Flux Transport Methods

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IBEX Science Working Team Meeting
Flux Transport Methods Nathan Schwadron
Southwest Research InstituteMarch 9, 2009
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Outline of Analysis Steps

• Pipeline
• Forward Modeling
• Steps for Analysis
• Step 0
• Unpack Raw data for an orbit
• Step 1
• Generate DE or HB event lists and other orbit
  products
• NOTE Add culling step and background subtraction
  
• NOTE Steps 1 - 3 coupled in the analysis
• NOTE Add -- rate map, count map, each of the
  steps in analysis as a global map
• Step 2
• Use the sensor response to estimate local
  differential energy flux
• Step 3
• Translate from SC to Inertial Frame
• Step 4
• Trace flux back to Heliosphere
• Step 5
• Construct global maps of Helispheric emission

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Preamble Processing Pipeline

• The ISOC has a large set of tools
  (ISOCGNU/Linux)?
• They are assembled into a pipeline to perform the
  core processing tasks

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Forward Modeling -- Flux Mapper

• flux_mapper is a tool which ingests the
  heliospheric model
• It has most of the physics we presently know how
  to use
• Charge exchange cross sections
• Radiation pressure
• Solar wind model...
• It has ENA tracing capabilities
• It has representations for both sensors and IBEX
• IBEX-Hi Collimator response (doubles and
  triples)?
• IBEX-Lo Collimator response (doubles and
  triples)?
• Model ephemeris for IBEX and a spin model
  (spinal_tap)?
• It has simulation fidelity flags
• It's a beast. (My daughter says that's a
  complement.)?

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Step 0a - Basic to Primary Processing

• CCSDS packets are processed into a number of
  working products
• Various databases on-time, spin-info and
  attitude history
• Event list (binary) files
• DE o0009.hide-1 .. o0009.hide-6 for the six
  IBEX-Hi ESA channels
• DE o0009.lode-1 .. o0009.lode-8 for the 8
  IBEX-Lo ESA channels
• HB o0009.hihb-1 .. o0009.hihb-6 for the
  histogram bins
• HB o0009.lohb-1 .. o909.lohb-8 for the H and O
  histograms, and sectored monitor rates
• Also background monitor, star sensor and a few
  other types would be generated (if there was
  something to generate).
• exposure files (o0009.hi_exp and o0009.lo_exp)
  are generated to track exposure for each sky 6
  sky bin.
• DE's and HB's are stored in a compact, efficient
  binary (meta-event or ME) format.

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Step 0b - Primary/Quick data Processing

• The events are updated with aspect and IBEX
  location information so that they can be sliced
  and diced.

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Step 1a - IBEX-Hi Direct Event Lists

• IBEX-Hi direct events DE's

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Step 1a - IBEX-Lo Direct Event Lists

• IBEX-Lo direct events DE's

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Step 1b - Primary/Quick data Processing, 2

• P/L housekeeping packets also be passed to
  filters to provide
• Plots of various HK quanitites
• Backstop MAESTRO red/yellow alarm limits (ISOC
  orange limits)?
• 1D 2D TOF plots for lo
• Time filters on various detector counts to
  identify bad-time intervals
• ...
• Various standard quick-look plots are made to be
  provided on the web
• Great-circle skymap
• Counts by Spin-bin and Spin
• Raw count rates by DE or HB type

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Step 2a - Counting Rates for an Orbit

• For any pixel (in any geometry), for each of the
  14 ESA channels, we can estimate the counting
  rate

• In general, counts is a weighted sum of different
  event types (possibly including noise and
  background corrections).
• This can be calculated for any cull of events
  we choose to make (e.g. typically heliospheric or
  magnetospheric)?
• This is handled by a tool called hilo_cntrate

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Step 2a - IBEX-Hi DE-1 (doubles) Rate
Counts
Exposure (ms)?
Rate (cts/s)?
(Ecliptic coordinates)?
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Step 2b - from Rates to Flux

• The Response Function
• A response function document describes in detail
  how an incident ENA flux translates in the count
  rates of various types (and species for IBEX-Lo)
• Start IBEX-Hi Response Function

NOTE WHAT IS THE DIFF BETWEEN HI AND LO POINTING?
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Step 2b - Rates to Flux in IBEX-Hi

• Simplest strategy for inferring flux

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Step 2b - Rates to Flux in IBEX-Hi

• Simplest strategy for inferring flux (from Bob
  Demajistre)

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Step 2b - Rates to Flux by Matrix Inversion

• Can define the response in terms of a Matrix
  multiplication
• The diff. flux can then be inferred by matrix
  inversion
• This should account for small amounts that creep
  from one passband to another

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Step 2b - Mat Inverse .. But negative results

• Scheme depends on the definition of energy bins
• A variety of choices with respect to definition
  of the forward matrix (I have not had time to
  optimize the matrix definition)
• We have also used an iterative matrix method
  using an initial best guess
• Matrix methods do not look encouraging

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Step 2b - Roelofs inversion scheme

• First guess for distribution by dividing by (GxE)
• Use the first guess to infer a piece-wise
  power-law distribution
• Infer a correction factor based on the
  convolution of the energy transmission function
  T(E) with the first guess for the distribution
• Method results are positive definite (a good
  thing compared to matrix method!)
• Iterate
• NOTE -- Roelof and Demagistre still developing
  the method

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Step 2b - IBEX Lo Rates to Flux

• In IBEX-Lo, we need an inversion method because
  of the sputtering and knock-off
• We have a matrix inversion ready, but it is not
  clear that the results will be positive
• We need to think about ways to test the method
• We have a module for converting rates to fluxes
  we can drop in new successful schemes as they are
  developed (provided that they are implementable)

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Step 2c - Orbit-Spin Frame

• The natural frame to work in for all of the above
  is a frame built around IBEX's mean spin for the
  orbit.

• For Direct Events the sky is well sampled in the
  spinward direction (a)?
• No information in the transverse direction (ß)?
• Our collimators are narrow enough that the
  effects are negligible for the moment. (A 1D FFT
  can be used if desired.)?

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Step 2 - Example - IBEX-Hi DE-1 Nominal Flux
Flux (ENAs/cm² s sr keV)

• Currently, we have implemented the simplest
  scheme

Rate (cts/s)?
(Ecliptic coordinates)?
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Step 3a - Convert to Inertial Frame

• In each energy bin and sky-pixel, we have central
  observed ENA energy and direction
• Corresponds to a central observed ENA velocity,
• Central velocity in inertial frame subtracts out
  the spacecraft velocity,
• Energy in inertial frame
• Distribution function invariance
• Infer the differential flux in the inertial frame

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Step 3a - Energy Diff. Flux in the Inertial
Frame

• Subtlety
• We have inferred the diff. flux for an energy
  that varies with spin-phase
• The CG correction can be used project or
  interpolate from an energy that varies with
  spin-phase to an energy that is fixed

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Step 3b Interpolation to a Fixed Energy (CG
Correction)

• We inferred a Diff. Flux in the hel Frame
  at an Energy
• We want a quantity that is interpolated to
• Take the ratio of the energy in Hel frame to SC
  frame
• (this depends on the ESA step i)
• Then we can solve for the interpolated flux at
• The k-indices are the piecewise log-log slopes
• This interpolation step can be done at 1 AU or 20
  AU ..

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Step 4 - Follow Trajectory out to 100 AU

• Trajectory can be traced backwards
• This can be as simple or as complicated as you
  chose to make it

• Simplest is central-force, constant-µ used
• Can be easily made more complicated and complex
• Ram effects on energy are important
• Survivability is important
• Deflection angle (d) is exaggerated

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Step 4 - Following ENA back through the
heliosphere

• Equation for translation of the ENA distribution
  function
• Solve using characteristics (e.g., Roelof and
  Gruntman)

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Step 4a - Following ENAs back through the
heliosphere

• Characterisic equations solved using either
  numerically (BzowskiSoft) or using an analytic
  approximation based on the central force law
  (assume constant mu)
• At each point along the ENA trajectory (run
  backward in time), we have ENA energy
  velocity and position.

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Step 4a - Following ENAs back --Analytic Model
Survival Prob.
Constant Mu Trajectory
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Step 4b - Interpolation

• The interpolation onto a fixed energy grid (e.g.,
  Compton-Getting correction) can be applied here
  at any radius
• The same basic method applies (Step 3b)

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Step 5a - Collecting Multiple Orbits

• Combining orbits can be done in any frame---I've
  used an ecliptic one here.
• I've exaggerated the deflection (d) for two
  orbits that are weeks apart
• The flux from pixels at 1 AU will contribute to
  one or more pixels at 100 AU.
• Different part of the band refer to different HS
  energies (E)?

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Step 5b - Maps -- Interpolation?

• Currently we use a scheme for painting the sky
  map which does not use interpolation
• If a ray from 1 AU hits a pixel at the outer
  boundary then only that pixel gets a sample
  contribution
• An interpolation scheme can also be adopted?

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Covariance

• Bob Demajistre currently writing a Latex document
  that summarizes how the covariance can be carried
  through the calculation and used
• Propagates the Poisson errors from the counting
  statistics to the global maps
• When do we need this (e.g., 1 week)?

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Fin

• Publication of the Response Function Document and
  the Flux Transport Document?
• No need yet
• Forward Mapping of the Maps to produce synthetic
  1 AU data products
• Zank lead Heerikhuisen, Mueller, Bzowski, Frisch
• How are we going to generate maps for Lo?
• Stephen to specify what product (write it down)
• Christina Nathan to work to generate that
  product
• Do we have adequate numerical transport methods
  (mapper) for IBEX-Lo? Who is going to test and
  refine this?
• Work on the interface
• Zank to look at this (H, O, He H first)
• Maciek to work with this as well

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• What is the distance to which we want our final
  maps?
• 80 AU
• What is the diff. between Hi Lo pointing?
• Hi Frederic and Brent
• Lo Eberhard, Marek
• Action to Ed Bob D. to work out an improved
  inversion method for the flux in spacecraft in
  the frame -- inversion of the response function
• The CG correction (energy Interpolation)
• Bob will review the algorithm for CG, and test it
• Do we do angular interpolation on the maps?

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Example Flux at 0.45 keV
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Fini
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Example Flux at 0.45 keV
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Example Flux at 0.45 keV
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Some Comments Here...

• Some comments on what I've shown you
• I've used 6hrs / orbit for my convenience
• These plots thus have serious Poisson noise
• primitive strategy for averaging contributions
  from multiple orbits
• Many projection options
• Some considerations for development
• Ram effects means that the same pixel will see a
  different energy on 2nd hit after 6 months. It
  takes a year to get the 3rd hit at the same E.
• With a flux model (e.g. a power-law) one could
  resolve mapped flux values to model-estimated
  values.
• These effects are least/most significant for
  IBEX-Hi/IBEX-Lo
• This will doubtless become a discussion topic
• The following slides step through IBEX-Hi from
  low to high E

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IBEX-Hi at 0.45 keV
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IBEX-Hi at 0.71 keV
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IBEX-Hi at 1.11 keV
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IBEX-Hi at 1.74 keV
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IBEX-Hi at 2.73 keV
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IBEX-Hi at 4.29 keV
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Summary Status

• The output fluxes in the maps shown don't exactly
  match the input fluxes for trivial reasons that
  can be fixed once we've got completed response
  models.
• The flux_mapper tool was run with detailed
  trajectory calculations turned off. The
  flux_translate tool can use the same code (it's a
  reversible path) but that is not yet implemented.
• We plan to make these improvements and then fully
  test all the modules. Thereafter it can be used
  as an analysis tool.
• It can be used as a test-bed to evaluate the
  importance of various heliospheric properties for
  having an impact on our final results.

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Pause

• General ISOC S/W Status

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ISOC Software Status

• S/W Build 3.2 was made this week.
• Work on Build 3.3 has already started and we'll
  most likely use it during the first few orbits.
  Build 4.0 when we're ready.
• All critical functionality is in place.
• P/L housekeeping capabilities will be enhanced
  (significantly) during commissioning when we see
  real data in HVSCI mode
• Toolbox functionality (and help) is not as mature
  as I'd like, but it will improve during the
  initial orbits
• MS/HS cull capability is demonstrated but not
  thoroughly tested with real MS models.
• Still have significant work on IBEX-Lo response
  (O) IBEX-Hi is more mature, but still incomplete.

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ISOC Software Status

• MOC-SOC interface is tested, but not fully
  automated (this is not a surprise, and also not a
  problem)?
• Basic Background/Noise issue analysis tools
  exist, but we'll have to wait and see what the
  first orbit(s) look like before putting them into
  the pipeline
• More routine orbit products are planned and may
  require the web page for each orbit to be split
  into several pieces
• ACS/Star Sensor tools exist but are not on web
  yet
• .... I'm sure there's something I've forgotten to
  mention ....
• We are GO FOR LAUNCH

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Assume a Heliosphere...
Kappa Dist. Opher Model
Kappa Dist. Pogorelov Model
Maxwellian, Opher Model

• The starting point is the output of some
  heliospheric model (such as Christina Prested
  described at the last SWT meeting) which
  describes the source differential energy flux of
  ENAs
• Require flux estimates on the full sky across all
  IBEX energies

0.45 keV
1.1 keV
2.6 keV
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Fake Telemetry

• The IBEX-Hi and IBEX-Lo SSR simulations are
  combined with simulated ACS (Attitude Control
  System) quaternion data (spinal_tap) and passed
  to a simulation of the telemetry process. (I'll
  skip the details.)?
• As an aside, quite a few things are missing
• No simulation of the background monitor (yet)?
• Star Sensor simulator exists but isn't presently
  included
• No realistic singles or monitor rates
• No housekeeping whatsoever
• The resulting VCID2 (SSR) file of telemetry
  frames is then acquired via SFTP and
  collected by the raw telemetry ingester (a
  really crude simulator of ops2raw_filer.pl).

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Step 0 - Raw to Basic Processing

• The raw data for a single orbit (in this case
  simulated orbit 9023) is gathered and processed
  to regenerate the original CCSDS packets stored
  in the SSR
• Useful collections of packets are made for
  further work
• o9023.pkt_sc (s/c housekeeping)?
• o9023.pkt_pl (all p/l telemetry)?
• Several operational tasks are carried out at this
  time (missing SSR blocks, c.)?

Fake telemetry file
Other flux_mapper products
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Data Product Foundation Science Telemetry Types
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Quick Look Plots
Totally bogus J2000 counts on sky
Fake Magnetosphere at NEP
Totally bogus counts with time
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Incident Flux at 1 AU

• We have 14 channels hide-1 .. hide-6, lode-1
  .. lode-8
• We have one (H) differential energy flux j(E) (O
  is later)?

• The channels are coupled through the sensor
  response

• Invertible? hilo_reflux