Presented by: Dave McComas
Southwest Research Institute
San Antonio, Texas on Behalf of the IBEX Science Team
PI: Dave McComas
Co-Is:
Peter Bochsler
Priscilla Frisch
Vlad Izmodenov
Don Mitchell
Maciej Bzowski Hans Fahr
Herb Funsten Steve Fuselier
Paul Knappenberger Marty Lee
Eberhard M öbius Tom Moore
Nathan Schwadron Peter Wurz Gary Zank
Collaborators:
Frederic Allegrini Mike Collier
Dan Reisenfeld Martin Wieser
Horst Fichtner
Mike Gruntman
Stefano Livi
Ed Roelof
George Gloeckler David Hollenbach
Manfred Witte

Picture from San Antonio Zoo
i·bex n. – Any of several wild goats of the genus Capra native to the mountains of Eurasia and northern Africa, having long, ridged, backward-curving horns.

■ The Heliosphere, Astrospheres and the
Interstellar Interaction
■ Energetic Neutral Atoms [ENAs], ENA
Imaging and IBEX Science
■ IBEX Flight System, Mission Design,
Launch, Orbit and Sky Coverage
■ IBEX Payload and Instrumentation
■ IBEX Operations, Science, Broad
Implications and E/PO

The Sun and Local Interstellar Medium (LISM)
Image courtesy of L. Huff/P. Frisch

Complicated Heliosphere – LISM Interaction
■ Indirect observations
● Anomalous Cosmic Rays
(ACR)
● Radio emissions
■ Inferred complications
● Inner/Outer heliosheaths
● Hydrogen wall
■ Until ~1 year ago, everything we thought we knew had been from models and indirect observations
Simulation courtesy of G. Zank.

Voyager 1 Reaches the Termination Shock

■ Two precursor events (A&C)
● Enhancements in particle fluxes
● Slowing of flow
● No magnetic field enhancements
■ TS crossing in the end of 2004 - 94 AU
● Nearly no flow
● Enhanced mag field
● Single polarity field
Decker et al., 2005

■ Energetic particle spectra just past TS
● Low energy particles fit power law
■ High Energy ACRs
● Still modulated below
~100 MeV
● ACR spectrum not
“unfolded” into single power law as predicted
Decker et al., 2005

New Results from Voyager 1
■ Voyager 1 just crossed through the TS at 94 AU
● Energetic particle enhancements
● Abrupt increase in the magnetic field magnitude
■ These observations are, however, puzzling
● Contradict essentially all prior model predictions
● No evidence of local generation of Anomalous Cosmic Rays (ACRs)
■ Clearly show how little we really know about our local cosmic accelerator
● Are ACRs generated only at special, favored acceleration regions on the shock?
● Are they accelerated only at some times at any given shock location?
● Are we completely wrong and ACRs are accelerated at some location further out, beyond the termination shock?
■ Many mysteries surround Voyager’s detailed single-point observations
■ Local observations beg the question of the global interaction

Left image courtesy of
R. Casalegno, C. Conselice et al., WIYN, NOAO
Other images from
HubbleSite.org
Closeup of IRS8, resolving the bow-shock of a fast-moving star

What would it look like?
Image courtesy of L. Huff/P. Frisch; box image courtesy of R. Casalegno, C. Conselice et al., WIYN, NOAO

ENAs Illuminate the Global Termination Shock
■ Supersonic solar wind must slow down and heat before it reaches the interstellar medium
■ Large numbers of interstellar neutrals drift into heliosphere
● Lya backscatter
● interstellar pickup ions
■ Hot solar wind charge exchanges with interstellar neutrals to produce ENAs
■ Substantial ENA signal from outside the termination shock guaranteed from first principles

ENA Observations Image the 3-D Heliosphere

■ IBEX’s sole, focused science objective is to discover the global interaction between the solar wind and the interstellar medium.
■ IBEX achieves this objective by taking a set of global energetic neutral atom (ENA) images that answer four fundamental science questions:
I.
What is the global strength and structure of the termination shock?
II.
How are energetic protons accelerated at the termination shock?
III.
What are the global properties of the solar wind flow beyond the termination shock and in the heliotail?
IV.
How does the interstellar flow interact with the heliosphere beyond the heliopause?

IBEX Science Critical to NASA and NRC Plans
The Sun to the Earth
– and Beyond: A Decadal Research Strategy in Solar and Space
Physics (2002)
Challenge 2: Understanding heliospheric structure, the distribution of magnetic fields and matter throughout the solar system, and the interaction of the solar atmosphere with the local interstellar medium.
“
The boundary between the solar wind and the local interstellar medium (LISM) is one of the last unexplored regions of the heliosphere.
Very little is currently known about this boundary or the nature of the LISM that lies beyond it. … certain aspects of these regions can be studied by a combination of remote sensing and in situ sampling techniques. This investigation could be accomplished by a mission … to obtain energetic neutral atom images… of the heliospheric boundary.
Such a mission is gauged to be feasible within the resource limits of the Explorer program
…”
Sun-Earth Connection Roadmap 2003-2028: Understand how the Sun, Heliosphere, and the
Planetary Environments are Connected in a Single System (January 2003)
“An entirely new level of information on the interface between the heliosphere and the
LISM is required.
…
Imaging of the outer boundaries ~100 AU away can also be done from orbits near 1AU.
…Remote-sensing techniques such as energetic neutral atom (ENA) imaging of energetic protons
…near the termination shock and in the heliosheath should provide additional diagnostics of the interfaces with the galaxy.
”
National Aeronautics and Space Administration 2003 Strategic Plan
Objective 5.13: Understand the changing flow of energy and matter throughout the
Sun, heliosphere, and planetary environments.
“We also will show how the outer layers of the solar atmosphere are energized, and we will track the causes of terrestrial disturbances…
Even the interstellar gas that enters the solar system can be analyzed using remote sensing.”

■ Global ENA images easily differentiate types of TS interactions
■ Gross Differences:
● Upstream/Downstream
● Dawn/Dusk
● North/South
■ Subtle asymmetries in global images illuminate flow patterns beyond the termination shock
Extremes of differential ENA fluxes from 0.3-0.6 keV predicted for a strong gas-dynamical TS (top) and a TS weakened by a large pickup ion pressure (bottom) [Gruntman et al., 2001].

■ ENA energy spectra provide direct measures of ions beyond TS:
● Solar wind
●
Pickup Protons
● Energetic protons
■ Spectra as a function of direction show 3D configuration of the shock and energy partition of the ions at the shock
■ Spectra also provide information about how EP pressure modifies the TS and what types of injection processes may be at work there
Predicted ENA distributions near HSp nose for strong (black) and weak (green) TS [Gruntman et al., 2001]. ENAs >1 keV are accelerated inner heliosheath protons based on projecting observed distributions beyond TS.

■ Question IV-Interstellar
Flow and interaction
■ First direct measurements of filtered interstellar neutral oxygen
■ Measure speed, direction and temperature of the interstellar oxygen inside TS
■ Compare to unfiltered He
■ Provide information about filtration and the interstellar interaction further out, beyond the heliopause
Neutral O flux as a function of velocity angle measured during optimum times twice each year. The filtered secondary population is slower, hotter and more strongly deflected than the primary population.

Broadly scoped science strategy with three levels of exploration:
■ Discovery level
● Discover global, fundamental properties of the interstellar interaction
● Directly available from IBEX data products –
MODEL INDEPENDENT!
■ Exploration Level
● Explore global fundamental properties of interstellar interaction
● Combining IBEX data products with simple physics-based calculations, theory and limited modeling –
ONLY SLIGHTLY MODEL DEPENDENT
■ Understanding Level
● Understand in depth global properties of the interstellar interaction
● Iterative analysis using IBEX data to test refined 3D models of the heliosphere MODEL DEPENDENT & DRIVES MODELS

■ Launch ops
● Pegasus XL
● First use of
Solid Rocket
Motor (SRM) on top of Pegasus
■ Orbit raising
● STAR-27 SRM to ~12 R
E
● S/C hydrazine system boosts apogee to 25-50
R
E perigee to
7000 km

Mission Design Maximizes Heliospheric Viewing
Routine Operations
■ Nominal orbit – 25-50 Re x
7000 km altitude, 3-8 days per orbit
■ Sun-pointing spinning S/C
(4 rpm)
■ Science Observations
> 10 Re
■ Engineering < 10 Re
● Data download and command upload
● Adjust spin axis ~5 °
(Earth’s orbital motion)
■ Nearly full sky viewing each 6 months
Earth’s
Magnetosphere

High Sensitivity Observations Provide Good Statistics

IBEX-Lo:
■ Energy range: 0.01-2 keV
■ Team: LMATC (Lead),
UNH, GSFC, APL
IBEX-Hi:
■ Energy range: 0.3-6 keV
■ Team: LANL (Lead), UNH, SwRI
CEU:
■ Provides electronic support and control for payload
■ Developed by SwRI

TOF (Cluster/CODIF)
Collimator (Phase A Prototype)
Ion ESA (Polar/TIMAS)
ENA  Ion Conversion (IMAGE/LENA)

■ IBEX prototype
● Flight quality CVD DLC conversion surface
● Verified ion optics
● Verified background suppression
■ Separate collimator tests
■ Separate mass (TOF) subsystem tests using
Stereo/PLASTIC

Collimator (Phase A Prototype)
ENA  Ion Conversion (IMAGE/MENA)
Coincidence Subsystem
Standard ESA

■ IBEX-Hi prototype verified all major sensor characteristics
● Ionization of hydrogen ENAs
● Verification of ion optics
● Double and triple coincidence
● Good agreement with electrooptic simulations
● Detector backgrounds
■ Separate collimator tests

■ Noise: the result of particles that generate uncorrelated (noncoincident) counts in the sensor detectors
● UV
● X-rays
● Photo and secondary electrons
● Penetrating radiation
■ Background: the result of an ion or atom that masquerades as a signal ENA in the IBEX sensors
● ENAs
● Ions
Noise Source
Diffuse UV, UV from stars
X-rays from photoelectron acceleration toward, and impact with, biased collimator grids
Photoelectrons and secondary electrons generated at conversion surface
Penetrating radiation: radionuclide decay in detectors
Penetrating radiation: cosmic rays
Penetrating radiation: Solar
Energetic Particle events
Penetrating radiation:
Magnetospheric energetic particles
Background Source
ENAs from planetary magnetospheres
Ions from magnetosheath and foreshock
Charge exchange of plasma ions with outgassing spacecraft species
Secondary ions generated in entrance subsystem
ENAs from CMEs, CIRs, and pickup ion charge exchange in the heliosphere

IBEX-Hi
IBEX-Lo
CEU

Antenna Sites
(USN)
Mission Control
Center (MCC)
(Orbital)
IBEX Science
Operations Center
(ISOC)
(SwRI)

■ Critical new heliospheric observations
■ $ 2M IBEX-funded GI program
● NASA peer-reviewed and selected
● Supports researchers outside of IBEX science team
■ Astrophysical connections
● Composition of LISM
● Heliosphere – Astrosphere comparisons  ground truth
● Team astrophysicists help ensure broad astrophysics connections
■ High sensitivity magnetospheric ENA observations

■ Led by Adler Planetarium & Astronomy Museum with 12 national partners
■ Active engagement of PI & science team
■ Full 2% funding (~ $1.8M) guaranteed as Level
1 programmatic requirement
■ Additional Adler contribution of ~ $650k
Single aspect of IBEX that will most engage the general public:
Visualization of our home in the galaxy and how it may have evolved over time and affected the formation and development of life in the solar system

Audience Member Unveiled

■ ENA imaging is the only way to globally observe the interaction between the solar wind and the interstellar medium (structures, dynamics, energetic particle acceleration and charged particle propagation) in the complex region that separates our solar system from the galactic environment
■ IBEX launches in June 2008 to make the first global observations of the outer heliosphere, discovering the global interaction between the solar wind and the interstellar medium on a low-cost (SMEX) budget
■ IBEX’s first global observations of the interstellar interaction will disclose its fundamental nature and provide the observations needed for detailed modeling and in-depth understanding

Interstellar Boundary Explorer – IBEX
It is time for IBEX’s breakthrough mission of exploration and discovery beyond the planets!
Imaging the
Edge of Our
Solar System and Beyond