Wristwatch-like device enables assessment of health risks for astronauts on mission to the moon

Just a few hours before the Orion spacecraft crossed the sky en route to the moon on April 1, mechatronics engineer Rodrigo Trevisan Okamoto received confirmation he had been waiting for since the Artemis 2 mission was announced in 2023. The email from NASA stated that the crew of the first crewed mission to orbit the moon in half a century would carry a device developed by Okamoto and his team at Condor Instruments, a São Paulo-based startup.

“The NASA announcement was sudden and caught us by surprise. And it was only after the mission concluded that we learned the astronauts had been using the equipment in tests for the past two years,” Okamoto told Agência FAPESP.

The device, called an actigraph, is shaped like a wristwatch and incorporates accelerometers, as well as light and temperature sensors, to precisely map the user’s sleep and wake patterns over the course of days or weeks.

It works by using an activity sensor that monitors the frequency and intensity of arm movements. By analyzing this data, it is possible to infer periods of rest (an absence of movement) and periods of alertness (the presence of movement). This allows for the accurate recording of an individual’s circadian behavior. This approximately 24-hour “biological clock,” which regulates the physical and behavioral functions of most living beings, is primarily influenced by light.

To monitor this clock, the device features ten onboard sensors that detect light exposure across different spectral bands. This data is crucial because it allows us to characterize the intensity and spectral composition of light throughout the light-dark cycle. This cycle is the primary external regulator that synchronizes the internal biological clock with the environment.

“The light-dark cycle is defined by Earth’s rotation, and it’s based on this that the brain anticipates the time to sleep. In space, that reference is lost, as astronauts may remain in constant light or darkness, depending on their position relative to the sun,” explains Mario Pedrazzoli Neto, a professor at the School of Arts, Sciences, and Humanities at the University of São Paulo (EACH-USP). Pedrazzoli is an expert in chronobiology, the science that studies the rhythms and internal biological clocks of living beings. He coordinated studies that formed the basis for the development of the Brazilian actigraph.

Disrupted sleep

On the International Space Station (ISS), for example, astronauts experience 16 sunrises and sunsets per day, which can severely disrupt the sleep-wake cycle. To mitigate this stress, light-emitting diode (LED) systems were installed on the station to simulate Earth’s cycle and help maintain the crew’s sleep hygiene.

“Due to these and other factors still under investigation, such as the effect of gravity, astronauts tend to experience sleep deprivation. In space, rest is inherently disrupted,” says Pedrazzoli.

Since sleep deprivation causes cognitive and motor deficits that can compromise long-duration missions, agencies like NASA commonly conduct studies to assess how irregular light cycles and sleep disturbances impact the human body. These disturbances pose both short- and long-term health risks, the researcher explains.

For example, researchers affiliated with the agency are investigating how factors such as light and caffeine consumption affect the crews’ biological clocks and influence sleep quality.

“Chronobiology was born precisely because of the need to understand how astronauts sleep in space,” Pedrazzoli emphasizes.

In 2023, for the Artemis campaign, the U.S. space agency launched a study to monitor astronauts’ well-being, activity levels, sleep patterns, and interactions. The ARCHeR (Artemis Research for Crew Health and Readiness) project was motivated by the critical environment of the Orion capsule, which is a confined and cramped space where the crew faces prolonged biological and psychological challenges, including isolation and radiation, during deep-space missions.

To make the study feasible, NASA engineers searched the global market for actigraphs capable of monitoring the crew in real time. The agency took notice of the device from Condor Instruments after startup representatives participated in international scientific conferences on chronobiology, sleep, and light.

“In 2023, they contacted us looking for a new supplier. Initially, they made a small purchase for the science and engineering sectors. Since then, we’ve participated in several meetings as the project evolved. The device underwent rigorous testing to assess whether the data met the needs of the mission and whether it was safe and reliable for flight,” Okamoto recalls.

Although there had been indications of its use on Artemis 2 since late 2025, official confirmation only came on launch day. “It wasn’t until the spacecraft took off that we knew the device was actually on board,” says Okamoto.

Technological advantages

According to Okamoto, the Brazilian actigraph stands out from its international competitors because it monitors motor activity, light exposure, and body temperature. Body temperature is a crucial piece of data because it drops by 1 to 2 °C during sleep as part of the circadian cycle, promoting relaxation and energy conservation.

Another unique feature is its ability to measure melanopic light, which is the blue-cyan light spectrum (around 490 nanometers) that impacts the human non-visual system. Melanopic light activates photosensitive ganglion cells in the retina, which inhibits melatonin production and signals to the brain that it is daytime. This increases alertness and suppresses sleep.

“Cell phones emit light precisely at that wavelength. That’s why using these devices at night radically alters the brain’s sleep regulation,” Pedrazzoli comments.

The device also features an events button that the astronauts activated together during historic moments, such as on April 6, when Orion reached a distance of 406,777 km from Earth—the farthest point ever reached by humans.

During the post-mission press conference, Commander Reid Wiseman highlighted another use for the device: “Using that device over the past two years allowed us to regain our focus whenever we got distracted.”

According to NASA, the actigraph data collected during the flight will be compared to motor coordination tests and pre- and post-launch questionnaires. The goal is to optimize the design of future spacecraft to ensure safety on long-duration missions.

“What we learn will help us understand how astronauts can survive and thrive farther from Earth,” the agency states.

Journey to space

The development of the actigraph began with a need identified by Pedrazzoli while conducting studies at the Sleep Studies Center, a Research, Innovation, and Dissemination Center (RIDC) affiliated with the Federal University of São Paulo (UNIFESP). The first prototypes were used to assess the impact of daylight saving time on the population.

“We realized that we needed to scale up production to meet the demands of our research and have specialized technical support,” the professor explains. Through a referral from Arturo Forner-Cordero, a professor at USP’s Engineering School (POLI), Pedrazzoli met Okamoto and Luis Filipe Rossi, then master’s students at POLI-USP who were interested in launching a tech startup. The engineers ultimately transformed the prototype into a high-precision commercial product.

Today, the startup exports 80% of its production—200 to 300 devices per month—to more than 40 countries, serving major universities and research centers. The device is used in studies ranging from the myopia epidemic in Asia to the recovery of premature babies in neonatal ICUs.

The goal now is to maintain the partnership with NASA for the next phases of the Artemis campaign, including the 2028 landing at the moon’s south pole.

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Stephanie Baum

Master’s in TESOL from The New School. Passionate about language learning and editing science news on biology and space exploration.

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Robert Egan

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