An unmanned aerial vehicle (UAV) named “Osaka University Sky-1” was developed as a field survey tool based on the concept that the researchers and the staff of the municipality who investigate volcanic field were able to operate it easily, safely, and at low cost. Sky-1 is a radio control airplane with wingspan of 90cm. It is controlled by three channel signal for motor, aileron, and elevator. Remote control distance is about 400m limited by human distance vision. The strong points of Sky-1 are as follows; custom-designed manufacturing of the black polypropylene foam for the airframe material, an electric ducted fan is employed to secure the safety, portable on one's back because of the new design of the airframe division, the payload that reaches 300g is secured, and achievement of the high flight performance against the strong wind around 10m/s. Field test for Sky-1 was performed at Kusatsu-Shirane volcano on 15 May 2008. During the field tests, Sky-1 obtained movies of the crater lake and data of H₂S gas concentration in the air. A training course in assembly and operation of Sky-1 was held at Osaka University and Kansai Mokei Airport (KMA) on 3-4 August 2008. By the field test and the training course, we proved that the development concept of Sky-1 had been achieved.

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Asama volcano erupted in the midnight of 2 February 2009 with the ejection of ash and ballistics. The ash was dispersed toward the southeast, and observed in areas up to the southeast of the Kanto plain in the next morning. The ash fall deposits at the southeastern foot of the volcano were surveyed in order to determine a dispersal axis and detail isopleth contours. Isopleth contours of the ash fall deposit stretch out long from northwest to southeast, and they are denser in the western side of the dispersal axis than in the east. In the summit crater area, the ash is not recognized in the northern side. These indicate that the distribution of ash fall was strongly affected by a wind from the northwest. Based on the isopleth contour map, the total weight of ash fall is estimated to be 27,000-31,000ton, using a log area (m²)-log weight (g/m²) plot. The weight is approximately three fifth of the eruption on 1 September 2004 and the same order as ones on 13 November 2004 and 26 April 1982. Major components of the ash sampled at about 8km southeast from the source are non-altered and altered lava, individual crystals, and ceramisite, but minor glass particles (less than 1wt%) are also included in fine grains. The glass particles can be identified as juveniles and divided into two groups based on their shape and glass composition. One is 'dense-type' with rhyolitic composition which is the same as juveniles in the 2004 eruption, and the other is 'vesicular-type' with dacitic composition which is different from any juveniles in the recent eruptions including the 1783 Tenmei eruption. These chemical characteristics of juvenile particles indicate that two-types of magma have recently coexisted beneath Asama volcano and were erupted on 2 February 2009.

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