FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute

Report No: DOT/FAA/AM-14/13

Title and Subtitle: CARI-NAIRAS: Calculating Flight Doses from NAIRAS Data using CARI

Report Date: December 2014

Authors: Copeland K, Mertens C

Abstract: The CARI computer program is galactic cosmic radiation (GCR) dose calculation software developed by the U.S. Federal Aviation Administration. It serves the aerospace industry and flying public by providing a means of calculating GCR doses for flights, and as such, is a valuable radiation monitoring tool aiding industry and individuals in their radiation protection efforts. The information the software provides is also used by research scientists to investigate health effects of chronic exposure to low levels of ionizing radiation present in the atmosphere. CARI-6 and previous versions were increasingly inaccurate above 60,000 feet because of the superposition approximation built in to their global dose rate tables.

Cognitive capacities of participants were assessed using the Minicog rapid assessment battery before and after the task. Acquired EEG signals were epoched into multiple segments of 10 minutes over time, and these segmented EEG data were statistically compared with each other using non-parametric statistical analysis to identify neurophysiological patterns due to the time-on-task effect. Significant changes in EEG power spectra were localized to the midline regions from the frontal and parietal areas of the human brain. Significant changes in performance data were also observed in response time and routing time.

This report describes CARI-NAIRAS, a new version of CARI that uses pre-calculated global tables of dose rates generated by the NAIRAS (Now-Cast of Atmospheric Ionizing Radiation for Aviation Safety) system developed at National Aeronautics and Space Administration (NASA) Langley Research Center. The NAIRAS system uses the NASA radiation transport code HZETRN (High charge (Z) and Energy TRaNsport), which does not use the superposition approximation, as well as satellite and ground-based data inputs to generate the global tables. CARI-NAIRAS is shown to be in good agreement with Monte Carlo based calculations in the altitude range 27,000 to 87,000 feet, thus eliminating the need for the altitude limit of 60,000 ft. Flight dose estimates are similar to those of CARI-6 and CARI-7. For 24 of the 32 flights investigated, CARI-NAIRAS estimated an effective dose within 20% of the mean of the three programs (CARI-6W, CARI-7, and CARI-NAIRAS). CARI-NAIRAS estimates are expected to improve once the latest version of HZETRN is incorporated into NAIRAS.

Key Words: CARI, Galactic Cosmic Radiation, HZETRN, In-Flight Radiation, Ionizing Radiation, NAIRAS, Space Weather

No. of Pages: 64