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There is always Space for Quality

Dr Mark English

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Space and Software

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Cassini / Huygens – the plan

3.5 Billion kms

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Cassini/HuygensMariner MKII spacecraft

Source: NASA

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CassiniMariner MKII

spacecraft

Source: NASA

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Cassini/Huygens Flight ModelMariner MKII

spacecraft

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The Surface Science Package

Source: John Zarnecki, PSSRI, Open University, UK

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Cassini / Huygens – the plan

3.5 Billion kms

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TitanTitan’s vital statistics:

Diameter – 5150km; Orbital/rotational period – 15.95 days

Only planetary satellite with atmosphereColumn mass ~ 10 x value for Earth

Atmospheric CompositionNitrogen and rich array of hydrocarbons and nitriles

Hidden SurfaceObscured by photochemical hazeIndirect evidence for surface seas/lakes

Model for early Earth?

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Overall model of Titan

Source: R. Lorenz

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Considerations

Delivery mechanisms

Target environment

Transition environment

Duration of operation

Nature of operation

Sound familiar?

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Design and Build

Look at key facts – with tolerance

Temperature

Vacuum

Radiation

Time

Chemistry

Zero gravity

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The Mission

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Survival

Launch – shaking (a lot)

Cruise – radiation & vacuum

Cruise – thermal control

Cruise – temperature cycling

Trajectory and SOI – accuracy

Entry & Surface mission - cold

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Launch

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Getting through Launch

Make it ... then shake it

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Cruise

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The flight planVVEJGA

Source: NASA

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The flight plan

Source: BBC

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Temperature Control

Gets cold out there

No solar panels for electric heatingToo far, sun too weak

Too much dust

Use RTGs for power

Use RHUs for on-platform heat

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Keeping warm

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Keeping warm

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Radiation

SourcesNatural (Sun, Cosmic)

RTGs

RHUs

Total dose to outside of shield24.15 kRads

Qual level ... double it

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Proven technology

No Moving partsNo lubricant

Solid actuators

No normal solderCrystallisation

Outgassed plasticsNo nasty condensation

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Proven technology

Radhard ICs

Care with Digital and analogue lines

Waiver and qualification for E2PROMS

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You can never go back Dorothy

Once it is launched there is no maintenance ...

It has to work first time, the first time...

How do you get to this level of quality?

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Systems engineering

Developed through Minuteman,

Used on Apollo

Working to interfaces, and specifications

Big design, modular breakdown

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Modules

See this in Software ...

Code libraries (NAG)

Component based development

Requires very strict library management and definition

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Libraries

Numerical Algorithms Group

http://www.nag.co.uk/

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Libraries

Not enough to know what things do

How were they tested?

What tolerances were on that data?

What operational environment?

What Units?

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Failures

Mars has swallowed 12 missions

Mars observer 1993

Mars global surveyor 1996

Mars climate orbiter 1999

Ariane 5 1996

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Caveat

Any well meaning highly skilled operator can try and do something and screw it up like any of us

You get this in all industries.

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Cassini / Huygens – the plan

3.5 Billion kms

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SOI

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Arriving at SaturnSaturn Orbit Insertion

Turned spacecraft roundFired motors for 96 Minutes

Source: Huygens Mission Operations Plan

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Arriving at Saturn

Source: Huygens Mission Operations Plan

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Ejection

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Source: NASA

How Cassini supports HuygensRadio uplink during mission using HGA

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Atmospheric Entry and Surface Mission

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Any other risks?

Hm......

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Atmospheric Models

Yelle et al. 1997

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Huygens descent timelines

Source: John Zarnecki, PSSRI, Open University, UK / ESA

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Parachute TestA test drop was done on Earth

Source: ESA

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SSP

Measure:TemperatureSpeed of soundAccelerationRefractive propertiesLiquid DensityThermal PropertiesElectrical PropertiesAngle of tilt

Source: PSSRI

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SSP

Measure:TemperatureSpeed of soundAccelerationRefractive propertiesLiquid DensityThermal PropertiesElectrical PropertiesAngle of tilt

Source: PSSRI

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Shake and Bake (!)

Source: John Zarnecki, PSSRI, Open University, UK

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Prepare the spacecraft

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CassiniMariner MKII

spacecraft

Source: NASA

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Design ConstraintsSurvive Launch

Very high G shockRadiation proof (Rad hard)

Solar radiationRHUs and RTGs

Reliable over 7 years cruiseVacuumZero gravity

Reliable during 69 orbitsSurface mission

Atmospheric entryCryogenic cooling (-200 degC)Dunking into Liquid Ethane/Methane mix

Manufactured in 1994

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QualificationLaunch

Calculate the resonant frequencies

Shake it on a test bed

Radiation proof (Rad hard)Irradiate all components

Reliable over 7 years cruiseBake out all volatiles

Reliable during 69 orbits (!)

Surface missionCryogenic cooling (-200 degC)

Dunking into Liquid Ethane/Methane mix

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Project Management

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Documentation

ISO 9000, BS5750

Fully documented

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Documentation

ISO 9000, BS5750

Each operation mapped out

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The results

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The Landing Site

Source: ESA

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Descent to Titan - Surface mode

Dull thud

Major Instruments:SSP

DISR

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Surface View

Titan surface

Credits: ESA/NASA/JPL/University of Arizona

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DISR – Panorama

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Summary

ExplorationA lot of engineeringA lot of planningA lot of people

Science objectives, Risk driven development

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Source: NASA

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Acknowledgements

PSSRI of the Open University, UKAccess to Huygens datastore

Mark Leese, SSP programme manager

NASA

ESA

Proxima Ltd.

Ralph Lorenz, LPL, Univ. Arizona

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Resources

European Space Agencyhttp://sci.esa.int/Huygens

National Aeronautics and Space Administrationhttp://saturn.jpl.nasa.gov

Planetary and Space Science Research Institutehttp://pssri.open.ac.uk/missions/mis-casa.htm

Zen, and the art of motorcycle maintenance, Robert Pirsig

The New Solar System, J. Kelly Beatty and Andrew Chaikin (eds), Sky Publications.

Software Engineering Standards, Mazza et. al., Prentice Hall