1 There is always Space for Quality Dr Mark English

2 Space and Software

3 Cassini / Huygens – the plan 3.5 Billion kms

4 Cassini/Huygens Mariner MKII spacecraft Source: NASA

5 Cassini Mariner MKII spacecraft Source: NASA

6 Cassini/Huygens Flight Model Mariner MKII spacecraft

7 The Surface Science Package Source: John Zarnecki, PSSRI, Open University, UK

8 Cassini / Huygens – the plan 3.5 Billion kms

9 Titan Titan’s vital statistics: Diameter – 5150km; Orbital/rotational period – 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?

10 Overall model of Titan Source: R. Lorenz

11 Considerations Delivery mechanisms Target environment Transition environment Duration of operation Nature of operation Sound familiar?

12 Design and Build Look at key facts – with tolerance Temperature Vacuum Radiation Time Chemistry Zero gravity

13 The Mission

14 Survival Launch – shaking (a lot) Cruise – radiation & vacuum Cruise – thermal control Cruise – temperature cycling Trajectory and SOI – accuracy Entry & Surface mission - cold

15 Launch

16 Getting through Launch Make it... then shake it

17 Cruise

18 The flight plan VVEJGA Source: NASA

19 The flight plan Source: BBC

20 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

21 Keeping warm

22 Keeping warm

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

24 Proven technology No Moving parts No lubricant Solid actuators No normal solder Crystallisation Outgassed plastics No nasty condensation

25 Proven technology Radhard ICs Care with Digital and analogue lines Waiver and qualification for E 2 PROMS

26

27 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?

28 Systems engineering Developed through Minuteman, Used on Apollo Working to interfaces, and specifications Big design, modular breakdown

29 Modules See this in Software... Code libraries (NAG) Component based development Requires very strict library management and definition

30 Libraries Numerical Algorithms Group

31 Libraries Not enough to know what things do How were they tested? What tolerances were on that data? What operational environment? What Units?

32 Failures Mars has swallowed 12 missions Mars observer 1993 Mars global surveyor 1996 Mars climate orbiter 1999 Ariane

33 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.

34 Cassini / Huygens – the plan 3.5 Billion kms

35 SOI

36 Arriving at Saturn Saturn Orbit Insertion Turned spacecraft round Fired motors for 96 Minutes Source: Huygens Mission Operations Plan

37 Arriving at Saturn Source: Huygens Mission Operations Plan

38 Ejection

39 Source: NASA How Cassini supports Huygens Radio uplink during mission using HGA

40 Atmospheric Entry and Surface Mission

41 Any other risks? Hm......

42 Atmospheric Models Yelle et al. 1997

43 Huygens descent timelines Source: John Zarnecki, PSSRI, Open University, UK / ESA

44 Parachute Test A test drop was done on Earth Source: ESA

45 SSP Measure: Temperature Speed of sound Acceleration Refractive properties Liquid Density Thermal Properties Electrical Properties Angle of tilt Source: PSSRI

46 SSP Measure: Temperature Speed of sound Acceleration Refractive properties Liquid Density Thermal Properties Electrical Properties Angle of tilt Source: PSSRI

47 Shake and Bake (!) Source: John Zarnecki, PSSRI, Open University, UK

48 Prepare the spacecraft

49 Cassini Mariner MKII spacecraft Source: NASA

50 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

51 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

52 Project Management

53 Documentation ISO 9000, BS5750 Fully documented

54 Documentation ISO 9000, BS5750 Each operation mapped out

55 The results

56 The Landing Site Source: ESA

57 Descent to Titan - Surface mode Dull thud Major Instruments: SSP DISR

58 Surface View Titan surface Credits: ESA/NASA/JPL/University of Arizona

59 DISR – Panorama

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

61 Source: NASA

62 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

63 Resources European Space Agency National Aeronautics and Space Administration Planetary and Space Science Research Institute 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