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Working a Mars Sol (24.65-hr) Schedule on Earth
(Dec 4, 2003)
The Fatigue Countermeasures Group (FCG), Principal Investigator, Melissa M. Mallis, Ph.D., is currently exploring the ability of Mars Exploration Rover (MER) Surface Operations Personnel to maintain sleep working a Mars sol (24hr and 39min day) while being exposed to the 24hr light/dark cycle of Earth as well as the effects it will have on overall sleep patterns.

Since 1980, the Fatigue Countermeasures Group in the Human Factors Research and Technology Division at Ames has been examining the extent to which fatigue, sleep loss and circadian disruption affect aviation pilot performance. Rotating shifts, night shifts and exceptionally long days are all irregular schedules that can potentially result in sleep disruptions, sleep loss and performance decrements, thus reducing the safety margin. However, such disruptions are not limited to aviation but can also occur in other operational environments.

Scientists and engineers that will be controlling the operation and data collection of the Mars Exploration Rovers (MER) scheduled to land in January 2004 will be forced to work irregular schedules. They will be required to perform mission critical NASA tasks in accordance with a Mars day (sol) schedule, which is approximately 39 minutes longer than an earth day. Therefore, individuals will be required to remain awake 39 minutes longer each day, rotating around the clock. Remaining awake the additional 39 minutes every day results in a phase delay further complicated by a rotating shift work schedule. The human body's circadian system programs humans to live on a 24-hr cycle being awake during the day and asleep at night. This 24-hr cycle of sleep/wake patterns is also affected by light exposure, acting as a time giver for the circadian system. Therefore, when trying to sleep during the day while being exposed to daylight levels can result in sleep difficulties and trying to work at night when it is dark can result in performance decrements. This is due to misalignments of the circadian and sleep systems, being out of sync with the environmental time cues.

Although one cannot ever fully adapt to shiftwork, specific fatigue countermeasures can be implemented to help maintain alertness and reduce fatigue levels. However, proper use of the countermeasures, such as timing, is critical to have the desired effect. Therefore, it is necessary to educate individuals on proper use of fatigue countermeasures and how the circadian and sleep systems interact to regulate fatigue, alertness and performance. MER scientists and engineers have participated in Fatigue Education workshops to receive information on strategies and scheduling approaches to help them manage their fatigue. These workshops are based on the two-day Fatigue Education Training Module (ETM) that the FCG has offered since 1993 and continues to offer two times/year as part of the 'Operational Outreach' focus of the FCG. They were developed to transition all of the research findings of the FCG to the operational community.

Little scientific research has been done to investigate what impact living on a Mars schedule of shifting 39 minutes later each day will have on sleep/wake cycles. Therefore, as part of the FCG's 'Performance and Countermeasures' focus, Dr. Mallis, Principal Investigator, is performing an exploratory study measuring activity and sleep patterns to determine the ability of MER scientists and engineers to maintain Mars consistent sleep/wake cycles while being exposed to the 24hr light/dark cycle of Earth. The activity and sleep patterns of MER personnel will be recorded during both readiness tests and the 3-month mission.

MER personnel will wear a non-intrusive actiwatch device that measures activity levels and complete a subjective sleep/wake diary to collect data on sleep/wake cycles. The data collected will provide a reliable and objective estimate of the sleep-wake cycle.

The data collected will be used to improve our understanding of the ability of individuals to adapt their sleep/wake cycles to a Mars day (sol) while being exposed to Earth-based time cues. Results will be used in schedule development to help minimize fatigue and maximize performance and alertness for future Mars related operations.
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Curator: Phil So
NASA Official: Jessica Nowinski
Last Updated: September 11, 2023