Robert H. Thomas

Observing The Polar Regions From Space

Polar ice has a significant impact on world climate and on ocean characteristics. Transfer of heat from tropical oceans to the polar regions is regulated by sea ice, which locally insulates the ocean from the cold atmosphere. The continental ice sheets of Greenland and Antarctica represent vast reservoirs of fresh water which can significantly impact sea level if the ice sheets are changing in size. Satellite remote sensing gives information on many aspects of the ice cover: sea-ice extent and physical characteristics; detailed images of ice floes and open-water leads within the ice pack; sea-ice movement; zones of summer melting and snow-accumulation rates on the continental ice sheets; accurate estimates of ice-surface elevation, and detection of zones on the ice sheet that are either thickening or thinning; accurate, all-weather mapping of ice coastlines and large crevasses, and estimates of ice discharge rates from the ice sheets.

Satellite Observations of Sea Ice

Synoptic observations of the polar regions can be achieved only from space using sensors that collect data at regular intervals, night and day and in all weather. NASA has developed techniques for acquiring frequent global coverage of the polar ice cover, and for spotlighting selected regions to reveal detailed features within the ice pack.

Extending the reach of cabled ocean observatories

Industry publications indicate that most cabled ocean observatory systems are based on the same general architecture: primary and secondary infrastructure and nodes, junction-boxes, low voltage nodes and then extension cables to instrumentation and experiments. Non-repeatered datacom technology often limits such transmission to less than 100km reach without optical-electrical-optical regeneration. Undersea telecom repeaters (optical amplifiers) can be used to extend the reach of these systems by thousands of kilometers, opening up new and significant areas to observatory exploration. Undersea telecom amplifier designs have been tailored for use with existing low-cost transceiver technology already in use in these observatories. Another technological advancement, dual conductor cable (DCC), is available for use in fiber optic scientific networks and is currently in-service. It provides two independent electrical powering paths which, in combination with compatible repeaters, branching units, and joints, may be used to power branches and undersea devices from diverse power sources. One conductor may be used to power repeaters, while a second conductor can provide observatory power. In addition to powering nodes from shore, DCC can be used for multi-conductor subsea connectivity between observatory primary and secondary nodes. With industry standard armor packages available, DCC can be deployed and plow-buried between observatory elements in hazardous subsea environments. This cable can be terminated with wet-mate connectors to facilitate subsea connection by remotely operated vehicles. This paper provides an introduction to data transmission and powering architectures associated with cabled ocean observatories, and describes the elements needed to extend observatory exploration reach with undersea repeaters. Subsea connectivity beyond primary nodes using flying lead deployment pallets and direct connection devices is also discussed.