Diwata-1, the Philippines’ first microsatellite for scientific earth observation, again captured high resolution images during the satellite’s test phase. Diwata-1’s High Precision Telescope (HPT), one of the four cameras onboard, obtained images with a ground resolution of 3m at nadir (or lowest point), the highest resolution attained so far by a microsatellite in the 50-kg class. This was announced recently by the Department of Science and Technology’s Advanced Science and Technology Institute (DOST-ASTI) and the University of the Philippines Diliman (UPD) which have been collaborating with Japan’s Hokkaido and Tohoku Universities for the operation of Diwata-1.
Below is a comparison of the images taken by Diwata-1’s HPT and by the American earth observation satellite Landsat 8’s Operational Land Imager (OLI). The ground resolution of Landsat 8’ OLI is 30m. Landsat 8 has a launch mass of about 2,600 kg.
The photo on the left shows the RGB composite (normal color) images taken by Diwata-1’s HPT at 9:07am Philippine Standard Time (PHT) on 19 May 2016 and the photo on the right shows Landsat 8’s OLI at 10:06 on 21 May 2016 in PHT. The images show portions of Dumingag, Zamboanga, a mountainous area in Mindanao. The OLI image with a 30m- ground resolution can identify only rough structures of the mountain but the detailed geographical features are unclear (Figure 1b).
On the other hand, the Diwata-1’s HPT image can clearly identify trees, rock surface, mountain paths, river and some man-made objects (Figure 1a). With a clearer photo from Diwata-1’s HPT camera, it will be easier to see which areas are affected by natural and even man-made disasters such as floods and fires. It may be recalled that one of the missions of the HPT is to determine the extent of damages from natural hazards such as typhoons.
Figure 1. Comparison of two RGB color images: (a) Diwata-1’s High Precision Telescope (HPT), (b) Landsat 8’s Operational Land Imager (OLI). The images captured a mountainous area in Mindanao, Philippines at 9:07 Phil. Standard Time on 19 May 2016 by HPT and 10:06 Phil. Standard Time on 21 May 2016 by OLI. The Diwata-1 HPT image can clearly identify trees, rock surface, mountain paths, river and some man-made objects.
The photos below show a comparison of “false color” images of an urban area in Florida, United States, which were taken by Diwata-1’s HPT at 7:48am Eastern Daylight Time (EDT) on 30 June 2016 and by Landsat 8’s OLI, respectively. “False color” images are created to emphasize the difference between vegetation and other objects using three different bands. The photo on the left (Figure 2a) is an image constructed by stitching six successive images captured by Diwata-1’s HPT camera with one-second intervals.
As a successful demonstration of the target pointing capability of Diwata-1, the microsatellite was able to capture six images of the focused area with field-of-view of 2 km x 1.5 km even though it was orbiting the Earth with a velocity of ~7.7 km/s at an altitude of ~400 km. It can be seen that buildings and roads are clearly distinguishable from the vegetation in the HPT images (Figure 2a), while such features are very unclear in the OLI image (Figure 2b).
The ability of Diwata-1’s HPT camera to take pictures of places even outside the country is a good indication that through Diwata-1, the Philippines will be able to share and exchange images among a group or constellation of microsatellites with neighboring countries for mutual benefit. This is one of the objectives of the country’s microsatellite development program. (S&T Media Service, DOST-PCIEERD)
Figure 2. Comparison of two false color images: (a) Diwata-1’s HPT, (b) Landsat 8’s OLI. The images captured an urban area of Florida, United States at 7:48 Eastern Daylight Time (EDT) on 30 June 2016 by HPT and 11:55 EDT on 9 July 2016 by OLI. Figure 2a is created by stitching six successive images captured by Diwata-1 through its target pointing capability. The red-colored area indicates vegetation. The buildings and roads can be clearly distinguished from the vegetation in the Diwata-1 HPT image.