sammy.kayali
TRANSCRIPT
Slide - 1February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
NASA Project Management Challenge
Juno Project Overview and Challenges for a Jupiter Mission
Sammy KayaliMission Assurance Manager
February 9-10, 2010
Slide - 2February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Outline
• Juno Mission Overview• Spacecraft Design• Instrument Suite• The Juno Challenge• Jupiter Environment
– Radiation Environment– Charging Environment– Solid Particle Environment– Magnetic Environment
• Summary
Slide - 3February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Project Overview
ScienceTo improve our understanding of the solar system by Understanding the origin and evolution of Jupiter, Juno will:• Determine the global O/H ratio (water abundance) in Jupiter’s
atmosphere• Measure latitudinal variations in Jupiter’s deep atmosphere
(composition, temperature, cloud opacity, and dynamics)• Map Jupiter’s magnetic and gravitational fields• Characterize Jupiter’s polar magnetosphere and aurorae
Salient Features• First solar-powered mission to Jupiter• Eight instrument payload to conduct gravity, magnetic and
atmospheric investigations• Single polar orbiter (simple spinner) launches in August 2011
– 5 year cruise to Jupiter, JOI in July 2016– 1 year operations, EOM via de-orbit into Jupiter in 2017
• Elliptical 11 day orbit swings below radiation belts to minimize radiation exposure
• Key Juno partners: SwRI, JPL, ASI, LM-Denver and GSFC
Launch8/05/2011
EFB10/9/2013
DSMSep 2012
JOI7/5/2016
Tilted Ecliptic Pole View (Vernal Equinox Direction Up) 30-day Tick Marks
Slide - 4February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
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.
• Polar Magnetosphere– Explore the three-dimensional structure of Jupiter's polar
magnetosphere and aurorae.
Slide - 5February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Juno Flight System
Spacecraft: 1600 Kg dry mass 3625 kg wet mass
Power at 1 Au (theoretical): 15 kWPower at JOI: 486 WPower at EOM: 428 W
8.86 m
2.647 m 2.02 m
2.64 m2.36 m
SA Wing #1
SA Wing #3
SA Wing #2
Slide - 6February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Spacecraft
55 Ah Li Ion Battery (2)
Solar Wing #2
Fuel Tank
Waves MSC MWR A2
Oxidizer Tank
JEDI (3)
Nutation Damper
JADE Electron (3)
Solar Wing #1
Solar Wing #3
Main EngineCover
A3A4
MWR A5
MWR A6
Toroidal Antenna
HGA
Slide - 7February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Instrument Suite
Slide - 8February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
The Juno Challenge
System Design
Environments
Science SpacecraftDesign
Input
Measurement
Signal Noise
Requirement
Capability
SolarThermalRadiationParticlesPlasmaEM FieldsMagnetics
Instruments need to measure Jupiter’s environment
But environmental exposure is a threat to the spacecraft
The spacecraft cannot create excess noise which would disguise instrument signals
Slide - 9February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Juno Trajectory Through Radiation Belts
• Juno trajectory exposes spacecraft to the Jovian radiation belts for less than one day per orbit– Electrons– Protons
• Early orbits are relatively benign– ~25% of the mission
TID received by the end of Orbit 17
• Late orbits are severe– ~25% of the mission
TID received over the last 4 orbits
Perijove Passage through Jupiter’s Radiation Environment
Slide - 10February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Juno Radiation Environment
• Juno radiation environment has several challenging features
– Large population of electrons > 10 MeV that cause high mission TID and DDD
– High electron flux near Perijove that causes noise in sensors and charging of surfaces and shielded dielectric materials
Jupiter Trapped Peak Average Proton & Electron Flux
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1 10 100 1000
Energy (MeV)
Prot
on &
Ele
ctro
n Fl
ux
(par
ticle
s/cm
2 -s) Electrons
Protons
Slide - 11February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Juno TID Environment Comparison
1.0E+02
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
1.0E+08
1.0E+09
1 10 100 1000 10000
Aluminum Spherical Shell Thickness, mil
Mis
sion
TID
rad(
Si)
GLL dose through J35 (GIRE)
Cassini
JunoMRO
• Galileo TID > Juno TID > Cassini > MRO TID• Juno TID behavior parallels Galileo for shield thickness > 100 mils aluminum
Juno TID is ~ 1/4 of Galileo TID
Slide - 12February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Solar Wing #2
Solar Wing #3
Solar Wing #1
MAG Boom
Z
End of Mission Radiation TID Levels
Vault Electronics(25 Krad)
Solar Cell Junctions (3 Mrad)
Instruments Outside Vault(<0.6 Mrad in 60 mil housing)
Deck ComponentSurface Dose (under blanket)(11 Mrad)
Solar Cell Coverglass(> 100 Mrad)
Slide - 13February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Titanium Vault Protects Electronics
• Juno spacecraft electronics are shielded by a vault
– The thickness and composition of the vault walls are optimized to attenuate Juno’s mix of electrons and protons using the minimum mass
– Vault equipment packing factor maximizes shielding from neighboring electronics boxes
– Vault shielding designed to limit the TID of all internal electronics to 25 Krad or less
– Divided into zones for equipment with different lifetimes and radiation hardness
• Electronics outside the vault have local shielding designed for their location and part hardness
Slide - 14February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
14
Juno Charging Environment – Comparison
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
1.E+10
0.1 1 10 100
Energy, MeV
Flux
, (cm
2 s)-1
Juno WC IESD Flux (10x)Galileo Orbiter Peak FluxJuno Spatially Worst 10-hour flux (1x)GEO WC Flux
• The Jovian electron environment deposits charge in materials
– Dielectric materials – Ungrounded metals
• Juno electron charging environment threat is severe
– ~2X higher than Galileo– >10X higher than GEO
spacecraft threat• Juno charging mitigation
– Grounding non-conducting surface materials
– Prohibit ungrounded metals– Analyze charge deposition in
internal dielectric materials– Test hardware that is
expected to discharge• Harness
Slide - 15February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
IESD Mitigation – Analysis and Test
G10 Washer (20mil thick, .33” dia.)
Steel Connector Housing
Aluminum Walls (40mil thick each)
BeCu Probe
Hollow Brass Annulus (15mil thick walls, .26” dia.)
Space View
Spacecraft
Aluminum Wall with Slots (40mil thick)
G10 Washer (20mil thick, .33” dia.)
Steel Connector Housing
Aluminum Walls (40mil thick each)
BeCu Probe
Hollow Brass Annulus (15mil thick walls, .26” dia.)
Space View
Spacecraft
Aluminum Wall with Slots (40mil thick)
• Electric field analysis of dielectrics– Circuit boards– Gaskets and washers
• Testing to characterize IESD pulses– Harness
MWR G10 washer in antenna element Electric field: 1.02 x 104 V/cm No discharges expected
Coax cable in test chamber
Slide - 16February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Juno Micrometeoroid Environment
• Spacecraft velocity and Jupiter gravity well result in impact velocities > 100 km/sec
• Jupiter environment has a significant high velocity meteoroid flux relative to cruise
• Spacecraft and payloads analyzed to determine probability of failure due to meteoroid strikes
– Shielding is used to reduce impact damage
Slide - 17February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Micrometeoroid Analysis - Example
• Micrometeoroid analyses determine the probability of failure of critical spacecraft components.
– View factors and shielding– Equipment redundancy– Materials of construction– Failure criteria– Minimum science requirements
JIRAM Instrument
Instrument Component AssumptionsView
Factor Failure Criteria
JIRAM Instrument Material: Al, Impact Angle: 0, 0.125Assuming penetration of the
60 mil top of sensor will cause failure
Data Cables
Material: Cu, Thermal Blanket: Kapton, Impact Angle: 0, ASSUMES NO STAND OFF B/W
THERMAL BLANKET AND CABLE. 40 of 155 conductors exposed. 0.8 m exposed length.
0.125
Particle penetrating 29.6 mils of Cu (includes 4 mil of Cu over wrap, 3.4mils of Cu
shielding (twisted pair braid), and full conductor diameter 16); Insulator and thermal blanket converted in to Cu
thickness using areal density. Failure is severance of one of
the exposed conductors.
JIRAM Instrument 98.1%
Data Cables 99.1%
Instrument Component Survival Probability
Slide - 18February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Juno Magnetic Field Challenge
• The Juno spacecraft is exposed to intense magnetic fields at each perijove pass– 5-6 Gauss typical, 12 Gauss maximum– ~10X LEO spacecraft magnetic field strength; ~1000X GEO magnetic field strength
• The AC magnetic field represents an operational challenge – Developed an AC Magnetic Susceptibility requirement and extensive test program
• The effects of a spinning spacecraft in a magnetic field (VxB) were addressed • DC Magnetic cleanliness requirement represented a challenge for material selection and usage.
JOI
Earth LEO
Slide - 19February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology AC Magnetic Susceptibility
Mitigation Approach
• Implemented plan of early assessment and mitigation by identifying and testing hardware that is susceptible to rapidly changing magnetic fields– Components with soft magnetic materials, solenoids, isolators, ferrites, large
current loop areas etc.• AC magnetic susceptibility test approach developed
– 2X margin on expected magnetic field at JOI and 1.3 during science – Equipment tested to +/- 9 Gauss at 5 RPM at JOI– Equipment tested to +/-16 Gauss at 2 RPM during science
Design Shield Model Shield Build & Test Shield
Slide - 20February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology Effects on Spinning Spacecraft in a
Magnetic Field (VxB)
Juno Spacecraft
B
v
θ
φ = 0
φ -300 V
φ -615 V
• Plasma sees a potential difference across the moving spacecraft
• Most positive part of the ITO coated array floats near local plasma potential
• Maximum difference between spacecraft and plasma is vxB potential plus array voltage –full batttery charge
• Vmax -615 V• Grounding design practices implemented
throughout the spacecraft mitigate the issue•Solar Array coupon tests conducted to validate analysis
≈
≈≈
Slide - 21February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology DC Magnetic Cleanliness
Mitigation Approach
• Key magnetic cleanliness impact items identified early, tracked and resolved– Latch valves identified as significant magnetic field contributors
• Self compensation design implemented – Telecom components identified as a potential magnetic cleanliness contributor
• Key components were analyzed, tested and self-compensated • Complete review of all materials for magnetic contribution
– Expert panel reviewed material lists and identified areas of concerns– Changed or modified magnetic materials to suitable non-magnetic materials – Analysed and approved use of magnetic materials if low risk was determined
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Juno Telecom x4 Multiplier
Typical Mag
Mapping Tests of
Small and Large Items
Slide - 22February 9-10, 2010
Jet Propulsion LaboratoryCalifornia Institute of Technology
Summary
• The environmental challenges on Juno are considerable but surmountable
• Early planning and attention to details have been essential in avoiding environmentally related problems
– Having the “right” experts– Team Education– Utilize appropriate analysis tools– Detailed and thorough test to prove
the design• Minimize new designs and rely on proven
architecture