Descope of the ALIA mission

The present work reports on a feasibility study commissioned by the Chinese Academy of Sciences of China to explore various possible mission options to detect gravitational waves in space alternative to that of the eLISA/LISA mission concept. Based on the relative merits assigned to science and technological viability, a few representative mission options descoped from the ALIA mission are considered. A semi-analytic Monte Carlo simulation is carried out to understand the cosmic black hole merger histories starting from intermediate mass black holes at high redshift as well as the possible scientific merits of the mission options considered in probing the light seed black holes and their coevolution with galaxies in early Universe. The study indicates that, by choosing the armlength of the interferometer to be three million kilometers and shifting the sensitivity floor to around one-hundredth Hz, together with a very moderate improvement on the position noise budget, there are certain mission options capable of exploring light seed, intermediate mass black hole binaries at high redshift that are not readily accessible to eLISA/LISA, and yet the technological requirements seem to within reach in the next few decades for China

Research on submarine underwater acoustic effectiveness against airborne sonar

To get the best strategy of submarine underwater acoustic countermeasure against active/passive airborne sonar in normal conditions, this paper constructs the underwater acoustic environment model, sonar detection model and submarine underwater acoustic countermeasure model, proposes an airborne sonar information processing model considering acoustic contact, tracking, positioning and recognition processing, and simulates and analyzes the effectiveness of different submarine underwater acoustic countermeasure in the conditions of sonar contacting submarines. The results show that it is more effective to reduce the radiated noise than to increase the speed against the passive sonar. Submarines should adopt greater depth, minimum noise speed and shortest distance separation. If the submarine recognizes the position of the passive sonar buoy based on electronic reconnaissance or listening to the sound of sonobuoy impacting water, it can insert the bubble shell to worsen the common view condition of the passive buoy array, which avoids tracking and positioning and improves the effectiveness of countermeasures. It is the best strategy for the submarine to counter the active sonar, change the course, and release the wideband jammers and decoys at a high speed.The bubble shell can be released to worsen the sonar tracking, positioning and recognition environment while submarine fleeing, which providing conditions for the submarine to extend the distance from the sonar. The research in this paper can provide a simulation environment and decision-making reference for submarine underwater acoustic countermeasure active/passive airborne sonar