There is always Space for Quality

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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/Huygens

• Mariner MKII spacecraft

Source NASA
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Cassini

• Mariner MKII spacecraft

Source NASA
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Cassini/Huygens Flight Model
Mariner 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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Titan

• Titans vital statistics
• Diameter 5150km Orbital/rotational period
  15.95 days
• Only planetary satellite with atmosphere
• Column mass 10 x value for Earth
• Atmospheric Composition
• Nitrogen and rich array of hydrocarbons and
  nitriles
• Hidden Surface
• Obscured by photochemical haze
• Indirect 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 plan

• VVEJGA

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 heating
• Too 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

• Sources
• Natural (Sun, Cosmic)
• RTGs
• RHUs
• Total dose to outside of shield
• 24.15 kRads
• Qual level ... double it

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Proven technology

• No Moving parts
• No lubricant
• Solid actuators
• No normal solder
• Crystallisation
• Outgassed plastics
• No 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 Saturn

• Saturn Orbit Insertion
• Turned spacecraft round
• Fired 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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How Cassini supports Huygens
Radio uplink during mission using HGA
Source NASA
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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 Test

• A test drop was done on Earth

Source ESA
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SSP

• Measure
• Temperature
• Speed of sound
• Acceleration
• Refractive properties
• Liquid Density
• Thermal Properties
• Electrical Properties
• Angle of tilt

Source PSSRI
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SSP

• Measure
• Temperature
• Speed of sound
• Acceleration
• Refractive properties
• Liquid Density
• Thermal Properties
• Electrical Properties
• Angle 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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Cassini

• Mariner MKII spacecraft

Source NASA
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Design Constraints

• Survive Launch
• Very high G shock
• Radiation proof (Rad hard)
• Solar radiation
• RHUs and RTGs
• Reliable over 7 years cruise
• Vacuum
• Zero gravity
• Reliable during 69 orbits
• Surface mission
• Atmospheric entry
• Cryogenic cooling (-200 degC)
• Dunking into Liquid Ethane/Methane mix
• Manufactured in 1994

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Qualification

• Launch
• Calculate the resonant frequencies
• Shake it on a test bed
• Radiation proof (Rad hard)
• Irradiate all components
• Reliable over 7 years cruise
• Bake out all volatiles
• Reliable during 69 orbits (!)
• Surface mission
• Cryogenic 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

• Exploration
• A lot of engineering
• A lot of planning
• A lot of people
• Science objectives, Risk driven development

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Source NASA
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Acknowledgements

• PSSRI of the Open University, UK
• Access to Huygens datastore
• Mark Leese, SSP programme manager
• NASA
• ESA
• Proxima Ltd.
• Ralph Lorenz, LPL, Univ. Arizona

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Resources

• European Space Agency
• http//sci.esa.int/Huygens
• National Aeronautics and Space Administration
• http//saturn.jpl.nasa.gov
• Planetary and Space Science Research Institute
• http//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