Whether they are used to study the earth’s atmosphere and climate or our galaxy and the universe, balloons play a complementary role to satellites and offer an inexpensive and environmentally-friendly means to carry a range of high-performance and reusable scientific instruments to the edge of space.
The Montgolfier brothers, who launched the first hot air balloon flight in 1783, would have been proud: for a week, the aerostats used today for scientific purposes stood alongside the life-size model of the Ariane 5 rocket at the Cité de l’Espace in Toulouse.
From small meteorological balloons to monsters that could hold Paris’ Notre‑Dame cathedral or two Airbus 380s, the entire range of balloons used by the French National Centre for Space Studies (CNES) was on display for visitors as part of the exhibit “Balloons for Science, at the edge of space” (4 to 10 April).
“In terms of balloons, CNES is number 2 in the world, behind NASA, the US space agency, and ahead of Japan,” stressed Marc Pircher, the director of the space centre in Toulouse, in his opening speech at an evening conference event organised at the Cité de l’espace with the French National Aeronautical and Astronautical Association (3AF).
Furthermore, according to Jean Evrard of the CNES Balloons division, the centre has “the most extensive range of aerostats,” with balloons that can carry scientific instruments and technological innovations on very different missions at altitudes ranging from 1 to 45 km.
The “balloons” programme has been an essential part of CNES since the centre was created over 50 years ago. Far less expensive than airplanes or satellites, balloons are also unique in that they are able to manoeuvre for long periods of time in the different layers of the atmosphere, some of which are too high for airplanes, and others too low for satellites.
Their missions are highly diverse. In the realm of science, balloons are used for a variety of purposes, including studying the atmosphere (taking samples, measuring components related to greenhouse gases, etc.); meteorology (tracking the movement of air masses); and astronomy, in layers above the earth’s atmosphere. At such levels, balloons can detect radiation that is not visible from the ground (such as infrared, ultraviolet, X- and gamma rays).
Furthermore, balloons make it possible to calibrate instruments flying on satellites by comparing measurements made by the latter in a given area with readings taken on site by aerostats. Balloons are also used to test materials to be used on satellites (cameras, star sensors, etc.) and serve to study the influence of cosmic radiation at very high altitudes on living organisms. Finally, balloons function as “cranes”, launching re-entry vehicle models for supersonic aircraft into the atmosphere to study their aerodynamics.
To give an example, balloons are used in the HyMeX international research programme coordinated by Météo-France and CNRS. This programme aims to better predict extreme events around the Mediterranean such as the so-called “Cévennes episodes”, violent storms in and around the Cévennes mountains in south-central France that often producing severe flooding.
In Africa, balloons have been used by the French Research Institute for Development (IRD) and the National Centre for Scientific Research (CNRS) in the international programme AMMA, a study of the West African monsoon (2002-2007).
In 2010, a fleet of 19 stratospheric balloons designed by CNES was released from McMurdo Station, the US base in Antarctica, in order to study the mechanisms of ozone depletion in the lower stratosphere as part of the Concordiasi campaign.
In 2007 and 2009, during the Franco-American FIREBall experiment (in which CNES partnered with the Laboratory of Astrophysics of Marseille), a one-tonne astrophysics gondola able to carry a telescope made it possible at an altitude of 40 km to focus in on warm dust filaments near galaxy clusters.
For all of the missions described above, CNES has a full range of exceptionally reliable balloons. For example, in 2001, one of the Centre’s balloons, the Infrared Montgolfier (MIR), circumnavigated the globe three times in 71 days, a new record.
The airship-shaped Aéroclipper can fly when necessary at an altitude of only 50 m for long distances to observe oceans and their climatic environment, which is useful, for example, in programmes that study the birth of hurricanes.
Pressurised tropospheric balloons can fly at altitudes ranging from 1 to 5 km and can travel distances of 5,000 km for atmospheric studies. Pressurised stratospheric balloons, on the other hand, can fly at an altitude of 20 km for a distance of around 80,000 km and can remain in flight for several months. The Infrared Montgolfier (MIR) can climb up to 28 km. For its part, the open stratospheric balloon has a volume of 400,000 m3 and can carry one-tonne payloads up to altitudes of 45 km.
The choice of the Cité de l’espace for the CNES balloon exhibit hints at future missions. In fact, the centre is already working on “space” balloons that one day will fly to celestial bodies like Titan, Venus or Mars. It is certainly no coincidence that the balloons were shown in the Cité de l’espace next to the model of the robot Curiosity, which is currently on Mars…