetic particle — a heavy ion or a proton/neutron nuclear reaction secondary — through a sensitive region of a device. The ionization trail deposits sufficient charge to cause an observable effect. SEE are stochastic (probabilistic) rather than cumulative, and a single event can occur at any point during a mission. The primary SEE types are described in detail in Section 8.
The Part Number Lookup field accepts a manufacturer part number and attempts to classify the device into one of 17 recognized device type categories. The lookup uses pattern matching against common part number prefixes and families to identify the device type automatically.
Enter a part number such as LM324, IRF540, or AD7606 and the tool will attempt to match it against a database of known part families. The matching considers manufacturer prefixes (e.g., AD, LM, TL, IRF, MAX) and standard device family designations. When a match is found, the corresponding device type is automatically selected, and the assessment proceeds using the statistical data for that category.
If the part number is not recognized, the tool will default to prompting you to manually select the device type from the 17 available categories. Manual selection is always available and can override the automatic classification if needed.
| Device Type | Example Part Numbers |
|---|---|
| BJT | 2N2222, 2N3904, MMBT3906 |
| Op-Amp | LM324, OP07, AD8628, TL072 |
| Comparator | LM393, LM311, MAX9042 |
| Voltage Reference | LM4040, REF5025, AD780 |
| Linear Regulator | LM317, LM7805, TPS7A4501 |
| Power Converter | LM2596, TPS5430, MAX1556 |
| ADC | AD7606, ADS1256, MAX1202 |
| DAC | DAC8564, AD5662, MAX5134 |
| FPGA | XC7A35T, RT4G150, RTAX2000 |
| MOSFET | IRF540, BSS138, SI2302 |
| Optocoupler | 6N136, HCPL-7840, IL300 |
| SRAM | IS61WV102416, CY62256, AS6C4008 |
| Flash Memory | S29GL512, MT25QL256, SST39VF1601 |
| Logic / Interface | SN74LVC244, MAX3232, SN65LVDS388 |
| MCU / Processor | STM32F407, MSP430, SAMV71 |
| Sensor | AD590, LM75, BME280 |
| Other | Any device not matching the above categories |
The mission environment configuration determines the expected radiation exposure for your component. The tool uses a simplified orbit model to estimate total ionizing dose and proton fluence levels for the selected orbit and mission duration. All dose estimates assume 100 mil (2.54 mm) aluminum shielding, which is a common reference shielding thickness used throughout the radiation effects community [10, 11].
| Orbit | Altitude | Characteristics |
|---|---|---|
| LEO-ISS | 400–500 km, 51.6° | Low dose rates (~5–15 krad/yr behind 100 mil Al). Moderate proton exposure from South Atlantic Anomaly (SAA) passages. The ISS inclination provides limited exposure to the inner radiation belt. |
| LEO-SSO | 600–800 km | Sun-synchronous orbits at higher altitude see increased trapped proton flux compared to ISS. Dose rates are moderately higher, and proton fluence is more significant for displacement damage. |
| LEO-High | 1000–1500 km | Orbits at the fringe of the inner radiation belt. Significantly elevated trapped proton and electron fluxes. TID can be an order of magnitude higher than ISS-altitude orbits. Displacement damage is a primary concern. |
| MEO Navigation | ~20,200 km | GPS/GNSS constellation altitude. Passes through the heart of the outer electron belt and the slot region between belts. High electron dose rates and significant proton exposure during solar particle events. Requires radiation-hardened or radiation-tolerant parts for long missions. |
| GEO | 35,786 km | Geosynchronous orbit. Located in the outer electron belt with high electron-dominated TID rates. Minimal trapped proton flux, but fully exposed to GCR and solar proton events without geomagnetic shielding. Standard 15-year GEO missions typically require parts tolerant to 50–100+ krad(Si). |
The mission duration slider ranges from 1 to 20 years. Total dose scales approximately linearly with mission duration (for a constant orbit), while SEE probabilities scale as 1 − exp(−Rate × T), approaching certainty for long missions with non-negligible rates. The tool computes expected dose as:
The design margin multiplier accounts for uncertainties in the radiation environment models, shielding analysis, and part-to-part variability. Three options are provided:
| Margin | Usage |
|---|---|
| 1.5× | Minimum margin for well-characterized environments and parts with substantial test data |
| 2× | Standard design margin recommended by most radiation hardness assurance programs [8, 11] |
| 3× | Conservative margin for missions with high reliability requirements, poorly characterized environments, or parts susceptible to ELDRS |
When enabled, the solar flare toggle adds the estimated contribution from solar particle events to the baseline trapped particle and GCR dose. Solar proton events can deliver significant acute dose contributions, particularly for orbits above LEO where geomagnetic shielding is reduced (MEO, GEO). The flare contribution is estimated based on statistical models of solar proton event frequency and severity over the solar cycle.
All dose levels quoted by the tool are approximate values for 100 mil (2.54 mm) of aluminum equivalent shielding. This is the standard reference shielding thickness used throughout the radiation effects community for comparing device susceptibility and mission dose requirements. Actual spacecraft shielding varies widely — from less than 50 mil for lightly shielded external units to several hundred mil equivalent for well-protected avionics bays. Users should perform detailed shielding analysis (e.g., using NOVICE, SHIELDOSE, or sector analysis) for mission-specific dose predictions.
The assessment engine uses compiled statistical data from the Radiation Effects Data Workshop (REDW) to characterize the typical radiation performance of each device type category. The REDW compendium is the most comprehensive publicly available collection of radiation test data for electronic components, spanning over three decades of testing (1992–2025) contributed by government, industry, and academic laboratories [1].
The REDW database includes TID test results, displacement damage measurements, heavy-ion SEE cross-section data, and proton SEE data for thousands of device types. For each device type category, the tool maintains distributions of:
| Metric | Description |
|---|---|
| TID Hardness Level | Dose at which parametric or functional failure occurs, typically reported as the lowest dose at which any parameter exceeds specification |
| SEL LET Threshold | Minimum LET at which single-event latchup is observed (MeV-cm²/mg) |
| SEL Immunity | Fraction of tested devices showing no SEL up to the maximum test LET (typically 60–80 MeV-cm²/mg) |
| SEU/SET Susceptibility | Qualitative assessment based on observed upset rates and cross-sections |
These distributions are presented as percentile ranges (e.g., 25th, 50th, 75th percentile TID hardness) to convey the spread of performance across different manufacturers, process nodes, and fabrication lots within each device type category.
After selecting a device type, the tool presents context-dependent usage configuration questions that refine the risk assessment. These questions address application-specific factors that influence radiation susceptibility, such as:
| Question Type | Example | Why It Matters |
|---|---|---|
| Bias voltage | "What is the operating voltage?" | Higher bias increases susceptibility to SEL and can worsen TID degradation in some technologies |
| Switching frequency | "What is the switching frequency?" | High-frequency circuits are more sensitive to timing degradation from TID and SET-induced glitches |
| Analog precision | "What analog precision is required?" | High-precision analog circuits (voltage references, ADCs) degrade at lower doses than digital logic |
| Redundancy | "Is the component redundant?" | Redundant architectures can tolerate SEL if power cycling is possible |
The TID assessment compares the expected mission dose (including design margin) against the statistical distribution of TID hardness levels from the REDW database for the selected device type. This provides a risk-informed picture of whether the device is likely to survive the mission dose environment.
The tool computes the expected mission TID as described in Section 4, then compares it against the empirical distribution of failure doses for the device type category. The assessment reports:
Expected dose vs. typical hardness. The tool shows where the expected mission dose (with margin) falls relative to the distribution of tested devices. If the design dose falls below the 25th percentile of the failure dose distribution, most devices of that type have historically survived comparable doses. If it exceeds the 75th percentile, most devices have failed at or below the design dose, indicating high risk.
Technology-dependent considerations. The assessment accounts for known technology-dependent trends. For example, commercial CMOS processes below 65 nm generally exhibit good TID tolerance due to thin gate oxides, while bipolar technologies show greater variability and are susceptible to ELDRS (see Section 10).
| Device Type | Primary TID Failure Mechanism |
|---|---|
| Op-Amp, Comparator | Input bias current increase, offset voltage shift, gain degradation |
| Voltage Reference | Output voltage drift (can be sub-mV level for precision references) |
| Linear Regulator | Dropout voltage increase, output voltage drift, increased quiescent current |
| ADC / DAC | INL/DNL degradation, gain error, reference drift (analog front-end dominated) |
| MOSFET | Threshold voltage shift, on-resistance increase, leakage current increase |
| FPGA | Configuration memory upset (SRAM-based), increased static current, I/O degradation |
| MCU / Processor | Increased standby current, Flash/EEPROM retention loss, analog peripheral drift |
| Optocoupler | CTR degradation (dominated by displacement damage, see Section 7) |
Displacement damage is caused by non-ionizing energy loss (NIEL) from energetic particles — primarily protons and neutrons — that displace atoms from their lattice sites. The resulting defects degrade minority carrier lifetime and carrier removal, producing effects that are distinct from ionization damage and can dominate the radiation response of certain device types.
The tool estimates the total proton fluence for the selected orbit and mission duration. Proton fluence drives displacement damage and is particularly important for orbits that traverse the inner radiation belt (LEO-High, MEO) or that are exposed to solar proton events (MEO, GEO). The fluence is expressed as equivalent 10 MeV proton fluence (p/cm²), which is the standard reference energy for displacement damage comparison.
Optocouplers are among the most displacement-damage-sensitive devices in space systems. The internal LED emitter suffers progressive light output degradation as displacement damage reduces minority carrier lifetime in the active region. This manifests as a decrease in current transfer ratio (CTR), which can cause circuit failure when CTR drops below the minimum required by the application.
The tool flags optocouplers as high-risk for displacement damage and recommends design approaches such as operating with sufficient CTR margin (typically 2× to 3× the minimum required CTR at beginning of life), selecting radiation- hardened optocoupler families, or replacing optocouplers with magnetic or capacitive isolation where possible.
Image sensors (CCDs and CMOS active pixel sensors), photodiodes, and other photosensitive devices experience increased dark current as displacement damage creates generation centers in the depletion region. Dark current increases approximately linearly with proton fluence and is strongly temperature dependent. The tool provides guidance on expected dark current degradation and recommends cooling and dark current calibration strategies where applicable.
BJTs can experience current gain (β) degradation from displacement damage, particularly at low collector currents. Solar cells suffer efficiency loss as minority carrier diffusion length decreases. The tool considers these effects when evaluating BJTs and sensors, noting that displacement damage effects can compound with TID effects in proton-rich environments.
Single event effects are caused by the transient charge deposited when an energetic ion or proton nuclear reaction secondary traverses a sensitive region of a semiconductor device. The tool evaluates susceptibility to four primary SEE types, providing risk ratings and LET threshold context based on REDW data [1] and JEDEC standards [4, 5].
SEL is a potentially destructive condition in which a parasitic thyristor (PNPN path) in a CMOS device is triggered by ionizing radiation, creating a low-impedance path between the power supply and ground. The resulting high current can cause permanent damage through thermal destruction of metallization or junction burnout if not interrupted promptly.
The tool reports SEL susceptibility based on the statistical distribution of SEL LET thresholds from REDW data for the device type category. Key context:
| SEL LET Threshold | Risk Assessment |
|---|---|
| LETth > 80 MeV-cm²/mg | SEL-immune per standard testing (tested to maximum available LET) |
| 40 < LETth ≤ 80 | Moderate risk — hardened against most trapped proton and GCR secondaries but vulnerable to heavy GCR ions |
| LETth ≤ 40 | High risk — susceptible to a significant fraction of the GCR heavy-ion environment |
SEU is a non-destructive change of state in a memory element (flip-flop, latch, SRAM cell, register) caused by charge deposition from a single particle. SEU is the most common SEE in digital circuits and can corrupt data, alter configuration states, or cause software errors. SRAM-based FPGAs are particularly vulnerable because SEU can modify the configuration memory, altering the implemented logic function.
The tool assesses SEU risk based on device type (digital devices with memory elements are most susceptible) and technology node (smaller feature sizes generally have lower critical charge but smaller collection volumes, with complex scaling behavior). SRAM and FPGA categories receive the most detailed SEU assessment.
SET is a transient voltage or current pulse generated in an analog or combinational logic circuit by the charge deposited by a single particle. In analog circuits, SETs can appear as voltage spikes on outputs of op-amps, comparators, or voltage references. In digital combinational logic, SETs can propagate to and be captured by downstream latches, resulting in soft errors.
SET susceptibility is particularly important for precision analog circuits (voltage references, ADCs, DACs) where even brief transients can corrupt measurements, and for high-speed digital circuits where SET pulse widths may exceed clock periods. The tool flags SET risk for analog device categories and recommends filtering and sampling strategies.
SEFI is a special category of SEE in which a single event causes a device to enter an undefined or unintended operating state, requiring a reset or power cycle to recover. SEFI is most commonly observed in complex digital devices such as FPGAs, MCUs, ADCs, DACs, and Flash memories, where control registers, state machines, or configuration memory can be corrupted by a single event.
The tool assesses SEFI risk for complex digital device categories and recommends watchdog timers, periodic refresh, and power-cycle recovery capabilities as mitigation strategies.
The tool provides device-type-specific derating rules and mitigation strategies based on established radiation hardness assurance practices, MIL-STD-1547B [8], and lessons learned from the radiation effects community.
Voltage derating reduces the applied voltage below the device maximum rating to provide margin against radiation-induced leakage increases and to reduce SEL susceptibility. MIL-STD-1547B [8] specifies derating factors for various device types:
| Device Type | Typical Voltage Derating | Rationale |
|---|---|---|
| MOSFET | VDS ≤ 70% of rated VDSS | Reduces gate oxide stress and SEB susceptibility in power MOSFETs |
| BJT | VCE ≤ 70% of rated VCEO | Reduces secondary breakdown susceptibility |
| Capacitors (ceramic) | Vapplied ≤ 60% of rated voltage | Accounts for radiation-induced dielectric degradation |
| Linear Regulators | Operate with adequate headroom above dropout voltage | TID increases dropout voltage; insufficient headroom causes regulation loss |
For devices susceptible to SEL, current limiting is the primary hardware-level mitigation. The objective is to limit the current during an SEL event to prevent thermal damage while allowing time for detection and power cycling. Recommended approaches include:
Series current limiters. A current-limiting circuit (foldback or constant-current) in the power supply path limits the maximum current to a safe value during latchup. The limit should be set above the maximum normal operating current but below the level that would cause thermal damage.
Power cycling. Autonomous power cycling capability allows the system to remove power from a latched device, clearing the SEL condition, and then restore power. This requires current monitoring to detect the anomalous current draw and a switch (typically a FET) to interrupt power.
For MCUs, processors, and FPGAs susceptible to SEFI, external watchdog timers provide a recovery mechanism. The watchdog must be implemented externally to the protected device (an internal watchdog can itself be affected by radiation). The watchdog timeout should be set to allow normal operation while ensuring prompt reset in the event of a SEFI-induced hang.
Triple Modular Redundancy (TMR). For critical digital functions, TMR with majority voting masks single-point SEU failures. TMR is commonly implemented in FPGA designs and can be applied to configuration memory (in SRAM-based FPGAs) or user logic.
EDAC (Error Detection and Correction). EDAC codes (typically single-error-correct, double-error-detect Hamming codes) protect memory arrays against SEU. EDAC should be combined with periodic memory scrubbing to prevent accumulation of multiple errors in the same code word.
Configuration scrubbing. SRAM-based FPGAs require periodic scrubbing of the configuration memory to correct SEU-induced bit flips before they accumulate to the point of functional failure.
Enhanced Low Dose Rate Sensitivity (ELDRS) is a phenomenon observed primarily in bipolar and BiCMOS technologies in which the radiation damage at low dose rates (characteristic of the space environment, typically 0.001–0.01 rad/s) is more severe than the damage measured at the high dose rates used in standard laboratory testing (50–300 rad/s per MIL-STD-883 TM 1019 [2]). A device exhibiting ELDRS may pass high-dose-rate qualification testing but fail in the actual space environment at the same total dose [6, 7].
ELDRS has been observed in a wide range of bipolar device types [6, 7]:
| Device Type | ELDRS Susceptibility |
|---|---|
| BJT (discrete) | High — current gain degradation can be significantly worse at low dose rates |
| Op-Amp (bipolar input) | High — input bias current increase is a primary ELDRS-sensitive parameter |
| Comparator (bipolar) | Moderate to High — similar mechanisms to op-amps |
| Voltage Reference | Moderate to High — bandgap references using lateral PNP transistors are particularly susceptible |
| Linear Regulator (bipolar) | Moderate — pass transistor and error amplifier may be ELDRS-sensitive |
| Optocoupler | Moderate — phototransistor receiver can exhibit ELDRS; CTR degradation may be worse at low dose rates |
| CMOS-only devices | Generally not susceptible (ELDRS is a bipolar oxide/interface effect) |
The ELDRS mechanism involves the competition between radiation-generated hole trapping and hydrogen-related interface trap formation at the Si/SiO2 interface of bipolar base oxides [6, 9]. At high dose rates, space charge buildup from trapped holes creates an electric field that retards subsequent hole transport to the interface, partially suppressing interface trap formation. At low dose rates, holes have time to transport to the interface before significant space charge accumulates, resulting in greater interface trap density per unit dose.
The net effect is that the threshold voltage shift and surface recombination velocity — which control input bias current, offset voltage, and gain in bipolar circuits — can be substantially larger at space-like dose rates than at laboratory dose rates. Enhancement factors of 2× to 10× have been observed, with some devices showing more than an order of magnitude greater degradation at low dose rates [7].
MIL-STD-883 TM 1019 [2] addresses ELDRS through a tiered test approach:
Step 1: Standard high-dose-rate (HDR) testing at 50–300 rad(Si)/s. If the device passes at 2× the required dose level, it is considered qualified without further testing.
Step 2: If the device does not pass at 2× dose, low-dose-rate (LDR) testing at ≤ 0.01 rad(Si)/s is required. LDR testing at the actual space dose rate can take weeks to months, making it expensive and time-consuming.
Alternative: Accelerated aging (elevated temperature irradiation at 100°C) can be used as a surrogate for LDR testing to screen for ELDRS susceptibility, per TM 1019.9.
The Parts Radiation Advisor is a screening and educational tool that provides generalized guidance based on statistical data. Users should be aware of the following limitations when interpreting assessment results.
The assessment is based on aggregate data for device type categories, not on test results for the specific part number entered. A specific device may perform significantly better or worse than the statistical distribution for its category. There is no substitute for device-specific radiation test data when qualifying parts for flight hardware. The tool results should be used for screening, preliminary risk assessment, and identifying which radiation effects require further investigation — not as a substitute for testing.
Radiation performance can vary substantially between different fabrication lots of the same part number, especially for commercial (non-radiation-hardened) devices. Process changes, wafer source variations, and die revisions can alter radiation response without any change in part number. Lot-specific qualification testing is required for flight hardware per standard radiation hardness assurance practices [11].
The REDW statistical distributions include data spanning multiple technology generations and process nodes. Modern deep-submicron CMOS devices (≤ 65 nm gate length) generally have improved TID tolerance due to thin gate oxides but may have increased susceptibility to single event effects due to reduced critical charge and increased charge sharing. The tool provides general guidance on these trends but cannot predict the response of a specific process node.
As discussed in Section 10, the standard TID test data in the REDW database is predominantly from high-dose-rate testing. Devices susceptible to ELDRS may show worse performance in the actual space environment than indicated by the database statistics. The ELDRS warning is provided for affected device types, but the magnitude of the enhancement is not quantified for specific parts.
The orbit dose rates used in the tool are approximate values derived from standard environment models. Actual dose rates depend on the specific orbit parameters, solar cycle phase, magnetic field models, and detailed shielding geometry, all of which vary with mission specifics. The tool values are suitable for preliminary screening but should not be used as final mission dose predictions.
The SEE risk assessment provides qualitative risk ratings (low, moderate, high) rather than quantitative event rates. For quantitative SEE rate prediction, device-specific heavy-ion and proton cross-section data should be used with a dedicated rate prediction tool such as the Space RHA SEE Cross-Section Tool or CREME96.