Fast Neutron Spectrometer (FNS) - 09.05.18

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Neutron spectrometers are used to make a wide range of measurements, including studies of a planetary body’s composition and measuring the flux of high-energy neutrons that could be harmful to humans. The Fast Neutron Spectrometer (FNS) investigation studies a new neutron measurement technique that is better suited for the mixed radiation fields found in deep space. Future manned and exploration missions benefit from clearer, more error-free measurement of the neutron flux present in an environment with multiple types of radiation.
Science Results for Everyone
Information Pending

The following content was provided by Mark Joseph Christl, and is maintained in a database by the ISS Program Science Office.
Experiment Details


Principal Investigator(s)
Mark Joseph Christl, MSFC, Huntsville, AL, United States

Information Pending

NASA Marshall Space Flight Center, Huntsville, AL, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
Technology Demonstration Office (TDO)

Research Benefits
Earth Benefits, Space Exploration

ISS Expedition Duration
September 2016 - October 2018

Expeditions Assigned

Previous Missions
Information Pending

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Experiment Description

Research Overview

  • Neutrons contribute to the radiation exposure of crews and must be measured to assess the exposure levels.
  • The new technology employed in the Fast Neutron Spectrometer (FNS) investigation is less susceptible to false triggers from other forms of radiation and provides a clear measurement of the neutron component in a mixed radiation environment.

Neutrons are difficult to detect because they are electrically neutral particles and pass through most detector systems without detection. The Fast Neutron Spectrometer (FNS) uses a new instrument design that can significantly improve the reliability of identifying neutrons in the mixed radiation field found in deep space. This instrument design uses the gate and capture technique that slows down the neutrons and then "captures" them in an isotope of Lithium. The FNS uses special glass fibers loaded with Lithium to absorb the slowed neutrons and produce a small flash of light unique to the neutron capture process. The FNS uses custom electronics to recognize and trigger on the distinct neutron capture signal, which is then processed and analyzed to determine the radiation levels. The objective is to measure the neutron flux on the International Space Station (ISS) with the FNS. The ISS provides a valuable testbed for evaluating the instrument performance in a mixed radiation that includes sources from galactic cosmic rays, solar energetic particles, trapped radiation belts and albedo neutrons from Earth's atmosphere. The structure and contents of the ISS serve as a realistic spacecraft for exploration.

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Space Applications
Neutrons are subatomic particles that form one component of space radiation, which is harmful to humans. Current and future space missions must monitor the flux of neutrons to help safeguard crew health and protect sensitive equipment and experiments. There are many sources of radiation in space, including cosmic rays from the galaxy, energetic particles from the sun, and particles from Earth’s Van Allen belts. All these high energy particles can interact with a spacecraft, habitat or planetary surface to produce neutrons. This investigation studies a new type of neutron spectrometer that is less susceptible to false alarms from all the other high-energy particles found in space radiation. Future space missions benefit from clearer measurements of neutron radiation.

Earth Applications
Particle accelerators are used to develop, test and evaluate the instrument performance and its application in deep space missions.

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Operational Requirements and Protocols
Transfer FNS from the launch vehicle as a softstow payload. Install FNS in the US portion of the ISS. Connect the FNS power cable and USB cable to the ISS 28VDC power and the ISS laptop. Initiate startup sequence. No additional crew intervention is required until several weeks/months have passed. Changing the location of FNS is needed 2 to 3 times during the mission in order to evaluate the neutron flux on ISS at different locations. The FNS launches on SpaceX-10 to the ISS. FNS is mounted internal to the ISS and monitor neutron flux starting in Increment 49/50. FNS is moved 3 times during the 6 month primary mission to evaluate the neutron flux in different locations: USLAB, NODE1, NODE2. FNS stays onboard ISS for the duration of ISS if resources permit

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Decadal Survey Recommendations

Information Pending

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Results/More Information

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Related Websites

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Assembly drawing of ANS-ISS payload.

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Detector Section Drawing.

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NASA Image: ISS050E013233 - Fast Neutron Spectrometer (FNS) Hardware Setup, in the U.S. Laboratory. Photo taken during Expedition 50.

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