Description

The following points list the main areas where the Constellation system will be different from RADARSAT-2:

  • The Constellation is conceived as a government-owned system, providing a large amount of data to government departments for operational monitoring over wide areas.

  • The ground segment is driven by requirements for fast data delivery of images acquired over Canada, and for fast tasking over international areas.

  • The majority of acquisitions in Canada concerns large areas to be covered on seasonal basis and therefore most of the acquisitions can be pre-planned.

  • Conflicts between main users can be resolved in advance.

Imaging requirements are tailored to cover the areas identified by the government users, including both Canadian imaging and international imaging for Canadian users. Allocations are made for extra imaging capacity that may be used to fulfill international commitments.

Main Operational Modes

The system is designed as a medium resolution mission primarily dedicated to regular monitoring of broad geographic areas. This provides a 'big picture' overview of Canada's land mass and proximate water areas. Combined with higher resolution imagery from foreign missions going forward in the same time-frame, the data are expected to dramatically enhance Canada's ability to manage resources and the environment and improve security by providing an operational surveillance system. The system also includes high resolution modes at 3m and 5m, primarily designed for disaster management.

Operational Modes
Beam Modes Approximate
Incidence
Angle
Nominal
Swath Width
Gnd Rg x Az
Approximate
Resolution
Number of
Looks Rg x
Az
Low Resolution 19º - 54º 500 km 100 x 100 m 8 x 1
Medium Resolution (Maritime) 19º - 58º 350 km 50 x 50 m 4 x 1
Medium Resolution (Land) 20º - 47º 30 km 16 x 16 m 1 x 4
Medium Resolution (Land) 21º - 47º 125 km 30 x 30 m 2 x 2
High Resolution 19º - 54º 30 km 5 x 5 m 1 x 1
Very High Resolution 18º - 54º 20 km 3 x 3 m 1 x 1
Ice/Oil Low Noise 19º - 58º 350 km 100 x 100 m 4 x 2
25 m ship mode 19º - 58º 350 km variable variable x 1

The RADARSAT Constellation payload is being designed to provide a beam mode similar to the RADARSAT-1 ScanSAR narrow, which is referred to in the following as the medium resolution mode. The medium resolution mode, which could be used for wide area coverage, was used to size the antenna dimension and power. Other beam modes (stripmap, high-resolution and low-resolution) are designed to be compatible with the system capabilities determined by the medium resolution mode. Starting from the medium resolution mode, the system can provide the following modes:

  • High-Resolution Mode, which is simply the natural stripmap mode provided by the SAR. It has a single-look resolution approximately equal to half the antenna length.

  • Very-High Resolution Mode, which can be either a stripmap mode or a spotlight mode.

  • Low-Resolution Mode, which is simply a variant of the medium resolution mode where resolution is reduced in favour of a larger swath.

Beam Modes

Modes faisceaux de la Constellation RADARSAT
Radarsat Constellation
Imaging Modes

The three-satellite configuration will provide complete coverage of Canada's land and waters offering an average daily revisit at 50m resolution, as well as a significant coverage of international areas for Canadian and international users. It will also offer average daily access to 95% of the world. The satellites will be interoperable, enabling tasking from one satellite to the next and will be equally spaced in a 600 km low earth orbit. The constellation has a flexible design, allowing up to six satellites to fly in the same plane.

Data Availability

One of the most important project objectives is to increase data availability to the main operational users of SAR data in Canada. The system will be available when the first satellite will be on orbit then the availability of SAR data will increase as more satellites are launched. Requirements are set to ensure continuity with RADARSAT-2. The project will provide continuity for RADARSAT-1 and RADARSAT-2 users, but the system is not designed to be identical. The mission focuses on core applications and products and the provision of best value for money for the government of Canada. Some advanced features like GMTI mode present on RADARSAT-2 are not included. The system performance requirements (NESZ essentially) and data quality (radiometric accuracy) specified for RADARSAT-1 and 2 are maintained. Some aspects of the data quality that were not originally specified for RADARSAT (like ScanSAR beam discontinuities) are now specified based on experience gained through the RADARSAT mission.

For the main system users, the operations should be simplified. Most of the acquisitions in Canada should be pre-planned and data made available to the users in near real-time. In some cases users will process the data; in other cases, specific products will be made available to user organizations. For non-operational users, the interaction with the system for data ordering and distribution should be similar to what is being implemented for RADARSAT-2. It will be possible to order data from an archive, but long-term archiving of the data will be dealt with separately by the CSA's Framework Data Policy and the practices of user organizations and CCRS.

Coverage, Access and Imaging Time

The design should be such that sufficient volume of data can be collected to enable both Canadian and international applications. Their core needs at the highest level can be summarised as:

  • Daily coverage of Canada's inland, territorial and adjacent waters to support maritime surveillance, including ice monitoring, marine wind monitoring, oil pollution monitoring and ship detection;

  • Ability to image any disaster location in the world within 24 hours to establish the state of critical infrastructure; and

  • Ability to monitor all of Canada for disaster mitigation on a regular basis (monthly to twice-weekly) to assess risks and identify damage prone areas; and,

  • Regular coverage of Canada's land mass and inland waters, up to several times weekly in critical periods, for resource and ecosystem monitoring.

The RADARSAT Constellation shall provide 12 minutes imaging time on average per orbit per satellite, with peak imaging of 20 minutes per orbit per satellite. A significant increase in imaging time for the constellation is possible if more satellites are launched. Analysis is ongoing to determine international imaging requirements and their impact on overall imaging requirements.

RADARSAT Constellation

Revisit and Re-look

The RADARSAT Constellation shall provide a 4-day exact revisit, allowing coherent change detection using an INSAR mode. The RADARSAT Constellation shall provide an average daily global re-look capability in both medium and high resolution modes. Most of the applications considered required at least daily re-look and an exact revisit once to twice weekly (interferometric change detection applications). Very frequent re-look capability is critical to certain disaster management applications.

Timeliness and Data Latency

The timelines and data latency requirement is highly variable according to the application area. For many ecosystem monitoring applications, data delivered several days or in some cases several weeks later may be sufficient. However, maritime surveillance and disaster monitoring have much more demanding timeliness requirements. For maritime surveillance applications in Canadian and adjacent waters, RADARSAT Constellation shall provide 10 minute data latency from acquisition to delivery of data. For ice monitoring and global and Canadian disaster management applications, RADARSAT Constellation shall provide 2 hour data latency from acquisition to data delivery. For ecosystem monitoring applications, RADARSAT Constellation shall provide 24 hour data latency from acquisition to data delivery.

The following table summarizes geographic coverage, revisit, data latency and other system's main technical characteristics for each application area.

Timeliness and Data Latency

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