Interrogation, Recording, and Location System

The interrogation, recording, and location system (IRLS) is a satellite technological experiment designed to demonstrate the feasibility of determining position location and collecting scientific data from remote instrumented platforms deployed on a global scale on, or above, the surface of the earth. The system utilizes a range-range location technique which yields solutions as the intersection of ranging spheres; up to 28 channels of sensory data are collected with each platform interrogation. In operation, discrete addresses of platforms expected in radioview are programmed on an orbit-by-orbit basis from a central ground acquisition and command station; data retrieval is accomplished one orbit later. The experiment commenced in April, 1969 (Nimbus III launch) and has since achieved its major objectives in accordance with a preestablished operational plan wherein the satellite, ground computer, and platforms functioned as an entity during orbit-to-orbit operation to provide locations and data collection from balloonborne, shipborne, ice-island, buoy, and land-deployed platforms, with a total complement numbering 10. In addition, the experiment has afforded an opportunity to the potential user community to participate in and contribute to the system technological evaluation while also performing specific scientific experiments. This participation has consisted in the installation and operation of platforms in the field. The results of the individual platform data collection and tracking experiments together with an analysis of overall system performance in terms of data quality and location accuracy achieved are described. In addition, future experiments planned for Nimbus D are discussed.