High-altitude balloons are unmanned balloon

Balloon

A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig...

s, usually filled with helium

Helium

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

 or hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 that are released into the stratosphere

Stratosphere

The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...

, generally reaching between 60000 to 120000 ft (18.3 to 36.6 km).

The most common type of high altitude balloons are weather balloon

Weather balloon

A weather or sounding balloon is a balloon which carries instruments aloft to send back information on atmospheric pressure, temperature, humidity and wind speed by means of a small, expendable measuring device called a radiosonde...

s. Other purposes use as a platform experiments in the upper atmosphere. Modern balloons generally contain electronic equipment such as radio transmitters, camera

Camera

A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...

s, or satellite navigation systems, such as GPS

Global Positioning System

The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...

 receivers.

These balloons are launched into what is termed "near space

Near space

Near space is the region of Earth's atmosphere that lies between 65,000 and 325,000–350,000 feet above sea level, encompassing the stratosphere, mesosphere, and thermosphere. A more understandable definition would be above where a commercial airliner flies but below the realm of an orbiting...

"—the area of Earth's atmosphere

Earth's atmosphere

The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 where there is very little air, but which is not high enough to be in the realm of satellite

Satellite

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

s.

A seasonal vortex in Antarctica allows balloons to be recovered very close to their launch site, making it a popular location for balloon-based research.

Due to the low cost of GPS and communications equipment, high altitude ballooning is an emerging hobby.
In France during 1783, the first public experiment with hydrogen-filled balloons involved Jacques Charles

Jacques Charles

Jacques Alexandre César Charles was a French inventor, scientist, mathematician, and balloonist.Charles and the Robert brothers launched the world's first hydrogen-filled balloon in August 1783, then in December 1783, Charles and his co-pilot Nicolas-Louis Robert ascended to a height of about...

, a French professor of Physics and the Robert brothers

Robert brothers

Les Frères Robert were two French brothers. Anne-Jean Robert , and Nicolas-Louis Robert , The brothers were the engineers who built the world's first hydrogen balloon for professor Jacques Charles; it flew from central Paris on...

, renowned constructors of physics instruments.
Charles provided large quantities of hydrogen, which had only been produced in small quantities previously, by mixing 540 kg of iron and 270 kg of sulfuric acid.