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 degUnit Price: 0.5M$One is required, two for redundancyEngineering – Heritage from many missions

Earth Horizon Sensor (2 axis only)Accuracy: 5x10-2 degUnit Price: 300K$Engineering – Significant Effort

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Attitude Determination (cont.) Sun Sensors & Magnetometers

Accuracy: 3x10-1 degUnit Price: negligibleEngineering – Minor Adaptations in Control

Law MEMS Rate Gyro

Accuracy: 1 deg/secUnit Price: negligibleEngineering – Heritage from other missions

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Attitude Actuators Reaction Wheels

Maximum Torque: 4 NmUnit Price: 300K$Engineering – Heritage from many missions

Hydrazine ThrustersMaximum Torque: ~5 NmUnit Price: Combined with Propulsion systemEngineering – Heritage from other missions

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Attitude Actuators (cont.) Magneto-torquers

Maximum torque: 0.4 mNmUnit Price: NegligibleEngineering – 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 15mUnit 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 / 45AhUnit Cost: 150K$ / 250K$Engineering: Heritage from previous missions

Deployable Solar ArraysTriple Junction GaAs cells ~25% efficiencyPower generation: 800 W @ 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