What is BioSentinel? – NASA

Editor’s note: This article was updated on November 21, 2025, shortly after the BioSentinel 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 Earth in weightless 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. Earth’s magnetic field protects the space station crew from much of the radiation that can damage the DNA in our cells and cause serious health problems. When future astronauts undertake long journeys deeper into space, they will venture into more perilous radiological environments and will need substantial protection. With the help of a biological experiment conducted in a small satellite called BioSentinel, scientists at NASA’s Ames Research Center in California’s Silicon Valley are taking the first 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 to show more clearly the differences between what happens in space and on Earth. For BioSentinel, NASA uses yeast – the same yeast that makes bread rise and beer brew. In both our cells and our yeast cells, the type of high-energy radiation encountered in deep space can cause breaks in the two intertwined strands of DNA that carry genetic information. Often, DNA damage can be repaired by cells in a very similar process between yeast and humans.

BioSentinel was intended to be the first long-term biological experiment to take place beyond the orbit of the near-Earth space station. The BioSentinel spacecraft is one of 10 CubeSats launched aboard Artemis I, the first flight of the Space Launch System of the Artemis program, NASA’s powerful new rocket. The cereal box-sized satellite traveled into deep space aboard the rocket, then flew past the Moon toward the Sun. Once the satellite was in position beyond our planet’s protective magnetic field, the BioSentinel team triggered a series of remote experiments, activating the growth of two strains of Saccharomyces cerevisiae yeast in the presence of space radiation. Yeast samples were activated at different times throughout the six- to 12-month mission.

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

During the initial phase of the mission, which began in December 2022 and concluded 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 carried out four experiments lasting two weeks each, but observed no growth of yeast cells. 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 yeast expiration after a prolonged period of spacecraft storage before launch.

Although the yeast has not activated as planned to collect observations on the impact of radiation on living yeast cells, BioSentinel’s onboard radiation detector – which measures the type and dose of radiation hitting the spacecraft – continues to collect data in deep space.

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

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

The BioSentinel project builds on Ames’ experience conducting biological studies in space using CubeSats – small satellites built from individual units of about four cubic inches each. BioSentinel is a spacecraft made up of six units weighing approximately 30 pounds. It houses yeast cells in tiny compartments inside microfluidic boards – custom hardware that allows the controlled flow of extremely low volumes of liquids that will activate and sustain the yeast. Data on radiation levels and yeast growth and metabolism will be collected and stored on board the spacecraft, 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 from the Sun that poses a particularly serious health risk for future deep space explorers.

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

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

• December 2021: Launch of the BioSentinel ISS Control experiment to the International Space Station aboard SpaceX’s 24th Commercial Resupply Services mission.
• January 2022: The BioSentinel ISS Control experiment began scientific 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 has completed scientific operations. The hardware was returned to Earth in August aboard SpaceX’s CRS-25 Dragon.
• October 2022: The BioSentinel ISS Control experiment has completed ground control science operations at NASA Ames.
• November 16, 2022: BioSentinel launched into deep space aboard Artemis I.
• December 5, 2022: BioSentinel begins deep space science operations.
• December 19, 2022: BioSentinel began ground control science operations at NASA Ames.
• November 16, 2024: BioSentinel marks two years of continuous observations of radiation in deep space, now more than 30 million kilometers from Earth.
• November 16, 2025: BioSentinel marks three years of continuous observations of radiation in deep space, now more than 30 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 Washington, MCO, and the NASA Electronic Parts and Packaging Program within the NASA Space Technology Mission Directorate at NASA Headquarters Washington.

Learn more:

• NASA Story: NASA BioSentinel studies solar radiation as Earth observes auroras (September 2024)
• NASA Story: NASA Expands BioSentinel Mission to Measure Deep Space Radiation, August 2023
• NASA Story: First Deep Space Biology Experiment Begins, Tracked in Real Time, December 2022
• NASA Story: BioSentinel underway after successful lunar flyby, November 2022
• NASA Story: Artemis I to Launch First Deep Space Biology Mission, August 2022
• NASA Video: Why NASA is sending yeast into deep space, February 2022
• NASA Podcast: “Houston We Have a Podcast,” Deep Space Biology, January 2022
• NASA Blog: All Artemis I Secondary Payloads Installed in Rocket’s Orion Stage Adapter, October 2021
• NASA Blog; NASA prepares three more CubeSat payloads for the Artemis I mission. Jul 2021
• NASA Story: NASA’s BioSentinel team prepares CubeSat for deep space flight, April 2021
• NASA in Silicon Valley Podcast Episode: Sharmila Bhattacharya on Studying Evolutionary Biology in Space, March 2018
• NASA Story: For Holiday Celebrations and Space Radiation, Yeast is Key, December 2018

For researchers:

For news media:

• Members of the media interested in covering this topic should contact the NASA Ames newsroom.