Obligation of cooperation in the field of navigation systems in international space law

Difficulty environmental conditions of space and the fact that space technologies require a very high level of technical ability and high cost are the main factors that make cooperation indispensable between states. In this context, the importance of cooperation within the scope of navigation systems, which provide great advantages to states, especially in the civil and military fields, has become indisputable today. Currently, there are four global systems: GPS (United States of America), GLONASS (Russia), GALILEO (European Union) and BEIDOU (China) and two regional systems: QZSS (Japan), NAVIC (India). In order to ensure the better functioning of these systems, states are cooperating at global, regional and bilateral levels. Since navigation systems are a space application, these activities must be carried out in accordance with space law. There are significant regulations regarding cooperation in space law, especially the UN Charter and the Outer Space Treaty. The regulations made in this field are not limited to this; important studies on the subject have been carried out by international organizations such as the International Telecommunication Union, the International Maritime Organization and the International Civil Aviation Organization. In the light of current regulations, there are different opinions in the doctrine regarding the issue of evaluating cooperation as an obligation in space law. In this study, the issue of whether the principle of cooperation, which has an important place in space law, constitutes an obligation in the context of navigation systems will be examined. This review will be based on international agreements, customary rules, court decisions, state practices and doctrine.