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

2. 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

3. 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

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

5. 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

6. Attitude Determination
Fiber Optical Gyros (Shlomi)
In development

7. 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

8. 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

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

10. 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

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

12. 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

13. 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.

14. 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.

15. 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 end of life

16. 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

17. 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