NAIRAS

The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model is a prototype operational model currently under development at NASA Langley Research Center. The NAIRAS model provides global, real-time, data-driven predictions of atmospheric ionizing radiation exposure for archiving and assessing the biologically harmful radiation levels at commercial airline altitudes.

Current Dose Rates

The NAIRAS (V2) model predicts atmospheric radiation exposure from galactic cosmic rays (GCR) and solar energetic particle (SEP) events. GCR particles are propagated from local interstellar space to Earth using an extension of the Badhwar and O’Neill model, where the solar modulation has been parameterized using high-latitude real-time neutron monitor measurements at Oulu, Thule, Lomnicky, and Moscow. During radiation storms, the SEP spectrum is derived using ion flux measurements taken from the NOAA/GOES and NASA/ACE satellites. The cosmic ray particles – GCR and SEP – are transported through the magnetosphere using the CISM-Dartmouth particle trajectory geomagnetic cutoff rigidity code, driven by real-time solar wind parameters and interplanetary magnetic field data measured by the NASA/ACE satellite. Cosmic ray transport through the neutral atmosphere is based on analytical solutions of coupled Boltzmann transport equations obtained from NASA Langley Research Center’s HZETRN transport code.

The current figures below show the NAIRAS prediction of the radiation exposure quantity related to biological risk – Effective dose rate (uSv/hr) – at several altitudes. To put the exposure rates into perspective, one chest X-ray is about 100 uSv, and a CT scan is about 8,000 uSv.

Effective Dose Rate, 0-100 uSv/hr, 5km

Effective Dose Rate (uSv/hr),11km

Effective Dose Rate, 0-100 uSv/hr, 15km

Effective Dose Rate, 0-100 uSv/hr, 90km

Overview

Overview

The Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model is a prototype operational model currently under development at NASA Langley Research Center. The NAIRAS model provides global, real-time, data-driven predictions of atmospheric ionizing radiation exposure for archiving and assessing the biologically harmful radiation levels at commercial airline altitudes. The sources of ionizing radiation are galactic cosmic rays (GCR) and solar energetic particle (SEP) events which can accompany disturbances on the Sun’s surface. The composition and energy spectra of atmospheric ionizing radiation originate from and are subject to variability in space weather phenomena. As such, the NAIRAS model provides a space weather decision support tool related to radiation impacts on crew and passengers of long-range aircraft, an area of national priority for NASA’s Applied Science Program.

The NAIRAS model will enhance the performance of the decision support tools provided by the NOAA Space Weather Prediction Center (SWPC), since this decision support system does not currently monitor or estimate the ionizing radiation present in the atmosphere at commercial airline altitudes. The end-user communities that will benefit from the NAIRAS model are the commercial airline industry (airline corporation and aircrew professional association), the FAA, the National Institute of Occupational Safety and Health (NIOSH), and NOAA/SWPC. Results from the NAIRAS model will provide tools for its end-user organizations to develop policy and operational procedures for mitigating biologically harmful radiation exposure and provide an aircrew career planning tool – especially during SEP events. NAIRAS results will also aid in the formulation of recommended aircrew annual and career radiation exposure limits, and will enhance epidemiological studies conducted to better understand the biological effects of atmospheric ionizing radiation on passengers and crew.

The key NAIRAS data products are global distributions of vertical profiles of radiation exposure rates, computed from the Earth’s surface to approximately 100 km in real-time. NAIRAS output will be made available at NOAA’s National Weather Service, Aviation Digital Data Service (ADDS). NOAA/ADDS is a decision support system whereby NAIRAS results can provide a tool for commercial airlines and aircrew to monitor current and accumulated radiation exposure. The long-term goal is to transition the prototype NAIRAS model into an operational system that will be adopted by NOAA/SWPC.

System Development

The development of the critical input data stream formats and I/O interface modules between the input datasets and the distributed network server database is complete. Input datasets for historical storm periods were prepared for NAIRAS verification and validation studies. A real-time prototype operational NAIRAS global GCR radiation exposure prediction has been demonstrated.

The previous dosimetric quantity computed by the NAIRAS model was the dose equivalent rate at the tissue boundary without transport through the body. This approximation overestimates the radiation exposure, and the overestimation is significant for SEP events. All ICRP radiation exposure limits are given in terms of effective dose, which is representative of the average full-body exposure. The NAIRAS model has been updated to compute effective dose rates.

A real-time GCR model was developed and integrated into NAIRAS. The Badhwar and O’Neill GCR model was adapted to real-time predictions by cross correlating the Climax-based solar modulation potential with four real-time, high-latitude, ground-based neutron monitor count rate measurements. The GCR model specifies the GCR spectral flux incident on Earth’s atmosphere for transport through the atmosphere. This effort provided a student research opportunity through the NASA Langley Aerospace Research Summer Scholars (LARSS) program.

Considerable effort was made in increasing the computational efficiency and assessing the accuracy of the CISM-Dartmouth geomagnetic cutoff rigidity model. The model is suitable for a real-time nowcast and integration into the NAIRAS distributed network operational architecture.

Design

Gallery and Videos

Conferences Presentations and Journal Articles

Conference and Workshop Presentations

  • Mertens, C. J., et al., Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) Project, Joint Interagency Weather Research Meeting, March 22-24, 2010.

  • Mertens, C. J., et al., NAIRAS model predictions of aircraft radiation exposure during the Halloween 2003 storms, NASA Exploration Technology Development Program (ETDP) Workshop, Hampton, Virginia, March 2-3, 2010.
  • Wiltberger, M., C. J. Mertens, B. T. Kress, and S. C. Solomon, Results from the NAIRAS model for the Halloween storm, 90th American Meteorological Society Annual Meeting, Space Weather Symposium, Atlanta, Georgia, January 17-21, 2010.
  • Kress, B. T., Modeling geomagnetic shielding of solar energetic particles and cosmic rays, Fall AGU, San Francisco, California, December 14-18, 2009.
  • Mertens, C. J., et al., Prototype development of an operational global aircraft radiation exposure nowcast, Fall AGU, San Francisco, California, December 14-18, 2009.

  • Mertens, C. J., Models of atmospheric response to low- and high-energy particle precipitation, seminar at George Mason University, Fairfax, Virginia, October 28, 2009.
  • Mertens, C. J., M. Wiltberger, B. T. Kress, and S. C. Solomon, NAIRAS model predictions of aircraft radiation exposure during the Halloween 2003 storms, 2nd International High Energy Particle Precipitation in the Atmosphere (HEPPA) 2009 Workshop, Boulder, Colorado, October 6-8, 2009.
  • Mertens, C. J., Development of the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model, brief to the FAA Air Traffic Organization, FAA Office of Commercial Space Flight and FAA Technical Center, Washington, DC, September 10, 2009.
  • Mertens, C. J., W. K. Tobiska, D. Bouwer, B. T. Kress, M. Wiltberger, S. C. Solomon, and J. J. Murray, Development of the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model, 1st AIAA Atmospheric and Space Environments Conference, AIAA San Antonio, Texas, June 22-25, 2009.
  • Kress, B. T., C. J. Mertens, and M. Wiltberger, Solar energetic particle cutoff variations during the 26-31 October 2003 geomagnetic storm, Space Weather Conference, Boulder, Colorado, April 28 – May 1, 2009.
  • Mertens, C. J., B. T. Kress, M. Wiltberger, S. C. Solomon, and S. Blattnig, NAIRAS prediction of aircraft radiation exposure during a high-energy solar energetic particle event in October 2003, Space Weather Conference, Boulder, Colorado, April 28 – May 1, 2009.

Journal Articles

  • Kress, B. T., C. J. Mertens, and M. Wiltberger, Solar energetic particle cutoff variations during the 28-31 October 2003 geomagnetic storm, Space Weather, in press, 2010.
  • Mertens, C. J., B. T. Kress, M. Wiltberger, S. Blattnig, T. S. Slaba, S. C. Solomon, and M. Engel, Geomagnetic influence on aircraft radiation exposure during a solar energetic particle event in October 2003, Space Weather, 8, S03006, doi:10.1029/2009SW000487, 2010.
  • Tobiska, W. K., Operational space weather entering a new era, Space Weather, 7, S10003, doi:10.1029/2009SW000510, 2009.
  • Mertens, C. J., W. K. Tobiska, D. Bouwer, B. T. Kress, M. Wiltberger, S. C. Solomon, and J. J. Murray, Development of the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model, AIAA 2009-3633-978, 2009.

Funding

  • NASA Applied Science Program, ROSES solicitation “Decision Support through Earth Science Research Results” (NNH07ZDA001N-DEC, 07-DEC07-0005) NASA Langley Research Center, Hampton, Virginia

Documents

    • NAIRAS Operations Report 1

    • Increased frequency of chromosome translocations in airline pilots with long-term flying experience

    • Operational Space Weather Entering a New Era

    • Cosmic Ray Atmospheric Transport and Dosimetry (Tutorial – 12 MB)

    • Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NASA Headquarters Brief)

    • World Health Organization: Cosmic Radiation and Air Travel

  • What Aircrews Should Know About Their Occupational Exposure to Ionizing Radiation
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