What is BioSentinel? – NASA

Editor's note: This article was updated on November 21, 2025, shortly after the BioSentinel mission celebrated three years of deep space activity..

Astronauts live in rather extreme conditions on board a spacecraft. International Space Station. Located about 250 miles above Earth in the weightless microgravity environment, they rely on commercial cargo missions approximately every two months to deliver new materials and experiments. And yet this place is relatively protected from the point of view cosmic radiation. Earth's magnetic field shields the space station crew from most of the radiation that can damage the DNA in our cells and lead to serious health problems. When future astronauts embark on long journeys deep into space, they will find themselves in a more dangerous radiation environment and will need significant protection. With the help of a biology experiment on a small satellite called BioSentinel, scientists at NASA's Ames Research Center in California's Silicon Valley are taking the first step toward finding a solution.

To study the basics of what happens to life in space, researchers often use “model organisms” that we understand relatively well. This helps 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 brew beer. In both our cells and yeast cells, high-energy radiation encountered in deep space can cause breaks in the two intertwined strands of DNA that carry genetic information. DNA damage can often be repaired by cells through a process very similar in yeast and humans.

BioSentinel intended to be the first long-term biological experiment to take place outside the space station's orbit near Earth. The BioSentinel spacecraft is one of 10 CubeSats launched on board. Artemis Ifirst flight Artemis Space Launch System, NASA's powerful new rocket. A satellite the size of a cereal box was launched into deep space on a rocket, and then flew past the moon in the direction of revolution around the Sun. Once the satellite was outside of our planet's protective magnetic field, the BioSentinel team remotely launched a series of experiments, activating two strains of the yeast Saccharomyces cerevisiae to grow in the presence of cosmic radiation. The yeast samples were activated at different times throughout the six- to 12-month mission.

One strain is a yeast commonly found in nature, and the other was chosen because it has trouble repairing its DNA. By comparing how these two strains respond to the radiation environment of deep space, researchers will learn more about the risks to human health during long-term studies and can develop evidence-based strategies to reduce potential damage.

During the mission's initial phase, which began in December 2022 and ended in April 2023, the BioSentinel team successfully operated the BioSentinel BioSensor hardware—a miniature biotechnology laboratory designed to measure how living yeast cells respond to long-term exposure to cosmic radiation—in deep space. The team conducted four experiments lasting two weeks each, but did not notice any growth of yeast cells. They determined that deep space radiation was not the cause of the inactive yeast cells, and the lack of growth was likely due to the yeast expiring after the spacecraft was stored for a long time before launch.

Although the yeast did not activate as intended to collect data on the effects of radiation on living yeast cells, the onboard BioSentinel radiation detector, which measures the type and dose of radiation hitting the spacecraft, continues to collect data in deep space.

NASA has expanded the BioSentinel 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 during which solar activity rises and falls in the form of powerful solar flares and giant eruptions called coronal mass ejections. As the solar cycle moves from its peak to its decline phase, scientists expect strong solar activity to continue until 2026, with some of the strongest storms occurring during this decline phase. These events send powerful bursts of energy, magnetic fields and plasma into space that cause auroras and can interfere with satellite signals. Solar radiation from particles accelerated to high speeds can also pose a threat to astronauts in space.

The BioSentinel project builds on Ames's history of conducting biological research in space using CubeSats—small satellites built from individual units, each about four inches cubic inch. BioSentinel is a six-unit spacecraft weighing about 30 pounds. It places yeast cells in tiny compartments inside microfluidic cards—special equipment that controls the flow of extremely small volumes of liquid that activates and maintains the yeast. Data on the radiation levels, growth and metabolism of the yeast will be collected and stored on board the spacecraft, and then transmitted to the science team on Earth.

A backup set of microfluidic cards containing yeast samples will be activated if the satellite encounters a solar particle event, a radiation storm emanating from the Sun that poses a particularly serious health risk to future deep space explorers.

In addition to the pioneering BioSentinel mission, which will traverse deep space, similar experiments are being conducted under varying radiation and gravity conditions. One ran on a space station in microgravity, similar to deep space but with comparatively less radiation. Other experiments were conducted on earth to compare Earth's gravity and radiation levels. These additional versions show scientists how to compare scientific experiments on Earth and space stations, which can be carried out much more easily, with the brutal radiation that future astronauts will encounter in space.

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

• December 2021: The BioSentinel ISS Control experiment launches to the International Space Station on SpaceX's 24th commercial resupply mission.
• January 2022: ISS Control's BioSentinel experiment begins science operations aboard the International Space Station.
• February 2022: The BioSentinel ISS Control experiment began ground science control operations at NASA Ames.
• June 2022: The BioSentinel ISS Control experiment has completed scientific operations. The equipment was returned to Earth in August aboard SpaceX's CRS-25 Dragon.
• October 2022: The BioSentinel ISS Control experiment completed ground science control 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 science operations at NASA Ames.
• November 16, 2024: BioSentinel celebrates two years of continuous radiation observations in deep space, now more than 30 million miles from Earth.
• November 16, 2025: BioSentinel celebrates three years of continuous radiation observations in deep space, now more than 48 million miles from Earth.

Partners:

• NASA Ames leads the scientific research, 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 Office (MCO) of the Exploration Systems Development Mission Directorate at NASA Headquarters in Washington.
• The extended BioSentinel 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 at NASA's Space Technology Mission Directorate at NASA Headquarters, Washington.

Find out more:

• NASA History: NASA's BioSentinel studies solar radiation as Earth observes Aurora (September 2024)
• NASA History: NASA expands BioSentinel mission to measure deep space RadiationAugust 2023
• NASA History: The first biology experiment in deep space begins, follow the progress in real timeDecember 2022
• NASA History: BioSentinel works after successful flyby of the MoonNovember 2022
• NASA History: Artemis I will launch a first-of-its-kind deep space biology missionAugust 2022
• NASA video: Why NASA is sending yeast into deep spaceFebruary 2022
• NASA Podcast: “Houston, we have a podcast,” Deep Space Biology.January 2022
• NASA blog: All Artemis I secondary payloads are installed in the Orion rocket stage adapter. October 2021
• NASA blog; NASA is preparing three more CubeSat payloads for the Artemis I mission. July 2021
• NASA History: NASA BioSentinel team prepares CubeSat for deep space flightApril 2021
• Episode of the NASA in Silicon Valley podcast: Sharmila Bhattacharya on studying how biology changes in spaceMarch 2018
• NASA History: Yeast is the Key to Holiday Celebrations and Cosmic RadiationDecember 2018

For researchers:

For news media:

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