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Going Deep: The Juno Mission to Jupiter

Going Deep: The Juno Mission to Jupiter. Michael Janssen Research Colloquium University of Idaho Department of Electrical & Computer Engineering 5 April 2007. Outline. Juno Mission The Juno Microwave Radiometer Experiment. Mission Timeline:. May 2005 Juno Selected. Jan 2006

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Going Deep: The Juno Mission to Jupiter

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  1. Going Deep: The Juno Mission to Jupiter Michael Janssen Research Colloquium University of Idaho Department of Electrical & Computer Engineering 5 April 2007

  2. Outline • Juno Mission • The Juno Microwave Radiometer Experiment

  3. Mission Timeline: May 2005 Juno Selected Jan 2006 Phase B start August 2011 Launch October 2013 Earth Flyby August October 2016 Jupiter Arrival October 2017 Mission End 2017-2018 Data Analysis Juno • Juno is a new mission to Jupiter • 1st competed New Frontiers Mission • Experiments: • Gravity Science Experiment • Doppler tracking • Magnetic Field Investigation • Magnetometers & star camera • Microwave Radiometer (MWR) • 6 Frequencies 0.6 - 23 GHz • Polar Magnetospheric Suite • 5 Instruments • Junocam, optical camera for EPO Website: http://www.juno.wisc.edu/

  4. From Mount Olympus, Juno, the god-sister-wife of Jupiter, ruler of the heavens, kept a constant and jealous vigil over her god-husband. When Jupiter had his trysts with Io he spread a veil of clouds around the whole planet to conceal his dalliance from Juno. Juno perceived the planet to suddenly grow dark, and immediately suspected that her husband had raised a cloud to hide some of his activities that would not bear the light. The cloud cover served only to arouse Juno's suspicions, and she came down from Mount Olympus. With her special powers, she penetrated the cloud to see the true nature of Jupiter. Juno

  5. Science Team PI Scott Bolton, SWRI Interior Atmosphere Magnetosphere Mike Allison Andrew Ingersoll John Anderson Michael Janssen Sushil Atreya Michael Klein Fran Bagenal William Kurth Michel Blanc Steve Levin Jeremy Bloxham Jonathan Lunine Jack Connerney Barry Mauk Angioletta Coradini David McComas Stan Cowley Tobias Owen Daniel Gautier Ed Smith Randy Gladstone Paul Steffes Tristan Guillot David Stevenson Samuel Gulkis Ed Stone Candice Hansen Richard Thorne William Hubbard

  6. Juno Science Objectives Origin Determine O/H ratio (water abundance) and constrain core mass to decide among alternative theories of origin. Interior Understand Jupiter's interior structure and dynamical properties by mapping its gravitational and magnetic fields Atmosphere Map variations in atmospheric composition, temperature, cloud opacity and dynamics to depths greater than 100 bars at all latitudes. Magnetosphere Characterize and explore the three-dimensional structure of Jupiter's polar magnetosphere and auroras.

  7. Probing Deep and Globally Juno probes deep into Jupiter in three ways: • Radiometry probes deep into meteorological layer • Magnetic fields probe into dynamo region of metallic hydrogen layer • Gravity fields probe into central core region

  8. Mag Boom Spin-Stabilized Rad-Hard Solar-Powered 20+ m Diameter Spacecraft Characteristics

  9. 8/2/16 Trajectory Y DSM, 9/18/12 (date varies) Earth flyby, 800 km alt., 10/18/13 Jupiter Arrival, 10/19/16 X Launch, 8/18/11 View from above ecliptic plane with ecliptic X to right

  10. Orbits • Juno makes 31 highly eccentric orbits of 11 days each • The eccentric polar orbit allows the spacecraft to get close to Jupiter without getting fried in the intense radiation belts

  11. Orbit Trajectory 31st orbit is shown

  12. Magnetic Investigation • Led by Jack Connerney (GSFC), with Ed Smith and Neil Murphy (JPL) • The Juno MAG experiment maps the innermost magnetic field structure of Jupiter at all longitudes • Measurement system has the following components: • Dual Fluxgate Magnetometers for vector field (GSFC) • Advanced Stellar Compass (ASC/DTU) for attitude determination • Scalar Helium Magnetometer for field magnitude (JPL) • Dedicated MAG boom at end of the solar array Multiple polar orbits phased to map Jupiter’s magnetic field

  13. Magnetic Field Mapping

  14. Gravity • Led by John Anderson, Anthony Mittsakus • Precise measurements of spacecraft motion measure gravity field • Juno polar orbit measures full gravity field • Distribution of mass reveals core and deep structure Close polar orbit is ideal to measure Jupiter’s gravity field

  15. Gravity Determination of Core Mass and Deep Winds • J2, J4, J6 and tides give core mass once water abundance is known • J8 - J30 give deep winds down to r ~ 0.8 RJ • Red is signature of deep winds; dash is signature of solid body rotation • Blue dots (X/Ka uplink) show accuracy for baseline mission

  16. Jupiter’s Polar Magnetosphere • Jupiter’s aurora from the Hubble Space Telescope (Clarke et al.) Rotating with Jupiter Shown in magnetic coordinates

  17. Juno instruments will measure: Currents EM emissions Energetic particles & plasma UV and IR auroral emissions Jovian Aurora Distribution Experiment (JADE) David McComas (Southwest Research Institute) Energetic Particle Detector (EPD) Barry Mauk (APL/Johns Hopkins University) WAVES (radio & plasma spectral measurement) William Kurth (University of Iowa) UV spectrograph (UVS) Randy Gladstone (Southwest Research Institute) Jovian InfraRed Auroral Mapper (JIRAM) Angioletta Coradini (Agenzia Spaziale Italiana) Auroral Investigation Polar Magnetosphere Suite:

  18. How did Jupiter form? How deep are the atmospheric circulations? > 200 bars? ~ 6 bars? Water is key to understanding the formation of Jupiter. We need to distinguish between 3solar and 9solar abundance. MWR Science Objectives Microwave sounding will address two key questions:

  19. Cosmic Abundances - Why is Water Important? H2O, NH3, CH4 Water, Ammonia, Methane Hydrogen compounds

  20. Galileo Probe Results for Jupiter’s abundances • Galileo results show similar enrichment, independent of volatility • Results imply Jupiter formed colder and/or further out than 5 AU • Solid material that enriched Jupiter was most abundant solid material in early solar system Galileo showed us planetary formation theories were wrong

  21. Microwave Radiometry • Led by Michael Janssen • Radiometry sounds atmosphere to 1000-bar depth • Determines water and ammonia global abundances • 6 wavelengths between 1.3 and 50 cm

  22. The First Deep Space Radiometer • 20 lbs, 5 w • 1.9 and 1.35 cm-l • Crystal detectors (!) • 5-month project start to delivery (!) • Verified hot surface, deep atmosphere

  23. Flight Microwave RadiometersSince Mariner 2 • Planetary (dedicated radiometers) • 0! • Earth-orbiting • Lots (too numerous to list) • Other Planetary • MIRO (submillimeter spectrometer) • Magellan (incorporated into radar instrument) • Cassini (incorporated into radar instrument) • Future planetary • Juno Microwave Radiometer

  24. 30 km 3 km 300 m Aperture size for 1 arcsec resolution 30 m 3 m 30 cm 10 mm 100 mm 1 mm 1 cm 10 cm 1 mm Wavelength Resolution is a Problem

  25. What do We See in the Microwave Region? Jupiter, 20 cm-l Cosmic background, thermal fluctuations at mm-l (from WMAP) Jupiter, 2 cm-l Energetic Electrons Thermal Blackbody Spectral lines Synchrotron emission Thermal bremsstrahlung 10m 1m 10 cm 1 cm 1 mm 100 mm Wavelength

  26. Planetary Science Targets radiometry spectroscopy Deep Atmospheres Surfaces Particles and Fields Upper Atmospheres Composition Winds Energetic Electrons Thermal Blackbody Spectral lines Synchrotron emission Thermal bremsstrahlung Surfaces deep shallow 10m 1m 10 cm 1 cm 1 mm 100 mm Wavelength

  27. Planck’s Radiation Law Wavelength 10 cm 1 cm 1 mm 100 mm 10 mm 1 mm 0.1mm 10 -12 3000 K 10 -14 Rayleigh-Jeans limit: 300 K 10 -16 Specific Intensity (J s-1 m-2 ster-1 Hz-1) 30 K 10 -18 Planck function: 10 -20 3 K 10 -22 10 -24 Frequency (cm-1)

  28. Brightness Temperature In microwave region, brightness of a Blackbody is linear with kinetic temperature T: Redefine radiant intensity in units of Kelvin by scaling: This is “Brightness Temperature”

  29. T(h) h W(h) Atmospheric Sounding Radiative transfer equation: f1 f2 where W(f)= weighting function at frequency f

  30. T(h) h W(h) Atmospheric Sounding (continued) • Weighting function depends on composition • E.g., NH3, H2O • Brightness spectrum tells about the distribution of: • Temperature • Composition f1 f2

  31. Jupiter Seen from the Earth Resolution on Jupiter’s microwave brightness is modest at present Jupiter, 2 cm-l Jupiter, 20 cm-l

  32. 4-M Radar Location The Cassini RADAR Radiometer • Frequency = 13.68 GHz (2.1 cm l) • Beamwidth = 0.35° (uses the HGA) • Measurement precision 0.025K /s • Absolute uncertainty 2% • Polarization: 1 linear • Observes in all RADAR modes: • Radiometer only • Scatterometer • Altimeter • SAR (5 beams alternating) • Science Objectives • Titan • Rings • Saturn atmosphere • Icy satellites The radiometer is built into the Radar receiver system

  33. Saturn at Microwave Frequencies • Best previous maps of Saturn at millimeter/centimeter wavelengths are Earth-based: (from Grossman, Muhleman, & Berge, 1989)

  34. Saturn from Cassini • 2.1-cm image formed by continuous pole-to-pole scanning in three separate time segments • Shows NH3 cloud humidity, seen to vary 100%

  35. spin axis solar panels MWR Sounding • The Juno microwave instrument will use six radiometers to measure the thermal emission from Jupiter’s deep atmosphere • Ammonia and water are the principal sources of microwave emission • Their concentration and distribution will be measured 25-cm  antenna 12.5, 6.25, 3.125, 1.3-cm  antennas 50-cm  antenna

  36. Spacecraft tracks 10° foot- prints • Synchrotron emission avoided • High spatial resolution obtained Emission angle dependence uniquely measured by along-track scanning Juno Observations • Unique microwave measurements obtained This is a new and powerful approach Along-track scanning

  37. Jupiter’s Spectrum Measured from Earth De Pater et al., Icarus 173, Vol 2, pp 425-438, 2005 Ammonia Opacity only Ammonia and Water Opacity

  38. Water’s Effect on the Spectrum Very high accuracy is required to measure water abundance using brightness temperature spectrum • Inversion requires measurements at different wavelengths • Knowledge of the absolute gains at the 2% level is very difficult • Uncertainties in gains at different wavelengths are uncorrelated • Another technique is required! 2 % accuracy

  39. Emission Angle Dependence Off-Nadir View Nadir View  Tb (nadir) – Tb ()  100 R(%) = Tb (nadir) R is a dimensionless parameter that can be measured to high precision (Janssen et al., Icarus 173, 2005, 447-453)

  40. Two-Point Spectrum of Relative Brightness • Relies on relative measurement that can be measured to precision of 0.1% • Does not rely on absolute calibration that is limited to 2% • Note: not restricted to 2 points

  41. Juno Spacecraft Forward LGA 2.5 m HGA (Fix-Mount) MGA 2X SpinningSun Sensor Electronics Vault SASU 2X Battery Fwd REM Fwd REM Thermal Louver Solar ArrayArticulation Mechanism MWR Antenna Panel MWR600 MHz Antenna

  42. 600 MHz 4.8 GHz 9.6 GHz 23 GHz 1.2 GHz 2.4 GHz MWR Antennas All 12° Beamwidth (Full-Width at Half Power) 20° Beamwidth (Full-Width at Half Power)

  43. Patch Antenna for 0.6 and 1.2 GHz Antennas Patch Radiator (cavity resonator) Honeycomb Support Structure Coax fed probe from feed to patch Feed Network (power dividers) Rear View Cross-Sectional View

  44. Computed Radiation Patterns for Patch Antennas 20° MoM Analysis on Infinite Ground Plane

  45. 2.4 - 9.6 GHz Antennas • 2.4 - 9.6 GHz Antennas will be 8x8 Waveguide Slot Array Antennas (5x5 Slot Arrays Shown) Half-wavelength slots leak power into the radiation field in a precisely controlled manner Top View Metal waveguides form a sturdy box beam mechanical structure Top View – Radiating Face Removed

  46. Breadboard of 1.2 GHz Radiometer DC side RF side Bandpass Filter LNA LNAs Lowpass Filter Detector Circuits Bandpass Filter Noise Diode Isolator Test Port Noise Diode RF Input Dicke Switch Noise Diodes Directional Couplers (4x)

  47. Breadboard Stability • Exceeds NEDT requirement • Exceeds stability requirement by ~ order of magnitude

  48. Spacecraft Electronics Vault

  49. MWR Electronics PIU ASC Electronics (not visible) 2X X Band EPC KA Band SDST-SSPA X Band Transponder X Band Transponder Radiometer Modules (MWR) FGM Electronics 2X IMU UVS Electronics BATT Electronics Waves Electronics JADE Electronics SHM Electronics 2X SRU Electronics Solar Array Switching Unit (SASU) PDDU 2X C&DH 2X Sun Sensor Electronics Electronics Vault Interior

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