Half-year, and occasional one-year stints aboard the ISS, and especially lifetime totals nearing 2.5 years are possible ethically because these missions take place within the Earth's magnetosphere where exposure to ionizing radiation which has both steady, slowly varying, and episodic/catastrophic spikes is significantly lower than beyond it in cis-lunar space.

Qestion: What radiation data was actually available at the time of the Apollo missions to the Moon?

Where did the data available in the late 1960's come from? Are there specific satellites that can be identified which provided much of the particle rate data that were then converted to estimates of whole-body radiation dose?

Were predictions of accumulated dose possible with any reliability? When compared to dosimetry data presumably measured aboard the Apollo missions to Lunar orbit and landing, did they turn out to be close? Were the dangers of solar flares spiking the dose received appreciated back then?


1 Answer 1


Some of the earliest satellites were scientific missions aimed at exploring the environment in Earth orbit.

The Explorer series mapped the radiation environment to an altitude of ~2500 km. Explorer 1 data was used to discover the Van Allen belts - they used a Geiger counter and an altimeter to get a plot of radiation level vs altitude.

During the flight, radiation levels seemed to increase and then suddenly drop to zero and then again to increase, then suddenly drop to zero. What the team soon realized was that regions appearing as zero were really off the scale! These high-radiation regions were mapped and are now known as the Van Allen radiation belts.

all Explorer 1 data

the Geiger counter data set

Pioneer 3 measured the radiation environment to an altitude of ~100,000 km. Pioneer 4 passed by the Moon and measured the environment there.

all Pioneer 3 data

Pioneer 6-9 studied cosmic rays and the solar wind.

List of data collections from all NASA missions

  • $\begingroup$ Thanks, I'm primarily interested in "What data..." There are good explanations of the instruments and/or the types and energies of particles those spacecraft measured within your linked articles, any chance you could address "What data..." a little more explicitly? $\endgroup$
    – uhoh
    Commented Jun 2, 2018 at 0:54
  • 1
    $\begingroup$ I've tried that. Wasn't able to find the paper that describes the discovery of the van Allen belts, but NASA does have the data from all Explorer 1 experiments online. $\endgroup$
    – Hobbes
    Commented Jun 4, 2018 at 19:51

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