In recent years, Japan has been working hard to transform from an economic power to a political and military power. The aerospace system integrates modern high technology and plays an increasingly important role in gaining battlefield information advantages, supporting military operations, and improving the combat effectiveness of weapons and equipment. It is an essential factor for Japan to become a military power. Therefore, Japan has been actively developing its aerospace system, improving its aerospace technology capabilities, and laying the foundation for it to become a military power.
Characteristics of the development of Japan’s aerospace reconnaissance capabilities
Actively developing civilian remote sensing satellites
Over the years, Japan has invested a large amount of resources in actively developing civilian satellite projects. In May 1987, the Japan Space Development Agency (NASDA) proposed a long-term plan for the development of space-based systems. The plan sets out the ambitious goal of comprehensively building Japan’s space system at a cost of 9 trillion yen. By the end of 1996, Japan had launched Earth observation satellites such as the "Ocean Observation Satellite-1A" (MOS-1A) and the "Advanced Earth Observation Satellite-1" (ADEOS-1). In December 2002, the "Advanced Earth Observation Satellite-2" (ADEOS-2) with a full color resolution of 2.5 meters was launched. However, the satellite lost contact with the ground less than a year after entering orbit. Since then, in order to provide the country with much-needed space intelligence capabilities, Japan launched the Advanced Land Observation Satellite-1 (ALOS-1) with a panchromatic resolution of 2.5 meters and a multispectral resolution of 10 meters in January 2006. Although it encountered many problems during the development process, Japan has always relied on its own strength to develop satellite observation systems and develop optical and all-day and all-weather radar imaging technologies, laying a solid foundation for the independent development of military reconnaissance satellites in the future.
Japan’s civilian remote sensing satellites are all dual-use systems, which can be gradually transformed into military systems according to the needs of military strategy. Some of the remote sensors on its military reconnaissance satellites are developed based on civilian optical remote sensors and synthetic aperture radar (SAR) technology. For example, the remote sensors of some military optical reconnaissance satellites are derived from the multi-spectral electronic automatic scanning radiometers carried by the "Ocean Observation Satellite-1" series of satellites, and through the optical remote sensors of the "Japan Earth Resources Satellite" and the "Advanced Earth Observation" Improvements in satellite's advanced visible and near-infrared radiometers are further improving the resolution of military remote sensors. Military radar reconnaissance satellites are based on the synthetic aperture radar on the "Japanese Earth Resources Satellite" and the phased array L-band synthetic aperture radar technology on the "Advanced Land Observation Satellite", and developed a resolution of 1 to 3 meters. The synthetic aperture radar uses a high-gain active phased array antenna.
Obtaining high-resolution remote sensing satellite images through international cooperation
From the early 1970s to the mid-to-late 1990s, the Japanese Defense Agency has been using the imported image intelligence processing system to receive U.S. Images taken by LANDSAT and the French SPOT satellite. In addition, Japan also receives remote sensing data from the "IKONOS" and "Earth Remote Sensing Observation Satellite-A" (EROS-A) through the American Space Imaging Corporation and the Israeli Imaging Satellite International Corporation respectively. The IKONOS satellite can collect data in 4 multispectral bands. Its calibrated ground resolution is 4 meters, and there is also a panchromatic band with a resolution of 1 meter. The panchromatic band and multispectral band can be combined to generate "Panchromatic enhanced" multispectral image with an effective resolution of 1 meter. The nominal resolution of the EROS-A satellite is 1.8 meters, and the resolution can reach 1 meter and 0.6 meters when using "oversampling" and "supersampling" technologies. Japan's Hiroshima Institute of Technology has built a receiving center for receiving EROS-A satellite data.
Independently develop reconnaissance satellites and seek to have independent space-based reconnaissance means
As early as the late 1970s, the Japanese Defense Agency began to seek to establish independent satellite reconnaissance means, but was subject to domestic Due to legal and US restrictions, the plan was put on hold for a long time. Entering the 1990s, Japan accelerated the pace of building its space-based reconnaissance and intelligence capabilities. Japan's 1997 "Defense White Paper" proposed that satellite systems used for communications, navigation, and reconnaissance should be developed as the focus of "special attention."
In May 2008, the Japanese Parliament passed the "Basic Space Law", allowing Japan to develop and utilize space for military purposes "for defense purposes."
This bill completely breaks Japan's nearly 40-year legal restrictions in the space field, paving the way for Japan's military use of space, the development of higher-resolution reconnaissance satellites, and even the development of ballistic missile early warning satellites.
In January 2009, the Japanese Ministry of Defense (on January 9, 2007, the Defense Agency was upgraded to the Ministry of Defense) issued the first basic military aerospace guidelines for the development and utilization of outer space, deciding on the 2020 ~The main trend of Japan's aerospace policy in 2015 has determined the development of more high-resolution imaging satellites to supplement the existing four "Intelligence Collection Satellite" (IGS) constellations; the development of missile early warning satellites; the development of a series of satellites such as signal intelligence satellites goal.
Analysis of Japan’s aerospace reconnaissance capabilities
General survey and detailed survey capabilities
At present, Japan’s satellite reconnaissance methods are limited to imaging reconnaissance. Imaging satellites can be divided into census type and detailed survey type according to their tasks. A study by the United Nations Satellite Reconnaissance Agency shows that a ground resolution of 3 to 5 meters is required to perform a census mission, a ground resolution of 0.2 to 2 meters is required to perform a detailed survey mission, and a detailed description of a target requires a resolution of 0.15 to 0.3 meters. Rate.
In terms of the ground resolution that Japan’s on-orbit imaging satellite can achieve when taking panchromatic images, the resolution of the IGS-4A optical satellite launched on September 23, 2011 is 0.6 meters, which is the same as that of the United States. The 0.66-meter level of the KH-7 optical imaging satellite in the 1960s and 1970s was comparable, but it did not reach the 0.15-meter level of the KH-11 satellite. The IGS-R3 radar satellite launched on December 12, 2011 uses a third-generation synthetic aperture radar with a resolution of approximately 1 meter. It can be seen that the capabilities of Japan's reconnaissance satellites have developed rapidly. They now fully possess the survey capabilities required for space-based reconnaissance, and have a certain degree of detailed survey capabilities, which is at a high level worldwide.
All-day and all-weather reconnaissance capabilities
The timeliness of reconnaissance is mainly reflected in the need to achieve all-day and all-weather reconnaissance; real-time or near-real-time transmission of information; rapid detection of reconnaissance targets Three aspects revisited. All-day and all-weather space-based reconnaissance is mainly achieved by multiple means of spaceborne remote sensors. Currently, the more commonly used equipment of reconnaissance satellites include: visible light cameras, infrared cameras, multi-spectral cameras and synthetic aperture radars, among which synthetic aperture radars It can overcome the influence of adverse photographic conditions and achieve all-day and all-weather reconnaissance.
Although Japan’s independent development of space-based reconnaissance equipment started late, it has a high technical starting point and strong financial support. In just a few years, it has optical and radar imaging satellites with relatively advanced performance. , with all-day and all-weather imaging reconnaissance capabilities. From the beginning of the design, Japan has loaded two types of remote sensors on its optical imaging satellite at the same time to complement each other's advantages and save launch and development funds. For example, the IGS-AN satellite is equipped with a three-line array visible light remote sensor (PRISM) and a multispectral remote sensor (AVNIR2). In addition, the IGS-B satellite carries an L-band synthetic aperture radar (some scholars believe that it uses C-band or X-band).
What is particularly noteworthy is that according to Japan’s reconnaissance satellite plan, it usually uses an optical imaging satellite and a synthetic aperture radar satellite as a launch unit to work together. It can be seen that Japan's unique combination of launch methods allows it to efficiently obtain all-day and all-weather satellite reconnaissance capabilities through a single launch, and has thus become the second country after the United States to have both optical and radar capabilities. A powerhouse of space-based reconnaissance with imaging satellites.