Simple space radiation model ReadMe page
These are simple visualisation tools are designed to answer the question how do radiation effects change with orbit? Very little prior knowledge or expertise needed. These tools do not remove the need for detailed analysis, but serve as a visual guide to show how environments change with orbit.
How It Works
The TID tool calculates radiation environment requirements for spacecraft missions across different orbital regimes. It uses a "fix two, solve one" approach where you specify two of three parameters and the tool calculates the third across circular orbits from LEO to GEO and lunar orbits.
Input Parameters
Choose two fixed parameters and one variable to calculate required:
-
Shielding Thickness - Equivalent aluminum thickness protecting components
-
Survival TID - Radiation tolerance required for parts
-
Max Mission Lifetime - Time on orbit
How to Use
-
Step 1: Select which parameter to calculate (your variable)
-
Shielding thickness → Find required protection for given TID tolerance and lifetime
-
Survival TID → Find required part radiation hardness for given shielding and lifetime
-
Max lifetime → Find mission duration limit for given shielding and TID tolerance
-
-
Step 2: Set the two fixed parameters using these recommended ranges:
-
Shielding: 3-5 mm (default: 4 mm if unknown)
-
TID tolerance: 5-100 kRad (default: 5 kRad if unknown)
-
Lifetime: 3-15 years
-
-
Step 3: Interpret the output heatmaps:
-
X-axis: Orbital altitude
-
Y-axis: Orbital inclination
-
Color scale: Your calculated variable
-
Note: Values are capped for readability (shielding >99 mm, TID >999 kRad, lifetime >99 years displayed at maximum). Only circular orbits are shown.
How It Works
The Petersen Figure of Merit (FOM)[1] method has been used to plot heat maps of altitude vs inclination with colour indicating Single Event Effect (SEE) rates. Petersen developed a Figure of Merit (FOM) as a useful parameter to describe part upset sensitivity, and to approximate upset rates. The approach correlates ground based test data with on-orbit event rates, providing a relation that gives order of magnitude event rates for different orbits.
How to Use
The tool was made by following Petersen's 1998 paper*, using the FOM equations and rate coefficients for different orbits. Test data is needed to calculate on orbit event rates, and four types of data can be used:
-
Proton test data - A single data point is needed, the limiting cross-section, described as events per proton per cm^2 (where protons are 100 - 200 MeV).
-
Heavy ion test data - Full Weibull fit parameters for a heavy ion test, where event cross-sections are taken at multiple Linear Energy Transfer's (LET)
-
On orbit event rates - Space Radiation Services added this as a way to correlate on-orbit data to different orbits
-
Manual FOM entry - For users with their own calculated FOM or used for proton SEL.
Limitations
-
The FOM methods is targeted at soft error rates and should not be used for destructive SEE analysis.
-
This approach is not accurate, and should only be used to give order of magnitude results for event rates.
-
All of the correlated data is from before 1998, and may not be as accurate for modern day electronics.
-
There is an artificial low spot just over 7000 km due to limited data in the 1998 paper, as a result, some proton effects are missing over 7000 km.
-
When using proton cross-section data, note that some events do not occur with protons to certain types of events can be missed.
* E. L Petersen, "The SEU Figure of Merit and Proton Upset Rate Calculations," IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 45, NO. 6, DECEMBER 1998
How It Works
The atomic oxygen (AO) tool calculates AO densities, fluxes, and erosion rates across different orbital regimes. Data is based on published AO densities at different solar conditions. Atomic oxygen densities increase with higher solar activity, as indicated by rising F10.7 and Ap indices, due to enhanced solar radiation and geomagnetic activity that heat the thermosphere, expand it, and increase AO density in LEO. The tool presents two scenarions based on an assumed solar mean condition, and solar max condition:
-
Solar mean, where F10.7 = 145 Ap = 15
-
Solar max, where F10.7 = 250 Ap = 45
How to Use
-
AO Density and Flux:
-
These scenarios are relatively self explanatory and give the density of atomic oxygen in a specific orbit and the flux of particles on an exposed face in the ram direction.
-
-
Erosion Rate (μm/year):
-
This requires users to input erosion yeild data (cm³/atom) to get erosion rats in um per year
-
It is recommended that published NASA MISSE data is used as a staring point as most common materials have published values as part of these missions.
-
How It Works
The Internal Charging tool calculates internal charging risk and shielding requirements for spacecraft missions across different orbital regimes. Data is based on simple charging current values on a planar surface, after aluminum shielding. In simple terms, internal charging can be evaluated based on charging current (A/cm²), which quantifies the penetrating electron flux reaching a particular depth in the spacecraft structure. A common threshold, based on NASA-HDBK-4002B, is 1 × 10⁻¹³ A/cm²; above this level, spacecraft designers generally consider mitigation necessary. More detailed analysis tools can also determine depositied charge, voltage, and E-max values for a given dialectric geometry. Howerver this requires more detailed analysis with more complex modelling tools.
How to Use
-
Minimum required shielding:
-
Set acceptable threshold for charging current (we recommend 1E-13 A/cm² per NASA-HDBK-4002B).
-
The results will show the minimum aluminium shield required to meet the charging current.
-
-
Charging current:
-
Select your shielding level (mm aluminium) to get the internal charging current in different orbits.
-
Select the acceptable charging current threshold (we recommend 1E-13 A/cm² per NASA-HDBK-4002B) which will set the green/red pass/fail color threshold on the plots.
-
Note: This tool has not been benchmarked