Transcript Israeli Universal Bus Characteristics and Design Trade-Offs

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
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IMPS AOCS* system
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
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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
10-3 deg
 Unit Price: 0.5M$
 One is required, two for redundancy
 Engineering – Heritage from many missions
 Accuracy:

Earth Horizon Sensor (2 axis only)
5x10-2 deg
 Unit Price: 300K$
 Engineering – Significant Effort
 Accuracy:
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Attitude Determination (cont.)

Sun Sensors & Magnetometers
3x10-1 deg
 Unit Price: negligible
 Engineering – Minor Adaptations in Control
Law
 Accuracy:

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




Low Speed S-band transceiver





Bandwidth: up to 750 Mbps
Unit Price: 300K$ per 150 Mbps unit
Engineering – Heritage from other missions
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 @ 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
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