Radiation environment
Radiation Dose vs. Shielding
How much total ionizing dose your electronics take, and how much aluminum it takes to survive it — the dose-depth curve, for any orbit from LEO to GEO.
// Trapped-electron + bremsstrahlung + proton dose vs. aluminum depth, tuned to SHIELDOSE-2 reference points. A first-order screen for shielding trades and part-tolerance selection — run AE9/AP9 + SHIELDOSE-2 in SPENVIS for the design value.
This calculator estimates the dose-depth curve — total ionizing dose (TID) versus aluminum shielding thickness — for any orbit from low Earth orbit (LEO) to geostationary (GEO), summing trapped electrons, the bremsstrahlung X-rays they generate in the shield, and trapped-plus-solar protons. It is a parametric analytic model tuned to reproduce published SHIELDOSE-2 reference points (Seltzer 1994), with belt geometry vs. altitude and geomagnetic screening vs. inclination built in — a first-order screen for shielding trades and part-tolerance selection. The design value still comes from AE9/AP9 + SHIELDOSE-2 run in SPENVIS.
How this model works & what it omits
Every electronic part has a total-ionizing-dose (TID) tolerance, measured in krad(Si) — the accumulated dose at which it stops working reliably. The mission's job is to keep the dose behind the shielding below that number. The relationship between shield thickness and dose is the dose-depth curve, and it is the first thing a radiation engineer builds for a new orbit. This tool estimates it.
The dominant driver is altitude, because it sets which radiation belt you sit in. LEO below ~800 km sees only the inner-belt tail and South Atlantic Anomaly passes — a benign few krad/yr behind a couple of millimetres. The MEO region around 20,000 km (the GPS / O3b belt) is the worst place to be: it sits in the heart of the outer electron belt and can exceed 100 krad/yr thin-shielded. GEO at 35,786 km is electron-dominated at tens of krad/yr. Inclination matters too: Earth's magnetic field deflects charged particles, so a low-inclination orbit is better screened than a polar one that runs through the belt horns and polar cusps.
The dose-depth curve has a characteristic shape driven by three sources. Trapped electrons dominate at thin shielding and attenuate steeply (short range in aluminum), so the curve falls fast over the first few millimetres. Protons — trapped plus solar — attenuate more slowly and take over at depth. Bremsstrahlung — penetrating X-rays generated when electrons stop in the shield — barely attenuates at all and forms the deep-shield floor. The practical consequence is diminishing returns: in an electron-dominated orbit the first 2–4 mm of aluminum buys most of the reduction, and beyond ~5–10 mm you are fighting protons and the bremsstrahlung floor. That is why spot-shielding a few sensitive parts usually beats shielding the whole box.
What this tool does not do: it is a parametric analytic model, tuned to reproduce published SHIELDOSE-2 reference points, not a physics-first transport code. Real design uses AE9/AP9-IRENE for the trapped-particle environment and SHIELDOSE-2 (in SPENVIS) for the dose-depth integral, followed by a geometry-specific 3D sector-shielding analysis of the actual spacecraft — a slab model like this one assumes uniform shielding in all directions. It also does not model displacement damage (a separate failure mode from TID), single-event effects (see the companion single-event-effect rate tool), or solar-particle-event worst-case transients. Treat the numbers as a first-order screen for shielding trades and part-tolerance selection.
// pick an orbit, then dial the shield thickness and mission.
Orbit
// altitude sets which radiation belt you sit in.
Mission & shield
// dose scales with time; thickness sets the depth point.
Solar condition
// min fills the electron belt; max raises protons + SPEs.
LEO — inner-belt tail / SAA passes
Total ionizing dose
// LEO — inner-belt tail / SAA passes · dominated by protons at 2.5 mm
14 krad
mission dose (5.0 yr)
2.74 krad/yr
annual dose rate
protons
dominant source
5.6 mm
Al for <10 krad part
// dose-depth curve (log dose vs. aluminum thickness)
// screening only
Parametric analytic model tuned to published SHIELDOSE-2 reference points — right magnitudes and dose-depth shape for shielding trades and part-tolerance selection. For a design value, run AE9/AP9-IRENE + SHIELDOSE-2 in SPENVIS with 3D sector-shielding geometry.
// shareable URL encodes every input. no backend.
// ai-generated breakdown of what these numbers mean — with diagrams.
Common questions
How much shielding thickness does a CubeSat need?
It is set almost entirely by the orbit. The International Space Station (ISS)-like preset (550 km, 51.6°) accumulates roughly 2.7 krad(Si) per year behind 2.5 mm of aluminum — a 5-year mission stays under a typical 10 krad(Si) commercial-off-the-shelf (COTS) tolerance with about 5.6 mm, which the tool's shield-sizing helper reports directly. The polar Sun-synchronous preset (700 km, 98°) runs about three times hotter, so the same 5-year tolerance needs roughly 17.5 mm. Run your own orbit and mission length — the shielding thickness answer moves fast with both.
Why does adding more aluminum stop helping?
Because the three dose sources attenuate at very different rates. Trapped electrons have short range, so the first 2–4 mm knock their dose down steeply. Protons penetrate further and roll off over ~5–10 mm. Bremsstrahlung — the X-rays electrons generate as they stop in the shield — barely attenuates at all and forms the deep-shield floor. Past that crossover you pay full mass for almost no dose reduction, which is why spot-shielding a few sensitive parts usually beats thickening the whole box.
Which orbit has the worst radiation environment?
Medium Earth orbit (MEO) around 20,000 km — the GPS belt — sits in the heart of the outer electron belt: the 10-year MEO preset accumulates over 200 krad(Si) per year behind 3 mm of aluminum, and no thickness on this tool's 50 mm grid brings the mission dose under a COTS tolerance. GEO is electron-dominated at tens of krad per year; LEO below ~800 km is the benign regime at a few krad per year. Altitude decides which belt you live in, and that decides everything else.
Does orbit inclination change the dose?
Substantially, in LEO. Earth's magnetic field deflects charged particles, so a low-inclination orbit is well screened, while a polar orbit runs through the belt horns and the open polar cusps — in this model a 90° orbit sees nearly twice the dose of a 28.5° orbit at the same altitude. Near GEO the orbit sits largely outside the shielding field, so the effect saturates.
Is TID the only radiation effect I need to design for?
No. TID is the slow accumulation that degrades parts over years; single-event effects (SEE) are instant faults from individual particle strikes — bit flips through destructive latch-up — and more shielding thickness barely helps against the high-energy particles that cause them. Screen those with the companion single-event-effect rate tool. Displacement damage and worst-case solar-particle transients are separate analyses again — this page screens TID only.
References
- // Seltzer, S. M. (1994). Updated Calculations for Routine Space-Shielding Radiation Dose Estimates: SHIELDOSE-2. NIST.
- // Ginet, G. P. et al. (2013). AE9, AP9 and SPM: New Models for Specifying the Trapped Energetic Particle and Space Plasma Environment. Space Sci. Rev. (AE9/AP9-IRENE).
- // ESA SPENVIS — Space Environment Information System (the standard AE9/AP9 + SHIELDOSE-2 pipeline).
- // ECSS-E-ST-10-04C — Space Environment standard.
- // Reference dose points cross-checked against published SHIELDOSE-2 runs (LEO ~1–3 krad/yr behind a few mm Al; GEO tens of krad/yr; MEO the hottest).
