I like balloons! And I am not talking about the kind used for birthdays or other celebrations. I am thinking of something on a much grander scale. Before the advent of heavier than air flying machines, balloons were the only way scientists could take instruments aloft to study the atmosphere. The very earliest balloons were of the hot air variety and had to be large enough to carry the weight of the scientist as well as his instruments.
Since France led the way in large balloon development, Paris became the center of ballooning achievement. In Paris on 21 November 1783, Joseph and Etienne Montgolfier became the first humans to ascend in an untethered hot air balloon. Only days later, on 1 December, Professor Jacques Charles and the Robert bothers ascended in a hydrogen balloon constructed from sheets of silk stitched together and varnished with rubber dissolved in turpentine. Their flight lasted over two hours and covered 36 kilometers. Not only was this the first human flight in a hydrogen balloon, but since they carried a barometer and thermometer, this was the first flight to carry meteorological instruments.
A year later, Dr. John Jeffries, an American physician and the very first American to fly, took air samples and measured air temperature, humidity, and pressure during in flights over London. He and Frenchman Jean-Pierre Blanchard were the first to cross the English Channel by balloon in1785, but unfortunately while crossing, they had to throw all their scientific instruments overboard to keep their balloon basket out of the water.
Polar exploration by balloon was attempted in 1897 when Swedish engineer and explorer, Salomon August Andrée, led an airborne expedition with the goal of being the first to reach the North Pole. Unfortunately for him and his two companions, their hydrogen-filled balloon leaked so badly that it only remained aloft for less than 3 days; landing far short of the North Pole and well away from land. But more on his misadventures in a future blog.
With the advent of radio, instruments could be sent aloft and measurements transmitted to a station on the ground via telemetry. Balloons became smaller and travelled higher since they only had to lift the weight of the instruments and could forgo the weight of an observer to function as a recorder. Thousands of balloons are launched every day around the world to obtain the atmospheric information required for weather predictions. The South Pole is no exception, especially since weather conditions in Antarctica affect weather patterns in the rest of the world. We launch balloons daily to better study and understand the weather, both the typical rubber weather balloons as well as high-altitude polyethylene balloons. Rubber balloons are used when temperatures are relatively warm (by Antarctic standards) since the rubber becomes brittle at extremely cold temperatures, resulting in much lower altitudes achieved by the instrument packages. These balloons measure barometric pressure, temperature, and humidity. They also contain a global positioning system device that allows the precise determination of altitude, rate of ascent, and wind velocity.
At the end of the summer season, I was fortunate enough to assist one of the South Pole meteorologists in launching a rubber weather balloon. The balloon was carefully inflated with helium and reached an altitude of 85,300 feet before bursting, which is almost 3 times higher than commercial aircraft fly.
Over the past decade, high altitude unmanned balloons have become an increasingly popular pastime for amateur scientists. In addition to the usual meteorological measurements, these balloons often carry Geiger counters to measure radiation, cameras to photograph the balloon as well as the terrain below, and amateur radio tracking devices to allow recovery of the instrument package. A photograph from one of these amateur flights, as shown below, provides a view of the Earth from the perspective of the balloon near peak altitude.
Aside from the Weather Service, the National Oceanic and Atmosphere Administration (NOAA) also launch balloons at the South Pole. These balloons are usually much larger than the typical meteorological balloon and are sent aloft less frequently. Their primary function is to measure ozone levels in the stratosphere, but they typically take along that particular day’s meteorological package to conserve both helium and balloons. These high-altitude polyurethane balloons are only partially filled with helium to provide just enough buoyancy or lift to allow the instrument package to ascend at the reasonable rate. This not only reduces the amount of helium required for the mission, but also provides room for the helium to expand as the balloon rises, enabling them to reach the highest possible altitude which is usually 100,000 feet or higher. Launched in the darkness of the Antarctic winter, they quickly disappear from sight.
The meticulous preparation and launching of these large balloons requires considerable expertise, especially in windy conditions. Fortunately, the NOAA staff has mastered the technique and most flights are highly successful. Ozone profiles, such as the one shown below, are adding to our knowledge of the atmosphere and the changes that are influencing the climate of our planet.