Radiation Dosimeters & Rad-Hard ICs | In-Flight TID Measurement for Space Missions

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Features

UDOS001-H and UDOS007-H Micro Dosimeters: compact hybrid microcircuits measuring TID
Patented integrator architecture producing flat energy response across electrons, protons, and gamma rays
Measurement range up to 40 krad(Si) with dose resolution of 15 µrad(Si)
Three cascaded DC linear outputs (Low, Medium, High range) plus one pseudo-logarithmic output; 0 to 5 V range
Mechanical dimensions 1.4 x 1.0 x 0.2 inches; 20 g; 10 mA from 13 V dc to 40 V dc input
Class H-equivalent MIL-PRF-38534 screening; latch-up immunity demonstrated to 67.8 LET MeV·cm²/mg

Benefits

Direct TID measurement enables routine monitoring of the spacecraft radiation environment throughout the mission
Flat energy response provides consistent dose accuracy across the full range of space radiation particle types and energies
Compact 20 g package with minimal power draw (10 mA) supports multi-location mounting without significant mass or power budget impact
Simple 0 to 5 V analog output connects directly to existing spacecraft housekeeping analog inputs without additional interface hardware
Total mission dose data supports diagnosis of spacecraft anomalies attributable to changes in radiation environmental fluxes
Correlates environmental models and ray-tracing analyses with real in-flight measurements for improved mission radiation understanding

Applications

Routine spacecraft radiation environment monitoring throughout satellite mission lifetime
In-flight TID measurement on GEO, MEO, and LEO satellites to characterise the actual radiation dose received
Correlation of pre-launch environmental models and ray-tracing analyses with real in-flight dose measurements
Diagnosis of spacecraft anomalies resulting from changes in radiation environmental fluxes
Multi-location dose mapping across a spacecraft to characterise shielding effectiveness
Scientific and technology demonstration missions requiring in-situ radiation dose measurement capability

Specifications

Part numbers: UDOS001-H (Class H), UDOS007-H (Class H Extended Temperature Range)
Measurement range: Up to 40 krad(Si)
Dose resolution: 15 µrad(Si) per step
Supply voltage / current: 13 V dc to 40 V dc; 10 mA typical supply current
Outputs: Three cascaded linear DAC outputs (Low/Medium/High range) plus pseudo-logarithmic output; 0 to 5 V range
Package / weight: Hermetic hybrid; 1.4 x 1.0 x 0.2 inches; 20 g; Class H-equivalent MIL-PRF-38534 screening

FAQ

What does the UDOS001/007 Micro Dosimeter measure?

• The Micro Dosimeters directly measure total ionizing dose absorbed by an internal silicon test mass simulating the silicon die of spacecraft ICs.

• Radiation measured includes electrons, protons, and gamma rays; the device measures energy absorbed in the silicon detector, not incident energy directly.

• Measurement range extends to 40 krad(Si) with dose resolution of 15 urad(Si) per step.

What is the difference between UDOS001 and UDOS007?

• UDOS007 is the High LET extended temperature range version.

• UDOS007 incorporates a raised energy level input threshold allowing accumulation of higher levels of detected ionizing radiation.

• UDOS007 has an extended operating temperature range: -30 to +70 degrees C versus -30 to +40 degrees C for UDOS001.

What outputs does the Micro Dosimeter provide?

• Low range (Pin 5): 15 urad(Si)/19.5 mV step, 0-3.8 mrad range.

• Medium range (Pin 6): 256x Low range, 0-0.98 rad range.

• High range (Pin 7): 256x Medium range, 0-252 rad range.

• Pseudo-logarithmic output (Pin 8): 0-40 krad(Si) range for low-rate total dose monitoring.

What is the patented integrator architecture and why does it matter?

• The patented integrator architecture produces a flat energy response to ionizing radiation across the measurement energy range.

• A flat energy response means consistent dose measurement accuracy regardless of the energy of the incident particles.

• This makes UDOS001/007 the first compact microcircuit providing repeatable TID measurement over a wide range of radiation energies.

How do the Micro Dosimeter outputs connect to spacecraft systems?

• Analog outputs connect directly to standard ADCs or spacecraft housekeeping analog inputs in the 0-5V range.

• Minimal host vehicle demands -- no special interface hardware required.

• DAC output impedance is 8-12 kilohms; outputs should be connected to high impedance ADC or buffered.

What screening and qualification is available?

• Commercial grade (electrical test only): UDOS001-C and UDOS007-C.

• Class H-equivalent MIL-PRF-38534 screening: UDOS001-H and UDOS007-H.

• Class H screening includes internal visual, temperature cycling (-65 to +150 degrees C x10), constant acceleration 3,000 G, burn-in 160 hours at 125 degrees C PDA 10%, seal, and electrical test at min/max/room temperature.

What radiation survivability has the Micro Dosimeter demonstrated?

• Xenon-beam testing at Lawrence Berkeley Labs demonstrated latch-up immunity up to 67.8 LET (MeV-cm2/mg).

• Harsh proton susceptibility testing showed no degradation of UDOS001 up to 40 krad(Si).

• The dosimeter measures across the full 40 krad(Si) range without functional degradation.

Can the Micro Dosimeter be mounted at multiple locations on a spacecraft?

• Yes. The compact 1.4 x 1.0 x 0.2 inch package and 20-gram weight support mounting at multiple locations.

• Multi-location mounting enables spatial dose mapping to characterize shielding effectiveness across the spacecraft.

• Positioning and area shielding can be used for directional mapping of radiation events.

Total Ionizing Dose Measurement in Spacecraft

Total Ionizing Dose accumulates from trapped electrons and protons in the Van Allen belts, solar energetic particle events, and galactic cosmic rays. The rate of accumulation depends on orbit altitude and inclination, solar cycle phase, and shielding provided by spacecraft structure and component placement.

How the UDOS001/007 Measures TID

The Micro Dosimeter incorporates a silicon detector (3 mm x 7 mm x 250 um) and a pulse-processing architecture that generates a shaped pulse for each ionizing radiation event. Each pulse is integrated into an accumulator circuit. When the integrator reaches a preset threshold, a quanta of 15 urads is removed, a counter is incremented, and the process continues. The counter is divided into 8-bit sub-groups presented to a DAC, providing the three cascaded linear output ranges.

Calibration Guidance

Each dosimeter can be calibrated to a known fixed source level by the end user to verify the dosage input to DAC output relationship
Positioning and area shielding can be used for directional mapping of radiation events
DAC and Log outputs should be sampled simultaneously to avoid TID ambiguity during readout
Supply voltage should be stable and free of ripple; on-board supply should be clean

DAC Output Dose Conversion Ranges

Low (Pin 5): 15 urad(Si)/19.5 mV step -- 0 to 3.8 mrad(Si) -- suited for dose rate measurement
Medium (Pin 6): 3.8 mrad(Si)/19.5 mV step -- 0 to 0.98 rad(Si) -- intermediate range monitoring
High (Pin 7): 0.98 rad(Si)/19.5 mV step -- 0 to 252 rad(Si) -- long-duration cumulative dose
Log (Pin 8): pseudo-logarithmic -- 0 to 40 krad(Si) -- very low rate sampling of total mission dose