Since the late 19^th century, scientists have mostly used balloons to study the atmosphere or for astronomical research.

In the atmosphere, balloon-borne instruments can acquire in-situ measurements of winds, greenhouse gases, aerosols and radiation. Balloons also enable astronomers to observe the universe through telescopes weighing several hundred kilograms flown above the dense layers of the atmosphere.

Balloons can thus complement satellite observations and ground-based measurements.

Balloons drift through the atmosphere, enabling scientists to study physical and chemical phenomena and take air samples. For example, they have been used to study the ozone layer, to search for greenhouse gases and particles, and to investigate monsoon mechanisms in India and Africa.

With the development of space activities, the range of balloon applications has widened to include testing of new technologies. Instruments and equipment designed to be flown on satellites—like star trackers, thermal cameras and solar cells—are tested under balloons at very high altitudes.

Balloons meet the needs of many scientific communities. Astronomers use balloons flying above the dense layers of the atmosphere to capture invisible radiation that either scarcely reaches the ground—like infrared or ultraviolet rays—or not at all, like X-rays and gamma rays. Astrophysicists take advantage of certain flights to validate instrument techniques while collecting valuable science data.

Balloons are sometimes sent up to high altitudes to release the mock-up of a body for re-entry into Earth’s atmosphere (e.g., the heat shield of a planetary probe, a suborbital aircraft, a space shuttle, a decelerator for Mars, etc.) to study aerodynamics on a more representative scale than in a wind tunnel.

IN-AIR (Infrastructure Nationale des Aéronefs Instrumentés pour la Recherche)

This infrastructure operates a vast flotilla of instrumented aircraft and lighter-than-air vehicles to conduct a range of Earth and space observations, and to validate innovative aviation and space technologies for the scientific community. These include:

• Flying laboratories (ATR 42 and Piper Aztec aircraft) carrying scientific payloads of up to two tonnes
• Zero-pressure stratospheric balloons (ZPB), the only way to loft scientific payloads of several hundreds of kilograms into the stratosphere
• Superpressure balloons able to acquire measurements in the tropopause for up to several months
• Weather balloons able to sound the troposphere and stratosphere with limited payloads

Flight data are exploited through a central database developed in partnership with the Data Terra research infrastructure’s AERIS data and services hub.

MAGIC: Releases of balloon-borne atmospheric sounding instruments combined with aerial surveys to measure concentrations of carbon dioxide and methane, the two main human-induced greenhouse gases. The SAFIRE fleet of instrumented aircraft, national weather service Meteo France and national scientific research centre CNRS are partnering CNES on this project. Flight campaigns began in 2018 and the most recent was in 2023.
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STRATO-SCIENCE: Stratospheric balloon flight campaign operated by CNES and the Canadian Space Agency (CSA). The first campaign ran from August to September 2014 from the Timmins base in Canada. Balloons carrying the PILOT and SPECIES instruments were notably launched during the 2015, 2018, 2019 et 2023 campaigns. The most recent campaign took place from August to September 2023 at Timmins.
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AUSTRAL: Three launches of stratospheric balloons from CNES and CSA were made from Alice Springs, Australia, from 17 March to 21 April 2017.
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TRANSAT: Campaign in 2024 from the Esrange launch base in northern Sweden, operating short-duration ZPB flights over Scandinavia and long-duration flights like the transatlantic balloon recovered in the Canadian Arctic.

STRATEOLE 2: Project dedicated to studying atmospheric phenomena around the equator. It is being led by France with research scientists from the United States and other nations. It operates balloons capable of staying aloft for more than three months at altitudes of 18 to 20 kilometres. The first science campaign took place over the winter of 2021-2022. The second and last campaign is scheduled for the winter of 2026-2027.
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BalMan: Manoeuvrable stratospheric balloon capable of controlling its flight trajectory. Project in development.
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JEM-EUSO Collaboration: Stratospheric balloon-borne experiments designed to demonstrate the ability to detect cosmic rays penetrating Earth’s atmosphere from space. Flights took place in August 2014 (EUSO-ZPB), April 2017 (EUSO-SPB) and May 2023 (EUSO-SPB2). A EUSO-SPB3 flight is under study for 2025.
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FIREBall: (Faint Intergalactic Redshifted Emission Balloon) is a French-U.S. stratospheric-balloon-borne experiment conceived to detect the faint and diffuse emission of the intergalactic medium. The experiment flew for the first time on 22 July 2007 and is still ongoing. The most recent flight was on 25 September 2023. It is borne by a ZPB.
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PILOT: An international project led by CNES and the IRAP astrophysics and planetology research institute to measure the submillimetre polarized emission from interstellar dust for the first time on three stratospheric balloon flights (borne by a ZPB) between 2015 and 2019.
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SPECIES: (SPECtromètre Infrarouge à lasErs in Situ) is a rackable instrument to acquire targeted measurements of major and trace gases in Earth’s atmosphere that can be carried inside a stratospheric balloon gondola or aircraft, or operated on the ground. CNES is partnering the Canadian Space Agency (CSA) and the LPC2E environmental and space physics and chemistry laboratory, which is developing this infrared spectrometer built around OFCEAS technology (Optical Feedback Cavity Enhanced Absorption Spectroscopy). The first flight took place in August 2018 from Timmins, Canada. The experiment is borne by a ZPB.
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