Mission

RADARSAT-2 is Canada's next-generation commercial SAR satellite, the follow-on to RADARSAT-1. The new satellite was launched in December, 2007 on a Soyuz vehicle from Russia's Baikonur Cosmodrome in Kazakhstan. RADARSAT-2 has been designed with significant and powerful technical advancements which include 3m high-resolution imaging, flexibility in selection of polarization, left and right-looking imaging options, superior data storage and more precise measurements of spacecraft position and attitude.

RADARSAT-2 is a unique collaboration between government - the Canadian Space Agency, and industry - MacDonald, Dettwiler and Associates Ltd. (MDA). MDA is responsible for the operations of the satellite and the ground segment. The CSA, who contributed funds for the construction and launch of the satellite, will recover its financial investment in the program through the supply of RADARSAT-2 data to Canadian government agencies during the lifetime of the mission.

The SAR Payload

The SAR Payload includes the SAR antenna and associated sensor electronics required for imaging. EMS Canada (now MDA Montreal) was the SAR Payload subcontractor.

Operating in C-band, the RADARSAT-2 SAR Payload ensures continuity of all existing RADARSAT-1 modes, and offers an extensive range of additional features ranging from improvement in resolution to full flexibility in the selection of polarization options.

The enhanced capabilities are provided by a significant improvement in instrument design, employing a state-of-the-art phased array antenna composed of an array of hundreds of miniature transmit-receive modules. Fully computer-controlled, the antenna is capable of being steered electronically over the full range of the swath and can switch between operating modes virtually instantaneously.

The Bus

The Bus module contains all the systems and interfaces which are necessary to operate and maintain the satellite and support the SAR Payload. These include systems that support attitude measurement and control, telemetry and command, data storage and retrieval, power generation and storage, and thermal control. Alenia Spazio of Rome, Italy was the Bus sub-contractor.

The bus performs the following functions:

• Power Generation and Storage: The Electrical Power subsystem is responsible for generating, storing, and regulating electrical power for the satellite. Power is generated from the two solar array wings, each consisting of three panels. The solar panels are designed to generate 2400 Watts at End-Of-Life. Power is stored on-board in a Nickel-Hydrogen (NiH2) battery.
• Attitude Determination and Control: RADARSAT-2 is a 3-axis stabilised, zero-momentum satellite. Various sensors and actuators determine and maintain the spacecraft's orientation and ensure that the spacecraft meets its performance requirements for precisely pointing the SAR antenna in either left- or right-looking mode and for controlling the transition between these two modes.
  
  Attitude Determination and Control System Characteristics »
  

Subsystem	Components	Accuracy
Attitude Determination	Sun Sensors 3-axis Magnetometers 3-axis Gyros Star Trackers	± 0.02° (3σ in each axis)
Attitude Control	Reaction Wheel Assembly Magnetotorquers	± 0.05° (3σ in each axis)




• Orbit Determination and Control: The primary method for orbit determination is through the use of onboard Global Positioning System (GPS) receivers, and by Precision Orbit Determination software which will be implemented by MDA. Orbit control is achieved by the Propulsion System.
  
  Orbit Position Knowledge »
  

Fast-Delivery Position Knowledge	± 60 metres (3σ in each axis)
Post-Processed Position Knowledge	± 15 metres (3σ in each axis)




• Telemetry, Tracking and Command (TT&C): The TT&C subsystem is the communications interface between the spacecraft and the Ground Segment. Commands, such as when to conduct imaging operations, are up-linked to the spacecraft. Telemetry data - information on the status or health of various sub-systems on the spacecraft - are recorded throughout each orbit, and down-linked to the ground. Two omni-directional S-Band antennae, positioned on opposite corners of the spacecraft, provide ground-facing communications in any spacecraft orientation. Up-linked command data will be encrypted.
  
  TT&C Communications Characteristics »
  

	Frequency	Data Rate
Up-Link (command)	2053.458 MHz	4 kbps
Down-Link (telemetry)	2230.00 MHz	16, 128, 512 kbps




• Payload Data Handling and Transmission (PDHT): The acquired SAR image data, along with ancillary (e.g., GPS) data, is stored onboard and transmitted to the ground via the X-Band communications down-link. Image data will be encrypted using the Data Encryption Standard (DES).
  
  Payload Data Transmission Characteristics »
  

	Frequency	Data Rate
Channel 1	8.105 GHz (X-Band)	105 Mbps
Channel 2	8.230 GHz (X-Band)	105 Mbps




• Propulsion Sub-system: The spacecraft has six 1-Newton thrusters which are used initially to manoeuvre the spacecraft into its operational orbit (correcting any launch dispersions), then to maintain the spacecraft's orbit to keep the ground track within a strict tolerance range (better than ± 5km, with a goal of ± 1km) during its operational lifetime. RADARSAT-2 will use mono-propellant hydrazine fuel.
• Thermal Subsystem: In its sun-synchronous orbit, one side of RADARSAT-2 is usually exposed to continuous sunlight. Between the left- and right-looking imaging modes, different areas of the SAR antenna are exposed to varying intensities of sunlight. Thermal control is required to reflect or dissipate the heat of the sun on the spacecraft body and SAR antenna, as well as to dissipate the heat which is generated internally by the satellite's electronics.

The Extendible Support Structure (ESS).

The ESS is the mechanical interface between the Bus and Antenna structure used to deploy the radar antenna and maintain it in a stable, precise position for accurate imaging. AEC-ABLE of Santa Barbara, California was the ESS subcontractor.