Israeli Universal Spacecraft Bus Characteristics and Design Trade-Offs

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Israeli Universal Spacecraft Bus Characteristics
and Design Trade-Offs

• June 2010

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The IMPS Bus

• Used by TECSAR Venµs satellites.
• Onboard processor Intel 486 / LEON-3
• Power Supply 800W
• Bus Power Consumption 250W
• Battery Capacity 30/45 Ah
• Bus Dry Mass 190 Kg
• Payload Mass 150 Kg

IMPS IAI Multi Purpose Satellite
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IMPS AOCS system

• Sensors
• 2 sun-sensors.
• 2 magneto-meters.
• MEMS coarse rate gyro.
• GPS Receiver.
• 2 Star Trackers.
• Actuators
• 4 reaction wheels (1 spare).
• 2 X 3-axis magento-torquers
• 2 X 4 X 5N Hydrazine Thrusters
• Propulsion System for orbit control (Four
  Alternatives)
• 2 Hydrazine Thrusters (25N)
• Hall Effect Thruster (0.1N)
• Both
• None

AOCS Attitude Orbit Control System
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Design Trade Offs

• AOCS system Accuracy
• Propulsion system Orbit Accuracy
• Data Storage Volume
• Communication Bandwidth
• Power System Mission Requirements

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Attitude Determination

• Star Tracker
• Accuracy 10-3 deg
• Unit Price 0.5M
• One is required, two for redundancy
• Engineering Heritage from many missions
• Earth Horizon Sensor (2 axis only)
• Accuracy 5x10-2 deg
• Unit Price 300K
• Engineering Significant Effort

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Attitude Determination

• Fiber Optical Gyros (Shlomi)
• In development

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Attitude Determination (cont.)

• Sun Sensors Magnetometers
• Accuracy 3x10-1 deg
• Unit Price negligible
• Engineering Minor Adaptations in Control Law
• MEMS Rate Gyro
• Accuracy 1 deg/sec
• Unit Price negligible
• Engineering Heritage from other missions

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Attitude Actuators

• Reaction Wheels
• Maximum Torque 4 Nm
• Unit Price 300K
• Engineering Heritage from many missions
• Hydrazine Thrusters
• Maximum Torque 5 Nm
• Unit Price Combined with Propulsion system
• Engineering Heritage from other missions

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Attitude Actuators (cont.)

• Magneto-torquers
• Maximum torque 0.4 mNm
• Unit Price Negligible
• Engineering Heritage from other missions

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Propulsion System

• Hydrazine Thrusters
• Thrust 1N/5N/25N
• 7 or 30 kg hydrazine tank
• Unit Price 1.6M
• Engineering Heritage from previous missions
• Hall Effect Thruster
• Thrust 0.1 N
• 5 kg Xe tank (equivalent to 30 kg hydrazine)
• Unit Price 5M
• Engineering In development for other mission
• Both/None

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Orbit Determination

• GPS receiver
• Accuracy better than 15m
• Unit Cost 500K (fully redundant)
• Engineering Heritage from previous missions

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Communication System

• Hi-Speed X-band downlink
• Bandwidth up to 750 Mbps
• Unit Price 300K per 150 Mbps unit
• Engineering Heritage from other missions
• Low Speed S-band transceiver
• Bandwidth up 2.5Kbps, down 12.5 Kbps
• Unit Price 400K
• Engineering Heritage from other missions
• Both solution require a ground station
• Communication only during a pass

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Communication System (cont.)

• Satellite Phone
• Bandwidth 50Kbps
• Unit cost TBD
• Engineering Integrating new system
• TDRSS
• Bandwidth up to 10 Mbits/Sec
• Unit cost 0.5M
• Engineering Integrating new system
• Both solutions have near continuous communication.

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Onboard Storage

• Onboard Recorder
• Capacity Redundant 120Gbits upgradeable to
  480Gbits
• Unit Cost 350K
• Engineering Heritage from previous missions.
• LEON-3 Avionics Computer
• Capacity 2GB
• Unit Cost Built in
• Engineering New unit in an advanced development
  stage.

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Power System

• Battery
• Capacity 30Ah / 45Ah
• Unit Cost 150K / 250K
• Engineering Heritage from previous missions
• Deployable Solar Arrays
• Triple Junction GaAs cells 25 efficiency
• Power generation 800 W _at_ end of life

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IMPS AOCS system

• Sensors
• 2 sun-sensors.
• 2 magneto-meters.
• MEMS coarse rate gyro.
• GPS Receiver.
• 2 Star Trackers.
• Actuators
• 4 reaction wheels (1 spare).
• 2 X 3-axis magento-torquers
• 2 X 4 X 5N Hydrazine Thrusters
• Propulsion System for orbit control (Four
  Alternatives)
• 2 Hydrazine Thrusters (25N)
• Hall Effect Thruster (0.1N)
• Ground Station
• Engineering

AOCS Attitude Orbit Control System
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Recommended Configuration

• Sensors
• Sun Sensors, Magnetometer, and MEMS rate gyro,
  GPS receiver
• Star Trackers only if the mission requires
  accurate attitude determination.
• Actuators
• Reaction Wheels, Hydrazine Thrusters, and
  magneto-torquers.
• Propulsion System
• Hydrazine Thrusters or none