 This paper shows how fractionated space systems can be beneficial in some cases to reduce problem complexity. In particular, their physical architecture enables decoupling conflicting requirements and isolate requirement change propagation during system development. DOI: http://dx.doi.org/10.2514/6.2013-5416

1. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
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©2013 Stevens Institute of Technology
Date: 11th of September of 2013
By: Alejandro Salado and Roshanak Nilchiani
Fractionated Space Systems: Decoupling Conflicting
Requirements and Isolating Requirement Change
Propagation
AIAA SPACE 2013 Conference &Exposition
San Diego, CA (USA)

2. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2011 Stevens Institute of Technology10/16/20152
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.

3. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/20153
Source: wikipedia

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| ©2013 Stevens Institute of Technology10/16/20154
Value vs Compliance
Adaptability & Flexibility
Uncertain futures
Why fractionation?
What about adaptability during DEVELOPMENT?

5. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/20155
Conflicting Requirements
Requirements Change

6. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/20156
Stakeholder needs
N1. Continuous high-resolution real-time image information in VNIR/SWIR
spectral ranges (Optical).
N2. Continuous high-resolution real-time image information (RADAR).
System requirements
R1. 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).

7. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/20157
Platform
Optical
instrument
RADAR
Monolithic satellite
GroundControlSegment
Earthsurface
Image data
VNIR/SWIR radiation
X band transmission & reflection

8. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/20158
Platform
Optical
instrument
Fractionated satellite
GroundControlSegment
Earthsurface
Fraction 1
Image data
VNIR/SWIR radiation
X band transmission & reflection
RADAR
Fraction 3
Fraction 2
Life support
system
Life support
system

9. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2011 Stevens Institute of Technology9 10/16/2015
Social difficulty
Inherent
difficulty
Conflicting Requirements
𝐶𝑒𝑞 = 𝐷𝑖𝑛ℎ ∙ (1 + 𝐷𝑠𝑜𝑐)

10. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201510
System requirements
R1. VNIR/SWIR spectral range.
R2. X band (RADAR).
R3. Transmit image data.
R4. Continuously image.
R5. Synchronization.
Platform
Optical
instrument
RADAR
Monolithic satellite
GroundControlSegment
Earthsurface
Image data
VNIR/SWIR radiation
X band transmission & reflection
Platform
Optical
instrument
Fractionated satelliteGroundControlSegment
Earthsurface
Fraction 1
Image data
VNIR/SWIR radiation
X band transmission & reflection
RADAR
Fraction 3
Fraction 2
Life support
system
Life support
system

11. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
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Impacts of Fractionation wrt Conflicting Requirements
10/16/201511 ©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

12. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2011 Stevens Institute of Technology12 10/16/2015
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)

13. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201513
System requirements: R1, R2, R3, R4, and R5.
Implementation requirements
TP1. 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 TP9
R1 X X X
R2 X X
R3 X X X
R4 X X X
R5 X

14. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201514
Design
parameter
Monolithic
satellite
Fractionated Space System
Fraction 1 Fraction 2 Fraction 3
TP1 X X
TP2 X X
TP3 X X
TP4 X X X
TP5 X X
TP6 X X
TP7 X X
TP8 X X
TP9 X X

15. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201515
TP2
Point. Acc.
RADAR
TP4
Power
dissipation
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L4
L5
L6
L7
L8
L9 (-)
(+)
(-)
(-)
(-) (+)
(+)
(+)
Monolithic

16. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201516
TP2
Point. Acc.
RADAR
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L7
(-)
(+)
(-)
Fraction 3
Fraction 1
Fraction 2
TP2
Point. Acc.
RADAR
TP4
Power
dissipation
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L4
L5
L6
L7
L8
L9 (-)
(+)
(-)
(-)
(-) (+)
(+)
(+)
Monolithic

17. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201517
Higher RADAR performance
Higher IR performance
Lower processing capability
Requirements change

18. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201518
TP2
Point. Acc.
RADAR
TP4
Power
dissipation
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L4
L5
L6
L7
L8
L9 (-)
(+)
(-)
(-)
(-) (+)
(+)
(+)
Monolithic
Higher RADAR performance

19. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201519
TP2
Point. Acc.
RADAR
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L7
(-)
(+)
(-)
Fraction 3
Fraction 1
Fraction 2
TP2
Point. Acc.
RADAR
TP4
Power
dissipation
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L4
L5
L6
L7
L8
L9 (-)
(+)
(-)
(-)
(-) (+)
(+)
(+)
Monolithic
Higher RADAR performance

20. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201520
TP2
Point. Acc.
RADAR
TP4
Power
dissipation
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L4
L5
L6
L7
L8
L9 (-)
(+)
(-)
(-)
(-) (+)
(+)
(+)
Monolithic
Higher IR performance

21. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201521
TP2
Point. Acc.
RADAR
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L7
(-)
(+)
(-)
Fraction 3
Fraction 1
Fraction 2
TP2
Point. Acc.
RADAR
TP4
Power
dissipation
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L4
L5
L6
L7
L8
L9 (-)
(+)
(-)
(-)
(-) (+)
(+)
(+)
Monolithic
Higher IR performance

22. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201522
TP2
Point. Acc.
RADAR
TP4
Power
dissipation
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L4
L5
L6
L7
L8
L9 (-)
(+)
(-)
(-)
(-) (+)
(+)
(+)
Monolithic
Lower processing capability

23. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
| ©2013 Stevens Institute of Technology10/16/201523
TP2
Point. Acc.
RADAR
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L7
(-)
(+)
(-)
Fraction 3
Fraction 1
Fraction 2
TP2
Point. Acc.
RADAR
TP4
Power
dissipation
TP3
Point. Acc. TX
TP1
Point. Acc.
Optical
TP5
Data proc.
TP6
EIRP TX
TP7
Optical perf.
TP8
RADAR perf.
TP9
Image sync.
(+)
L1
L2
L3
L4
L5
L6
L7
L8
L9 (-)
(+)
(-)
(-)
(-) (+)
(+)
(+)
Monolithic
Lower processing capability

24. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
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Impacts of Fractionation wrt Requirements Change
10/16/201524 ©2011 Stevens Institute of Technology
Dependencies seem to decrease
Changes do NOT propagate outside fractions
Impact of development uncertainty decreases

25. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
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Wrap-up
10/16/201525 ©2011 Stevens Institute of Technology
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

26. ©2011 Stevens Institute of TechnologyP. 2/3 | 01/01/11
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©2013 Stevens Institute of Technology
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