Communication Duration and Missed Passes among Terminals and Satellites for Search and Rescue Services

Aims: NOAA’s (National Oceanic and Atmospheric Administration) - LEO environmental satellites provide continuous coverage of Earth, supplying high-resolution global meteorological, oceanic and space observation data. These satellites are part of the international Search and Rescue Satellite Aided Tracking (SARSAT) system. SARSAT is designed to provide distress alert and location data in order to assist on search and rescue operation. SARSAT system detects and locates distress beacons (406MHz) activated at distress location. System calculates the distress event location using Doppler processing techniques. Each satellite pass transmits information about distress location. Passes with too short communication duration, are considered as missed passes. Communication duration analysis, among SARSAT satellites and local user terminal (LUT) dedicated for search and rescue services are provided. LUT implementation process and the mask record are also given.
Study Design: Simulation
Place and Duration of Study: NOAA Satellite Operations Facility, Suitland, MD, USA, October, 28 - December 24, 2009.
Methodology: Communication analysis, are based on the hypothetical terminal assumed to be implemented in Kosovo (LUTKOS). Four hypothetical beacons indicating random distress locations are considered. Satellite orbital altitude of 860 km, orbital time of 102 minutes and inclination of 98.7 º. Communication duration is considered for period 1-30, October 2009. 57560 satellite passes were considered to conclude about missed passes.
Results: For Doppler processing at least four events are required. Duration of 250s is considered as the lower margin, providing at least four Doppler events. The highest events density was in between 300s to 700s, sufficient for distress location determination. Only 3% of total considered passes were below 250s. The ratio of missed passes over total passes for the whole ground segment results as 0.17%, or in average 0.021% per month.
Conclusion: Through LUTKOS simulation, it is confirmed communication reliability and proper functionality of LUTKOS with a single SARSAT satellite.