Scientific Ballooning

JAXA announced first balloon launch campaign for 2017

Taiki, Hokkaido, Japan.- A few days ago in their Japanese page, the Institute of Space and Astronautical Science (ISAS) -part of the Japan Aerospace Exploration Agency (JAXA) since 2003- announced the realization of the first series of stratospheric balloon launches for 2017.

The campaign will be performed at the Taiki Aerospace Research Field (TARF), the dedicated launch facility that the agency have in Hokkaido Island in northern Japan, near the town of Taiki-Cho.

According to the brief press release, four missions will be carried out -as long as the weather cooperates- starting on June 5th.

In no particular order, these will be the experiments to be performed:

• Test flight of a VLBI (Very-long-baseline interferometry) platform. The VLBI is a type of astronomical interferometry used in radio astronomy on which a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth. The distance between the radio telescopes is then calculated using the time difference between the arrivals of the radio signal at different telescopes. This allows observations of an object that are made simultaneously by many radio telescopes to be combined, emulating a telescope with a size equal to the maximum separation between the telescopes.
  
  The platform being developed by JAXA / ISAS (image above right) aims to conduct a feasibility study and technological demonstration to determine the prospects for a future high-frequency VLBI project. The first balloon-borne VLBI gondola system has been designed to obtain VLBI fringes at 19–23 GHz toward ground-based radio telescopes of the Japanese VLBI Network with a very high signal-to-noise ratio.


• A balloon flight for the BIOPAUSE program developed by Chiba Institute of Technology. The objective of the project is to develop an overview of the stratospheric biosphere and the dynamics of biological flux in the stratosphere. This will be the 2nd. flight for the program. The first balloon-borne mission was carried out on June 8, 2016 also from TARF, using a newly developed descending inertial impactor.

• After following for many years the development of a pumping-shaped super-pressure balloon for long duration constant-level flight, recently ISAS R&D team found that the small local curvature in the gore to whistand a high differential pressure can also be obtained if the balloon is covered by a diamond-shaped net with a vertically elongated shape. Thus, as part of the developmental road for this design, a balloon flight will be performed during this season.
  
  Last test was performed in 2012 in a tandem configuration using a zero-pressure balloon with a volume of 15,000 m3 (image above right). During that flight the test model developed a hole, which was believed due to stress concentration. To overcome this, the balloon to be launched this year will have a longer size of the net diamond shape to equal the film length and thus to relax the stress concentration around the polar area.


• Finally another technological balloon flight will be made to evaluate the performance of a balloon manufactured using a new kind of load tapes developed by ISAS.

Peculiarities of a balloon program

The Japanese balloon program which was established in early 50's, has grown during more than six decades to become a very sophisticated and innovative program.

Founded on the premises of a ground-landing scheme in the 50's and 60's, the fast growth of the population and aerial traffic forced to evolve to the actual scheme of performing the balloon flights and payload recoveries from the sea.

Also they would became experts in maximize the use of physical space for balloon launches. In 1975 a dedicated balloon launch facility was built in a mountanious region near Sanriku. First using a vertical balloon launch method, soon the needs for bigger balloons and payloads forced to built a special platform which would allow a semi-dynamic launch system to be introduced. And that was another characteristic of the program: the development of new techniques and devices to perform this activity.

In 2008, the program moved to the Island of Hokkaido, to establish a new balloon facility in the Taiki Aerospace Research Field (TARF). Instead of changing their balloon operations philosophy to take advantage of the greater space available turning to a conventional dynamic launch technique, they decided to improve more the semi-dynamic launch system. Thus was born the "Sliding launch system" whose main advantage is that it allows to inflate a balloon inside the hangar to avoid sudden gusts of wind during that critical part of the launch process and when the right conditions are met, the inflated balloon can be pulled out and launched. By combining the ability to inflate the balloon inside the huge hangar and the vast launch pad around, this updated semi-dynamic launching method allows to launch balloons with a volume up to 2.000.000 m3. More details can be obtained in our detailed account on the subject.

A key detail for stratospheric ballooning in marine ambients is to minimize the environmental impact of such activities. Japanese law is extremely restrictive on this regard and so, JAXA adapted their operations to safety regulations.

An example of this can be found in a recent modification made to the materials used to manufacture a super-pressure balloon model known as "Tawara". Due to an additional requirement from the Japan Coast Guard to eliminate the possibility of balloons sinking at sea in order to minimize the risk of marine pollution it was necessary to use lighter materials so the envelope balloon originally made of multilayer "BH25" was replaced by a 20 microns thick polyethylene while the load ropes made of a special Kevlar composite were replaced by one made of ultra-high-molecular-weight polyethylene (UHMWP).

A detailed account of the procedures and systems developed to support balloon operations at sea was recently published in the Journal of Astronomical Instrumentation.

The article entitled "Marine Search-and-Recovery Operation of Scientific Balloons in Japan" is available for free and is detailed enough to appreciate the effort put by the agency on this issue.

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