Overview of the Radiation Dosimetry Experiment (RaD-X) flight mission

Abstract

The NASA Radiation Dosimetry Experiment (RaD‐X) stratospheric balloon flight mission addresses the need to reduce the uncertainty in predicting human exposure to cosmic radiation in the aircraft environment. Measurements were taken that characterize the dosimetric properties of cosmic ray primaries, the ultimate source of aviation radiation exposure, and the cosmic ray secondary radiations that are produced and transported to aviation altitudes. In addition, radiation detectors were flown to assess their potential application to long‐term, continuous monitoring of the aircraft radiation environment. RaD‐X was successfully launched from Fort Sumner, New Mexico (34.5°N, 104.2°W), on 25 September 2015. Over 18 h of science data were obtained from a total of four different type dosimeters at altitudes above 20 km. The RaD‐X flight mission was supported by laboratory radiation exposure testing of the balloon flight dosimeters and also by coordinated radiation measurements taken on ER‐2 and commercial aircraft. This paper provides the science background and motivation for the RaD‐X flight mission, a brief description of the balloon flight profile and the supporting aircraft flights, and a summary of the articles included in the RaD‐X special collection and their contributions to the science goals of the RaD‐X mission.

Measuring ionizing radiation in the atmosphere with a new balloon‐borne detector

“…Recently, however, ongoing research into the atmospheric effects of energetic particles has motivated additional measurements. The available data are mainly from limited balloon ascents, usually on special campaigns carrying expensive payloads for recovery after descent [ Mertens , ], and surface GCR measurements from the worldwide network of neutron monitors. It has become clear that one‐off campaigns and neutron monitor data do not adequately represent the spatial and temporal variability of measured ionization profiles [ Aplin et al ., ; Harrison et al ., ; Makhmutov et al ., ], particularly in the weather‐forming region of the atmosphere.…”

Cosmic radiation dose measurements from the RaD-X flight campaign

“…The second RaD‐X science goal is to assess the feasibility of specific compact radiation detectors as potential technologies for long‐term, continuous monitoring of the aircraft radiation environment. A more detailed discussion of the background and motivation for the RaD‐X science mission goals is given in the overview of this special issue [ Mertens , ].…”

“…These altitudes, combined with the dosimeter and spectrometer instruments, provide a unique measurement data set for improving aviation radiation models. The dose and spectral measurements above the Pfotzer maximum facilitate the characterization of the source of cosmic radiation exposure at aviation altitudes [ Mertens , ]. The balloon flight trajectory near Fort Sumner is located at cutoff rigidities where aviation radiation model uncertainty is near its maximum [ Bottollier‐Depois et al , ].…”

Assessment of the influence of the RaD-X balloon payload on the onboard radiation detectors

“…The RaD‐X science mission goals are the following: (1) provide measurements that will improve aviation radiation models, such as the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model [ Mertens et al , , ] and (2) intercompare radiation detection instruments to assess their potential application to continuous monitoring of the aviation radiation environment [ Mertens , ]. The RaD‐X balloon flew mainly in two pressure regions: A (18–48 hPa, approximately 21–27 km) and B (<8 hPa, approximately >32 km).…”

“…The RaD‐X balloon flew mainly in two pressure regions: A (18–48 hPa, approximately 21–27 km) and B (<8 hPa, approximately >32 km). These regions are above the Pfotzer maximum, i.e., the altitude at which the maximum ionization rate due to the cosmic rays occurs [ Mertens , ]. The radiation environment in these regions is characterized by the influence of cosmic ray primaries, with high‐Z particles (nuclei heavier than the alpha particle) present in Region B and low‐Z and low‐mass particles dominating in Region A.…”