What is BioSentinel?

BioSentinel is a NASA mission that launched on Artemis I in December 2022 to study the effects of space radiation on living organisms. The spacecraft, one of 10 CubeSats, flew past the Moon and entered deep space, where it has been collecting data on space radiation levels.
The mission uses yeast as a model organism to study how life responds to space radiation. By comparing the behavior of two strains of yeast – one that is naturally resistant to DNA damage and another that is more susceptible – scientists can gain insights into the health risks posed to humans during long-term space exploration.
BioSentinel has been operating in deep space for over three years, collecting data on radiation levels and monitoring the growth and metabolism of the yeast. The mission has also provided valuable insights into the effects of solar particle events on living organisms.
The BioSentinel project builds on NASA’s history of conducting biology studies in space using CubeSats. The mission is part of a larger effort to understand how life adapts to different environments, including microgravity and high-radiation conditions.
The data collected by BioSentinel will be critical for interpreting the effects of space radiation exposure and reducing the risks associated with long-term human exploration. The mission has already provided valuable insights into the health risks posed by solar particle events and will continue to inform future space missions.

Illustration of the BioSentinel spacecraft, flying past the Moon with the CubeSat's solar arrays fully deployed, facing the Sun.

llustration of BioSentinel’s spacecraft flying past the Moon.

NASA/Daniel Rutter

Editor’s Note: This article was updated Nov. 21, 2025 shortly after BioSentinel’s mission marked three years of operation in deep space.

Astronauts live in a pretty extreme environment aboard the International Space Station. Orbiting about 250 miles above the Earth in the weightlessness of microgravity, they rely on commercial cargo missions about every two months to deliver new supplies and experiments. And yet, this place is relatively protected in terms of space radiation. The Earth’s magnetic field shields space station crew from much of the radiation that can damage the DNA in our cells and lead to serious health problems. When future astronauts set off on long journeys deeper into space, they will be venturing into more perilous radiation environments and will need substantial protection. With the help of a biology experiment within a small satellite called BioSentinel, scientists at NASA’s Ames Research Center, in California’s Silicon Valley, are taking an early step toward finding solutions.

To learn the basics of what happens to life in space, researchers often use “model organisms” that we understand relatively well. This helps show the differences between what happens in space and on Earth more clearly. For BioSentinel, NASA is using yeast – the very same yeast that makes bread rise and beer brew. In both our cells and yeast cells, the type of high-energy radiation encountered in deep space can cause breaks in the two entwined strands of DNA that carry genetic information. Often, DNA damage can be repaired by cells in a process that is very similar between yeast and humans.

Conceptual graphic of a radiation particle causing a DNA DSB

Conceptual graphic of a radiation particle causing a double-stranded DNA break.

BioSentinel set out to be the first long-duration biology experiment to take place beyond where the space station orbits near Earth. BioSentinel’s spacecraft is one of 10 CubeSats that launched aboard Artemis I, the first flight of the Artemis program’s Space Launch System, NASA’s powerful new rocket. The cereal box-sized satellite traveled to deep space on the rocket then flew past the Moon in a direction to orbit the Sun. Once the satellite was in position beyond our planet’s protective magnetic field, the BioSentinel team triggered a series of experiments remotely, activating two strains of the yeast Saccharomyces cerevisiae to grow in the presence of space radiation. Samples of yeast were activated at different time points throughout the six- to twelve-month mission.

One strain is the yeast commonly found in nature, while the other was selected because it has trouble repairing its DNA. By comparing how the two strains respond to the deep space radiation environment, researchers will learn more about the health risks posed to humans during long-term exploration and be able to develop informed strategies for reducing potential damage.

During the initial phase of the mission, which began in December 2022 and completed in April 2023, the BioSentinel team successfully operated BioSentinel’s BioSensor hardware – a miniature biotechnology laboratory designed to measure how living yeast cells respond to long-term exposure to space radiation – in deep space. The team completed four experiments lasting two-weeks each but did not observe any yeast cell growth. They determined that deep space radiation was not the cause of the inactive yeast cells, but that their lack of growth was likely due to the yeast expiring after extended storage time of the spacecraft ahead of launch.

Although the yeast did not activate as intended to gather observations on the impact of radiation on living yeast cells, BioSentinel’s onboard radiation detector – that measures the type and dose of radiation hitting the spacecraft – continues to collect data in deep space.

Two people looking at data on several computer monitors, with a model of the BioSentinel spacecraft in the background.

Jesse Fusco, left, and James Milsk, right, at the BioSentinel command console at the Multi-Mission Operations Center at NASA’s Ames Research Center in Silicon Valley. The team is receiving spacecraft telemetry at the three-year timepoint since the mission launched on Artemis I. BioSentinel continues to fly in its heliocentric orbit, now more than 48 million miles from Earth.

NASA/Don Richey

NASA has extended BioSentinel’s mission to continue collecting valuable deep space radiation data in the unique, high-radiation environment beyond low Earth orbit.

The Sun has an 11-year cycle, in which solar activity rises and falls in the form of powerful solar flares and giant eruptions called coronal mass ejections. As the solar cycle progresses from maximum to a declining phase, scientists expect strong solar activity to continue through 2026, with some of the strongest storms seen during this declining phase. These events send powerful bursts of energy, magnetic fields, and plasma into space which causes the aurora and can interfere with satellite signals. Solar radiation events from particles accelerated to high speeds can also pose a threat to astronauts in space.

Built on a history of small-satellite biology

The BioSentinel project builds on Ames’ history of carrying out biology studies in space using CubeSats – small satellites built from individual units each about four inches cubed. BioSentinel is a six-unit spacecraft weighing about 30 pounds. It houses the yeast cells in tiny compartments inside microfluidic cards – custom hardware that allows for the controlled flow of extremely small volumes of liquids that will activate and sustain the yeast. Data about radiation levels and the yeast’s growth and metabolism will be collected and stored aboard the spacecraft and then transmitted to the science team back on Earth.

A reserve set of microfluidic cards containing yeast samples will be activated if the satellite encounters a solar particle event, a radiation storm coming from the Sun that is a particularly severe health risk for future deep space explorers.

BioSentinel’s microfluidics card, designed at NASA’s Ames Research Center in Silicon Valley, California, will be used to study the impact of interplanetary space radiation on yeast. Once in orbit, the growth and metabolic activity of the yeast will be measured using a three-color LED detection system and a dye that provides a readout of yeast cell activity. Here, pink wells contain actively growing yeast cells that have turned the dye from blue to pink color.

NASA/Dominic Hart

Multiple BioSentinels will compare various gravity and radiation environments

In addition to the pioneering BioSentinel mission that will traverse the deep space environment, identical experiments take place under different radiation and gravity conditions. One ran on the space station, in microgravity that is similar to deep space, but with comparatively less radiation. Other experiments took place on the ground, for comparison with Earth’s gravity and radiation levels. These additional versions show scientists how to compare Earth and space station-based science experiments – which can be conducted much more readily – to the fierce radiation that future astronauts will encounter in space.

Taken together, the BioSentinel data will be critical for interpreting the effects of space radiation exposure, reducing the risks associated with long-term human exploration, and confirming existing models of the effects of space radiation on living organisms.

Milestones

December 2021: The BioSentinel ISS Control experiment launched to the International Space Station aboard SpaceX’s 24th commercial resupply services mission.
January 2022: The BioSentinel ISS Control experiment began science operations aboard the International Space Station.
February 2022: The BioSentinel ISS Control experiment began ground control science operations at NASA Ames.
June 2022: The BioSentinel ISS Control experiment completed science operations. The hardware was returned to Earth in August aboard SpaceX’s CRS-25 Dragon.
October 2022: The BioSentinel ISS Control experiment completed ground control science operations at NASA Ames.
Nov. 16, 2022: BioSentinel launched to deep space aboard Artemis I.
Dec. 5, 2022: BioSentinel began science operations in deep space.
Dec. 19, 2022: BioSentinel began ground control science operations at NASA Ames.
Nov. 16, 2024: BioSentinel marks two years of continuous radiation observations in deep space, now more than 30 million miles from Earth.
Nov. 16, 2025: BioSentinel marks three years of continuous radiation observations in deep space, now more than 48 million miles from Earth.

Partners:

NASA Ames leads the science, hardware design and development of the BioSentinel mission.
Partner organizations include NASA’s Johnson Space Center in Houston and NASA’s Jet Propulsion Laboratory in Southern California.
BioSentinel is funded by the Mars Campaign Development (MCO) Division within the Exploration Systems Development Mission Directorate at NASA headquarters in Washington.
BioSentinel’s extended mission is supported by the Heliophysics Division of NASA’s Science Mission Directorate at NASA headquarters in Washington, the MCO, and the NASA Electronic Parts and Packaging Program within NASA’s Space Technology Mission Directorate at NASA Headquarters in Washington.

Learn more:

NASA story: NASA’s BioSentinel Studies Solar Radiation as Earth Watches Aurora (Sept. 2024)
NASA story: NASA Extends BioSentinel’s Mission to Measure Deep Space Radiation, Aug. 2023
NASA story: First Deep Space Biology Experiment Begins, Follow Along in Real-Time, Dec. 2022
NASA story: BioSentinel Underway After Successful Lunar Flyby, Nov. 2022
NASA story: Artemis I to Launch First-of-a-Kind Deep Space Biology Mission, Aug. 2022
NASA video: Why NASA is Sending Yeast to Deep Space, Feb. 2022
NASA podcast: “Houston We Have a Podcast,” Deep Space Biology, Jan. 2022
NASA blog: All Artemis I Secondary Payloads Installed in Rocket’s Orion Stage Adapter, Oct. 2021
NASA blog; NASA Prepares Three More CubeSat Payloads for Artemis I Mission. Jul. 2021
NASA story: NASA’s BioSentinel Team Prepares CubeSat For Deep Space Flight, Apr. 2021
NASA in Silicon Valley podcast episode: Sharmila Bhattacharya on Studying How Biology Changes in Space, Mar. 2018
NASA story: For Holiday Celebrations and Space Radiation, Yeast is the Key, Dec. 2018

For researchers:

NASA Space Station Research Explorer: BioSentinel ISS Control Experiment
NASA technical webpage: BioSentinel

For news media:

Members of the news media interested in covering this topic should reach out to the NASA Ames newsroom.

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Q. What is BioSentinel?

A. BioSentinel is a small satellite that carries a biology experiment designed to study the effects of space radiation on living organisms, specifically yeast cells.

Q. Why did NASA launch BioSentinel into deep space?

A. NASA launched BioSentinel into deep space to study the health risks posed to humans during long-term exploration and to develop informed strategies for reducing potential damage from space radiation.

Q. What type of organism is being used in the BioSentinel experiment?

A. The yeast Saccharomyces cerevisiae, a common microorganism found in nature, is being used in the BioSentinel experiment to study its response to deep space radiation.

Q. Why did the initial phase of the BioSentinel mission not observe any yeast cell growth?

A. The initial phase of the BioSentinel mission did not observe any yeast cell growth because the yeast cells likely expired after extended storage time on the spacecraft ahead of launch.

Q. What is the purpose of the reserve set of microfluidic cards containing yeast samples?

A. The reserve set of microfluidic cards contains yeast samples that will be activated if the satellite encounters a solar particle event, providing additional data on the impact of radiation on living organisms.

Q. How many experiments are being conducted by BioSentinel in addition to its primary mission?

A. In addition to its primary mission, BioSentinel is conducting identical experiments under different radiation and gravity conditions, including one on the space station and another on Earth’s surface.

Q. What will the data from BioSentinel help scientists understand?

A. The data from BioSentinel will help scientists interpret the effects of space radiation exposure, reduce the risks associated with long-term human exploration, and confirm existing models of the effects of space radiation on living organisms.

Q. How far is BioSentinel currently located in deep space?

A. As of November 2025, BioSentinel is approximately 48 million miles from Earth, having traveled to its current location beyond low Earth orbit.

Q. Who are the partners involved in the BioSentinel mission?

A. The partners involved in the BioSentinel mission include NASA Ames, NASA’s Johnson Space Center, NASA’s Jet Propulsion Laboratory, and other organizations within NASA headquarters and its various divisions.