Israeli Universal Spacecraft Bus Characteristics and Design Trade-Offs June 2010

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

IMPS AOCS* system Sensors: Actuators: 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

Design Trade Offs AOCS system – Accuracy Propulsion system – Orbit Accuracy Data Storage – Volume Communication – Bandwidth Power System – Mission Requirements

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

Attitude Determination Fiber Optical Gyros (Shlomi) In development

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 Engineering – Heritage from other missions

Attitude Actuators Reaction Wheels Hydrazine Thrusters 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

Attitude Actuators (cont.) Magneto-torquers Maximum torque: 0.4 mNm Unit Price: Negligible Engineering – Heritage from other missions

Propulsion System Hydrazine Thrusters Hall Effect Thruster Both/None 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

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

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$ Both solution require a ground station Communication only during a pass

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$ Both solutions have near continuous communication.

Onboard Storage Onboard Recorder LEON-3 Avionics Computer 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.

Power System Battery: Deployable Solar Arrays 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 @ end of life

IMPS AOCS* system Sensors: Actuators: 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

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