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GREEN TEAM

Study the Uranian system to better understand planetary formation, the emergence of life, and the dynamics of the icy giants. This mission aims to improve models of planetary system formation and explore the conditions for planet formation and the emergence of life.

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GREEN TEAM

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  1. URANUS SYSTEM EXPLORER GREEN TEAM USE AlpbachSummerSchool 2012 2/08/2012

  2. Mission Summary www.planeten.ch We will achieve this with an orbiter and an atmospheric probe. Hubble Space Trelescope / NASA 2 Study the Uranian system with a focus on the interior, atmosphere and magnetosphere in order to better constrain the solar formation model and to understand how the icy giants formed and evolved.

  3. ESA Cosmic Vision 2015-2025 What are the conditions for Planet Formation and the Emergence of Life? • Observations of Uranus will help to improve existing models of planetary system formation • Understand icy giant planets (exoplanets) How does the Solar System Work? • What is the structure and dynamics of the icy giants? • How do they interact with their space environment?

  4. Outline [1] ScientificRationale [2] Baseline design [3] Mission analysis [5] Spacecraft and ground segment design [7] Conclusion Voyager 2 / NASA

  5. Basic facts of Uranus URANUS Interior Magnetosphere Atmosphere Voyager 2 Hubble Space Trelescope / NASA One of the 4 giant planets Distance: 19 AU RotationPeriod: 17h Orbit Period: 84 years OnlyvisitedbyVoyager 2 in 1986 5

  6. Atmosphere of Uranus Composition ? Drivers of atmospheric chemistry ? Dynamics (transport of heat)

  7. Magnetosphere of Uranus Field Intensity @ 1.4 Ru • Rotation axis tilt 98° • Dipole axis tilt by 59° • Large quadrupole moment Voyager 2 Source: Nicholas et al., AGU, 2011 How and where is the intrinsic field generated? A new class of dynamo? 7

  8. Magnetosphere of Uranus How does the magnetosphere interact with solar wind? • Rotation axis tilt 98° • Dipole axis tilt by 59° • Large quadrupole moment How is plasma transported in the Uranian magnetosphere? Voyager 2 Is there a significant internal plasma source on Uranus? Insight into Earth’s magnetosphere during magnetic reversals LASP, University of Colorado, Boulder 8

  9. Interior of Uranus Molecular H2 Inhomogeneous Metallic H Ices + Rocks Core? Rel. low heat flux Molecular H2 Helium + Ices Ices mixed with Rocks? Rocks? Uranus Jupiter

  10. Interior of Uranus Molecular H2 Inhomogeneous Metallic H Ices + Rocks Core? Why is the heat flux lower than expected? Implications for the interior and thermal evolution of the planet? Rel. low heat flux Molecular H2 Helium + Ices Why does Uranus have such a strong intrinsic magnetic field? How do its characteristics constrain the interior? Ices mixed with Rocks? Is there a rocky silicate core? Implications for solar system formation? Rocks? Uranus Jupiter

  11. Outline [1] ScientificRationale [2] Baseline design [3] Mission analysis [5] Spacecraft and ground segment design [7] Conclusion Voyager 2 / NASA

  12. Mission Payload Imaging Camera (CAM) Visible and Infrared Spectrometer (VIR-V & VIR-I) Thermal IR Spectrometer (TIR) UV-Specrtometer (UVS) Microwave Radiometer (MR) Electron and ion spectrometer (EIS) Scalar and Vector Magnetometer (SCM & MAG) Energetic Particle Detector (EPD) Radio and Plasma Wave Instrument (RPWI) Ion composition instrument (ICI) Remote Orbiter In situ Mass Spectrometer (ASS & GCMS) Nephelometer (NEP) Doppler wind instrument (DWI) Atmosphere Physical Properties Package (AP3) Atmospheric Probe 12

  13. Orbiter Payload • Imaging camera - New Horizons / Lorri • Study the cloud motion and winds of Uranus • Range: 0.35 – 0.85 μm ; FOV: 0,29 x 0,29 deg • Visible and Infrared Spectrometer - Dawn / VIR • Study chemical composition of the atmosphere • Range: 0.25 – 1.05 μm ; FOV: 3,67 x 3,67 deg • Range: 1.0 – 5.0 μm ; FOV: 0,22 x 0,22 arcmin • Thermal IR Spectrometer - Cassini / CIRS • Heat flux at different points to constrain models of the interior and thermal evolution • Range: 7.67 – 1000 µm ; Spectral Resolution 0.5 – 20/cm • UV Spectrometer - New Horizons • Morphology and source of Uranus auroral emission • Range: 52 – 187 nm ; Spectral Resolution < 3nm ; spatial res < 500 km

  14. Orbiter Payload • Electron and ion spectrometer – Rosetta/EIS • Measures electrons and ions • Range: 1-22 keV • Ion composition instrument – Rosetta / ICA • Measure magnetospheric plasma particles in order to study plasma composition and distribution • Range: 1eV/e to 22 keV/e ; Resolution: dE/E = 0.04 • Energetic Particle Detector - New Horizons / PEPPSI • Energetic charged particles that can be used to characterize and locate radiation belts • Range: 15 keV – 30 MeV ; energy resolution: 8 keV Voyager detections

  15. Orbiter Payload • Magnetometer - Juno • globally measure the magnetic field from low altitude to constrain the dynamics of the field generation layer • resolution < 1nT in range of 0.1 – 120000 nT • Radio Wave and Plasma Instrument - Cassini • Measure plasma waves • range: kHz – MHz • Microwave Radiometer - Juno / MWR • atmospheric and terrestrial radiation, air temperature, total amount of water vapor and total amount of liquid water • range: 1.3 – 50 cm • High gain antenna • Space craft tracking to make gravity field measurements We resolve the upper hybrid frequency < 1 MHz

  16. Probe Payload • Aerosol sampling system / Gas Chromatograph & Mass Spectrometer - Galileo • sample aerosols during descent and a gas chromatograph and measure heavy elements, noble gas abundances, key isotope ratios • range: 1 – 150 amu/e • Nephelometer - Galileo • studies dust particles in the clouds of Uranus' upper atmosphere • Doppler Wind Instrument - Huygens / DWE • height profile of Uranus zonal wind velocity • resolution: 1 m/s • Atmosphere Physical Properties Package - Huygens / HASI • measure the physical characteristics of the atmosphere • temperature sensor • pressure sensor • 3 axis accelerometer • electric field sensor

  17. Traceability Matrix - Interior

  18. Mission Requirements - Science Phase I • Interior (Gravity) • HGA visible from Earth • Low altitude 15 Ru Period ~11 days • Magnetosphere • Globally probe magnetosphere • Cross magnetopause 40 Ru 1.5 Ru ~20 Ru Sun • Atmosphere • Global coverage on day- and nightside • Occultation 25

  19. Mission Requirements • Science Phase II and III • Interior (Magnetic Field) • Global coverage with low altitude Period 4.3 days • Interior (Gravity) • HGA visible from Earth • Low altitude 10 Ru 20 Ru 1.5-1.05 Ru • Atmosphere • Global coverage on day- and nightside 26

  20. Mission requirements • Gravity and magnetic field • Higher orders can only be resolved at lower altitudes • Here: 2.5 Ru for degree 11 • Signal decays exponentially with altitude • Higher orders decay more efficiently

  21. Outline [1] ScientificRationale [2] Baseline design [3] Mission analysis [5] Spacecraft and ground segment design [7] Conclusion Voyager 2 / NASA

  22. Outline [1] ScientificRationale [2] Baseline design [3] Mission analysis [5] Spacecraft and ground segment design [7] Conclusion Voyager 2 / NASA

  23. Mission Baseline SCIENCE PHASE CRUISE PHASE Nov 2049 UOI May-Nov 2052 Science phase 3 Mar 2036 Jupiter GA Jun 2033 Earth GA Mar 2030 Venus GA Sep 2049 Probe release Feb 2031 Earth GA Nov 2049- Sep 2050 Science phase 1 May 2051-May 2052 Science phase 2 2031-Feb 2036-Mar 2029-Oct 2052 08 Oct 2029 Launch 26 Nov 2052 End of nominal mission

  24. Launch and Cruise phase 2036 2049 2033 2029 2030 2031 Launch 8 Oct 2029 02:18:41 • Ariane 5 launch. • 3.56 km/s (C3=12.67) • Total Mass available: 4185.1 kg -> Launch driven by mass maximization. Total time cruise phase: 20.139 years

  25. Launch and Cruise phase 2036 2049 2033 2029 2030 2031 Launch 8 Oct 2029 02:18:41 • Gravity Assist sequence: Venus-Earth-Earth-Jupiter. • Total ΔV = 0.21 km/s • 5% Margin and 25m/s maintenance for the 5 legs applied. • The mission is classified category II (COSPAR Planetary Protection). Total time cruise phase: 20.139 years

  26. Orbit insertion in Uranus 2036 2049 2033 2029 2030 2031 Orbit insertion in Uranus: 19 Nov 2049 13:33:00 • Uranus Orbit Insertion: 19 Nov 2049 with ΔV = 0.60 km/s burn. • Velocity at Uranus arrival: 3.36 km/s • Final orbit Inclination set to 90° at arrival.

  27. Probe insertion and descent 2036 2049 2033 2029 2030 2031 • Probe release: • Probe released 19 Sep 2049, 2 months before orbit insertion. • Release maneuver ΔV = 0.001 km/s burn. • Probe insertion • Entry at the atmosphere at 23 km/s. • Arrival at latitude of 20 deg. • Dayside arrival. • Probe descent

  28. Probe insertion and descent 0 Probe Entry, t = 0 min Δt ≈ 5 min Pressure (bar) Drogue Parachute Drogue Parachute Release Δt ≈ 2 min Top Cover Removed Heat Shield Drops Off 0.1 Probe Mission Terminates t = 90 min 100

  29. Science Phase Profile Insertion 10 months 6 months 12 months 6 months End of nominal mission Science Phase 1 Science Phase 2 Science Phase 3 Sep 2050 May 2051 May 2052 Nov 2052 Nov 2049 Total science phase duration: 34 months

  30. Science Phase 1 Orbits 10 months Sep 2050 Nov 2049 125 orbits • Highly elliptical polar orbit. • Large apoapsis to sample magnetosphere and cross magnetopause. • Low periapsis for gravity field measurements. • Dayside/Nightside global coverage. [3] Mission analysis

  31. Science Phase 2 Orbits 6 months 12 months 84 orbits Sep 2050 May 2051 May 2052 30 orbits • Orbit circularization lowering the apoapsis in 4 steps: 1.40-1.35-1.30-1.25-1.20 Ru • 10 orbits at each step, 84 at last orbit. • Total ΔV = 0.55 km/s • Detailed magnetosphere sampling at different Ru.

  32. Science Phase 3 Orbits 6 months Nov 2052 May 2052 42 orbits • Highly elliptical polar orbit with low periapsis. • Argument of perigee gain of 10 deg. • Avoiding dust hazards from the rings. • Internal gravity field sampling. • Enhanced magnetic field sampling. • Untargeted Uranian satellites fly-bys. • END OF MISSION: deorbiting maneuver at apoapsis of ΔV = 0.04 km/s to deliberately crash the orbiter to Uranus (avoiding satellite contamination).

  33. Extended mission orbits ? months Nov 2052 ?orbits ?????? • Highly elliptical polar orbit with low periapsis. • Argument of perigee gain (20 deg per year). • Enhanced magnetic field sampling. • Untargeted Uranian satellites fly-bys. • Aerobraking. • END OF MISSION?: Remaining ΔV or aerobraking

  34. ΔV and fuel budget - Cruise • Total ΔV = 0.21 km/s (includes 5% margin and 25m/s maintenance ) 1 2 3 5 4 6 2036 2049 2033 2029 2030 2031

  35. ΔV and fuel budget – Science Phase Mission total ΔV = 1.44 km/s • Total ΔV = 1.23 km/s Insertion Remaining ΔV = 0.47 km/s 10 months 6 months 12 months 6 months End of nominal mission 1 2 4 3 5 6 7 Sep 2050 May 2051 May 2052 Nov 2052 Nov 2049

  36. Science operations 6 kpbs / Downlink time 25% / Dedicated & normal modes

  37. Outline [1] ScientificRationale [2] Baseline design [3] Mission analysis [5] Spacecraft and ground segment design [7] Conclusion Voyager 2 / NASA

  38. Payload Configuration • Payload panel 1: Remote Sensing • Boom: Magnetometers • Payload panel 2 and 3 (opposite sides): Plasma package

  39. Subsystems Configuration • ASRGs: • 3 ASRGs 90° apart. • Back panel: • Probe • Sides panels: • Radiators • Low gain antennas

  40. Launcher • Ariane 5 ECA launcher • Total launch = 4185 kg • Fairing • Maximum diameter = 4570 m • Maximum height = 15589 mm Adapted from Ariane V user manual Adapted from Ariane V user manual

  41. Propulsion • Main engine: Leros-1b by AMPAC™ (JUNO Heritage) • Bipropellant engine: NTO-Hydrazins • Specific Impulse = 318 s • Nominal Thrust = 645 N • Status: Flight Proven Adapted from AMPAC™ website

  42. Probe layout • Probe configuration during cruise phase • Elements of the probe:

  43. Attitude Control • The AACS provides accurate dynamic control of the satellite in both rotation and translation. • Payload • 4 x Reaction Wheels • 4 xThrusters Clusters • 2 x Star Trackers • 2 x Sun Sensors • 3 x MIMU

  44. Attitude phases: • Possible + Z spinning during cruise. It is required to protect sensors, pointing HGA antenna to the Sun. AACS is automated with coarse Sun sensors. • 3-axis stability when approaching with RWA, compensation the realease of the proabe with thrusters; • During nominal phase, 3-axis attitude control is done with reaction wheels. The largest reaction torque is 0.13 Nm. Angular momenta less than 34 Nms (approx.: 2000 rpm); • fast maneuvers or accelerations must be achieved with less precise but faster thrusters (RCS); • Inertia Tensors calculated before and after probe releasing. In both cases the values are inferior to those in Cassini which uses the same actuators.

  45. Q & A – Inertia Calculations -> 1 N thrusters -> 0.13 Nm Good maneuverability ! Change in the CM

  46. Communication Overview • HGA for Orbiter-Earth communications • Ka-band downlink (35 GHz) • X-band uplink (7.2 GHz) • MGA for Orbiter-Earth communications near Venus • X-band downlink (8.1 GHz) • X-band uplink (7.2 GHz) • LGA for LEOPS • S-band downlink (2.2 GHz) • S-band uplink (2.1 GHz) • UHF for Probe-Orbiter communications • UHF (400/420 MHz) dual uplink

  47. High Gain Antenna • 4m Cassini-derived HGA  for Earth comms to ESTRACK 35m network. • Ka Band downlink (35GHz) • X-band uplink (7.2Ghz) • Ultrastable oscillator (HGA used for radio science) HGA

  48. High gain antenna link budget

  49. Medium Gain Antenna • Medium gain antenna for communications with orbiter near Venus when HGA used as sun shield. • Communications over X-band with Kourou. • 0.8m diameter steerable antenna. • Rosetta heritage. MGA ESA

  50. Medium gain antenna link budget

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