Radiation Level Survey

Any spacecraft placed into orbit around the Earth will experience a radiation dose depending on the characteristics of this orbit. This may occur due to crossing the Earth's radiation belts, in which case, a combination oftrapped electrons, protons and bremsstrahlung will be encountered. Alternatively, the main source of radiation may be solar protons, as occurs during interplanetary missions.


The total dose received during a given mission may be reduced by adding extra shielding to the spacecraft. Although only effective to a certain extent, a reduction in dose may in some cases prolong the life of a mission.


The dose received during a series of orbits has been analysed in order to predict radiation encountered by future missions. Analysis was performed using the UNIRAD software with AP8 and AE8 radiation belt models. The JPL solar proton model was also used. Results quoted correspond to a one year mission and solar maximum conditions.


The following three graphs show plots of total dose measured in Si [rad/yr], for ten orbits at shield thicknesses of 1, 4 (typical thickness) and 10 mm Al. Values of total dose are given, along with those for individual types of radiation.



Dose comparisons

The projects under consideration were

  • Circular Equatorial 6
  • Geostationary
  • Tundra
  • ERS-1
  • Global Star 3
  • XMM
  • Molniya 2
  • GTO
  • Odyssey
  • Interplanetary, or Solar Protons


Doses Received in Terms of Type of Particle

Calculated for shield dimension of 1 mm Al
Calculated for shield dimension of 1 mm Al
Calculated for shield dimension of 4 mm Al
Calculated for shield dimension of 4 mm Al
Calculated for shield dimension of 10 mm Al
Calculated for shield dimension of 10 mm Al