What is near space?
Near space is the region of Earth's atmosphere that lies between 20 to 100 km above sea level,encompassing the stratosphere, mesosphere, and thermosphere. A better definition would be above where a commercial airliner flies but below the realm of an orbiting satellite.
Near space is also the realm of an activity known as Amateur Radio High Altitude (ARHAB) Ballooning. Recently, due to falling costs of GPS technology, Amateur Radio High Altitude Ballooning has become a more common hobby with many amateurs launching balloons in many different locations around the world.
The terms "near space" and "upper atmosphere" are generally considered synonymous. However, some sources distinguish between the two. Where such a distinction is made, only the layers closest to the Karman line are called near space, while only the remaining layers between the lower atmosphere and near space are called the upper atmosphere.