Challenge the future Delft University of Technology Small Satellite Reliability Research on Spacecraft Under 50 Kg: Analysis on Component Level Jan Kolmas, Jian Guo, Eberhard Gill

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

3 Introduction Research Motivation Increasing interest on very small satellites >50% failure for satellites <50kg Very limited studies on statistical analysis TUD’s previous work on satellites <500kg

4 Introduction Research Innovations Looks specifically into satellites under 50 kg Specific Focuses more on failures on component level Focus Links statistical analysis with case studies Link

5 Small Satellites Anomalies Database 50 Empirical Data 141 anomalies / 117 satellites

6 Non-parametric Analysis Overall Reliability

7 Non-parametric Analysis Subsystem Contribution

8 Parametric Analysis Weibull Model Probability Density Function Weibull Parameters Shape parameter β: Scale parameter η [days]: 3062

9 Parametric Analysis Subsystem Level SubsystemScale ηShape β ADC C&DH EPS M&S TT&C SubsystemMinor failureMajor failureFatal failure Scale ηShape βScale ηShape βScale ηShape β ADC C&DH EPS M&S E TT&C SeverityFailure characteristics MinorProblem can be fixed from the ground or solved by redundancy. Possible degraded operation but no threat to mission objectives. MajorNon-repairable failure causing partial loss of functionality of the satellite or its subsystems on a permanent basis. FatalTotal loss of functionality of the satellite.

10 Parametric Analysis Component Level ComponentScale ηShape β Actuator Antenna1.26E Battery Deployment2.21E Internal Comm Memory OBC Payload Sensor Software Solar panel Thermal Transceiver Unknown

11 Parametric Analysis Component Level ComponentMinor failureMajor failureFatal failure Scale ηShape βScale ηShape βScale ηShape β Actuator Antenna7.99E E Battery Deployment--4.09E Internal Comm Memory1.06E OBC Payload Sensor E Software Solar panel Thermal Transceiver Unknown1.51E

12 Case Study QuakeSat 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

13 Case Study TUBSAT 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

14 Case Study Falconsat-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)

15 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

16 For further info, please contact: Dr Jian Guo