Fractionated Space Systems: Decoupling Conflicting Requirements and Isolating Requirement Change Propagation

©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11

| ©2013 Stevens Institute of Technology

Date: 11th of September of 2013By: Alejandro Salado and Roshanak Nilchiani

Fractionated Space Systems: Decoupling Conflicting Requirements and Isolating Requirement Change

Propagation

AIAA SPACE 2013 Conference &ExpositionSan Diego, CA (USA)


| ©2011 Stevens Institute of Technology05/03/20232

Disclaimer:

The views and opinions expressed during this presentation are those of the authors and do not necessarily reflect the official position of the Stevens Institute of Technology or any of its schools.



Source: wikipedia



Value vs Compliance

Adaptability & Flexibility

Uncertain futures

Why fractionation?

What about adaptability during DEVELOPMENT?



Conflicting Requirements

Requirements Change



Stakeholder needsN1. Continuous high-resolution real-time image information in VNIR/SWIR spectral ranges (Optical).N2. Continuous high-resolution real-time image information (RADAR).

System requirementsR1. The system shall image Earth surface in VNIR/SWIR spectral range with performance A better than X units.R2. The system shall image Earth surface in X band (RADAR) with performance B better than Y units.R3. The system shall transmit image data in less than Z s after image acquisition.R4. The system shall continuously image Earth surface.R5. The system shall image Earth surface in both spectral ranges at accuracy of 0.1 s (synchronization).



Platform

Optical instrument

RADAR

Monolithic satelliteGrou

nd C

ontr

ol S

egm

ent

Eart

h su

rfac

e

Image dataVNIR/SWIR radiationX band transmission & reflection



Platform

Optical instrument

Fractionated satellite

Grou

nd C

ontr

ol S

egm

ent

Eart

h su

rfac

e

Fraction 1


RADAR

Fraction 3

Fraction 2

Life support system

Life support system


| ©2011 Stevens Institute of Technology9 05/03/2023

Social difficultyInherent difficulty

Conflicting Requirements



System requirementsR1. VNIR/SWIR spectral range.R2. X band (RADAR).R3. Transmit image data.R4. Continuously image.R5. Synchronization.

Platform

Optical instrument

RADAR

Monolithic satelliteGrou

nd C

ontr

ol S

egm

ent

Eart

h su

rfac

e


Platform

Optical instrument

Fractionated satelliteGr

ound

Con

trol

Seg

men

t

Eart

h su

rfac

e

Fraction 1


RADAR

Fraction 3

Fraction 2

Life support system

Life support system


|

Impacts of Fractionation wrt Conflicting Requirements

05/03/202311 ©2011 Stevens Institute of Technology

Decrease social difficulty / Increase inherent difficulty

A decision to go for Fractionation is not trivial

Need rigorous determination of difficulty


| ©2011 Stevens Institute of Technology12 05/03/2023

Connectivity measured on

requirements inside this box

Level 0

Level 1

Level 2

Req. 1

Req. 2

Req. 3

Req. 4

Req. 5

Req. 6

Req. 7

Req. 8

Req. 9

Req. 10

22

3

0

4

4

2 4

3

4 (eq. 7)



System requirements: R1, R2, R3, R4, and R5.

Implementation requirementsTP1. Pointing accuracy optical sensor.TP2. Pointing accuracy microwave sensor (RADAR).TP3. Pointing accuracy transmitter antenna (data).TP4. Power dissipation.TP5. Data processing capability.TP6. EIRP data transmitter.TP7. Optical performance.TP8. Radar performance.TP9. Image synchronization.

TP1 TP2 TP3 TP4 TP5 TP6 TP7 TP8 TP9R1 X X X R2 X X R3 X X X R4 X X X R5 X



Design parameter

Monolithic satellite

Fractionated Space SystemFraction 1 Fraction 2 Fraction 3

TP1 X X TP2 X XTP3 X X TP4 X X XTP5 X X TP6 X X TP7 X X TP8 X XTP9 X X



TP2Point. Acc.

RADAR

TP4Power

dissipation

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L4

L5 L6 L7

L8

L9 (-)

(+)

(-)(-)

(-) (+)

(+)

(+)

Monolithic



TP2Point. Acc.

RADAR

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L7

(-)

(+)

(-)

Fraction 3

Fraction 1Fraction 2

TP2Point. Acc.

RADAR

TP4Power

dissipation

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L4

L5 L6 L7

L8

L9 (-)

(+)

(-)

(-)(-) (+)

(+)

(+)

Monolithic



Higher RADAR performance

Higher IR performance

Lower processing capability

Requirements change



TP2Point. Acc.

RADAR

TP4Power

dissipation

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L4

L5 L6 L7

L8

L9 (-)

(+)

(-)(-)

(-) (+)

(+)

(+)

Monolithic




TP2Point. Acc.

RADAR

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L7

(-)

(+)

(-)

Fraction 3


TP2Point. Acc.

RADAR

TP4Power

dissipation

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L4

L5 L6 L7

L8

L9 (-)

(+)

(-)(-)

(-) (+)

(+)

(+)

Monolithic




TP2Point. Acc.

RADAR

TP4Power

dissipation

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L4

L5 L6 L7

L8

L9 (-)

(+)

(-)(-)

(-) (+)

(+)

(+)

Monolithic




TP2Point. Acc.

RADAR

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L7

(-)

(+)

(-)

Fraction 3


TP2Point. Acc.

RADAR

TP4Power

dissipation

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L4

L5 L6 L7

L8

L9 (-)

(+)

(-)(-)

(-) (+)

(+)

(+)

Monolithic




TP2Point. Acc.

RADAR

TP4Power

dissipation

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L4

L5 L6 L7

L8

L9 (-)

(+)

(-)(-)

(-) (+)

(+)

(+)

Monolithic




TP2Point. Acc.

RADAR

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L7

(-)

(+)

(-)

Fraction 3


TP2Point. Acc.

RADAR

TP4Power

dissipation

TP3Point. Acc. TX

TP1Point. Acc.

OpticalTP5

Data proc.

TP6EIRP TX

TP7Optical perf.

TP8RADAR perf.

TP9Image sync.

(+)L1

L2

L3

L4

L5 L6 L7

L8

L9 (-)

(+)

(-)(-)

(-) (+)

(+)

(+)

Monolithic



|

Impacts of Fractionation wrt Requirements Change


Dependencies seem to decrease

Changes do NOT propagate outside fractions

Impact of development uncertainty decreases


|

Wrap-up


Fractionation could be a solution to deal with conflicting objectives

Fractionation could reduce risk in programs with high volatile requirements

Adaptability during development should also be pursued


| ©2013 Stevens Institute of Technology

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Engineering

Fractionated Space Systems: Decoupling Conflicting Requirements and Isolating Requirement Change Propagation