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
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
Mission Timeline:
May 2005
Juno Selected
Jan 2006
Phase B start
August 2011
Launch
October 2013
Earth Flyby
August
October 2016
Jupiter Arrival
– Junocam, optical camera for EPO
October 2017
Mission End
Website: http://www.juno.wisc.edu/
2017-2018
Data Analysis
Juno
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.
Science Team
PI Scott Bolton, SWRI
Interior
Atmosphere
Magnetosphere
Mike Allison
John Anderson
Sushil Atreya
Fran Bagenal
Michel Blanc
Jeremy Bloxham
Jack Connerney
Angioletta Coradini
Stan Cowley
Daniel Gautier
Randy Gladstone
Tristan Guillot
Samuel Gulkis
Candice Hansen
William Hubbard
Andrew Ingersoll
Michael Janssen
Michael Klein
William Kurth
Steve Levin
Jonathan Lunine
Barry Mauk
David McComas
Tobias Owen
Ed Smith
Paul Steffes
David Stevenson
Ed Stone
Richard Thorne
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.
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
Spacecraft Characteristics
Mag Boom
Spin-Stabilized
Rad-Hard
Solar-Powered
20+ m Diameter
Trajectory
Y
DSM, 9/18/12 (date varies)
Earth flyby, 800
km alt., 10/18/13
Jupiter
Arrival,
10/19/16
8/2/16
X
Launch, 8/18/11
View from above ecliptic
plane with ecliptic X to right
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
Orbit Trajectory
31st orbit is shown
QuickTime™ and a
BMP decompressor
are needed to see this picture.
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
Magnetic Field Mapping
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
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
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
Jupiter’s Polar
Magnetosphere
• Jupiter’s aurora from the Hubble Space Telescope
(Clarke et al.)
QuickTime™ and a
H.264 decompressor
are needed to see this picture.
QuickTime™ and a
PNG decompressor
are needed to see this picture.
Shown in magnetic coordinates
Rotating with Jupiter
Auroral Investigation
Polar Magnetosphere Suite:
•
Jovian Aurora Distribution Experiment (JADE)
–
•
Energetic Particle Detector (EPD)
–
•
–
–
–
–
Currents
EM emissions
Energetic particles & plasma
UV and IR auroral emissions
Randy Gladstone (Southwest Research Institute)
Jovian InfraRed Auroral Mapper (JIRAM)
–
• Juno instruments will measure:
William Kurth (University of Iowa)
UV spectrograph (UVS)
–
•
Barry Mauk (APL/Johns Hopkins University)
WAVES (radio & plasma spectral measurement)
–
•
David McComas (Southwest Research Institute)
Angioletta Coradini (Agenzia Spaziale Italiana)
MWR Science Objectives
Microwave sounding will address two key questions:
How did Jupiter form?
How deep are the
atmospheric circulations?
> 200 bars?
Water is key to understanding the
formation of Jupiter. We need to
distinguish between 3solar and
9solar abundance.
~ 6 bars?
Cosmic Abundances Why is Water Important?
H2O, NH3, CH4
Water, Ammonia, Methane
Hydrogen compounds
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
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
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
Flight Microwave Radiometers
Since 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
Resolution is a Problem
30 km
3 km
300 m
Aperture size
for 1 arcsec
resolution
30 m
3m
30 cm
1 mm
10 mm
100 mm
1 mm
1 cm
Wavelength
10 cm
What do We See in the
Microwave Region?
Jupiter, 20 cm-l
Jupiter, 2 cm-l
Cosmic background,
thermal fluctuations at
mm-l (from WMAP)
Energetic Electrons
Thermal Blackbody
Spectral lines
Synchrotron emission
Thermal bremsstrahlung
10m
1m
10 cm
1 cm
Wavelength
1 mm
100 mm
Planetary Science Targets
radiometry
Particles and
Fields
spectroscopy
Deep Atmospheres Upper Atmospheres
Surfaces
Composition
Winds
Energetic Electrons
Thermal Blackbody
Spectral lines
Synchrotron emission
Thermal bremsstrahlung
10m
1m
deep
10 cm
1 cm
Wavelength
Surfaces
1 mm
shallow
100 mm
Specific Intensity (J s-1 m-2 ster-1 Hz-1)
Planck’s Radiation Law
Wavelength
-12
10
1E-12
10 cm
1 cm
100 mm
1 mm
10 mm
1 mm
3000 K
1E-13
-14
10
1E-14
Rayleigh-Jeans limit: h  kT
1E-15
B T  
-16
10
1E-16
1E-17
2k
l
2
300 K
T

-18
10
1E-18
30 K
1E-19
Planck function:
1E-20

10
0.1mm
-20
2h 3
1
B T   2 h / kT
c e
1
3K
1E-21
-22
1E-22
10
1E-23
-24
1E-24
10
0.1
1
10

Frequency (cm-1)
100
1000
10000
100000
Brightness Temperature
In microwave region, brightness of a Blackbody is linear with
kinetic temperature T:
B T  
2k
l
2
T  Iv
Redefine radiant intensity in units of Kelvin by scaling:

TB   
l
2
2k
I
This is “Brightness Temperature”

Atmospheric Sounding
T(h)
Radiative transfer equation:
TB  f  

 W h, f  T h dh
0
f1
h
f2
where W(f) = weighting
function at frequency f
W(h)
Atmospheric Sounding
(continued)
T(h)
• Weighting function depends
on composition
– E.g., NH3, H2O
f1
h
• Brightness spectrum tells
about the distribution of:
f2
– Temperature
– Composition
W(h)
Jupiter Seen from the Earth
Resolution on Jupiter’s microwave brightness is modest
Jupiter, 2 cm-l
at present
Jupiter, 20 cm-l
The Cassini RADAR
Radiometer
4-M
Radar
Location
The radiometer is built
into the Radar receiver
system
•
•
•
•
•
•
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
Saturn at Microwave
Frequencies
• Best previous maps of Saturn at millimeter/centimeter
wavelengths are Earth-based:
(from Grossman, Muhleman, & Berge, 1989)
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%
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
solar
panels
spin axis
25-cm l
antenna
12.5, 6.25,
3.125, 1.3-cm l
antennas
50-cm l antenna
Juno Observations
• Unique microwave
measurements obtained
Spacecraft tracks
10° footprints
–Synchrotron
emission avoided
–High spatial
resolution obtained
Emission angle
dependence uniquely
measured by alongtrack scanning
This is a new and
powerful approach
Along-track scanning
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
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
2 % accuracy
• Knowledge of the absolute
gains at the 2% level is very
difficult
• Uncertainties in gains at
different wavelengths are
uncorrelated
• Another technique is required!
Emission Angle Dependence
Off-Nadir View

Nadir View
R(%) =
Tb (nadir) – Tb ()
Tb (nadir)
 100
R is a dimensionless parameter that
can be measured to high precision
(Janssen et al., Icarus 173, 2005, 447-453)
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
Juno Spacecraft
Forward LGA
MGA
2X Spinning
Sun Sensor
2X Battery
2.5 m HGA (Fix-Mount)
Electronics Vault
SASU
Fwd REM
Fwd REM
Thermal Louver
Solar Array
Articulation Mechanism
MWR
Antenna Panel
MWR
600 MHz Antenna
MWR Antennas
All 12° Beamwidth
(Full-Width at Half
Power)
600 MHz
4.8 GHz
20° Beamwidth
(Full-Width at Half
Power)
9.6 GHz
23 GHz
2.4 GHz
1.2 GHz
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
Computed Radiation
Patterns for Patch Antennas
Full-size 5x5 patch array, f=0.6GHz, MoM cuts, inf. GP
0
spec
20°
-10
E-total (dB)
-20
-30
-40
-50
-60
-80
-60
-40
-20
0
20
theta (deg)
40
MoM Analysis on Infinite Ground Plane
60
80
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
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)
Breadboard Stability
• Exceeds NEDT requirement
• Exceeds stability requirement by ~ order of magnitude
Spacecraft Electronics Vault
Electronics Vault Interior
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
Juno
Let's go!
Backup Slides
MWR vs Gravity Orbits
• Doppler tracking for gravity and MWR sounding have
different pointing pointing requirements
• Must be done on different orbits
MWR Top-Level Error Budget
TABLE: MWR Error Budget from C SR (R, %)
Wave length, cm
50
25
12.5
6.25
Random mea surement noise (1s)
0.06
0.05
0.04
0.04
Beam pa ttern knowledge
0.06
0.07
0.06
0.06
Synchrotron rejection
0.05
0.03
0.00
0.00
Short-term (20s) drift
0.02
0.02
0.03
0.04
Zero offset drift
0.05
0.03
0.02
0.02
Zero determination
0.04
0.01
0.00
0.00
Net Relative Error 0.10
0.09
0.08
0.08
3.125
0.03
0.06
0.00
0.04
0.01
0.00
0.08
1.3
0.03
0.06
0.00
0.05
0.01
0.00
0.08
Plan is to model and remove sidelobe contributions by
Modeling the sources - planet and synchrotron emission
Knowing the beam pattern
Error comes from
uncertainties in beam pattern (near sidelobes)
Inability to account for synchrotron contribution (far sidelobes)
The error modeling is complicated - sorry!
Far Sidelobes
R is calculated for 20% uncertainty in synchrotron
model
• Same beam knowledge table used
•
Juno Core Spacecraft - Aft
2X Fuel Tank
Pressure Transducer Vault
2X Nutation Damper
2X Helium Tank
2X Oxidizer Tank
WAVES Electric Antenna
2X SRU
Aft LGA (X)
WAVES Mag
Search Coil
2X Aft REM
3X Toggle link
SA articulation
Mechanism
Engine Cover
(open)
Engine Heat
Shield
Toroidal LGA
Collapse of the solar nebula
Cold planetesimals and heavy element enrichment
Requires T 30 K to trap N2 and Ar
2-4 solar H2O
Interstellar (ISM)
30K
KBOs
150K
5 au
30K
30 au