A mini-lidar to observe the activity of Martian atmosphere/dust was developed. Many researchers focused on the Martian atmosphere because of its unique and original activities. One of them is “Dust Devil”, which is a whirlwind on the ground. It is said that the dust devil will affect the atmospheric circulation and electric field of Mars. The 10cm-cube LED mini-lidar was designed to be onboard a Mars rover. A high power LED at 385nm wavelength was employed as a light source of the mini-lidar. LED was adopted as light source because of its toughness against circumference change and physical shock during launch. The pulsed power and the pulse repetition frequency of LED beam were designed as 0.75W (＝7.5 nJ / 10ns) and 500kHz, respectively. Lidar echoes were received by the specially designed Cassegrain telescope, which has the shorter telescope tube than the usual to meet the 10cm-cube size limit. The transmitting beam had a diameter of 30mm with a divergence of 67 mrad. The receiver’s field of view was set as 3 mrad. The ratio of the transmitted energy and received energy was estimated. The receiver always put its field within the transmitted beam even in rough treatment. The high-speed photon counter was also designed and developed to follow to the pulse repetition frequency of the LED light. The measurement range is longer than 30m. Its spatial resolution was improved as 0.15m (＝1ns) by this photon counter. The demonstrative experiment was conducted at the large wind tunnel facility of Japan Meteorological Agency. The measurement target was smoke of glycerin particles. The smoke was released in the wind tunnel with a wind speed of 0-5m/s. Smoke diffusion and convection due to the wind flow were evaluated by the LED mini-lidar. This result suggests that the developed lidar can measure the structure and the motion of dust devil of larger than 2m.
Synthetic aperture radar (SAR) plays a key role in monitoring water-damaged areas because of its flexible operability with a wide swath. To date, many studies have investigated floodwater detection by X-band SAR. However, uniform extraction of physical information is essential to realize seamless monitoring of a damaged area after a devastating disaster using a limited number of SAR satellites at various bands. In this paper, we examined and demonstrated the applicability of a spaceborne L-band SAR to flooded areas. A temporal change of Advanced Land Observation Satellite-2 (ALOS-2) images through flooding was carefully extracted by histogram analysis. A physical understanding of the experimental facts revealed that a temporal change of the strong backscattering cross sections in the histogram could be the most sensitive and reliable index. A floodwater-detection algorithm based on the criterion was applied to the ALOS-2 data sets for the devastating 2015 flood in Joso City, Japan, in day-by-day variation. The results were validated qualitatively with sufficient aerial photos. We found that the spaceborne L-band SAR has reasonable applicability to floodwater detection, not only in suburban but also in urban areas by means of the histogram analysis.
Alpine ecosystems are particularly vulnerable to the effects of climate change. Changes in temperature and snow conditions allow expansion of shrubs and changes in alpine vegetation structure globally. In Goshikigahara, in the snow-meadows of the Taisetsu Mountains, northern Japan, snowmelt time has advanced. Meanwhile, distribution of the dwarf bamboo (Sasa kurilensis) and alpine dwarf pine (Pinus pumila) has expanded, and the relative dominance of forbs (tall herbaceous species) has decreased due to changes in snowmelt and soil moisture conditions. Because S. kurilensis promotes soil drying by high transpiration, its expansion may further influence other alpine vegetation. Therefore, the ability to predict the distribution of future expansion is very useful for conservation measures. Manly’s selectivity index analyzed the preferences of S. kurilensis as it expands in terms of aspects such as slope and area solar radiation, calculated from DSM. In addition, potentially vulnerable places where S. kurilensis could easily expand were shown as a risk map. The risk map superimposes features of topographical preference from Manly’s selectively index, indicating a positive preference for easterly directions, gentle slopes, and substantial solar radiation. Furthermore, the risk map identified the most vulnerable places where Trollius riederianus, a tall herbaceous species, currently grows. The species has recently experienced a remarkable decrease. Expansion of dwarf bamboo and shrubs has been reported in alpine ecosystems all over Japan. This method is a useful tool, because it can consider the regionality of individual mountain areas, and formulate a conservation plan at key points where management costs are particularly limited.
Ground Based Synthetic Aperture Radar (GB-SAR) can monitor a wide range of displacement with high accuracy. In recent years, research has been progressed as a long-term monitoring method with steep terrain that is difficult to enter and wide-ranging landslide.
This time, the measurement characteristic of GB-SAR was verified as a monitoring method of cut slope surface for large scale cutting work which is the restoration work of the Kumamoto earthquake. A GB-SAR was installed at a position about 800m from the slope as the observation target, and measurement was carried out for 3 months. In order to verify the accuracy of GB-SAR, GNSS measurement were conducted, which is the conventional method at the same time, and confirmed that it has comparable accuracy by comparing the results. As a result, we were able to complete the construction while grasping the stability of the entire slope surface under severe weather conditions. In this paper, the outline of GB-SAR, observation method under construction and on the comparison of measurement result with GNSS are reported.