Sammy.kayali

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



Outline

• Juno Mission Overview• Spacecraft Design• Instrument Suite• The Juno Challenge• Jupiter Environment

– Radiation Environment– Charging Environment– Solid Particle Environment– Magnetic Environment

• Summary



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



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.



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



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



Instrument Suite



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



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



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



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



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)



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



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



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



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



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



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


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


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

≈

≈≈


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



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