, 0 Polar SAR Data for Operational Sea Ice Mapping
213
routinely. Obviously, this data-download technique was not a procedure extensible to
space-borne radar, so the development of high speed data downlinks became essential
for space-based radar remote sensing of ice in the operational environment.
Canada deployed radar data downlinks in conjunction with its SLAR in 1983, and the
Soviet Union soon followed suit. Receivers and film printers on board icebreakers
allowed navigators to view the radar image in real time as the aircraft flew along its projected track. By the end of the decade, SLAR and SAR imagery were routinely downlinked to computer display terminals on Canadian icebreakers, and an elaborate network of ground stations with satellite communications had been established. This Ice
Reconnaissance Data Network (Falkingham 1991) transmitted SLAR and SAR imagery
from ice reconnaissance aircraft flying over the Canadian Arctic or east coast to the Ice
Center in Ottawa. Analysts then transferred the essential ice information onto ice analysis charts for broadcast within a few hours.
Operational use of satellite SAR presented yet another challenge: how to get satellite
data processed into image form quickly enough for use by decisionmakers. When
Canada's SAR aircraft was introduced in 1989, the SAR processor was just fast enough
to keep up with the 600 km/h speed of the aircraft, which allowed image data to be
broadcast directly from the aircraft. Processing SAR data in realtime at the 20000+ km/h
speed of satellites was beyond onboard capabilities, so it was necessary to do the processing on the ground sometime after it was collected by the spacecraft. For example,
ERS-1 transmitted "raw" data to a worldwide network of ground receiving and processing stations.
Fast-delivery data processors were installed in the ground stations at Fairbanks
(Alaska), Gatineau (Canada) and Troms0 (Norway) specifically to provide imagery for
the demanding operational ice reconnaissance requirements. Troms0 has been the
most successful at meeting the time constraints, often providing ERS-1 images to icebreakers in the Baltic Sea within 2 h. TromS0 provides a similar capability for
RADARSAT data.
The RADARSAT ground processing system in Canada was specifically designed to
provide fast turnaround of SAR data for operational ice monitoring. A maximum delay
of 6 h was specified for receipt of imagery anywhere within the Canadian economic
zone, a vast area spanning 100 degrees of longitude and 50 degrees of latitude. Two
ground stations in eastern and western Canada feed raw data to a single processor at
Gatineau via high-speed satellite communications links. Another high-speed link
delivers images from the processor to the Canadian Ice Center in Ottawa (Fig. 5). Commercial marine communications satellites deliver images and ice analyses from the Ice
Center to ships anywhere in the world. At the time of this writing, images are usually
received at the Ice Center within 1-2 h and are made available to the ship communication system within another hour, exceeding the specified time requirements. Depending on the size of the image and the resolution required, delivery to the ship can be
accomplished within minutes.
The United States has developed a similar capability for its RADARSAT receiving station at the Alaska SAR Facility in Fairbanks. After data have been fast-turnaroundprocessed to image form, they are transmitted via a dedicated communication link to
the US National Ice Center in Washington, DC for analysis of ice conditions. In the true
spirit of international cooperation, Ottawa and Washington regularly exchange
RADARSAT data across a dedicated communication link (Fig. 6).
213
routinely. Obviously, this data-download technique was not a procedure extensible to
space-borne radar, so the development of high speed data downlinks became essential
for space-based radar remote sensing of ice in the operational environment.
Canada deployed radar data downlinks in conjunction with its SLAR in 1983, and the
Soviet Union soon followed suit. Receivers and film printers on board icebreakers
allowed navigators to view the radar image in real time as the aircraft flew along its projected track. By the end of the decade, SLAR and SAR imagery were routinely downlinked to computer display terminals on Canadian icebreakers, and an elaborate network of ground stations with satellite communications had been established. This Ice
Reconnaissance Data Network (Falkingham 1991) transmitted SLAR and SAR imagery
from ice reconnaissance aircraft flying over the Canadian Arctic or east coast to the Ice
Center in Ottawa. Analysts then transferred the essential ice information onto ice analysis charts for broadcast within a few hours.
Operational use of satellite SAR presented yet another challenge: how to get satellite
data processed into image form quickly enough for use by decisionmakers. When
Canada's SAR aircraft was introduced in 1989, the SAR processor was just fast enough
to keep up with the 600 km/h speed of the aircraft, which allowed image data to be
broadcast directly from the aircraft. Processing SAR data in realtime at the 20000+ km/h
speed of satellites was beyond onboard capabilities, so it was necessary to do the processing on the ground sometime after it was collected by the spacecraft. For example,
ERS-1 transmitted "raw" data to a worldwide network of ground receiving and processing stations.
Fast-delivery data processors were installed in the ground stations at Fairbanks
(Alaska), Gatineau (Canada) and Troms0 (Norway) specifically to provide imagery for
the demanding operational ice reconnaissance requirements. Troms0 has been the
most successful at meeting the time constraints, often providing ERS-1 images to icebreakers in the Baltic Sea within 2 h. TromS0 provides a similar capability for
RADARSAT data.
The RADARSAT ground processing system in Canada was specifically designed to
provide fast turnaround of SAR data for operational ice monitoring. A maximum delay
of 6 h was specified for receipt of imagery anywhere within the Canadian economic
zone, a vast area spanning 100 degrees of longitude and 50 degrees of latitude. Two
ground stations in eastern and western Canada feed raw data to a single processor at
Gatineau via high-speed satellite communications links. Another high-speed link
delivers images from the processor to the Canadian Ice Center in Ottawa (Fig. 5). Commercial marine communications satellites deliver images and ice analyses from the Ice
Center to ships anywhere in the world. At the time of this writing, images are usually
received at the Ice Center within 1-2 h and are made available to the ship communication system within another hour, exceeding the specified time requirements. Depending on the size of the image and the resolution required, delivery to the ship can be
accomplished within minutes.
The United States has developed a similar capability for its RADARSAT receiving station at the Alaska SAR Facility in Fairbanks. After data have been fast-turnaroundprocessed to image form, they are transmitted via a dedicated communication link to
the US National Ice Center in Washington, DC for analysis of ice conditions. In the true
spirit of international cooperation, Ottawa and Washington regularly exchange
RADARSAT data across a dedicated communication link (Fig. 6).