Option 1: Akash - Akash is indeed an Air Defence Missile system. It is a medium-range surface-to-air missile system developed by the Defence Research and Development Organisation (DRDO) in India.
Option 2: Trishul - Trishul is also an Air Defence Missile system. It is a short-range, quick reaction surface-to-air missile system designed and developed by DRDO.
Option 3: Tatra - Tatra is not an Air Defence Missile system. Tatra is a Czech truck manufacturer. It is known for producing heavy-duty trucks that are used by various armed forces for transportation purposes, but it is not directly related to air defense missiles.
Option 4: Astra - Astra is a state-of-the-art Air Defence Missile system. It is an indigenously developed beyond-visual-range air-to-air missile (BVRAAM) by DRDO. It is designed to engage and destroy enemy aircraft at various ranges and altitudes.
Therefore, the correct answer is option 3: Tatra, as it is not an Air Defence Missile system.