Radio refractivity observations over the oceans using airborne microwave refractometer in tropics

The coastal waters of Indian sub -continent do not have reliable measurements of fine structure of radio refractivity especially in near real-time basis needed to mitigate the effects of anomalous propagation for the defence communications as well as for antisubmarine warfare. This programme was designed to document the radio refractive layer structure and variations of the marine layer in tropical waters of India. The paper describes the above observations taken using the airborne microwave refractometer developed by the author at National Physical Laboratory, New Delhi. Typical observations taken (for the first time in India) under normal and anomalous propagation conditions are presented and the results are compared with the special shipborne observations made under MONEX operation over the coastal waters of India.

Co-occurrence of beaked whale strandings and naval sonar in the Mariana Islands, Western Pacific

Mid-frequency active sonar (MFAS), used for antisubmarine warfare (ASW), has been associated with multiple beaked whale (BW) mass stranding events. Multinational naval ASW exercises have used MFAS offshore of the Mariana Archipelago semi-annually since 2006. We report BW and MFAS acoustic activity near the islands of Saipan and Tinian from March 2010 to November 2014. Signals from Cuvier's ( Ziphius cavirostris) and Blainville's beaked whales ( Mesoplodon densirostris ), and a third unidentified BW species, were detected throughout the recording period. Both recorders documented MFAS on 21 August 2011 before two Cuvier's beaked whales stranded on 22–23 August 2011. We compared the history of known naval operations and BW strandings from the Mariana Archipelago to consider potential threats to BW populations. Eight BW stranding events between June 2006 and January 2019 each included one to three animals. Half of these strandings occurred during or within 6 days after naval activities, and this co-occurrence is highly significant. We highlight strandings of individual BWs can be associated with ASW, and emphasize the value of ongoing passive acoustic monitoring, especially for beaked whales that are difficult to visually detect at sea. We strongly recommend more visual monitoring efforts, at sea and along coastlines, for stranded cetaceans before, during and after naval exercises.

Conceal or Reveal? Managing Clandestine Military Capabilities in Peacetime Competition

International political outcomes are deeply shaped by the balance of power, but some military capabilities rely on secrecy to be effective. These “clandestine capabilities” pose problems for converting military advantages into political gains. If clandestine capabilities are revealed, adversaries may be able to take steps that attenuate the advantages they are supposed to provide. On the other hand, if these capabilities are not revealed, then adversaries will be unaware of, and unimpressed by, the real balance of power. Most of the existing literature emphasizes that states have few incentives to signal their clandestine capabilities. This conclusion deserves qualification: the condition of long-term peacetime competition can make signaling a profitable decision. Within this context, two important variables help determine whether a state will signal or conceal its secret capabilities: the uniqueness of the capability and the anticipated responsiveness of the adversary. An extended case study of Cold War strategic antisubmarine warfare confirms these predictions.

Recent Progress of Marine Survey Unmanned Surface Vehicle in China

Based on the ongoing techniques among control theory, communication networks, and sensor design, unmanned aerial vehicles (UAVs), unmanned undersea vehicles (UUVs) and unmanned surface vehicles (USVs) are experiencing rapid development. Research on these unmanned systems and those intelligent sectors inside has absorbed interests and investments from not only military but also civil organizations. The well-applied fields include surveillance and reconnaissance, surface warfare, antisubmarine warfare, mine countermeasures, oceanic environment monitoring, search and rescue, hydrographic survey, and so on. Comparing with those studies on UAVs and UUVs, the one focusing on USVs was started later and has been developed quickly in the past 20 years. Since 2013, USV has advanced considerably in China, particularly in the marine survey field. Owing to its characteristics of light-weighting, intelligence, and unmanned operations, USV is attractive for shallow water, extreme environments, and marine accidents. This paper comprehensively summarizes the recent progress of the marine survey USV in China. The structure of the paper is divided into three parts. First, we briefly recall the developing history and introduce several excellent USVs of China in recent years. The marine survey USVs invested by the State Oceanic Administration (SOA) are then summarized in the next section, along with the details of hydrographic survey in the South China Sea, Antarctic marine survey, and oil spill emergency response. Finally, the paper points out current deficiencies and future directions of the potential technique.