Variations of dose rate observed by MSL/RAD in transit to Mars

TL;DR

This study analyzes measurements from the RAD instrument during a Mars mission to model and predict radiation dose rates in transit to Mars, considering solar activity variations and their impact on radiation exposure for future human missions.

Contribution

It provides empirical models linking solar modulation potential to radiation dose rates measured during transit to Mars, aiding future mission planning.

Findings

Dose rate varies with solar activity and galactic cosmic ray flux.

Predicted dose equivalent during solar maximum could be significantly lower.

Empirical models estimate radiation exposure under different solar conditions.

Abstract

Aims: To predict the cruise radiation environment related to future human missions to Mars, the correlation between solar modulation potential and the dose rate measured by the Radiation Assessment Detector (RAD) has been analyzed and empirical models have been employed to quantify this correlation. Methods: The instrument RAD, onboard Mars Science Laboratory's (MSL) rover Curiosity, measures a broad spectrum of energetic particles along with the radiation dose rate during the 253-day cruise phase as well as on the surface of Mars. With these first ever measurements inside a spacecraft from Earth to Mars, RAD observed the impulsive enhancement of dose rate during solar particle events as well as a gradual evolution of the galactic cosmic ray (GCR) induced radiation dose rate due to the modulation of the primary GCR flux by the solar magnetic field, which correlates with long-term solar activities and heliospheric rotation. Results: We analyzed the dependence of the dose rate measured by RAD on solar modulation potentials and estimated the dose rate and dose equivalent under different solar modulation conditions. These estimations help us to have approximate predictions of the cruise radiation environment, such as the accumulated dose equivalent associated with future human missions to Mars. Conclusions: The predicted dose equivalent rate during solar maximum conditions could be as low as one-fourth of the current RAD cruise measurement. However, future measurements during solar maximum and minimum periods are essential to validate our estimations.