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There is always Space forQuality

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 MKIIspacecraft

Source: NASA

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Cassini/Huygens Flight Model

Mariner MKIIspacecraft

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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 atmosphereColumn mass ~ 10 x value for Earth

Atmospheric CompositionNitrogen and rich array of hydrocarbons and nitriles

Hidden Surface

Obscured 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 environmentDuration of operation

Nature of operation

Sound familiar?

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Design and Build

Look at key facts with tolerance

Temperature

VacuumRadiation

Time

ChemistryZero gravity

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The Mission

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Survival

Launch shaking (a lot)

Cruise radiation & vacuum

Cruise

thermal controlCruise 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 nomaintenance ...

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 skilledoperator 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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How Cassini supports Huygens

Radio 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 Test

A test drop was done on Earth

Source: ESA

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SSP

Measure:Temperature

Speed of sound

Acceleration

Refractive propertiesLiquid Density

Thermal Properties

Electrical Properties

Angle of tilt

Source: PSSRI

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SSP

Measure:Temperature

Speed of sound

Acceleration

Refractive propertiesLiquid 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 MKIIspacecraft

Source: NASA

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Design ConstraintsSurvive Launch

Very high G shock

Radiation proof (Rad hard)Solar radiation

RHUs and RTGs

Reliable over 7 years cruiseVacuum

Zero gravity

Reliable during 69 orbits

Surface missionAtmospheric entry

Cryogenic cooling (-200 degC)

Dunking into Liquid Ethane/Methane mix

Manufactured in 1994

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Qualification

LaunchCalculate 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

Th L di Si

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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 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

NASAESA

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

http://sci.esa.int/Huygenshttp://saturn.jpl.nasa.gov/http://pssri.open.ac.uk/missions/mis-casa.htmhttp://pssri.open.ac.uk/missions/mis-casa.htmhttp://pssri.open.ac.uk/missions/mis-casa.htmhttp://pssri.open.ac.uk/missions/mis-casa.htmhttp://saturn.jpl.nasa.gov/http://sci.esa.int/Huygens