<P> The mesosphere lies above altitude records for aircraft, while only the lowest few kilometers are accessible to balloons, for which the altitude record is 53.0 km . Meanwhile, the mesosphere is below the minimum altitude for orbital spacecraft due to high atmospheric drag . It has only been accessed through the use of sounding rockets, which are only capable of taking mesospheric measurements for a few minutes per mission . As a result, it is the least - understood part of the atmosphere, resulting in the humorous moniker ignorosphere . The presence of red sprites and blue jets (electrical discharges or lightning within the lower mesosphere), noctilucent clouds, and density shears within this poorly understood layer are of current scientific interest . </P> <P> Near space was first explored in the 1930s . The early flights flew to the edge of space without computers, spacesuits, and with only crude life support systems . Notable people who flew in near space were Jean Piccard and his wife Jeannette, on the nearcraft The Century of Progress . Later exploration was mainly carried out by unmanned craft, although there have been skydiving attempts made from high - altitude balloons . </P> <P> The area is of interest for military surveillance purposes, scientific study, as well as to commercial interests for communications, and tourism . Craft that fly in near space include high - altitude balloons, non-rigid airships, rockoons, sounding rockets, and the Lockheed U-2 aircraft . The region has been of interest to space travel . Early attempts used a craft known as a rockoon to reach extreme altitudes and orbit . These are still used today for sounding rockets . </P> <P> High - altitude platform stations have been proposed for applications such as communications relays . There has been a resurgence of interest in near space to launch manned spacecraft by man . Groups like ARCASPACE, as well as the da Vinci Project are planning on launching manned suborbital space vehicles from high - altitude balloons . JP Aerospace has a proposal for a spaceport in near space, as part of their Airship to Orbit program . </P>

Which hydrogen lines can be studied from earth's surface