Radi-N2: Tracking space radiation and its risks

Health Science

Radi-N2 uses bubble monitors, a Canadian-made technology which will lead to better protection of crews in Earth orbit and on deep-space missions.


From Earth, the Sun looks like a calm, unchanging source of light. But it is actually a highly active, constantly churning ball of gas. The Sun continuously releases not only heat and visible light, but also radiation in the form of massive streams of high-energy particles. Thankfully, Earth's atmosphere and magnetosphere largely shield us from this threat.

But space can be a potentially hazardous place to live and work. Astronauts aboard the International Space Station (ISS) are at higher risk of radiation exposure, and receive greater doses than they would here on Earth.

One of the most serious types is neutron radiation. It makes up about 30% of the radiation that astronauts receive on the Space Station, and can potentially cause cataracts, bone marrow damage, and even cancer over long-term exposure.

The Radi-N2 experiment measures neutron radiation using bubble monitors: finger-sized tubes filled with a clear polymer gel that contains liquid droplets. When struck by a high-energy neutron particle, a droplet vaporizes, leaving a visible bubble that can be counted.

Radi-N2: Detecting Neutron Radiation on the ISS

The Canadian Space Agency (CSA) astronaut Chris Hadfield explains the Canadian Radi-N2 experiment and displays the neutron bubble detectors used on the ISS. (Credits: CSA, NASA)


The Radi-N2 experiment is designed to:

Radi-N2 and You

The CSA is partnering with Let's Talk Science to engage students in a unique project with Canadian astronaut David Saint-Jacques during his six-month mission on the ISS.

Students in classrooms across Canada are participating in Radi-N2 & You. Students will measure neutron radiation levels on Earth using bubble detectors and compare their results to David's measurements on the Station.

How it works

There are two slightly different procedures for the Radi-N2 experiment. When a Canadian astronaut is aboard the Station, they are in charge of conducting a session according to the following steps:

  1. The astronaut retrieves a set of eight bubble detectors from storage on board the Station.
  2. These tubes are loaded into the automatic reader, and the number of bubbles is recorded for later comparison.
  3. The astronaut places six bubble monitors in specific locations around the Station. One of the bubble monitors is worn by the astronaut to measure the dose their body receives, and another is placed within their sleeping quarters. All of the monitors are left in place for one week.
  4. When seven days have passed, the monitors are collected and loaded into the automatic reader. The crewmember records the data, and scientists on the ground calculate how much neutron radiation the Station received.

When there are no Canadians on board the Station, an astronaut places all eight bubble monitors around the Station.

Did you know that the Sun has seasons? Our closest star goes through an 11-year cycle of activity, including a solar minimum and maximum.

During solar maximum, the Sun can release flares, powerful bursts of particles and gas that can contain high levels of radiation. Flares and other types of solar ejections produce spectacular displays of auroras in our skies, but they can also cause power outages, satellite malfunctions and even disruptions to GPS and other communications systems.


An earlier version of the experiment, Radi-N, took place during Robert Thirsk's mission to the ISS in .

Radi-N2 began during Chris Hadfield's ISS mission in and is scheduled to conclude in .


With support from the CSA, Bubble Technology Industries of Chalk River, Ontario, designed the bubble monitors used in space and continues to manufacture them.

The Radi-N2 study is a collaboration between the CSA and:

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