MMS Data Product Guide
Volume TBD Energetic Particle Detector System (EPD)
TABLE OF CONTENTS
1.0 EPD Instrumentation Description
1.1 Suite Overview
1.2 EIS Overview and Viewing
1.3 FEEPS Overview and Viewing
1.3.1 FEEPS spacecraft configuration
1.3.2 FEEPS Viewing
1.4 EPD Burst Triggers
2.0 EPD Science Algorithms
3.0 EPD Data Processing
4.0 EPD Data Descriptions
4.1 EPD Data Levels
Level 1a
Level 1b
Level 2
Level 3
4.2 Ephemeris and magnetic field information
4.3 Transfer Files and Fast Ion Data Products
4.3.1 EIS Transfer Files.
4.3.2 Fast Ion Products
4.4 EPD QuickLook Data.
4.5 EPD SITL Data
5.0 Detailed FEEPS and FAST-ION Data Descriptions
This section is TBD
6.0 Detailed EIS Data Descriptions
Appendix A: Onboard Burst Flag Algorithms.
A.1 EIS Burst Trigger Algorithms
A.2 FEEPS Burst Trigger Algorithms
Appendix B: Structure of the FEEPS Calibration Matrix
References
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1.0 EPD Instrumentation Description
The science objectives and overview of the Energetic Particle Detector (EPD)
investigation is provided in Mauk et al. (2013). EPD comprises 2 different instrument
types, the Energetic Ion Spectrometer (EIS; with a detailed description provided by Mauk
et al., 2013) and the Fly’s Eye Energetic Particle Spectrometer (FEEPS; with detailed
descriptions provided by Blake et al.; 2013). Here we provide summary information.
The Energetic Particle Detector Suite of sensors supports the study of the
fundamental physics of magnetic reconnection by:
1) Remotely sensing the positions and speeds of boundaries and other structures near
reconnection sites using energetic ions.
2) Sensing the magnetic topology of near reconnection sites using energetic
electrons.
3) Remotely sensing reconnection acceleration sites using both electrons and ions.
4) Determining the cause of energization of energetic electrons and ions by
reconnection.
The flow down from those science goals to the EPD measurement and performance
requirements is shown in Figure 1.0-1. The allocations of those requirements for the two
EPD sensors (EIS and FEEPS) as derived from Figure 1.0-1, and the connection to the
Program Level (Level-1) requirements, is shown in Figure 1.0-2.
Figure 1.0-1
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Figure 1.0-2.
1.1 Suite Overview
The Energetic Particle Detector (EPD) suite includes an Energetic Ion Spectrometer
(EIS) and an all-sky particle sampler called the Fly’s Eye Energetic Particle Sensor
(FEEPS). These instruments measure (Figure 1.0-2): 1) the energy-angle distribution
and composition of ions (20 to 500 keV, with a goal of 10 to 1000 keV) at a time
resolution of < 30 seconds, 2) the energy-angle distribution of total ions (45 - 500 keV,
with a goal of 40 - 1000 keV) at a time resolution of < 10 seconds, and 3) the coarse and
fine energy-angle distribution of energetic electrons (25 - 500 keV, with a goal of 20 1000 keV) at time resolutions of < 0.5 and < 10 seconds, respectively. Schematics of the
two sensor types, along with the EPD team members, is shown in Figure 1.1-1.
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Figure 1.1-1.
There are 2 FEEPS instruments and 1 EIS instrument on each spacecraft to yield an
instantaneous all-sky view for electrons and fast all-sky sampling for ions. This set of
sensors (2 FEEPS instruments plus 1 EIS instrument) is identical on all 4 of the MMS
spacecraft. Figure 1.1-2 shows where the sensors reside on each spacecraft and Figure
1.1-3 shows how those sensors are configured to give the maximum sky coverage.
FEEPS provides an instantaneous all-sky view of the electrons (with course angular
resolution), and then turns course into more refined angular resolution by means of
rotation. The 2 FEEPS ion “fans”, in conjunction with the one EIS ion fan, provides allsky total-ion coverage every 1/3 of a spin.
4
Figure 1.1-2.
Figure 1.1-3.
1.2 EIS Overview and Viewing
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Each EIS instrument contains a microchannel Plate (MCP) detector that, with the
help of thin foils from which secondary electrons are generated, measure particle Time
Of Flight (TOF) and pulse height (PH); and six Solid State Detectors (SSD) that measure
particle energy (E). The MCP has start and stop anodes. Measuring the time difference
between start and stop determines the particle’s TOF. The anodes are divided into six
angular segments; these provide a measure of the particle’s direction of travel. EIS
measures ion energy, directional, and compositional distributions using Time-of-Flight
by Energy for the higher energy ions (TOF x E) and Time-of-Flight by MCP-PulseHeight for the lower energy ions (TOF x PH). EIS also measures electron energy and
directional distributions using collimated solid-state-detector (SSD) energy
measurements (these electron SSD’s, as opposed to the ion SSD’s, have 2 microns of
aluminum flashing deposited on them to keep out protons with energies less than about
250 keV). EIS combines multidirectional viewing into single compact sensor heads
(Figure 1.2-1).
The EIS coordinate system and defined viewing directions are shown in
Figure 1.2.1a and 1.2.1b. There are 6 view directions per data product (V0, V1, ---,
V5), but only V0 and V5 are shown on the figure, along with (in Figure 1.2.1a) the
ordering of the electron (e-) and ion SSD pixels within those fields of view (Note that
the TOF x PH pixels encompass the entire V0, etc. sector, not just what is designated
on the figure as the “Ions” portion. However the response of those 6 TOF x PH views
are centered on the ion SSD’s.
The quantitative centroids of the view directions for all 6 view directions,
within the EIS coordinate system, for each of the EIS data products, are shown in
Figure 1.2.2. The central direction of the center of each TOF x PH, TOF x E, Ion-SSD
(the same as TOF x E), and Electron-SSD pixel is given as the angle from the X-axis
within the X-Y plane, with positive angles towards the -Y axis (also toward the
direction that has been designated the “V0” direction; we realize that it is unusual to
have positive angles towards the –Y axis rather than the +Y axis). To the right of
each angle in Figure A.2 is the unit vector of the view direction in the instrument
coordinate system. Views V2 and V3 have obstruction from the shielding needed to
keep the sun out (Figure 3.3), and that obstruction has not been yet folded into the
table (the off-color rows are the views that are substantially blocked).
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Figure 1.2-1a
Figure 1.2-1b
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Figure 1.2-2
The transformation matrix that transforms a vector (e. g. a unit view direction
such as those provided in Figure 1.2-2) into the MMS Spacecraft Frame (Figures 1.12 and 1.1-3) is provided here. V(sc) = T(EIS)  V(EIS) where V(EIS) is the vector in
the EIS frame of reference, T(EIS) is the 3 x 3 transformation matrix, and V(sc) is
the vector in the spacecraft frame. For this expression:
T(EIS) =
 -1/2
 1/2
 0
0
0
1
1/2 
1/2 
0 
1.3 FEEPS Overview and Viewing.
Each of the two FEEPS instruments on each spacecraft comprises 12 individual
fields of view; 9 electron views (Figure 1.3-1, left) and 3 ion views (Figure 1.3-1, right).
Eight of the electron views are clustered into 4 “heads” comprising 2 “eyes” each (Figure
1.3-2). Each electron eye comprises a shaped pinhole, a 2 micron aluminum foil that
keeps out protons with energy > 250 keV (not shown in Figure 1.3-2) , and a shaped, 1
mm Solid State Detector (SSD) to measure the energy of the incoming electron. The
shapes of the pinhole and of the SSD work together to yield a trapezoidal shape for the
field of view of each eye (Figure 1.3-1, left).
Figure 1.3-1
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Figure 1.3-2
Two of the ion sensors on each FEEPS instrument are combined into a single
“head” (Figure 1.3-3). Each ion eye comprises a slot shaped pin hole followed by a
rectangular shaped, 9 micron thick, SSD to measure the ions. The response of these
detectors to electrons is minimized by the thinness of the SSD’s; electrons tend to pass
right through leaving a signal below the detection threshold, and ions are stopped, leaving
above-threshold energies. There will be residual electron contamination in the ion
responses that needs to be managed. The 2 “equatorial” ion sensor each have a sun shade
(Figure 1.3-3) to keep the sun from illuminating the entrance slot (the ion sensor are very
sensitive to the sun, whereas the electron sensors are not). The slot shape of the pinhole
and the rectangular shape of the SSD yields a fan-like field of view (Figure 1.3-1); about
20 x 60.
Figure 1.3-3
A final set of electron and ion views is held by a 3rd type of head, the Electron-Ion Head
(Figure 1.3-4). This head contains 1 electron eye and 1 ion eye. Ideally the field-of-view
of the third ion head should be carefully aligned with the views of the other two ion heads
to effectively yield a broad, 280 fan-shaped field of view. However, to keep the third
ion sensor from viewing the axial electric field sensors, the third view had to be tilted
somewhat away from the ideal configuration (Figure 1.3-1, right).
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Figure 1.3-4
1.3.1 FEEPS spacecraft configuration
In order to get a true “all-sky” view from FEEPS, it was necessary to mount just
one of the instruments on the instrument deck and the other onto the spacecraft subsystem
deck (Figure 1.3-5). The 2 instruments are identical to each other, and they are designed
such that when one of them is turned upside down with respect to the other around the
right axis, the fields of view of one of the instruments exactly fills in the missing portions
of the other (Figure 1.1-3). Also, the orientation of the ion sensors is such that the
resulting 2 fan-shaped fields of view are configured to provide 2 out of 3 of the fans
spaced 120 apart, with EIS providing the 3rd fan (Figure 1.1-3).
Figure 1.3-5
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1.3.2 FEEPS Viewing
Figure 1.3-6 shows the labeling for the 12 different fields of view on each FEEPS
instrument, 9 electron views and 3 ion views. Note that all 12 of these views are used for
generating Burst data, however only a subset is used in the generation of Survey data.
For Survey data all of the ion views are used, but only the electron views with ID’s 3, 4,
5, 11, and 12 are used (see the ID’s in Figure 1.3-6) The FEEPS coordinate system is
shown in Figure 1.3-7 along with the unit vectors for each of the 12 eyes in the FEEPS
coordinate system. The “elevation” angle is the angle made by unit vectors pointing
normal to the front faces of the SSD’s. The “Weighted Elevation” takes into account the
non-symmetric shape of the electron fields of view (centered on the centroid of the solid
angle viewed). Note that The transformation of vectors from the FEEPS-1 (FEEPSpayload-deck or the “up” direction) to the spacecraft coordinate system is achieved using:
V(sc) = T1(FEEP-1)  V(FEEPS-1) using:
T1(FEEPS-1) =
 1/2
 1/2
 0
-1/2
1/2
0
0 
0 
1 
Similarly, The transformation of vectors from the FEEPS-2 (FEEPS-bottom-deck) to the
spacecraft coordinate system is achieved using: V(sc) = T2(FEEP-2)  V(FEEPS-2)
using:
T1(FEEPS-2) =
 -1/2
 -1/2
 0
-1/2
1/2
0
Figure 1.3-6
11
0 
0 
-1 
Figure 1.3-7 [TBR]
1.4 EPD Burst Triggers
All MMS Instrument Investigations generate “burst trigger flags” onboard the
spacecraft to provide summary information that might indicate that reconnection
activity or some other interesting activity is occurring in the vicinity of the
spacecraft. The EPD burst flag parameters are shown in Figure 1.4-1. The extent to
which these burst flags are useful will be determined only with experience with the
mission. The EPD data is different from other instrument data in that there are no
reliable or consensus simulations of the response of the energetic particle to
reconnection that can provide guidance as to as to what the EPD burst trigger flags
will tell us about the activity in the vicinity of the spacecraft. The algorithms for the
onboard generation of these flags are provided in Appendix A.
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Figure 1.4-1
2.0 EPD Science Algorithms
The data that comes down from both EIS and FEEPS is mostly in the form of counts
per accumulation period per channel. A “channel” is a small portion of
measurement parameter space, where the parameters correspond to “look
direction” (in 2 dimensions), “species” (e. g. electrons or ions; and sometimes for the
ion portion: protons, helium ions, and oxygen ions), and “energy”. For FEEPS
electrons for the Burst data products and for each accumulation period, there are 18
look directions per spacecraft (9 per instrument) and 16 logarithmically space
energy channels for each look direction. For FEEPS electron Survey products (Fast
and Slow), only 10 of the 18 electron look directions are utilized (Section 1.3.2). For
FEEPS ions for both Burst and Survey data products and for each accumulation
period, there are 6 look directions per spacecraft (3 per instrument) and, again, 16
energy channels. For EIS, there are 6 look directions for each of the standard data
products for both burst and survey (TOF x E ions, TOF x PH ions, and electrons). In
burst for TOF x E for each look direction there are up to 73 channels for various
combinations of species and energy, and for TOF x PH for each look direction there
are up to 33 channels for various combinations of species and energy. For electrons
there are up to 24 energy channels for each look direction. And so there are many
100’s of channels that represent the measurements that are made by FEEPS and EIS,
sorting the data by look direction, energy, and species.
The prime challenge for ground processing is to turn each of these channels from a
“Counts per Accumulation” to Intensity [1/ (cm2.s.sr.keV)] for the particular
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parameter state represented by the channel. The algorithm for doing so is
documented here.
1) Because a SSD response (output rate for a given channel) tends to be roughly
linear when rates are low, but non-linear when rates are high, for high rates one
must be prepared to perform a “dead time correction” to reconstruct the true
input rates. That correction is performed using a “live time (LT) counter” (for
FEEPS) or a “dead time counter” (for EIS). Depending on how this number is
generated, there is likely a conversion procedure to convert it into a “factional
live time” (e. g. FLT = C1 x LT + C2). (For low counting conditions the FLT might
be 0.95, whereas for high counting conditions FLT might be 0.5 or lower.
2) Covert Counts per Accumulation (C/A) to Counts per second (C/S R) using:
R[C/S] = (C/A)/(TA*FLT),
where:
TA = Channel accumulation period
FLT is the live time correction mentioned above.
3) Subtract off a background, generally caused by cosmic rays
RC[C/S] = R[C/S] – CR_BG[C/S]
4) Convert R into intensity (I)
Intensity[1/(cm^2.s.sr.keV)] = RC / [(E2-E1) x eG], where
eG is efficiency time geometric factor
E1, and E2 are the lower and higher energy bounds for the channel.
Note: eG, E1, and E2 are “calibration” factors that are provided in some kind
of spreadsheet to the processing software. There is one complete set of numbers
for each of the 100’s of channels. The structure of a notional FEEPS Calibration
Matrix is shown in Appendix B.
5) When plotting the data or using it for calculations, the Intensity is often
identified with a central energy, often estimated with Eplot = (E1 x E2)^0.5, an
estimate that would be exact if the spectral index “g” is 2 in the expression I =
CxE-g, where C is a constant and E is energy.
The result of all of this processing can be notionally thought of as filling one or more
spreadsheets with the column headings for each look direction like:
Spacecraft
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Instrument
Direction (,)
Pitch Angle
Species
Energy (E1, E2, EPlot)
Counts per Accummulation
Counts per Second
Intensity
The Pitch Angle is the angle of the look direction with respect to the magnetic field (PA
= ArcCos[Direction  b], where Direction is minus the unit view direction vector in
spacecraft coordinates and b is the unit magnetic field vector in spacecraft coordinates.
This angle is needed right away because the ordering of the particle data by the magnetic
field is so central to understanding the data. The “Direction” is the look direction in an
agreed upon coordinate system, like GSE.
The generation of low and high level data products from this notional spreadsheet is
all about organizing the data in different ways (e. g. choose one look direction – or
average all look directions - and one species generate an energy spectrum; etc.)
3.0 EPD Data Processing
Figure 3.0-1 shows the plan for processing the EPD (FEEPS and EIS data).
Algorithms for generating Level 1a and Level 1b data are generated by the FEEPS
EPD process at LASP/EPD for FEEPS data, and at APL for EIS, and transferred to the
SOC process at LASP (LASP/SOC) for execution. FEEPS Level 2 data is generated by
the FEEPS EPD process at LASP/EPD, but the procedures for doing so are certified
by Aerospace and the University of New Hampshire. The EIS Level 2 data is
generated by APL. The FEEPS and EIS Level 2 products are transmitted to the SOC
process at LASP. We note that because the Level-2 data products are very close to
the Level-1b products, it is possible that we might ask the LASP/SOC process to just
go ahead and generate those products as well. Figure 3.0-1 shows some of the
details of the processing, for example specifying the need for the availability of
magnetic field data and ephemeris data at various stages of the production.
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Figure 3.0-1
4.0 EPD Data Descriptions
4.1 EPD Data Levels
We will be discussing 4 levels of data products here. We provide high level
descriptions and lists here, and the go into formats and other details in the subsections to
follow (specifically Section 5).
1) Level 1a: These are instrument level data products (one set for each instrument; which
means 2 sets for FEEPS from each spacecraft and one set for EIS for each spacecraft).
The data is organized closely in the same way that the data packets onboard the
spacecraft are organized. The channel contents are in “counts per accumulation”. No
livetime or deadtime correction is applied to these counts. For each record the MET
(or equivalent) time must be recorded and a standard for whether that time is the
beginning or the middle of an accumulation time. Also, for each record the
“accumulation time” must be reported, unless a single accumulation time for a data
product file suffices and is reported in a file header. For each SSD detector (12 for
FEEPS and 12 out of the possible 24 for EIS) the “Livetime” or “Deadtime” must be
recorded. For each channel the “Counts per Accumulation” must be recorded. The
following is a preliminary list of the key Level 1a data products for both FEEPS (in
black) and EIS (in blue). Note that the “Survey” data includes both Fast Survey and
Slow Survey because these products have identical formats with the Fast Survey
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including every spin and the Slow Survey including only every 10th spin. The data
products with the notation (diagnostic) at the end are data products used primarily by
the instrument providers for better understanding the health and performance of the
instrument and for cross comparisons between FEEPS and EIS (electron products
from EIS, for example). They will not be generally provided to the scientific
community (they are not secret; we just will not go to the effort to make them
accessible). Our list of key Level 1a EPD data products for each spacecraft is here
(note that “top” and “bottom” refer to the FEEPS units mounted at the top (payload)
and bottom (spacecraft) mounting plants):
1. L1a-top-FEEPS-Electron- Burst
2. L1a-top-FEEPS-Ion-Burst
3. L1a-top-FEEPS-Integral-Electron-Burst
4. L1a-top-FEEPS-Electron- Survey
5. L1a-top-FEEPS-Ion-Survey
6. L1a-top-FEEPS-HK-Status-Fast (diagnostic; this is less complete than Slow)
7. L1a-top-FEEPS-HK-Status-Slow (diagnostic)
8. L1a-top-FEEPS-Burst-Trigger (diagnostic)
9. L1a-bottom-FEEPS-Electron- Burst
10. L1a-bottom-FEEPS-Ion-Burst
11. L1a-bottom-FEEPS-Integral-Electron-Burst
12. L1a-bottom-FEEPS-Electron- Survey
13. L1a-bottom-FEEPS-Ion-Survey
14. L1a-bottom-FEEPS-HK-Status-Fast (diagnostic; this is less complete than Slow)
15. L1a-bottom-FEEPS-HK-Status-Slow (diagnostic)
16. L1a-bottom-FEEPS-Burst Trigger (diagnostic)
17. L1a-EIS-PhxTOF-Ion-Burst
18. L1a-EIS-ExTOF-Ion-Burst
19. L1a-EIS-PhxTOF-Ion-Survey
20. L1a-EIS-ExTOF-Ion-Survey
21. L1a-EIS-HK-Status (diagnostic)
22. L1a-EIS-Ion-Energy-Burst (diagnostic)
23. L1a-EIS-Electron-Energy-Burst (diagnostic)
24. L1a-EIS-Electron-Events (diagnostic)
25. L1a-EIS-Ion-Events (diagnostic)
26. L1a-EIS-Species-Events (diagnostic)
27. L1a-EIS-Ion-Energy-Survey (diagnostic)
28. L1a-EIS-Electron-Energy-Survey (diagnostic)
29. L1a-EIS-Electron-Basic-Rates-Survey (diagnostic)
30. L1a-EIS-Ion-Basic-Rates-Survey (diagnostic)
31. L1a-EIS-Ion-Diagnostic-Rates-Survey (diagnostic)
32. L1a-EIS-Species-Basic-Rates-Survey (diagnostic)
33. L1a-EIS-Species-Diagnostic-Rates-Survey (diagnostic)
34. L1a-EIS-Electron-Basic-Rates-Burst (diagnostic)
35. L1a-EIS-Ion-Basic-Rates-Burst (diagnostic)
36. L1a-EIS-Ion-Diagnostic-Rates-Burst (diagnostic)
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37. L1a-EIS-Species-Basic-Rates-Burst (diagnostic)
38. L1a-EIS-Species-Diagnostic-Rates-Burst (diagnostic)
39. L1a-EIS-Burst Trigger (diagnostic)
2) Level 1b: These are observatory level data products (for each spacecraft there would be
one set from FEEPS (the two instruments combined) that incorporates some EIS data,
and one set from EIS. At the “Record” level there is time (MET or equivalent and
UTC), a quality flag, an accumulation time for each channel, a Spin Sector, perhaps a
Spin Number, and magnetic field and ephemeris data (Section 4.2) . At the detector or
look direction level there is Pitch Angle, GSE look direction (Solar Angle +
Elevation), Livetime or Deadtime, and the E1 of the lowest energy channel. At the
channel level, there are 4-position “vectors”, specifically: {EGM, counts-peraccumulation, counts-per-second, rough-intensity}, where EGM is the geometric
mean of E1 and E2 (Sqrt[E1.E2]), the energy bounds of the energy channel. At the
“look-direction” or detector level, the E1 for the lowest energy channel is captured so
that all E1’s and E2’s can be reconstructed. Maintaining the energy per channel is so
that information about the cleanliness of and errors within the channels is not lost.
Here the “rough-intensity” is results from the conversion of “counts-per-second” to
“intensity” using only approximate, uncertified calibration matrices, as are the
energies, E1 and E2. No livetime or deadtime correction is applied to the counts, the
counts/second, or the rough intensity. As with the Level-1a product, for each record
the MET time (or equivalent) must be recorded and a standard for whether that time
is the beginning or the middle of an accumulation time. The needed preliminary
magnetic field data in spacecraft coordinates, and predict-ephemeris data is defined in
Section 4.2. Quicklook data displays (Section 4.4) and any needed SITL data
products (Section 4.5) are generated at this level. Note that there are EIS and FEEPS
data that are joined together at this point in time. In order to generate these “Fast Ion”
products, “Transfer files” (shown in purple text below) are generated from the EIS
data, which is then used with the FEEPS process. More information about the
“Transfer Files” and the “Fast Ion” files are discussed in Section 4.3. What the
existence of these joint products means is that the EIS Level-1b must be created first,
followed by the creation of the FEEPS Level-1b data. The List of Level 1b data
products, with FEEPS in black, EIS in blue, and the joined data product in red, is here
(note that “top” and “bottom” sensors are now combined):
1. L1b-FEEPS-Electron- Burst
2. L1b-FEEPS-Integral-Electron-Burst
3. L1b-FEEPS-Electron- Survey
4. L1b-Fast-Ion-Burst
5. L1b-Fast-Ion-Survey
6. L1b-EIS-PhxTOF-Ion-Burst
7. L1b-EIS-ExTOF-Ion-Burst
8. L1b-EIS-PhxTOF-Ion-Survey
9. L1b-EIS-ExTOF-Ion-Survey
10. L1b-EIS-Transfer-burst (diagnostic)
11. L1b-EIS-Transfer-survey (diagnostic)
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12. L1b-EIS-Ion-Energy-Burst (diagnostic)
13. L1b-EIS-Electron-Energy-Burst (diagnostic)
14. L1b-EIS-Ion-Energy-Survey (diagnostic)
15. L1b-EIS-Electron-Energy-Survey (diagnostic)
16. L1b-EPD-Quicklook (Section 4.4)
17. L1b-EPD-SITL (Sections 4.5)
3) Level 2. This data is identical in format and content as the Level 1b data set. The
difference is: 1) Livetime or Deadtime corrections are applied to the counts per
second as reported in this product, and before the generation of intensity. 2) “roughintensity” values are replace with “refined-intensity”, 3) rough values of E1 and E2
are replaced with refined values, 4) preliminary magnetic field is replaced with
updated magnetic field, 5) predict ephemeris is replaced with updated ephemeris, and
6) the record-level quality flag is updated. The list of Level 2 data products is nearly
identical to the Level 1b products. Note that only Level-2 products 1-9 are generally
available to the scientific community.
1. L2-FEEPS-Electron- Burst
2. L2-FEEPS-Integral-Electron-Burst
3. L2-FEEPS-Electron- Survey
4. L2-Fast-Ion-Burst
5. L2-Fast-Ion-Survey
6. L2-EIS-PhxTOF-Ion-Burst
7. L2-EIS-ExTOF-Ion-Burst
8. L2-EIS-PhxTOF-Ion-Survey
9. L2-EIS-ExTOF-Ion-Survey
10. L2-EIS-Transfer-burst (diagnostic)
11. L2-EIS-Transfer-survey (diagnostic)
12. L2-EIS-Ion-Energy-Burst (diagnostic)
13. L2-EIS-Electron-Energy-Burst (diagnostic)
14. L2-EIS-Ion-Energy-Survey (diagnostic)
15. L2-EIS-Electron-Energy-Survey (diagnostic)
4) Level 3. This level contains a variety of products that is, to this date, not fully defined.
These products require: 1) Extensive calculations requiring hands-on certification, or
2) the joining of multiple data sets. Two specific data products are already known to
be required: i) A product that converts the rough all sky electron images into high
resolution all sky electron images via a field-of-view deconvolution process with the
FEEPS sensors (see a possible procedure at the end of this section), and ii) A product
that generates full ion spectra by combining the EIS TOFxE and TOFxPH data sets.
Other Level 3 products include moments, spectra derived by combining some
combinations of EPD with HPCA and FPI, etc. All of these products are at the
observatory level. A preliminary list of Level 3 EPD-involved data products would
include:
1. L3-FEEPS-Electron- Decon-Burst (All-sky electron energy distributions
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2.
3.
4.
5.
6.
7.
8.
deconvoluted with regard to angle)
L3-EIS-Ion-Spectra: Ion spectral data that smoothly joins the TOF x E and
TOF x PH products
L3- EPD Ion Spectra (TBD: Combine all EPD sources for ions spectral
information)
L3-EPD-Particle Moments (TBD: Combines all EPD sources to generate total
electron and ion integrated intensities, pressures, betas, energy-intensity)
Ion and electron all-sky images with magnetic field angles overlaid (is this a
plot of existing data or a data product?)
L3-EPD-and Plasma-Ion Spectra (TBD: Combines EPD, FPI, and HPCA to
generate complete ion spectra)
L3-EPD / Plasma electron spectra (TBD: Combines FEEPS and FPI electron
spectra into complete electron spectra).
L3-EPD and Plasma moments (TBD: Combines all particle sources to
generate total electron and ion integrated intensities, pressures, betas, energyintensity, and plasma flows)
A possible algorithm for generating the first of these Level 3 products, specifically L3FEEPS-Electron-Decon-Burst, is presented here: Do a spherical harmonic fit to “L2FEEPS-Electron- Burst”, with the z-axis pointing along the magnetic field direction and
assuming perfect symmetry around the magnetic field direction, where each fit uses all of
the data samples over 1/8 of a spacecraft spin. Report the fitting parameters followed by
a sampling of the fit to reconstruct the spin data to the 16 elevation angles x 32 spin
sector level. Report the 16 x 32 spin sector data out every 1/8 of a spin.
4.2 Ephemeris and magnetic field information requirements in Levels 1b and 2.
NOTE 1: Because EPD is Spin Based and because the Spin Phase relative to the
sun is known onboard, the transformation matrix between the SC coordinate system and
GSE can be estimated for Data Level-1b by the EPD team by assuming that roughly:
SC-Z(GSE) = (Sin(2.5), 0, Cos(2.5)). That estimate suffices for Level-1b but not for
Level-2. At the Level-1b level, there will be about +/- 30 degree uncertainty in the angle
that the SC-Z axis makes with respect to the GSE X-Z plane. Ideally that angle would be
zero (as assumed with the SC-Z(GSE) vector defined above), but the mission allows a
substantial amount of variability in that angle.
NOTE2: Things in PURPLE below are the things we might ask the SOC for using
Predict information prior to the time that the data comes down. Alternatively, EPD can
generate this information on its own if required.
•
For Each Detector Look Direction (within each spin sector)
1. Pitch Angle (using available magnetic field vector in SC coordinates)
2. GSE Solar Angle (0 to 360 degrees) [derived using SC to GSE Quaternion
below]
3. GSE Elevation Angle (-90 to 90 degrees) [derived using the SC to GSE
Quaternion below]
20
4. Alternative to 2. and 3. above: Unit Vector in GSE of Look Directions.
•
One set for each Spin Sector
1. BX, BY, BZ in SC coordinates
2. SC X Y Z in GSE
3. SC X Y Z in GSM
4. Moon position in GSE (Alternatively, the unit vector in GSE pointing from the
Spacecraft to the Moon. Note: needed because the Moonlight can contaminate
FEEPS ions.
5. SC to GSE Quaternion (4 numbers) or Transformation Matrix (9 numbers)
[derived as per NOTE 1 above]
6. GSE to GSM Quaternion (4 numbers) or Transformation Matrix (9 numbers)
7. MET (or the equivalent) of Sun Pulse
8. Spin Rate
Note: To within the accuracy required for Level-2, the vector formed by the negative of
#3 here combined with knowledge of the detector look directions in GSE (derived using
the look direction in SC coordinates and #5) suffices for determining the possibility of
Earth-Shine contamination of FEEPS ion detectors. This will be accurate at Level 2 but
less so at Level 1b. At the Level-1b level, there will be about +/- 30 degree
uncertainty in the angle that the SC-Z axis makes with respect to the GSE X-Z plane.
Note: To within the accuracy required, the angle that the detector look direction in GSE
(derived using the look direction in SC coordinates and #5) makes with respect to the
GSE X-axis suffices for determining the possibility of Sun-Shine contamination of
FEEPS ion detectors. This will be accurate at Level-2 and also fairly accurate at Level1b. It is fairly accurate at Level-1b because the primary uncertainty in the spacecraft
orientation resides in the role angle about the spacecraft-sun line.
4.3Transfer Files and Fast Ion Data Products
4.3.1 EIS Transfer Files.
The transfer files of EIS data to the FEEPS processes have two purposes: 1) the
generation of Fast Ion products, and 2) provide diagnostic information to help Aerospace
to diagnose cleanliness of the FEEPS data. The transfer file records will have the
following characteristics:
 6- view proton intensity spectrum (TOF x E) sampled every ~2/3 second but repeated
so that there is a 1/3 second cadence to match the 1/3 second cadence of FEEPS.
 6-View electron intensity spectrum: same story
 Central energies are the native energies for EIS and provided in the data file; for the
generation of the Fast Ion products, LASP will interpolate to match FEEPS ion
energies in the generation of FAST ION Product.
21
 For generation of FAST ION product, LASP will be taking the 6 EIS proton views
and combining them in a fashion specified by the EPD scientists into 2 views that
attempt to match the two, non-axial views of FEEPS. The way that the two views are
generated is: EIS-up = A x EIS(5) + B x EIS(4) + C x EIS(3), where A, B, and C are
constants. Similarly EIS-down = D x EIS(0) + E x EIS(1) + Fx EIS(2), where D, E,
and F are also constants, with D ~ A, E ~ B, and F ~ C. Note that as represented in
these equations, the EIS view directions are oriented such that look direction 5 is
closest to looking along the spacecraft spin axis in the “up” direction.
 Proton Intensity Spectra will comprise only EIS high energy channels from the TOF x
E product (The TOF x E product begins at about 50 keV protons).
4.3.2 Fast Ion Products
Fast Ion Product comprises three “fans” of 4 different view directions each. The 3 fans
contain some redundancy between fans (axial information). Specifically:
Fan 1 = FEEPS_1-axial, FEEPS_1-up, FEEPS_1-down, FEEPS_2-axial.
Fan 2 = FEEPS_1-axial, FEEPS_2-up, FEEPS_2-down, FEEPS_2-axial
Fan 3 = FEEPS_1-axial, EIS-up, EIS-down, FEEPS_2-down.
Note that in this description, the word “up” is in reference to the spacecraft coordinate
system, not the FEEPS or EIS coordinate systems. “Up” means towards the +Z axis of
the spacecraft which comes out of the payload deck end of the spacecraft.
Note that EIS-up and EIS-down are created from the 6 nominal view directions using an
algorithm to be provided (Section 4.3.1). Each look direction (4 look directions per fan)
comprises 16 energy channels. LASP will interpolate EIS energies to match FEEPS
energies.
4.4 EPD QuickLook Data Plots
Quicklook data is presented as plotted information only, it does not exist as digital
data. The SITL data, on the other hand (Section 4.5) exists as manipulatable data.
4.4.1 Example:
QuickLook data comprises pre-canned plots of selected portions of the EPD data.
Examples of QuickLook data can be found for APL’s Juno JEDI project at:
http://sd-www.jhuapl.edu/jedi/JMIDL/
Click on “Daily Summary Plots” and choose a sensor (e. g. JEDIA180), a date when the
sensor was on (e. g. 10/08/2013) and a data view (e. g. Spectrograms). If the above
suggestions are adopted, the following plot (Figure 4.4-1) will appear which shows
22
energy x time x electron (or ion) intensity (in color) for 12 different look directions
simultaneously. The exact QuickLook products for EPD have not yet been defined. For
each instrument (3 for JEDI) there are 4 different “pages” of QuickLook information,
right now for mostly engineering purposes. They will can and will be expanded for
Science Purposes.
Figure 4.4-1 Sample EPD QuickLook products
4.4.2 QuickLook Plots for MMS EPD.
The idea here is to create a number of elements or minimal units that can be
combined in different ways.
Elements of Science QuickLook.
1. Energy vs. Time vs. Electron Intensity Color Spectrogram; Angle Averaged or
Angle-Selected.
23
2. Electron Intensity (or C/S) vs. Time with multiple line plots. Angle Averaged or
Angle-Selected.
3. Energy vs. Time vs. Ion Intensity Color Spectrogram; Angle Averaged or AngleSelected.
4. Ion Intensity (or C/S) vs. Time with multiple line plots. Angle Averaged or AngleSelected.
5. PA vs. Time vs. Electron Intensity Color Spectrograms for selected energy range
6. PA vs. Time vs. Ion Intensity Color Spectrograms for selected energy range
7. Solar Angle (GSE) vs. Time vs. Electron Intensity color spectrograms for selected
energy range
8. SA(GSE) vs. Time vs. Ion Intensity color spectrograms for selected energy range
9. Individual Snapshots of SA(GSE) vs. Elevation(GSE) vs. Electron Intensity color
spectrograms with PA contours for selected energy range and selected time
cadence. A series of these can be created into a row or multiple rows.
10. Individual Snapshots of SA(GSE) vs. Elevation(GSE) vs. Ion Intensity color
spectrograms with PA contours for selected energy range and selected time
cadence. A series of these can be created into a row or multiple rows.
11. What else (particularly for the magnetopause)?
Canned Pages would be created from these elements
• A comprehensive set (8-12) for each spacecraft.
• A couple of elements from each of 4 spacecraft would be displayed (total of
perhaps 8-12 (TBD) panels per page?)
• User chooses what elements to be put on one page.
4.5 EPD SITL Data
As described in Section 1.4, EPD (EIS + FEEPS) generates onboard Burst Trigger Flags.
However, unlike data from the other investigations, there are no reliable or consensus
simulations that predict the behaviors of energetic particles in the vicinity of reconnection
sites. Therefore, it will be some time into the mission before we might see energetic
particles uses as a trigger for deciding to telemeter down to the ground segments of burst
data. However, it is likely that EPD data will be very useful for providing the context for
using other parameters to make decisions about the selection of burst data.
EPD SITL data can be in the form of the QuickLook data; e. g. color spectrograms like
that shown in Figure 4.3-1. However, it may be that simple digital parameters are needed
that can be plotted as simple line plots together with other parameters. The following are
some possibilities for simple EPD SITL data:
a. Nearly spin-aligned rate channels (as close as can be managed using look directions
5 or 0) of several selected EIS proton channels (obtained from the EIS Transfer
File),
b. Nearly spin-aligned rate channels of several selected FEEPS electron channels (It
would be best to represent these with the “crude intensity” available at the L1b data
level),
24
c. Spin averaged rate channels of the same several selected EIS proton channels that
view perpendicular to the spin axis (average of view 2 and 3),
d. All-sky average of several selected FEEPS electron sensor rate channels (average of
all 18 electron views).
e. Some single parameter representation of the spin anisotropy for each of several of
the EIS proton channels (maximum rate within the spin minus the minimum rate
within the spin, all divided by the average rate within the spin (this formulation
avoids dividing by small numbers),
f. Single parameter representation of angular anisotropies of the FEEPS electrons for
several rate channels; for example: maximum rate from the 18 look directions minus
the average rate, all divided by the average rate.
5.0 Detailed FEEPS and FAST ION Data Descriptions (Owned by Jim Craft)
6.0 Detailed EIS Data Descriptions (Owned by Larry Brown).
Appendix A: Onboard Burst Flag Algorithms.
A.1 EIS Burst Trigger Algorithms
Presented here is a special data product for telemetering Burst Flag Data from EIS.
Mnemonic
EISimTRIGDAT
APID
Length
(Octets)
0x11F
20
Description
The instruments send trigger data once each trigger cycle while in the
burst region.
Message Sub-Field Descriptions
Size
(Octets)
Offset
(Octets)
Primary Header
6
0
CCSDS Primary Header w/APID above
Secondary Header
8
6
Telemetry Secondary Header
TDN: Ion Intensity
1
14
Indexed to 0 – 255.
Hemisphere average of on energy-integrated protons every 10
seconds.
Spectral Range: 25 – 500 keV
TDN: Ion Anisotropy
1
15
Indexed to 0 – 255.
Ratios of selected look directions for common energy ranges.
Maximum values within 10 second intervals.
Spectral Range: 25 – 500 keV
Reserved
2
16
Set to 0.
Checksum
2
18
Unsigned add ignoring carry
Sub-Field Name
Description
1) We generate useful trigger information with a one spin cadence. However, the
CIDP is expecting trigger update every one half of spin. In response we will
25
generate 1 set of unique trigger indexes every spin, but we will report our
triggers twice per spin, because that is the cadence that is expected by the CIDP.
Specifically, at the end of a spin we will report our trigger indexes, and then ½ a
spin later we will report the very same set trigger indices.
2) For the “Ion Intensity” trigger: For each of 8 contiguous Fast Survey data frames
(constituting one full spin), add together the 2 lowest energy proton energy
channels from the “Low Res. TOF x Energy Ion Rates” from view directions (VD)
1 and 4 (view directions run from 0 to 5 within the EIS field of view). This sum
will look like: SUM = P1(VD1) + P2(VD1) + P1(VD4) + P2(VD4). Take this sum
from each of the 8 Fast Survey frames (FSF) and add them all together into a
SUM_total. Lets us define a maximum possible sum = MPS, which is a number
that we can change with a command (I hope). Then the TRIGGER1 = SUM_total *
255/MPS (with the additional code that says, if SUM_total > MPS then TRIGGER1
= 255).
3) For the “Ion Anisotropy” trigger: Let us assume that the boundary between Fast
Survey Frame accumulation 1 and Fast Survey Frame 8 is roughly the direction
of the sun (the initiation of the spin is a sun pulse or a sun phase = 0). We will
label the Fast Survey Frames: FSF1, FSF2, ---, FSF8. Form the following sums:
SUMA = Add together P1 and P2 for VD2 and VD3 for FSF2 and FSF3, all into a
single sum. Let SUMB = Add together P1 and P2 for VD2 and VD3 for FSF6 and
FSF7, all into a single sum. Form the “Anisotropy” AN = ABS(SUMB –
SUMA)/(SUMB + SUMA). Then, TRIGGER2 = AN * 255 (since the maximum value
that AN can have – I think – is “1”).
Description from John Hayes’ EIS document: Burst Trigger
Once per spin, EIS computes ion intensity and anisotropy. The two results are
sent to the CIDP for use in its burst trigger algorithm. The results, termed
Trigger Data Numbers (TDNs), are scaled to the range 0 - 255, where 0
represents the least interesting result and 255 the most interesting. The TDNs
are sent to the CIDP every ten seconds in a telemetry packet; note that this is
more often than the values are computed.
Ion intensity is computed using the sum of selected high-resolution TOF x
energy ion bins. Both the number of bins, 1 - 7, and the bins to use, are
uploadable parameters. Only bins from SSD channels 1 and 4 are used; note
that these channels look above and below the spacecraft spin plane. The sum is
integrated over the entire spin. The intensity TDN is proportional to the ratio of
the sum to a maximum intensity; the maximum intensity is an
uploadable parameter.
26
Ion anisotropy is computed using the same high-resolution TOF x energy ion
bins used in the ion intensity calculation. However, bins from SSD channels 2
and 3 are used; these channels look along the spin plane. Two sums are
integrated; each sum represents one quarter of the spin, normal to the EIS-sun
line. This is illustrated in the following figure. The anisotropy TDN is
proportional to the ratio of the difference in the sums to the sum of the sums.
Note: because high-resolution bins are used, if the resolution is degraded, i.e.
S>4, then the algorithm's results will be degraded.
Figure 17. Ion Anisotropy
The following pseudo-code summarizes the trigger computations: compute
burst trigger:
TOFxEbins = list of TOFxE high-res. ion bins
# compute ion intensity
sumT = 0
for each sector
for each bin in TOFxEbins
sumT += TOFxEIons[1, bin] + TOFxEIons[4, bin]
if sumT < max-ion-intensity
intensity = 255*sumT/max-ion-intensity
else
intensity = 255
# compute ion anisotropy
sumA = sumB = 0
for sectors 4 - 11
for each bin in TOFxEbins
sumA += TOFxEIons[2, bin] + TOFxEIons[3, bin]
for sectors 20 - 27
27
for each bin in TOFxEbins
sumB += TOFxEIons[2, bin] + TOFxEIons[3, bin]
anisotropy = 255*abs(sumB - sumA)/(sumB + sumA)
A.2 FEEPS Burst Trigger Algorithms
Background: FEEPS data is spin based. There are 64 sectors per spin and 32 sectors
per half spin. Each FEEPS head will generate 1 set of 3 burst trigger parameters
every half of a spin or every 32 sectors. The cadence will therefore be roughly 10
seconds for a 20 second spin period, but not exactly because of variances in the spin
rate. Therefore, the FEEPS triggers will be generated asynchronously with respect
to the nominal trigger system, which is time based with a cadence of exactly 10
seconds. I would recommend that the CIDP generate the FEEPS burst triggers with
a half spin cadence and then query the resulting data base of FEEPS triggers every
10 seconds. With this system there may be cases when the same set of parameters
is sent twice in a row (or alternatively, we may jump over a set of flags and miss
them altogether).
There are 3 FEEPS trigger parameters from Each FEEPS head, for a total of 6 FEEPS
parameters from the two heads, all based on the electron measurements. The EIS
sensor will provide burst triggers for energetic ions.
1) FEEPS Electron Intensity: For each spin sector and for each of the Sensors 1-5
and 9-12, sum together the energy channels 2-9 (the lower energy half but
avoiding the lowest energy channel), and then sum together the result from each
of the Sensors 1-5 and 9-12, and then sum together the results for the first 32
spin sectors, generating the parameter SUM1. Convert SUM1 to a number
between 0 and 255 by scaling with the provided parameter SUMMAX
(Flag1=255*SUM1/SUMMAX). The result is the “Electron Intensity” burst flag for
the first half spin. Repeat this operation for spin sectors 33-64, and then
continue repeating this operation for each half spin.
2) FEEPS Electron Variability: For each spin sector and for each of the Sensors 1-5
and 9-12, sum together the energy channels 2-9. Call the result for each of the
first 32 spin sectors “sum(n)” where “n” is a number between 1 and 32. At the
end of the half spin, perform a scaled standard deviation calculation, specifically:
SSD = 255* Sum[(sum(n) - SUM1/32)^2, {for n, 1-32}] / (SUM1^2)
Construct Flag2 with the following operation: Flag2 = If(Flag1 > SUMMIN2, SDD,
0), where SUMMIN2 is a provided parameter. Repeat this operation for sectors
33-64, and then for all subsequent ½ spins.
28
3) FEEPS Electron Anisotropy: For each spin sector and Sensors 1 and 2, sum
together the energy channels 2-9. Call the result for each of the first 32 spin
sectors “sum12(n)”. Sensors 1 and 2 are two “equatorial” sensors at one
extreme side of the FEEPS sensor. Also, for each spin sector and Sensors 11 and
12, sum together energy channels 2-9, and call the result “sum1112(n)”. Sensors
11 and 12 are two “equatorial” sensors at the other side of the FEEPs sensor.
Perform the following operation:
Anisotropy = 255*Sum[Abs((sum12(n) – sum1112(n))/(sum12(n) +
sum1112(n)), {for n, 1-32}]
Construct Flag3 with the following operation: Flag3 = If(Flag1 > SUMMIN3,
Anisotropy, 0), where SUMMIN3 is a provided parameter. Repeat this operation
for sectors 33-64, and then for all subsequent ½ spins.
Appendix B: Structure of the FEEPS Calibration Matix.
The FEEPS Calibration Matrix will consist of an Excel or ASCII listing with one row per
channel per energy. The start of such a calibration matrix for one spacecraft is shown
below. This Calibration Matrix would contain 384 lines for each spacecraft (comprising
2 FEEPS heads, “top” and “bottom”). “LT_A” and “LT_B” are parameters used for live
time correction (may not be needed on a line-by-line basis, but it may be convenient to
keep it this way).
29
Line_# Spacecraft Instrument
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
top
Sensor Look_Dir Species Channel
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
Electrons
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
LT_A
LT_B
E1
E2
Eff
G
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
20
30
45
60
90
140
220
300
450
600
800
1200
1600
2000
3000
4500
20
30
45
60
90
140
220
300
450
600
800
1200
1600
2000
3000
4500
30
45
60
90
140
220
300
450
600
800
1200
1600
2000
3000
4500
6000
30
45
60
90
140
220
300
450
600
800
1200
1600
2000
3000
4500
6000
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
References
J. B. Blake et al. (2014), the Fly’s Eye Energetic Particle Spectrometer (FEEPS) for the
Magnetospheric Magnetospace (MMS) Mission, Space Sci. Rev., In Preparation.
B. H. Mauk et al. (2014), The Energetic Particle Detector (EPD) Investigation and the
Energetic Ion Spectrometer (EIS) for the Magnetospheric Magnetoscale (MMS)
Mission, Space Sci. Rev., Published online: DOI 10.1007/s11214-014-0055-5
30