Transcript Slide 1
There is always Space for Quality Dr Mark English 1 Space and Software 2 Cassini / Huygens – the plan 3.5 Billion kms 3 Cassini/Huygens Mariner MKII spacecraft 4 Source: NASA Cassini Mariner MKII spacecraft 5 Source: NASA Cassini/Huygens Flight Model Mariner MKII spacecraft 6 The Surface Science Package 7 Source: John Zarnecki, PSSRI, Open University, UK Cassini / Huygens – the plan 3.5 Billion kms 8 Titan Titan’s 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? 9 Overall model of Titan Source: R. Lorenz 10 Considerations Delivery mechanisms Target environment Transition environment Duration of operation Nature of operation Sound familiar? 11 Design and Build Look at key facts – with tolerance Temperature Vacuum Radiation Time Chemistry Zero gravity 12 The Mission 13 Survival Launch – shaking (a lot) Cruise – radiation & vacuum Cruise – thermal control Cruise – temperature cycling Trajectory and SOI – accuracy Entry & Surface mission - cold 14 Launch 15 Getting through Launch Make it ... then shake it 16 Cruise 17 The flight plan VVEJGA 18 Source: NASA The flight plan 19 Source: BBC 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 20 Keeping warm 21 Keeping warm 22 Radiation Sources Natural (Sun, Cosmic) RTGs RHUs Total dose to outside of shield 24.15 kRads Qual level ... double it 23 Proven technology No Moving parts No lubricant Solid actuators No normal solder Crystallisation Outgassed plastics No nasty condensation 24 Proven technology Radhard ICs Care with Digital and analogue lines Waiver and qualification for E2PROMS 25 26 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? 27 Systems engineering Developed through Minuteman, Used on Apollo Working to interfaces, and specifications Big design, modular breakdown 28 Modules See this in Software ... Code libraries (NAG) Component based development Requires very strict library management and definition 29 Libraries Numerical Algorithms Group http://www.nag.co.uk/ 30 Libraries Not enough to know what things do How were they tested? What tolerances were on that data? What operational environment? What Units? 31 Failures Mars has swallowed 12 missions Mars observer 1993 Mars global surveyor 1996 Mars climate orbiter 1999 Ariane 5 1996 32 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. 33 Cassini / Huygens – the plan 3.5 Billion kms 34 SOI 35 Arriving at Saturn Saturn Orbit Insertion Turned spacecraft round Fired motors for 96 Minutes 36 Source: Huygens Mission Operations Plan Arriving at Saturn 37 Source: Huygens Mission Operations Plan Ejection 38 How Cassini supports Huygens Radio uplink during mission using HGA 39 Source: NASA Atmospheric Entry and Surface Mission 40 Any other risks? Hm...... 41 Atmospheric Models Yelle et al. 1997 42 Huygens descent timelines 43 Source: John Zarnecki, PSSRI, Open University, UK / ESA Parachute Test A test drop was done on Earth 44 Source: ESA SSP Measure: Temperature Speed of sound Acceleration Refractive properties Liquid Density Thermal Properties Electrical Properties Angle of tilt 45 Source: PSSRI SSP Measure: Temperature Speed of sound Acceleration Refractive properties Liquid Density Thermal Properties Electrical Properties Angle of tilt 46 Source: PSSRI Shake and Bake (!) 47 Source: John Zarnecki, PSSRI, Open University, UK Prepare the spacecraft 48 Cassini Mariner MKII spacecraft 49 Source: NASA 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 50 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 51 Project Management 52 Documentation ISO 9000, BS5750 Fully documented 53 Documentation ISO 9000, BS5750 Each operation mapped out 54 The results 55 The Landing Site 56 Source: ESA Descent to Titan - Surface mode Dull thud Major Instruments: SSP DISR 57 Surface View Titan surface 58 Credits: ESA/NASA/JPL/University of Arizona DISR – Panorama 59 Summary Exploration A lot of engineering A lot of planning A lot of people Science objectives, Risk driven development 60 61 Source: NASA 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 62 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 63