<table><caption>**Table 17** CODMAC level descriptions</caption><thead><tr><td>Level</td><td>Description</td></tr></thead><tbody><tr><td>1</td><td>Raw data: Telemetry with data embedded.</td></tr><tr><td>2</td><td>Edited data: Corrected for telemetry errors and split or decommutated into a data set for a given instrument. Sometimes called experimental Data Record. Data are also tagged with time and location of acquisition.</td></tr><tr><td>3</td><td>Calibrated data: Edited data that are still in units produced by instrument, but that have been corrected so that values are expressed in or are proportional to some physical unit such as radiance. No resampling, so edited data can be reconstructed.</td></tr><tr><td>4</td><td>Resampled data: Data that have been resampled in the time or space domains in such a way that the original edited data cannot be reconstructed. Could be calibrated in addition to being resampled.</td></tr><tr><td>5</td><td>Derived data: Derived results, as maps, reports, graphics, etc. NASA Levels 1C through 5.</td></tr><tr><td>6</td><td>Ancillary data: Non-science data needed to generate calibrated or resampled data sets. Consists of instrument gains, offsets; pointing information for scan platforms, etc.</td></tr><tr><td>7</td><td>Correlative data: Other science data needed to interpret spaceborne data sets. May include ground-based data observations such as soil type or ocean buoy measurements of wind drift.</td></tr><tr><td>8</td><td>User description: Description of why the data were required, any peculiarities associated with the data sets, and enough documentation to allow secondary user to extract information from the data.</td></tr><tr><td>N</td><td>Not applicable.</td></tr></tbody></table>

* Level 2 Edited: Reformatted Engineering Data Records. Raw level 1 data is unpacked to separate science/engineering products and decompressed if required. Data are time-ordered, redundant data packets are removed, and missing expected data flagged. No other calibration is carried out, e.g. data are left as counts per accumulation period for energy step *i* and deflection step *j*.

* Level 3 Calibrated: Counts are converted to scientific units (i.e. counts per second, electron flux, energy is given in eV and deflection direction in degrees).

* Level 4 Resampled data: not relevant to JADE, data will not be resampled.

* Level 5 Derived: Pitch-angle distributions, electron/ion plasma parameters such as density, temperature and velocity. This may require additional calibrated information from other Juno instruments, i.e. magnetometer data for pitch angles.

* Level 6 Ancillary: Spacecraft position, velocity, orientation, spin-phase, quality flags, efficiency/voltage/energy tables used for level 3 products.

Figure 78 shows the planned data flow of the data from level 1 data from JPL (where the level 1 JADE data from Juno is gathered and transferred to the instrument team) through to level 3. The following subsections discuss currently planned data products at each level.

### 4.5.1 Level 2 Reformatted Engineering Data Records

#### 4.5.1.1 Science Data
Reformatted Engineering Data Records (REDRs) take the raw data and divide it into separate files depending on the JADE Data Product IDentifier (DPID) number. Table 18 separates these out by data type (rows) and telemetry mode (columns).

In addition to the above science data there are five operations-related data products concerning the whole JADE instrument suite: (1) BOOT_HK—Engineering/Housekeeping packet of the Boot Program (i.e. General monitors and power status’), (2) BOOT_MEM_STAT—Memory Status packet of the Boot Program (i.e. checksums and counts of single/double-bit errors), MEM_DMP—Memory Dump packet (a complete dump of the
<figure><img src="image_84.png" /><figcaption>Fig. 78 Data processing pipeline flow</figcaption></figure>
<table><caption>**Table 18** All JADE science products</caption><thead><tr><th>Type of histogram</th><th>Low rate science</th><th>High rate science</th><th>Burst science</th><th>MCP calibration (ops use)</th><th>High voltage engineering science (ops use)</th></tr></thead><tbody><tr><td>Electron E060</td><td>✓</td><td></td><td></td><td>✓</td><td></td></tr><tr><td>Electron E180</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td></tr><tr><td>Electron E300</td><td>✓</td><td></td><td></td><td>✓</td><td></td></tr><tr><td>Ion species 0</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td></tr><tr><td>Ion species 1</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td></td></tr><tr><td>Ion species 2</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td></td></tr><tr><td>Ion species 3</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td></td></tr><tr><td>Ion species 4</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td></td></tr><tr><td>Ion species 5</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td></td></tr><tr><td>Ion species 6</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td></td></tr><tr><td>Ion species 7</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td></td></tr><tr><td>Ion time of flight</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td></tr><tr><td>Ion logicals</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td><td>✓</td></tr><tr><td>Direct Events<sup>a</sup></td><td>✓</td><td>✓</td><td>X</td><td>✓</td><td>✓</td></tr></tbody></table>

memory), SCI_ENG—Engineering/Housekeeping packet of the Science Program (i.e. General monitors and power status), SCI_EVENT—Event Message packet of the Science Program (describes an unusual or unexpected occurrence, i.e. a command rejection).

### 4.5.1.2 Ion Species Identification
The JADE-I sensor uses a loadable LUT to separate the measured events on the anodes to different species mappings. Events that register on a single or two adjacent STOP anodes get mapped to a species. Events that result in only a START event, Background events, or any events that get mapped to non-adjacent STOP anodes are not mapped to a species.

There are 8 potential species, numbered 0 through 7. Species 0 is defined as any event that is seen on either a single or two adjacent STOP anodes. No START is required, so species 0 includes events that do not have a valid TOF measurement (a valid TOF measurement includes a valid START and STOP within a defined time range). For species 1–7 there is additional event masking possible so that events that have a ‘bad’ TOF can be masked out. Bad TOF events are durations shorter than 1 ns or longer than 330 ns. Also, events that have multiple starts prior to the stop signal, or events that result in STOPS in adjacent anodes can be masked out of species 1–7. In the case of measuring STOPS in adjacent anodes, the event is mapped to the lower anode number in addition to incrementing a counter of the number of adjacent events. The mask setting is adjustable based on table values. At launch, adjacent events are included in species 1–7, but bad TOF events and events with multiple starts are not.

Species 1 are all events that do have a valid TOF measurement. Species 1 is a subset of the species 0 events. Species 2–7 are reserved for specific mass ranges and each of species 2–7 are a subset of the species 1 data. Events are mapped to species 2–7 based on a LUT that defines a TOF range for each species and each ESA step. The TOF table in the LUT can be updated by uploading a new table or a new LUT. The species TOF table is currently defined

<footnote><sup>a</sup>Direct Events data are not histograms and do not occur during Burst science</footnote>
to have species 2 for M/q of 1 amu/q, species 3 for M/q between 2 and 5, and species 4 to be for M/q greater than 5 amu/q.

### 4.5.1.3 Ion Direct Events
There are two types of primary Science data products: histograms and direct events. Histograms are binned data and retain a complete history of the number of events that occurred within a given bin during an accumulation period. The duration of the accumulation period can be commanded, as noted earlier; low accumulation LRS has histograms that cover 300 or 600 s periods while intermediate accumulation LRS has histograms that cover 30 or 60 s periods. Because these events are simply counted, you can derive the number of particles from a given region from histograms but have no data on the order in which the particles were collected (i.e. if one section of the sky filled in preferentially earlier in the accumulation period and another section filled in later).

Direct events are individual events stored with time of collection, TOF, ESA and DFL information associated with them. A direct event carries with it all relevant information to describe the stored event, and thus is a much more detailed data product. Because the level of detailed information associated with just one direct event is large, telemetering many direct events quickly becomes a bandwidth issue. Juno is a telemetry-limited mission, so histograms are given priority storage. Direct events are stored on a low-priority basis and are transmitted when downlink allows.

### 4.5.1.4 Electron Data
The electron data are returned as histograms of energy vs. pitch angle, as described in Sect. 4.3.4. For electrons, there is no complexity of TOF data, nor species separation, as there is for JADE-I.

## 4.5.2 Level 3 Calibrated Data

The measurements need to be converted to scientific units, which often requires knowing which plasma species is being measured. This is straightforward for electrons (negative ions are not expected at Jupiter). However, the ion detectors measure a variety of positively charged ions with different masses and different charges, i.e. O⁺, S⁺⁺, S⁺, O⁺⁺S⁺⁺⁺, H⁺, in order of decreasing abundance. Therefore, the user must first partition the counts into their separate species, which is not possible if, as is usually the case, the velocity distributions overlap.

### 4.5.2.1 Conversion of Counts per Accumulation to Counts per Second
The first level of calibration is to convert the counts per accumulation ($C_{Accum.}$) into counts per second ($C_s$). This is a simple division of:

$$C_s = \frac{C_{Accum.}}{dt} \qquad (4.1)$$

where *dt* is the accumulation period, which is provided in each data file. Note this unit is independent of ion species or charge.

### 4.5.2.2 Convert to Differential Energy Flux
Differential energy flux, DEF, is counts per second of a particular species (i.e. electrons or protons) divided by the geometric factor (see Sects. 3.2.1.3, 3.3.1.1 and Table 6) and has units of cm⁻² sr⁻¹ s⁻¹.

$$DEF = \frac{C_s}{G} = \frac{C_{Accum.}}{G dt} \qquad (4.2)$$

where the MCP efficiencies are already included in the effective geometric factors as they were derived from laboratory calibration measurements.
### 4.5.2.3 Convert to Differential Number Flux
Differential number flux, DNF, of a particular species is DEF divided by the energy (E, in eV) and modulus of charge (q, in Coulombs) of the particle and has units of cm⁻² sr⁻¹ s⁻¹ J⁻¹. For electrons or singularly charged ions, q = 1.602 × 10⁻¹⁹ C.

$$DNF = \frac{DEF}{E|q|} = \frac{C_{Accum.}}{E|q|Gdt} \qquad (4.3)$$

### 4.5.2.4 Convert to Phase Space Density
If the mass and charge of the species is known (or assumed), the Phase Space Density, PSD, is calculated from dividing the DEF by v⁴ (where v is found from E/q = 1/2mv²),

$$PSD = \frac{DEF}{(2E/mq)^2} = \frac{m^2 q^2 C_{Accum.}}{4E^2 G dt} \qquad (4.4)$$

Note that this equation assumes there is zero spacecraft potential accelerating/decelerating the incident electrons/ions. This equation also shows the necessity of partitioning the ion counts into separate ion species. Note the strong dependence of this conversion of DEF to phase space density on the mass and charge of the particles: H⁺ has an (mq)² = 1 amu²e², O⁺ has (mq)² = 256 (= 16²) amu²e², while S⁺⁺ has (mq)² = 4096 amu²e². The net effect is that the resulting PSD, the desired scientific measurement, is very sensitive to assumption of what species is being detected.

### 4.5.3 Level 5 Derived Data

Once level 3 calibrated data exists; other data products may be derived. Examples include plasma density, flow velocity, isotropic temperatures, anisotropic temperatures and temperature anisotropies, and plasma β. Many methods for these derivations exist, however a few are discussed below.

#### 4.5.3.1 Pitch-Angle Distributions
In order to calculate pitch-angle distributions with respect to the magnetic field, one must know the magnetic field direction at the time of the particle measurement as accurately as possible, ideally with level 3 data from Juno's magnetometer. Calculating pitch-angle distributions requires reordering the data to refer to the particle's (ion or electron) direction of motion relative to the magnetic field direction, such that 0° is parallel to the magnetic field, 90° is perpendicular, and 180° is anti-parallel. A dot product between the particle's flow direction and the magnetic field vector (in the same co-ordinate system) is then used to find the pitch angle. Note that the instrument FOV measures incoming particles, so that the flow FOV is the opposite direction (i.e. the instrument aperture must include the direction opposite to the particle motion).

#### 4.5.3.2 Methods of Calculating Plasma Moments
Methods of calculating single species moments of the velocity distribution function, f(v), are well known (Baumjohann and Treumann 1999; Boyd and Sanderson 1969; Paschmann and Daly 1998) and particularly well suited to spinning spacecraft and electron data.

The ith moment, $M_i$, of a given species is:

$$M_i = \int f(v) v^i d^3 v \qquad (4.5)$$
As such density, $n$, may be calculated by setting $i = 0$:

$$n = M_0 = \int f(v)d^3v \qquad (4.6)$$

$i = 1$ provides $M_1$, which is equal to $nV$:

$$nV = M_1 = \int f(v)vd^3v \qquad (4.7)$$

Since $n$ was found from the previous equation we can divide to obtain velocity, $V$. Continuing to higher orders of $i$ can provide temperatures and pressures.

This technique is excellent for electron data where the plasma species has a known mass and charge (at Jupiter we do not expect to find the negative ions that are found near Titan or Enceladus at Saturn), and can give a cadence of one set of moments values per spin per sensor. Another benefit is that no plasma distribution (Maxwellian, Kappa, or other) is assumed.

However it is more complicated to use this technique for ion data because of the multiple species with differing masses and charges. Partitioning the ion data into single species to calculate $f(v)$ is complicated because the different species often overlap in velocity space. Therefore, a forward modeling method is generally preferred for magnetospheric ions.

### 4.5.3.3 Methods of Calculating Plasma Parameters via Forward Modeling
If multiple plasma species exist and overlap in velocity space, then plasma parameters can also be obtained by a forward modeling. This requires assuming which plasma species are present and the nature of their velocity distribution (i.e. Maxwellian, kappa, etc.). These assumptions are then used to create a virtual model of the instrument response for a specified density, temperature and velocity of each plasma species. The simulated histogram (for a given density, temperature and velocity per plasma species) is then compared with the measured histogram from JADE, and the model plasma properties adjusted until the model matches the measured data (e.g. as quantified by a reduced Chi-square measure of goodness of fit).

This technique is computationally expensive, but does not require partitioning of the data into separate species, allows exploration of the parameter space (usually not unique) that reasonably fit the data, and estimates statistical uncertainties of the output plasma properties. The disadvantage is it is necessary to assume the plasma species and distributions to use for the calculation; a poor assumption will give poor values.

### 4.5.3.4 Temperature Anisotropies and Plasma-$\beta$
Once densities and temperatures have been deduced by either moment summation or forward modeling, further values can be derived. For instance temperature anisotropy is the ratio of the perpendicular temperature to the parallel temperature. Likewise plasma $\beta$ is calculated as the ratio of plasma pressure to the magnetic pressure. Level 3 Juno magnetometer data provides $B$, and combined with the level 5 JADE data of density, $n$, and temperature, $T$ to compute:

$$\beta = \frac{n k_B T}{B^2 / 2 \mu_0} \qquad (4.8)$$

where $k_B$ is the Boltzmann constant and $\mu_0$ is the permeability of free space. Further plasma properties such as Mach numbers, scale lengths, wave and collision frequencies can be calculated from the JADE ion and electron plasma parameters.
### 4.5.4 Level 6 Ancillary Data

Level 6 data aid in understanding JADE data, but are not measured by JADE. For example, JADE data are time-stamped from the onboard Juno spacecraft clock and values included within all level 1 data records. For level 2 data, time is converted to UTC using NASA's Navigation and Ancillary Information Facility (NAIF) SPICE software suite (http://naif.jpl.nasa.gov). NAIF SPICE software is also used to generate all spacecraft orientation, position and velocity data. In addition, data from the magnetometer on Juno is used to convert JADE counting data in to pitch-angle distributions.

4.5.4.1 *Time* Time is expressed as a UTC string (yyyy-dddTHH:MM:SS.sss) and the corresponding Spacecraft clock time. Additionally, time to/since perijove is provided. These times and conversions are calculated using NAIF SPICE.

4.5.4.2 *Spacecraft Position/Orientations* Spacecraft position and velocity is provided in a variety of co-ordinate systems, including (but not limited to) Jupiter-centered radial distance, latitude and local time, SYS3 (with west longitude), RTN and J2000. The spacecraft's orientation is provided along with transformation matrices to convert this into several other co-ordinate systems. Finally, the spacecraft spin rate and a spin phase are given, where zero spin phase is when Juno scans past ecliptic north. All this information originates from NAIF SPICE routines, so the particular SPICE kernels used are also noted.

4.5.4.3 *JADE Instrument Information* JADE can take a variety of data products, but often runs a subset in order to meet telemetry bandwidth allowances, therefore the data products "on" at any given time are listed. In addition, quality and warning flags are provided to help give context to the data. Magnetic field information is provided, along with a flag describing its source (i.e. onboard uncalibrated or ground-calibrated CODMAC level 3 data from the Juno MAG team).

Different energy tables can be used for each of the JADE instruments. This information includes which table is used, and efficiency parameters required to convert raw data in to calibrated units for CODMAC level 3 products.

# 5 First Light Data

## 5.1 Overview

Juno was launched on August 5, 2011 from Cape Canaveral Air Force Station. After commissioning of the spacecraft, instrument turn on began, with the initial JADE turn on and low voltage checkout on Oct 20, 2011 and high voltage checkout from November 14–18, 2011. By this time, the round trip light time (communications) was already over 5 minutes. While some final testing and tuning had to be deferred to a later date, all four JADE sensors were ramped up to their full high voltages. This included bringing all thirteen 10 kV components to full operating voltage and ramping the MCP detectors up to their full operating voltages (saturation). Both JADE-I and all three JADE-Es immediately began taking science data in the solar wind, which demonstrated both their capabilities and scientific utility in the real space environment for the first time. This short section briefly highlights just a few of those “first light” observations.

Also after launch, the JADE-I sensor stabilized at a temperature ~20 °C hotter than predicted. During the course of the investigation, we found that the JADE-I radiator was
<figure><img src="image_85.png" /><figcaption>**Fig. 79** JADE-E LRS data for a 10 min integration in the solar wind</figcaption></figure>

not located where the original thermal analysts had presumed it to be. Closeout photographs showed that JADE-I was built according to the drawings, but there was a disconnect between the drawings and the assumptions of the analysis. This thermal design issue could only possibly affect operation for the perihelion part of Juno's orbit only. At all larger heliocentric distances, including science operations at Jupiter, there is no impact to JADE whatsoever. To assess any possible perihelion issue, a new thermal model was created to match the as-built condition; this model predicted JADE-I perihelion temperatures a few °C warmer than proto-flight thermal vacuum testing. To correlate the new thermal model, and to assess any risks of the perihelion thermal environment, we tested the flight-spare JADE-I sensor to well beyond that environment using the JPL solar illumination chamber. Detailed calibrations performed before and after testing showed that JADE-I should be totally unaffected by the perihelion environment.

## 5.2 JADE-E

We tested JADE in the LRS, HRS and Burst modes of operations during our initial turn on. The data presented here were collected during LRS in the solar wind. Figure 79 shows a spectrogram of energy versus spin angle taken by JADE-E060 (cf. Fig. 5) over a 10-min integration period, which corresponds to ~10 spacecraft spins. The energy ranges from 100 eV to 100 keV and the spin covers the entire 0°–360° rotation. The color codes the electron count rate per bin (~11.6% in energy by 15°). Below ~1 keV the data are clearly ordered by spin phase and provide measurements of the solar wind electrons (core, halo and Strahl). Above ~1 keV the 2–3 Hz rates are caused by penetrating radiation (cosmic rays) and MCP internal noise; these low background rates indicate that JADE-E is ready to make the important Jovian electron measurements once it enters the Jovian magnetosphere.

Figure 80 shows energy spectra for all three JADE-E sensors where all the spin phases have been collapsed. During LRS only one JADE-E is powered, and thus the three JADE-E spectra were taken at different times (dates indicated in the plot). The penetrating background above 1 keV has been averaged and subtracted from the spectra. We compare the JADE-E measurements to scaled (by distance and geometric factor) solar wind electron measurements (McComas et al. 1992) from the SWOOPS instrument on Ulysses. There is an excellent agreement between the spectra, which validates the JADE-E observations.

## 5.3 JADE-I

Like JADE-E, JADE-I was also operated in LRS, HRS and burst modes during HVCO, and was able to observe the solar wind. The energy spectra presented here (Fig. 81) were taken
**Fig. 80** Energy spectrum of solar wind electrons during a 10 min integration in LRS. The *dashed line* represents a typical solar wind electron spectrum scaled to JADE-E measurements from McComas et al. (1992)

<figure><img src="image_86.png" /></figure>

**Fig. 81** Solar wind ion energy spectrum measured by JADE-I during an ~2 hour period while JADE-I was operated in HRS mode. The *solid blue curve* is for species 1, which includes all mass per charges in the JADE-I measurement range. The *dashed orange curve* is for species 2, which is for TOF values which map to $M/q$ of 1 (protons). Note how the distinctive second peak from alphas at ~2 keV is not seen in the species 1 data

<figure><img src="image_87.png" /></figure>

while in HRS mode. While operating in HRS mode, the ESA sweep table scans the full energy range of JADE-I (10 eV to 45 keV). Over the entire HVCO (~6 days), the solar wind was relatively stable, with a flow speed of ~380–450 km s⁻¹ as measured by ACE at 1 AU. Plotted in Fig. 81 is the energy spectra for species 1 in the solid blue line and species 2 in the dashed orange line. Species 2 was defined to be the TOF values that map to $M/q$ of 1 (protons). Species 1 is for any TOF value, and therefore includes alpha ($M/q = 2$) and heavier masses in this energy per charge range. The alphas are seen as a peak at ~2 keV in the species 1 data is successfully filtered out in the species 2 data.

Figure 82 shows energy per charge and TOF data while JADE-I was in LRS mode and using two different sweep tables. Overplotted on the data are curves that show contours of constant $M/q$ (of 1, 2, 4 and 8, solid lines) and constant incident velocity (dashed lines). For lower energies, the total energies of the particles inside the TOF section is dominated by the 10 kV accelerating potential the particle experience as they are accelerated into the TOF section.

The top panel shows data taken when sweep with table 1. This sweep table covers the same energy steps as were used during when in HRS mode and shown in Fig. 81. The bottom panel shows sweep table 2, which is reduced in range about the typical solar wind energies. The color bar on the right is common to both panels. The data had a background due to false coincidence events subtracted. The events at low TOF values (<10) is due to electronic noise. The long tails to lower energies of each mass comes primarily from events measured by the anode that looks across the spacecraft deck face that is normal to the sun direction. This indicated that these lower energy tails come from some interaction with the solar wind with the spacecraft. While JADE-I was designed to measure magnetospheric plasmas and is
<figure><img src="image_88.png" /><figcaption>**Fig. 82** Energy-TOF spectrograms for two different sweep tables. Overplotted on the data are curves of constant *M/q* (*solid lines*) and constant incident velocity (*dashed lines*). The *top panel* shows data for sweep table 1, which covers from 10 eV–40 keV (the same energy steps as used during HRS mode and shown in Fig. 81). The *bottom panel* shows data for sweep table 2, which covers the typical solar wind energies of 0.3–8 keV</figcaption></figure>

not capable of making high resolution measurements of the solar wind, it is clearly capable
of measuring the protons, alpha, and heavier species in the solar wind.

**6 Summary and Conclusions**

The Jovian Auroral Distributions Experiment is a complete plasma instrument suite com-
prising three essentially identical electron sensors, a single ion sensor, and a common elec-
tronics box. Together, these provide unprecedented observations of the complicated Jovian
magnetospheric electron and ion plasma populations and provide the core *in situ* measure-
ments of the auroral particles populations needed to finally understand what creates the most
intense auroral emissions in the solar system. Collectively, JADE provides a remarkably
broad and detailed set of measurements of the Jovian auroral and magnetospheric plasmas,
which will surely revolutionize our understanding of these important and complex regions.

While the EBox resides in the Juno Radiation Vault the JADE-I sensor and three JADE-Es
look off of the edges of the spacecraft deck, with the latter being arrayed 120° apart so as to
be able to measure complete electron distributions at any spacecraft spin phase. The JADE-
Es measure electrons from ~0.1 to 100 keV and provide detailed pitch-angle distributions
at a 1 s cadence. JADE-I has an instantaneous field of view of 270° × 90° and in just 4 s,
measures ions from ~5 eV to ~50 keV and separates the ion species from 1 to 50 amu with
*m/*Δ*m* ~ 2.5; over each 30 s spacecraft rotation, JADE-I measures and analyzes ions from
all directions in space.
<figure><img src="image_89.png" /><figcaption>**Fig. 83** The Southwest Research Institute Electron Calibration Facility. The main vacuum vessel has an approximate volume of 580 liters. Access to the interior of the chamber is through a Viton sealed door inside a class 10,000 clean tent, which includes a class 100 clean bench to facilitate final work on the instrument prior to installation into the vacuum chamber. Vacuum feed throughs of varying sizes circle the chamber and are accessible outside the clean tent</figcaption></figure>

This paper describes in detail the JADE design, construction, calibration, planned science operations, data processing, and data products and documents the SwRI electron calibration facility, which was developed and used for the JADE-E calibrations. As such, this paper should be used as the citable reference for both JADE and for the SwRI electron calibration facility going forward.

**Acknowledgements** We are deeply indebted to all of the outstanding members of the JADE team who have made this exciting and challenging instrument suite a reality as well as to all of the dedicated people who have made the broader Juno program possible. This work was supported by NASA as a part of Juno mission, which is in NASA's New Frontiers Program.

**Open Access** This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.

# Appendix: The Southwest Research Institute Electron Instrument Calibration Facility

## A.1 Introduction

The Southwest Research Institute Electron Calibration Facility (Fig. 83) is used to prototype, develop, and calibrate space flight plasma instruments. This facility was developed to support the calibration of the JADE-E sensors based on the design (and uses much of the existing infrastructure) of the Southwest Research Institute Calibration Facility described by McComas et al. (2009).

In Sect. A.2 we describe the vacuum system and general lab layout. Sect. A.3 describes the electron source and electron optics, including external magnet coils. The positioning system is described in Sect. A.4.
<figure><img src="image_90.png" /><figcaption>**Fig. 84** Schematic of the electron calibration facility vacuum components. Only oil-free vacuum pumps are used in this system to minimize the possibility of contamination to the instruments under test. Cleanliness of the vacuum is monitored with a 200 amu Residual Gas Analyzer (RGA)</figcaption></figure>

## A.2 Vacuum System and Lab Layout

Space plasma instruments typically use either Microchannel Plates (MCPs) and/or Channel Electron Multipliers (CEMs) to detect single electrons, ions, or neutral atoms. Both of these types of detectors are extremely sensitive to contamination, especially complex hydrocarbons (e.g., McComas and Bame 1984; McComas et al. 1987, and references therein). Because it is not possible to replace detectors after launch, every effort must be made to maximize their useful lifetimes, which requires absolute cleanliness and the best possible vacuum conditions.

The control of the vacuum system was designed with instrument safety as the primary concern. All valves and pumps are controlled through a central control panel with internal logic that limits the actions available to the operator to prevent ‘unsafe’ actions. For example, venting of the system is not possible while the chamber is being actively pumped. If the facility loses power, all valves automatically close and the pumps turn off. The control system requires user intervention to bring the system back online to prevent a valve from opening into an unsafe state when power is re-established. The central control panel also isolates identified unsafe conditions or faults based on pressure and temperature monitors. If an overpressure is detected in one region of the vacuum system, valves close to isolate that portion of the system.

The vacuum chamber is divided into independently pumped subsections (Fig. 84). Each subsection can be valved off from the other portions and brought up to atmosphere while the others are held at high vacuum. These subsections are serviced by a common, oil-free, rough vacuum line that can pump them down independently or together from atmospheric pressure to a low pressure for cross-over to the cryogenic pumps.

The main vacuum vessel is a domed cylinder 76 cm (30 in) in diameter and 127 cm (50 in) long. The JADE-E sensors and any other test objects are mounted on a 3-axis positioning system (Sect. A.4). High vacuum pumping is supplied by 2 Helix-CTI Cryo-Torr 10 cryogenic pumps, each with a 3000 l/s pumping speed. These pumps were chosen for
the pumping speed and cleanliness; if one pump suffers a failure and has to be isolated, the capacity of the other pump is sufficient to maintain the main vessel at HV levels, providing redundancy in the vacuum system. The vacuum pressure is monitored by two independent Pfeiffer PBR 260 Pirani/Hot Filament full range pressure gauges. The cleanliness of the vacuum is monitored with a Dycor Dymaxion Residual Gas Analyzer (RGA) that measures masses up to 200 amu. The ultimate pressure of the main vessel (empty) is <1 × 10⁻⁹ Torr, with the RGA typically showing essentially no mass contaminants (>50 amu) above ~10⁻¹³ Torr.

The chamber door opens into and is accessed through a class 10,000 clean tent (Fig. 83), which contains a class 100 clean bench with ESD monitors. The ESD monitors are tied to the vacuum chamber walls and to Earth ground through grounding wells. High purity N₂ is available in the clean tent for instrument purge. A series of 2.75, 8, 10, and 13.25 inch Con-Flat flanges are available for electrical and mechanical feedthroughs. These feedthroughs are outside the clean tent to prevent compromising the clean area during instrument GSE set up. All flanges are the Con-Flat type except for the chamber doors, which use Viton seals.

The electron gun volume is connected to the main vessel through a 4.5" gate valve, which allows the electron gun to be serviced without bringing the main chamber up to atmospheric pressures. Once the electron gun volume is pumped to rough vacuum, high vacuum pumping is supplied by the 2 Helix-CTI Cryo-Torr 10 cryogenic pumps mounted on the main vessel.

All three vacuum subsections are serviced by a common rough vacuum line, which is pumped with a combination of a BOC Edwards scroll pump and a Drytel 100 series pump. This rough line is also used in the regeneration of the cryogenic pumps. Venting of all sections and pumps is performed with high purity (99.999 %) N₂.

### A.3 Electron Gun and External Magnetic Coils

The main electron source is a Kimball Physics model EMG-4212B with external power supply EGPS-4212B. The quoted energy range is 1 to 30 keV, but we are able to successfully operate the source down to 500 eV. Electrons are produced from a heated tantalum cathode, with a beam current up to ~100 µA. The source is equipped with focusing optics and two sets of deflection plates. The quoted spot size ranges from 500 µm to 25 mm.

We also utilize an alternate Kimball Physics model FRA-2X1-2 lower energy, flood source: with energy range from 5 eV to 1000 eV. The beam current for this source can be set up to ~400 µA. The beam profile is Gaussian, but because there are no focusing optics for this source, the spot size depends on the working distance and energy. The source can be mounted on an UHV flange or separately on a bracket inside the chamber quite close to the experiment. Both the low and the high energy source are computer controlled.

The electron calibration facility is also equipped with three pairs of roughly square coils (not shown in Fig. 83) that cancel the Earth's magnetic field or create a stronger, nearly uniform magnetic field in a volume of about 1 square foot around the center of the chamber. The magnetic field is computer controlled and can be set up to ~9 Gauss in any direction with a maximum current of 15 A per coil.

### A.4 Positioning System

The main vacuum chamber has a 3-axis positioning system that can handle instruments up to ~20 kg and that fit within a volume of 25 × 25 × 25 cm. These motions include a linear stage, which controls the horizontal position normal to the beam line and two nested, orthogonal rotational stages: horizontal (blue), outer rotation (yellow), and inner rotation
<figure><img src="image_91.png" /><figcaption>**Fig. 85** Cut away of main vacuum vessel showing the three stages of the positioning system: horizontal translation stage (blue), outer rotation stage (yellow), and inner rotation stage (green). For reference, a JADE-E sensor (white) is shown mounted onto the positioning system</figcaption></figure>

(green) in Fig. 85. These names were chosen to differ from standard Cartesian or polar coordinate names to prevent any confusion between the frame of reference of an instrument under test and that of the calibration facility.

The three stages are mounted so that both rotation stages ride on the horizontal stage, and the inner rotation stage rides on the outer stage. This means that for an instrument mounted with its aperture at the intersection of the two rotation axes, linear translations will not translate the aperture from the rotation axes. The rotation stages are mounted in an order that easily maps to a polar coordinate system with the outer stage mapping to the polar angle, and the inner stage mapping to the azimuth angle.

The inner stage is a Newport rotation stage model RV120 and the outer stage is a Newport rotation stage model RV160. Both rotation stages have a range of motion of ±170° with a resolution of 0.001°. The horizontal stage is a Newport linear stage model MTM250 with a range of motion of ±12.5 cm with a resolution of 1 µm. All stages are controlled by a Newport XPS motion controller, which is commanded either through a hand held controller accessible within the clean tent, or through computer control that can carry out intricate motion scripts.

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