Human Systems Integration Division @ NASA Ames

The demands of Mars Exploration Rover (MER) Surface Operations required personnel to perform mission critical tasks on a schedule corresponding to a Mars day (24.65h). Actigraphy activity monitors were used to evaluate sleep quality in personnel working this schedule. Preliminary results indicate that time in bed was reduced during the MER schedule and about half the participants subjectively found working a Mars sol schedule difficult. Other investigators have also evaluated changes in Actigraphy locomotor activity circadian rhythms as an indicator of changes in health status. However, some reports have criticized the suitability of Actigraphy data for reliable estimates of circadian rhythm metrics. In this project, mathematical techniques were successfully developed and tested which showed that statistically reliable estimates of circadian rhythm variables could be obtained from Actigraphy data and therefore used to quantify circadian rhythm changes in fatigue states associated with operational environments. These methods (data clipping and robust locally weighted regression) were applied to Actigraphy activity data from the MER study and a 40-day pilot transmeridian flight study. Preliminary evidence shows that the MER 24.65h work schedule was associated with decreased circadian rhythm stability and circadian waveform changes. Transmeridian flights, in the 40-day pilot study, were associated with profound circadian rhythm disruption or periodicity changes. The reliable statistical evaluation of circadian rhythm changes in locomotor activity provides the opportunity to document activity changes which are indicative and may be predictive of sleep disturbances and impaired performance in aeronautical work environments.