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DelftUniversity ofTechnology

Small Satellite Reliability Research on Spacecraft Under 50 Kg: Analysis on Component Level

Jan Kolmas, Jian Guo, Eberhard Gill

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Outline

• Introduction • Small Satellites Anomalies Database 50• Non-parametric Analysis• Parametric Analysis• Case Study• Conclusions

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IntroductionResearch Motivation

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IntroductionResearch Innovations

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Small Satellites Anomalies Database 50

Empirical Data

141 anomalies / 117 satellites

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Non-parametric AnalysisOverall Reliability

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Non-parametric AnalysisSubsystem Contribution

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Parametric AnalysisWeibull Model

Probability Density Function

Weibull ParametersShape parameter β: 0.3134 Scale parameter η [days]: 3062

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Parametric AnalysisSubsystem Level

Subsystem

Scale η Shape β

ADC 859 607 0.3013C&DH 29 447 0.3925EPS 13 684 0.3655M&S 74 895 526 0.2643TT&C 28 520 0.2513

Subsystem

Minor failure Major failure Fatal failureScale η Shape β Scale η Shape β Scale η Shape β

ADC 1 276 717 0.4202 146 935 036

0.2431 4 539 487 0.3849

C&DH 119 040 0.4025 907 034 0.3910 973 227 0.3961EPS 5 814 756 0.3851 286 086 0.3981 22 831 0.3820M&S 16 877

1920.3419 4.09E+9 0.2192 - -

TT&C 16 615 460

0.2609 6 394 683 0.2500 83 299 0.2841

Severity Failure characteristicsMinor Problem can be fixed from the ground or solved by redundancy. Possible degraded

operation but no threat to mission objectives.Major Non-repairable failure causing partial loss of functionality of the satellite or its

subsystems on a permanent basis.Fatal Total loss of functionality of the satellite.

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Parametric AnalysisComponent Level

Component Scale η Shape βActuator 3 152 966 0.3915Antenna 1.26E+11 0.1699Battery 25 985 0.4667Deployment 2.21E+11 0.2046Internal Comm

249 624 0.4994

Memory 39 048 197 0.2807OBC 177 911 0.6234Payload 9 805 344 0.3195Sensor 24 439 820 0.3128Software 4 346 081 671 0.2529Solar panel 1 881 645 0.3657Thermal 50 801 521 0.3197Transceiver 342 723 0.2748Unknown 29 547 0.2863

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Parametric AnalysisComponent Level

Component Minor failure Major failure Fatal failureScale η Shape β Scale η Shape β Scale η Shape β

Actuator 128 130 381

0.3754 6 544 262 0.4234 22 173 067

0.4321

Antenna 7.99E+13 0.1823 2.34E+12 0.1810 - -Battery 10 263

7110.4055 75 434 0.8142 31 215 0.4586

Deployment - - 4.09E+10 0.2191 - -Internal Comm

618 497 0.4397 28 508 1.6532 - -

Memory 1.06E+10 0.2365 36 423 015 0.4219 40 269 019

0.3460

OBC 28 175 1.2850 - - 5 259 361 0.4240Payload - - 18 818 907 0.3133 11 301

7210.4627

Sensor 1 976 214 0.4250 1.13E+15 0.1806 - -Software 961 211

4150.2726 - - - -

Solar panel 306 231 431

0.3505 12 956 779 0.3947 3 100 635 0.4027

Thermal 16 877 193

0.3419 - - - -

Transceiver 11 089 959

0.3053 60 503 142 0.2616 1 080 726 0.3143

Unknown 1.51E+9 0.2674 19 280 920 0.2716 23 639 0.3263

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Case StudyQuakeSat

• Minor failure

• CDHS – loss of a multiplexer and interrupted connections at the CPU

• Major failure

• EPS – loss of both batteries after 0.5 year

• Reason

• Temp caused electrolyte bake out as batteries sealed with non-space

packaging

• Lessons• GSE should not always replace batteries during testing• COTS components can be used only when fit to space conditions• Batteries should be on during thermal vacuum testing• Flight-like full testing shall be performed

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Case StudyTUBSAT C

• Fatal failure

• EPS – four NiH2 batteries failed after almost 10 years

• Reason

• A large number of charge-discharge cycles

• Lessons• An example of a good design and testing of satellite

• Normally space-rated or specifically designed batteries are better than COTS

• Full ground testing pays the money back

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Case StudyFalconsat-3

• Major failure• CDHS – flash memory used to boot CPU was corrupted (solved by using a

modified code using only the healthy part of the memory, but need to re-upload flight code every time the CPU was rebooted)

• ADCS – magnetic sensing and control malfunctioned due to interference (solved with a software modification)

• Reason• CDHS – ground testing found problem but no time to solve• ADCS – ground testing for sensor and actuator separately

• Lessons• Testing can easily discover problems, but still need resources to solve

problems• Integrated testing is necessary to find interference, especially for EMC issues• COTS components require additional testing for space qualification (e.g.

gravity boom)

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• Battery and transceiver are responsible for most fatal and major failures and deserve more attention

• Interference is also a main cause of failures

• COTS components could work well with extensive testing

• Root cause of failures is either the environment or design flaws

• Testing is the best way of preventing failures and should not be underestimated

• Next step is to make the SSAD50 public accessible after information sensitivity check

Conclusions

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For further info, please contact:

Dr Jian Guoj.guo@tudelft.nl