Analysis of future LAAS ‘availability’ at Hyderabad station for Precision Approach of aircraft

Local Area Augmentation System (LAAS) is basically designed by USA, to support aircraft precision approach and landing in poor visibility conditions. LAAS is still in conceptual stage in India. As LAAS is meant for safety-of-life systems, it must meet stringent requirement of achieving adequate service availability. LAAS availability varies with time and number of satellites in GPS constellation. It is dictated by Vertical Protection Level (VPL), the error bound in vertical direction. This paper analyzes the variation of instantaneous availability with time by computing VPL of all possible subset geometries visible over a period of one day at 24 different epochs. Also, availability is computed by varying Vertical Alert Limit (VAL). The results obtained are encouraging and agreeing with the results published elsewhere.