Unlike a satellite launch vehicle, a sounding rocket performs an observation mission during its flight in space before impact. It usually comprises one or two stages. When the experiment is completed, the rocket dives into the sea along with its observation instruments.
The observation instruments are usually fixed to the rocket's nose fairing and covered by a nosecone like a pointed hat for protection from aerodynamic heating. When the rocket reaches a given altitude, timer-fixed functions start to open the nosecone, extend antennas, sometimes release test samples for observation, and conduct other tasks to prepare for the planned observation. The observation starts before the rocket reaches its maximum altitude and ends before it splashes down in the sea.
While balloons cannot float above approx. 50 km, many satellites can fly over 250 km in altitude. Thus, only sounding rockets are capable of directly observing space between these two altitudes, which is called the mesosphere, thermosphere or ionosphere.
Observations are selected from proposals by researchers at universities and institutes across the country.
ISAS sounding rockets have been the pillar of Japan's space science, contributing to astrophysical observation, upper atmospheric studies, space plasma physics, etc. The ISAS engineering team is developing new flying-vehicle systems, including propulsion systems, attitude control systems, and re-entry, recovery and navigation technology.
Sounding rockets are also used in microgravity experiments for material and life sciences. Offering quick response to planning, implementation and results of experiments, sounding rockets also show excellent flexibility in function and performance confirmation tests of the new observation instruments and technical elements that are expected to be loaded on future satellites and space explorers.
ISAS currently uses three types of sounding rockets: S-310, S-520 and SS-520. One or two are launched annually from the Uchinoura Space Center located at the eastern tip of the Ohsumi Peninsula, Kagoshima Prefecture.
The S-310 was also used for observation in Antarctic exploration by the National Institute of Polar Research. The S-310 and S-520 were launched for direct observation of aurora in the Andoya Rocket Range, Norway.
The SS-520 was launched from Spitsbergen Island, Norway, to study a magnetospheric region called the “cusp”.
History of Sounding rockets