**8. Scientific Payload tt/11/jj 20:38**

**8.1 Measurement requirements**

The Helios, Ulysses, Yohkoh, SOHO and TRACE missions may be used as a
baseline for designing the payload of the Solar Orbiter. However, this
mission will take a scientific spaceprobe into closer vicinity of the
sun than has ever before been reached by a man-made object. In
particular, the thermal load of almost 25 solar constants means an
unprecedented technical challenge. The instruments have to be designed
accordingly. They may dwell on developments implemented in many space
missions in the past, but the extreme thermal environment requires
substantial redesign. In order to make sure that the ambitious mission
goals of the Solar Orbiter can really be achieved, all individual
instruments were given extraordinary attention. Some of them were
designed to such detail as is usually not the case at this phase of a
mission. Also, we made sure that the required technology is available
within Europe.

The strawman payload discussed in this chapter contains sufficient
detail for system design to demonstrate its feasibility. However, it is
important to note that no pre-selection of certain instruments or
instrument principles is implied.

The payload must be state-of-the-art, withstand the considerable thermal
load at 45 R~s~, comply with the general requirements of a low-mass,
compact and integrated design, make use of on-board data
compression/storage and require a modest data transmission rate. The
payload meeting the solar and heliospheric science objectives
encompasses two instrument packages:

-   *In-situ* heliospheric instruments (see Table 8.6 below): Solar wind
    plasma analyser measuring electrons and ions, magnetometer for DC
    and AC fields, particle detectors for solar energetic ions and
    electrons, interplanetary dust detector, neutral particle detector,
    radio instruments. Heritage for such instruments is from Helios,
    SOHO, Ulysses, Wind, ACE.

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-   Remote-sensing solar instruments (see Table 8.4 below): X-ray/EUV
    full-Sun imager; high-resolution EUV spectrometer covering selected
    emission lines from the chromosphere to corona; high-resolution
    visible light telescope and magnetograph; EUV and visible-light
    coronagraph; solar neutron and -ray detector and a radiometer.
    Heritage for such instruments is from Yohkoh, SOHO, TRACE.

    **8.2 *In-Situ* heliospheric instruments**

    **8.2.1 Solar Wind Plasma Analyser (SWA)**

##### 

##### Scientific drivers

Three principal science goals require the inclusion of a solar wind
plasma analyser in the payload:

-   to provide observational constraints on kinetic plasma properties
    for a fundamental and detailed theoretical treatment of all aspects
    of coronal heating,

-   to investigate charge- and mass-dependent fractionation processes of
    the solar wind acceleration process in the inner corona,

-   to correlate comprehensive in-situ plasma analysis and compositional
    tracer diagnostics with space-based and ground-based optical
    observations of individual stream elements.

Furthermore, the SWA will

-   investigate in detail ^3^He and "unusual" charge states in
    CME-related flows and to correlate the observations with other
    in-situ particle and field data and with optical observations,

-   investigate the "recycling" of solar wind ions on dust grains in the
    distance range which has been located as the "inner source". Freshly
    produced pick-up ions from this inner source are specially suited as
    test particles for studying the dynamics of incorporation of these
    particles into the solar wind.

The SWA will measure separately the three-dimensional distribution
functions of the major solar wind constituents: protons, particles and
electrons. The basic moments of the distributions, such as density,
velocity, temperature tensor, and heat flux vector will be obtained
under all solar wind conditions and be sampled fast enough to
characterise fully the fluid and kinetic state of the wind. In this way
we will be able to determine possible non-gyrotropic features of the
distributions, ion beams, temperature anisotropies, and particle
signatures of wave excitation and dissipation.

In addition, measurements of representative high-FIP elements (the C, O,
N group) and of low-FIP elements (such as Fe, Si or Mg) will be carried
out in order

-   to obtain their abundances, velocities, temperature anisotropies and
    charge states,

-   to probe the wave-particle couplings (heavy-ion wave surfing),

-   determine the freeze-in temperatures (as a proxy for the coronal
    electron temperature).

**Instrument concept**

In view of the limited resources of mass, volume and telemetry allocated
to the SWA, a compromise between sensitivity, mass/charge- and mass- and
time resolution has to be found. The SWA has to cover a large dynamic
range in ion fluxes. Since there is an enormous difference between the
proton fluxes at perihelion (typically 10^14^ m^-2^ s^-1^) and the
fluxes of relevant minor ion tracers at 1 AU (e.g. Fe^10+^ at typically
10^8^ m^-2^ s^-1^ etc.) it is suggested to implement three different
sensors:

1.  A Proton/Alpha-particle Sensor (PAS) with the principal aim to
    investigate the velocity distribution of the major ionic species at
    a time resolution equivalent to the ambient proton cyclotron
    frequency.

2.  An Electron Analysers System (EAS) consisting of two or three
    combined sensor heads covering a solid angle of almost 4and allowing
    the determination of the principal moments of the electron velocity
    distribution at a time resolution at least equivalent to the proton
    cyclotron period near perihelion.

3.  A Minor Ion Sensor (MIS) which allows the independent determination
    of the major charge states of oxygen and iron and a coarse mapping
    of the three-dimensional velocity distribution of some prominent
    minor species. Also, pick-up ions of various origins, such as
    weakly-ionised species (C^+^, N^+^, Ne^+^, Mg^+^, Si^+^, etc.), will
    be measured.

The PAS is designed to resolve the relevant ion-kinetic scales. It will
achieve a time resolution which is compatible with the characteristic
ion cyclotron periods near perihelion. The characteristic time scale is
about 100 ms. For the minor species (heavier than He) a time resolution
of 1 s is needed.

To fulfil the requirements of compositional diagnostics, at least the
charge state distributions of oxygen and iron should be measured
routinely and with a time resolution of better than 10 s.

The instrument specifications are outlined in Table 8.1:

+-------+------------+------------+----------+------------+----------+
| **Sen | **P        | **Field of | **Energy | **Angular  | **Time   |
| sor** | articles** | View**     | reso     | re         | reso     |
|       |            |            | lution** | solution** | lution** |
+-------+------------+------------+----------+------------+----------+
| ###   | Protons    | Conical    | E/E = 10 | Azimuth    | 10 ms    |
| # PAS | and        | ±45^o^    |          | 30^o^      |          |
|       |            |            |          |            |          |
|       | particles  |            |          | Zonal      |          |
|       |            |            |          | ±5^o^     |          |
+-------+------------+------------+----------+------------+----------+
| # **  | Electrons  | 4          | E/E = 10 | Azimuth    | 10 ms    |
| EAS** |            |            |          | 30^o^      |          |
|       |            |            |          |            |          |
|       |            |            |          | Zonal      |          |
|       |            |            |          | ±5^o^     |          |
+-------+------------+------------+----------+------------+----------+
| #     | O, (^3^He, | Conical    |          |            | 1 s      |
|       | C, Ne, Mg, | ±45^o^    |          |            |          |
| # **  | Si), Fe    |            |          |            |          |
| MIS** |            |            |          |            |          |
+-------+------------+------------+----------+------------+----------+

Table 8.1 Specifications of the SWA sensors

The instrument package proposed for SWA is a further development of
instruments successfully flown on several missions in the past, e.g.,
SWICS on Ulysses, CELIAS/CTOF on SOHO, TRIPLET on INTERBALL. A possible
scheme for PAS based upon the design of TRIPLET is shown in Fig. 8.1.

######## 

######## ![](media/image1.png)

######## Fig. 8.1 Basic schematic of the TRIPLET instrument as example for a possible PAS design. The points in the collimator layout correspond to pinhole channels. Each pinhole aperture gives one energy strip on the detector surface.

**Resources and requirements**

*Telemetry*

The transmission of velocity distributions of the major species
(protons, electrons and particles) drives the telemetry requirements of
SWA. In the normal mode of operation this information should be
compressed to transmit the principal moments of velocity distributions.
Periodically however, the transmission of the complete velocity
distributions of protons and particles with a (velocity) resolution of
10 x 10 x 10 pixels at a resolution limit of 5 b is needed. This
requires 5 kb per spectrum corresponding, at a time resolution of 10 ms,
to a telemetry rate of 500 kb/s. This rate should be maintained during
1s, i.e., typically 100 ion cyclotron periods to cover a growth time of
plasma instabilities. With an average telemetry rate of 5 kb/s a duty
cycle of the order of 1% can be achieved.

*Allocations of mass, volume, and power.*

-   A mass allocation for MIS of 4 kg, 1 kg for PAS and 1 kg for EAS
    (excluding the electronics) is foreseen.

-   The volume allocation for MIS is 20 x 20 x 20 cm^3^, and 10 x 10 x
    10 cm^3^ for PAS and for each of the two EAS sensors.

-   The total power allocated to SWA is 5 W.

*Thermal and radiation requirements*

The instrument should be able to operate under the specified spacecraft
conditions. Special attention has to be devoted to the extreme solar UV
radiation flux. The design of the particle instruments should reject
this radiation to a sufficiently low level in order not to compromise
the detection of rare particles.

*Electrostatic cleanliness*

Special care has to be taken to ensure near-equipotential conditions in
the vicinity of the EAS entrance apertures.

**Instrument summary**

+------------------+-----------+-----------+-------------+------------+
| **Instrument**   | **Mass**  | **Power** | **Volume    | **Data     |
|                  |           |           | (cm^3^)**   | rate       |
|                  | **(kg)**  | **(W)**   |             | (bps)**    |
+------------------+-----------+-----------+-------------+------------+
| **PAS**          | 1         | 1.2       | 1000        | 2000       |
+------------------+-----------+-----------+-------------+------------+
| **EAS**          | 1         | 0.8       | 1000        | 2000       |
+------------------+-----------+-----------+-------------+------------+
| **MIS**          | 4         | 3         | 8000        | 1000       |
+------------------+-----------+-----------+-------------+------------+
| **Total SWA**    | 6         | 5         | 10000       | 5000       |
+------------------+-----------+-----------+-------------+------------+

**8.2.2 Radio and Plasma Waves Analyser (RPW)**

**Science drivers**

*In-situ* wave investigations on many spacecraft (e.g., Ulysses, Wind)
have amply demonstrated the crucial role of wave observations in the
study of a broad range of solar terrestrial phenomena. Wave observations
have been particularly useful in correlation with SOHO optical and EUV
observations. Typical waves instrumentation provides measurements of
both the electric field and magnetic field in a broad frequency band,
usually from a fraction of a Hertz up to several tens of MHz, covering
characteristic frequencies in the solar corona and interplanetary
medium. Both electrostatic waves and electromagnetic waves can be
measured, leading to different diagnostics: electrostatic waves mostly
provide *in situ* information in the close vicinity of the spacecraft,
while electromagnetic waves can provide an extensive remote sensing of
energetic phenomena in the solar corona and interplanetary medium.

Solar radio astronomy in a broad range of frequencies provides a unique
means to monitor, track and analyse energetic phenomena taking place in
the solar corona and interplanetary medium, in association with solar
activity. Radio emission is essentially generated through the
interaction of energetic electrons (produced in solar flares and shock
waves) with the ambient solar wind plasma. Most radiation mechanisms
produce radiation at a frequency close to the local plasma frequency
which is directly proportional to the square root of the electron
density N~e~ , leading to the strong frequency-distance dependence shown
in Table 8.2.

  --------------------- -------------------------- -----------------------
                        electron density N~e~      radio frequency
                        (cm^-3^)                   

  low corona            \~ 10^8^ -- 10^10^         100 MHz -- 1 GHz

  medium corona         \~ 10^6^ -- 10^8^          10 MHz -- 100 MHz

  \~ 10 R~o~            \~ 10^4^                   \~1 MHz

  \~ 40 R~o~            \~ 10^3^                   \~ 300 kHz

  \~ 1 AU               \~ 10                      \~ 30 kHz
  --------------------- -------------------------- -----------------------

Table 8.2. Radio frequency as function of electron density

Using proven techniques, the Solar Orbiter mission profile will allow a
radio and plasma wave package to face quite different and new
situations: access to waves and turbulence that occur much closer to the
Sun; access to viewing angles from well out of the ecliptic plane,
permitting for the first time studies of the north-south beaming of the
radio radiation in the solar corona.

**Instrument concept**

The Radio and Plasma Waves Analyser (RPW) comprises two main
sub-systems: the Plasma Waves Analyser (PWA) covering *in situ*
measurements and the Radio Spectrometer (RAS) for remote sensing. The
two sub-systems share some of the sensors (essentially the low frequency
boom antenna) and have a common digital signal processing unit and
interface with the spacecraft.

The same receivers can be used to analyse the different types of waves
detected by different sensors, for instance electric antennae and
magnetic coils. There is a lot of experience in the design of the
sensors and receivers, as well as in the analysis techniques. Also all
aspects of electromagnetic cleanliness, are well understood and are no
longer a problem for modern spacecraft designs (e.g., ULYSSES,
WIND/POLAR, CASSINI, IMAGE, CLUSTER).

*Concept of the PWA*

The PWA will identify the various plasma waves and kinetic modes
comprising the high-frequency part of the fluctuation and turbulence
spectra. We provide below a brief description of the characteristics of
the plasma waves expected to be present at 0.2 AU.

The expected field strength may range between a few V/m and mV/m, and up
to about 1 V/m for the convection electric field. The magnetic field
strength is expected to vary between a few nT and T, with large
differences between the longitudinal and transverse components with
respect to the mean magnetic field and the solar wind flow direction
(substantial Doppler shifts are to be expected).

From Helios observations one can estimate that a sensitivity equal to
10^‑6^nT/(Hz)^1/2^ will be required at 0.2 AU to identify without
ambiguity whether the observed waves are electromagnetic or
electrostatic.

At and above the electron plasma frequency intense electron plasma
oscillations and solar radio waves are expected. Helios observations
show that wave intensities associated with type III bursts increase very
rapidly with decreasing radial distance from the Sun. Intense emission
could extend up to 10^-4^ nT/Hz^1/2^.

The measurement requirements necessary for the identification and
analysis of the various electromagnetic phenomena expected to be
measured at 0.2 AU are given in Table 8.3.

+---------------------+---+---------+---+-----------------+---+------------------+---+
| Phenomena           | F |         |   | minimum         |   | maximum          |   |
|                     | r |         |   | amplitude       |   | amplitude        |   |
|                     | e |         |   |                 |   |                  |   |
|                     | q |         |   | (nT/Hz^1/2^)    |   | (nT/Hz^1/2^)     |   |
|                     | u |         |   |                 |   |                  |   |
|                     | e |         |   |                 |   |                  |   |
|                     | n |         |   |                 |   |                  |   |
|                     | c |         |   |                 |   |                  |   |
|                     | y |         |   |                 |   |                  |   |
|                     |   |         |   |                 |   |                  |   |
|                     | b |         |   |                 |   |                  |   |
|                     | a |         |   |                 |   |                  |   |
|                     | n |         |   |                 |   |                  |   |
|                     | d |         |   |                 |   |                  |   |
+---------------------+---+---------+---+-----------------+---+------------------+---+
| Doppler-shifted     |   | 1 Hz    | 1 |                 | 1 |                  |   |
| ELF/VLF             |   |         | 0 |                 | 0 |                  |   |
|                     |   | -- 10   | ^ |                 | ^ |                  |   |
| waves and           |   | kHz     | - |                 | - |                  |   |
| turbulence          |   |         | - |                 | - |                  |   |
|                     |   |         | 5 |                 | 1 |                  |   |
|                     |   |         | ^ |                 | ^ |                  |   |
|                     |   |         | a |                 | a |                  |   |
|                     |   |         | t |                 | t |                  |   |
|                     |   |         | 1 |                 | 1 |                  |   |
|                     |   |         | 0 |                 | 0 |                  |   |
|                     |   |         | H |                 | H |                  |   |
|                     |   |         | z |                 | z |                  |   |
+---------------------+---+---------+---+-----------------+---+------------------+---+
| Ion acoustic waves  | 1 |         |   | A few 10 ^--7^  |   | 10 ^--4^         |   |
| and Radio waves     | 0 |         |   |                 |   |                  |   |
|                     | k |         |   | at 1 MHz        |   | at 1MHz          |   |
|                     | H |         |   |                 |   |                  |   |
|                     | z |         |   |                 |   |                  |   |
|                     |   |         |   |                 |   |                  |   |
|                     | - |         |   |                 |   |                  |   |
|                     | - |         |   |                 |   |                  |   |
|                     | 1 |         |   |                 |   |                  |   |
|                     | 0 |         |   |                 |   |                  |   |
|                     | M |         |   |                 |   |                  |   |
|                     | H |         |   |                 |   |                  |   |
|                     | z |         |   |                 |   |                  |   |
+---------------------+---+---------+---+-----------------+---+------------------+---+

# 

# Table 8.3: Measurement requirements for the fluctuating magnetic field 

The PWA will cover a broad band in frequencies, extending from about 1
Hz into the MHz range. Resolving the vector components of the electric
and magnetic fields is scientifically highly desirable to determine wave
modes unambiguously. However, due to different constraints of the
mission, we propose to measure one electric field component only, with a
boom antenna mounted in the anti-sun direction, i.e., in the shadow of
the spacecraft. The three components of the fluctuating magnetic field
can be easily measured with a 3-axial search coil magnetometer arranged
in a compact configuration and mounted on a short boom which should also
point into the anti-sun direction. This boom is required for magnetic
cleanliness reasons and could be shared with the MAG as long as a
minimum distance between the two sensors is respected. There is a strong
heritage for those sensors mounted on three-axis stabilised spacecraft,
e.g., on Galileo, Cassini, STEREO. The PWA will also benefit from
studies and developments under progress for the Solar Probe.

The PWA will perform on-board processing of the data and deliver
selectable wave forms (Time Domain Sampler, TDS), to identify non-linear
coherent fluctuations and correlate them with measurements from the EPD.

*Concept of the RAS*

The RAS will measure the solar and interplanetary radio waves in the
frequency range from 100 kHz to 1 GHz, with a sweep period between 0.1 s
and 10 s and a high spectral resolution (f/f 0.07). The RAS will observe
plasma processes associated with energetic electrons from the low corona
up to about 0.5 AU. It will probe the plasma at distances ranging from
the solar surface to the spacecraft location, thereby connecting the
low-altitude coronal regions observed by the optical instruments with
the near-Sun heliospheric conditions specified by the in-situ
measurements. Since radio radiation is generally beamed (beam widths
sometimes down to a few ten degrees) more or less along a radial
direction from the sun, this technique is particularly relevant for
different vantage points, for instance when the Solar Orbiter will
observe the far side of the sun. The time history provided by the
regular acquisition of the radio dynamic spectrum will help to trace the
development of the active region in a synthetic manner. Activity indices
could thus be produced.

The time resolution required to detect the rapidly varying solar bursts
vary with the radio frequency. Typically, the duration of a type III
burst (stream of energetic electrons) is t(s) = 220 / f(MHz). This
points to time resolutions of the order of 0.1 s or better for the high
frequencies and of 10 s for the low frequencies.

A single boom antenna can be used for the low frequency part of the band
(below, e.g., 20 MHz), where the sensitivity is essentially determined
by the sky background radiation. Above 20 MHz and particularly above
200 MHz, the background is determined by the receiver temperature and
gain is needed in order to detect solar radio bursts: a simple boom
cannot be used anymore. A broad-band antenna with significant gain is
thus required.

The RAS instrument could be divided into three sub-spectrometers, for
instance:

-   RAD1: 100 kHz - 16 MHz

-   RAD2: 16 MHz - 200 MHz

-   RAD3: 200 MHz - 1 GHz

Different designs are used on many space mission and have a lot of
heritage since the birth of space radio astronomy at long wavelengths.

Each one of the receivers will be fed by different antenna or search
coil systems.

*RPW instrument description*

An overall block diagram of the Solar Orbiter RPW instrument is shown on
Figure 8.2.

![](media/image2.png){width="6.522222222222222in"
height="4.049305555555556in"}

Figure 8.2: Block diagram of the Solar Orbiter RPW instrument

Plasma waves and low frequency activity will be monitored by a receiver
covering the band from about 1 kHz up to 100 kHz. In order to allow for
a high time resolution, while minimising resources, it can be of the
type flown on WIND and projected for STEREO, using a digital filtering
technique.

The wave form analyser or Time Domain Sampler (TDS) is a broad band
waveform sampler with 4 channels (1 electric field component and 3
magnetic field components). The signal from the boom antenna and search
coil are sampled at a rate up to 10^6^ samples per second. Events are
detected on board and transmitted according to the available bitrate.
This is done using "intelligent" algorithms which can return a quality
value for the events. A number of random events can be sent to the
ground without regard of their quality in order to provide unbiased
statistics. Real time triggers can be sent to the EPD for special
studies of wave-particle phenomena. The bitrate can be quite variable. A
compromise can be found in selecting the number of events that will be
transmitted per day.

The radio receivers can be of the classical super-heterodyne type.
Frequency synthesisers will allow for a maximum flexibility in the
choice of the observing frequencies (for instance to avoid polluted
frequencies on the spacecraft). Each sub-receiver can consist of up to
256 selectable channels. Only a selection of these channels could be
transmitted to the telemetry stream.

The DPU will command the different subsystems and interface with the
spacecraft. The variety of instruments call for a packetised telemetry
system, that can be managed by the DPU itself, as is done for similar
packages on the WIND spacecraft (fixed format telemetry system) and
STEREO. The DPU will interface with other instruments on board the
spacecraft, particularly the Energetic Particle Detector. The DPU could
be shared with some other instruments of the of the payload, e.g., with
MAG.

Tables 8.3a, 8.3b, 8.3c provide the main characteristics of the sensors
and analysers comprised in the RPW investigation. Numbers are indicative
and can vary according to design options

+-----+---------+----------+---------+----------+--------+----------+
|     | M       | f        | sens    | size     | mass   | power    |
|     | agnetic | requency | itivity |          | (g)    |          |
|     | sensors | band     |         |          |        |          |
|     |         |          | (nT/H   |          |        |          |
|     |         |          | z^1/2^) |          |        |          |
+-----+---------+----------+---------+----------+--------+----------+
| B1  | Search  | 1Hz      | 10^--5^ | 3 rods,  | 500    | 200 mW   |
|     | coils   |          |         |          |        |          |
|     |         | -- 10    | at 10   | 18 cm    |        |          |
|     |         | kHz      | Hz      | each     |        |          |
+-----+---------+----------+---------+----------+--------+----------+
| B2  | M       | 10 kHz   | 10^--6^ | 20 cm    | 600    | 200 mW   |
|     | agnetic |          |         |          |        |          |
|     | loop    | -- 10    | at 1MHz | diameter |        |          |
|     |         | MHz      |         |          |        |          |
|     | (op     |          |         |          |        |          |
|     | tional) |          |         |          |        |          |
+-----+---------+----------+---------+----------+--------+----------+
| *   |         |          |         |          | 1100   |          |
| Tot |         |          |         |          |        |          |
| al* |         |          |         |          |        |          |
+-----+---------+----------+---------+----------+--------+----------+

Table 8.3.a: Main characteristics of the RPW magnetic sensors

+------+-----------+-------------+-------------+----------+----------+
|      | Electric  | frequency   | size        | mass (g) | power    |
|      | sensors   | band        |             |          |          |
+------+-----------+-------------+-------------+----------+----------+
| E1   | radio     | 1 Hz        | 5 m boom    | 1300     | N/A      |
|      | boom      |             |             |          |          |
|      |           | -- 20 MHz   |             |          |          |
+------+-----------+-------------+-------------+----------+----------+
| E2   | active    | 20 MHz      | \~ 1m x 2cm | 800      | 300 mW   |
|      | dipole    |             | x 2 cm      | (TBC)    |          |
|      |           | -- 200 MHz  |             |          |          |
+------+-----------+-------------+-------------+----------+----------+
| E3   | Log       | 200 MHz     | \~ 1m x 1m  | 1500     | N/A      |
|      | -periodic |             | x 1cm       | (TBC)    |          |
|      | antenna   | -- 1 GHz    |             |          |          |
+------+-----------+-------------+-------------+----------+----------+
| *To  |           |             |             | 2600     |          |
| tal* |           |             |             |          |          |
+------+-----------+-------------+-------------+----------+----------+

Table 8.3.b: Main characteristics of the RPW electric sensors

+--------+-------------+--------+-----------------+----+-----+-----+
| an     | frequency   | Sen    | sensitivity     | ma | B   | Po  |
| alyser | band        | sor(s) |                 | ss | itr | wer |
|        |             |        |                 | (  | ate | (W) |
|        |             |        |                 | g) | (b  |     |
|        |             |        |                 |    | /s) |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| TDS    | wave form   | E1, B1 | 30mV/m, 0.2 pT  | 8  | 1   | 1.0 |
|        |             |        |                 | 00 | 700 |     |
|        | 1,000,000   |        |                 |    |     |     |
|        | samples/s   |        |                 |    |     |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| PWR    | 2 kHz       | E1, B1 | 10 nV/Hz^1/2^,  | 8  | 1   | 0.7 |
|        |             |        |                 | 00 | 250 |     |
|        | -- 128 kHz  |        | 10^--5^ nT/Hz   |    |     |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| RAD1   | 100 kHz     | E1,    | 10 nV/Hz^1/2^,  | 8  | 800 | 0.8 |
|        |             | (B2)   |                 | 00 |     |     |
|        | -- 16 MHz   |        | 10^--6^         |    |     |     |
|        |             |        | nT/Hz^1/2^      |    |     |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| RAD2   | 16 MHz      | E2     | \~ 10^-20^ W    | 7  | 600 | 0.7 |
|        |             |        | m^2^ Hz^-1^     | 00 |     |     |
|        | --200 MHz   |        |                 |    |     |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| RAD3   | 200 MHz     | E3     | \~ 10^-20^ W    | 7  | 600 | 0.7 |
|        |             |        | m^2^ Hz^-1^     | 00 |     |     |
|        | -- 1 GHz    |        |                 |    |     |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| D      |             |        |                 | 12 |     | 1.5 |
| SP/DPU |             |        |                 | 00 |     |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| Con    |             |        |                 | 8  |     | 1.2 |
| verter |             |        |                 | 00 |     |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| H      |             |        |                 | 5  | 50  |     |
| arness |             |        |                 | 00 | (H  |     |
| etc.   |             |        |                 |    | /K) |     |
+--------+-------------+--------+-----------------+----+-----+-----+
| *      |             |        |                 | 63 | 5   | 6.8 |
| Total* |             |        |                 | 00 | 000 |     |
+--------+-------------+--------+-----------------+----+-----+-----+

Table 8.3.c: Main characteristics of the RPW analysers and subsystems

**Resources and requirements**

*Antenna systems*

Antenna systems for the range from 20 MHz to 1 GHz are readily available
off the shelf for ground based systems, including "portable" ones.
Different types and techniques are available, and the theory of the
measurement is well known. They would have to be developed specifically
for the Solar Orbiter mission. The RAD2 band (16 MHz - 200 MHz) could be
covered by an active dipole antenna and the RAD3 band (200 MHz - 1 GHz)
by a log-periodic antenna. These two antenna systems can be grouped
together and mounted on the same boom in order to have a common
mechanical (deployment mechanism) and electrical interface with the
spacecraft. They would have to be pointed to the sun (accuracy of a few
degrees) and thus protected from the direct sunlight by a shield not
affecting the radio wave propagation (radome type). The whole system can
be kept to a reasonable size (longest element of the order of 1 m) and
provide the required gain. The beam shape of the antennas mounted on the
spacecraft will have to be modelled and measured using existing
techniques.

*Electro-Magnetic Cleanliness (EMC)*

Many of the RPW scientific objectives are based on the measurement of
low-level signals for which maximum sensitivity is required. Several
inexpensive measures can be taken at the spacecraft and project level to
ensure that the Solar Orbiter spacecraft is clean from the point of view
of both conducted and radiated electromagnetic interference. The
sensitivity of the Solar Orbiter/RPW instrument will be approximately
10^-8^ V/m/Hz^1/2^ in the frequency range of 1 kHz to 20 MHz and 310^-7^
V/m/Hz^1/2^ below 100 Hz. In addition, the wave form analyser is
sensitive to impulsive interference of duration as short as a fraction
of a microsecond. Although these sensitivities may appear to require an
excessively \"clean\" spacecraft, they are not difficult to achieve if
good EMC practices are incorporated in the spacecraft design.

It is important to realise that an EMC-clean spacecraft is beneficial
for all instruments, as well as for spacecraft systems. Given the
progress made in understanding the principles, these EMC controls are
easy to implement and do not require extensive or expensive testing. The
Project could set up a consultant EMC board to study the general
grounding and shielding philosophies, instrument-particular
exceptions/waivers, and test procedures for the mission. This committee
would define an inexpensive, coherent scheme for minimising
interference. For example, a single point or \"star\" ground has often
been suggested as the path to a clean spacecraft. This can be a
burdensome requirement on many types of measurement and has been shown
not to be very effective at high frequencies. Instead of such arbitrary
rules, the EMC committee would work to find acceptable compromise using
a \"best engineering practices\" point of view. Many of the interests of
an EMC committee will overlap with other spacecraft cleanliness issues
such as magnetic cleanliness and electrostatic cleanliness.

Currents induced in the spacecraft structure are a major source of EMC
disturbances because any voltage on the spacecraft surface induced by
such currents will couple readily into the antennas. Good grounding and
harness shielding practices will control these currents and should be
the basis of an EMC \"philosophy\". Power converters also represent a
serious source of interference if left uncontrolled. The EMC committee
would develop a plan for the use of crystal controlled DC-DC conversion
in all spacecraft systems (including instruments) which can limit the
interference to narrow frequency bands. The committee would review all
subsystem test results and, in the case of test results in excess of
defined limits, determine what remedial action (if any) is required.

**Instrument summary**

RPW Sensors:

-   triaxial search coil mounted on the magnetometer boom

-   magnetic loop antenna

-   boom antenna (5 to 6 m on side opposed to sun)

-   VHF/UHF system comprising an active dipole and a log-periodic
    antenna

Role of main subsystems:

-   RPW/PWA: identify plasma waves and kinetic modes (high frequency
    part of the fluctuation and turbulence spectra)

-   RPW/RAS: measure and track solar and interplanetary radio bursts;
    connect low-altitude coronal regions observed by the optical
    instruments with the *in situ*, local solar wind conditions at the
    spacecraft, study directivity of radio emissions

+------------------+-----------+-----------+-------------+------------+
| **Instrument**   | **Mass**  | **Power** | **Volume    | **Data     |
|                  |           |           | (cm^3^)**   | rate       |
|                  | **(kg)**  | **(W)**   |             | (bps)**    |
+------------------+-----------+-----------+-------------+------------+
| **Total RPW**    | 10        | 7.5       | 7500        | 5000       |
+------------------+-----------+-----------+-------------+------------+

**8.2.3 Coronal Radio Sounding (CRS)**

A passive radio science experiment can be carried out using the
available radio links. The S/C will pass behind the Sun (superior solar
conjunction) on many occasions, making it possible to investigate the
solar corona by radio sounding at solar distances much less than the
perihelion distance down to at least 2 R~s~. Integrated line-of-sight
parameters such as electron content (densities), Faraday rotation,
scintillations and angular broadening can be recorded. The Solar Orbiter
orbit and the proximity of the spacecraft to the sun will create unique
situations for this kind of analysis. The CRS investigation with a
two-way radio link via the S/C high-gain antenna (ranging capability)
would require a radio subsystem with dual-frequency phase coherent
downlinks at X-band and Ka-band. Linear polarisation of the downlink
signals would enable Faraday rotation measurements as an option. The RF
power for both radio links (X and Ka) planned for this mission is
sufficient for this investigation. A two-way dual-frequency coherent
radio link (X-band uplink; X-band and Ka-band simultaneous coherent
downlinks) is considered as the optimal configuration for a sufficiently
stable link and for detecting signatures of CME events traversing the
radio ray path.

It is presently unclear whether or not an ultra-stable oscillator would
be necessary to guarantee the frequency stability of the downlinks. If
only a one-way radio link (S/C to ground) is feasible due to operational
constraints during solar conjunction, the transmitted radio signal must
be stabilised by an onboard ultra-stable oscillator (frequency stability
10^-11^ to 10^-12^ at 3 s integration time, 200g, 3 W). The practicality
of using linear polarised signals for Faraday rotation measurements is
another trade-off to be explored. The final decision depends critically
on the geometry and mission operation plan. Considerable interaction
between the radio scientists and the spacecraft's radio subsystem
contractor is a prerequisite for conducting a successful coronal
sounding experiment. The occultation geometry during the solar
conjunctions is another aspect that needs to be worked in detail.

**8.2.4 Magnetometer (MAG)**

**Scientific drivers**

Knowledge of the magnetic field is of crucial importance for
characterising the state of the local interplanetary medium and
indispensable for the interpretation of measurements of energetic
particles and thermal plasma particles.

The magnetometer will measure the three orthogonal components of the
interplanetary magnetic field vector over a broad dynamic range from a
few nT up to the T range, and for frequencies well below the local
heavy-ion or proton gyrofrequencies.

**Instrument concept**

The magnetometer may consist of a triaxial identical sensor system. A
compromise has to be found between the requirements of the spacecraft
and payload systems and the demand of the magnetometer for magnetically
clean conditions.

The heritage of MAG includes dozens of similar instruments flown on
various magnetospheric, planetary and deep space missions. The MAG
proposed for the STEREO mission might serve as a guideline. It is in
turn based on the design used for the NEAR and ACE missions. The MAG
sensor and electronics for the Solar Orbiter require no new development.
State of the art instruments can be built for less than 1 kg. Further
mass savings appear possible.

MAG might consist of a 3-axis fluxgate magnetometer with the sensor
mounted at the end of an extendable boom (length \<1m) which is
positioned in the shadow of the Orbiter. Other mounting locations such
as on the high-gain antenna structure appear possible, provided MAG
stays in permanent shadow. It measures fields in 8 ranges (automatically
selected) from 4 nT to 65536 nT with a resolution of 30 ppm, from DC up
to AC frequencies of 500 Hz. The parameters can be adjusted according to
the particular needs of the Solar Orbiter mission. The DPU of MAG could
be shared with either the plasma instruments or the wave instruments.

##### 

##### 

##### Resources and requirements

The mass of the sensor package will be less than 1 kg, the average power
consumption is about 1 W, and the required telemetry is of the order of
200 b/s.

Magnetic cleanliness of a spacecraft as required by a magnetometer on
board has been a cost driver for some missions in the past. However,
more recent experience has shown that there are in fact acceptable
low-cost engineering solutions possible. A reasonable magnetic
cleanliness program can be performed, if the MAG experimenters work in
close contact with the all other teams in order to ensure proper
engineering at an early phase and to make other precautions without
impacting the mission schedule. Similar schemes were applied in the past
for several successful missions.

**Instrument summary**

Instrument triaxial fluxgate magnetometer

Telemetry \< 200 bps

Mass \< 1 kg

Power \< 1 Watt

Special requirements mounting on short boom (\<1 m), in shadow of
spacecraft, basic magnetic cleanliness of spacecraft.

5.  **Energetic Particle Detector (EPD)**

    **Scientific drivers**

The Solar Orbiter will allow to study the sources, acceleration and
propagation of solar energetic particles in association with coronal and
interplanetary shocks. Energetic pick-up particles originating from
outgassing or sputtering of near-Sun dust should be measured as well in
conjunction with the plasma measurements. It is essential that all
measurements are done fast, typically at 1 s, with complete angular
coverage to resolve the pitch-angle distributions. The EPD will

-   determine *in-situ* the generation, storage, release and propagation
    of different species of solar energetic particles in the inner
    heliosphere,

-   identify the links between magnetic activity and acceleration on the
    Sun of energetic particles, by virtue of combined remote-sensing of
    their source regions and *in-situ* measurements of their properties,
    while staying magnetically connected with the acceleration sites
    during solar corotation passes,

-   characterise gradual (CMEs) and impulsive (flares) particle events
    and trace their spatial and temporal evolution near the Sun

**Instrument concept**

The EPD will determine chemical and charge composition and energy
spectra of ions in a wide energy range, from about the typical solar
wind energies of a few keV to several 100 MeV/nucleon for protons and
heavy ions. Electrons should be measured from 10 keV to 10 MeV. The
combination of electrostatic E/Q-analysis with time-of-flight
E/M-determination and subsequent direct energy measurement in a solid
state detector has been employed in many EPDs in the past and is also a
possible design option for the Solar Orbiter.

The specific design suggested here resembles closely the one recently
selected for the IMPACT instrument on the STEREO mission. It is a
multi-head sensor system using solid state technology. Ongoing research
in this field is promising and will certainly lead to further
improvements concerning energy thresholds and noise level as well as to
size reduction.

**Resources and requirements**

The measurement requirements can readily be met by a low-mass and
compact sensor assembly with different look directions and modest
aperture sizes. We propose to place several detectors at different
positions onboard the spacecraft, in order to obtain a sufficient field
of view and angle-of-incidence coverage without using a scanning
platform. The whole EPD package will have a total mass not exceeding 4
kg and consume an average power of 3 W. The required telemetry rate is 2
kb/s.

The characteristics of the EPD could, e.g., resemble the 4 sensors of
the IMPACT instrument on STEREO, as given in Table 8.5.

+-------+---------------+-------------+--------+----------------------+
| **Sen | **Energy      | **GF**      | *      | **Name**             |
| sor** | (M            |             | *FOV** |                      |
|       | eV/nucleon)** | **(cm^2^sr  |        |                      |
|       |               | )**         | **(° x |                      |
|       |               |             | °)**   |                      |
+-------+---------------+-------------+--------+----------------------+
| **    | e: 0.02 -     | 4 x 0.30,   |        | Electron Proton      |
| EPT** | 0.40          |             |        |                      |
|       |               | 4 x 0.24,   |        | Telescope            |
|       | p: 0.02 -     |             |        |                      |
|       | 7.00          | 4 view      |        |                      |
|       |               | cones       |        |                      |
+-------+---------------+-------------+--------+----------------------+
| **    | 0.03 - 2      | 0.3,        | 17 x   | Supra-thermal Ion    |
| SIT** |               |             | 44     |                      |
|       |               | 1 view cone |        | Telescope (He -- Fe) |
+-------+---------------+-------------+--------+----------------------+
| **    | 1.5 - 40      | 4.5,        | 130 x  | Low Energy           |
| LET** |               |             | 30     |                      |
|       |               | 10 view     |        | Telescope (He -- Ni) |
|       |               | cones       |        |                      |
+-------+---------------+-------------+--------+----------------------+
| **    | 13 - 100      | 2.4,        | 48 x   | High Energy          |
| HET** |               |             | 48     | Telescope            |
|       |               | 2 view      |        |                      |
|       |               | cones       |        | (He -- Fe)           |
+-------+---------------+-------------+--------+----------------------+

Table 8.5: EPD instrument characteristics

**Instrument summary**

+------------------+-----------+-----------+-------------+------------+
| **Instrument**   | **Mass**  | **Power** | **Volume    | **Data     |
|                  |           |           | (cm^3^)**   | rate       |
|                  | **(kg)**  | **(W)**   |             | (b/s)**    |
+------------------+-----------+-----------+-------------+------------+
| **EPT**          | 0.94      | 0.60      | 300         | 300        |
+------------------+-----------+-----------+-------------+------------+
| **SIT**          | 0.78      | 0.55      | 620         | 600        |
+------------------+-----------+-----------+-------------+------------+
| **LET**          | 0.44      | 0.12      | 430         | 800        |
+------------------+-----------+-----------+-------------+------------+
| **HET**          | 0.27      | 0.04      | 210         | 300        |
+------------------+-----------+-----------+-------------+------------+
| **DPU/H-L-VPS**  | 1.37      | 1.17      | 3000        |            |
+------------------+-----------+-----------+-------------+------------+
| **Total EPD**    | **3.80**  | **2.48**  | **4560**    | **2000**   |
+------------------+-----------+-----------+-------------+------------+

**8.2.6 Dust Detector (DUD)**

**Science drivers**

The DUD will analyse interplanetary dust particles with respect to their
composition and orbital characteristics and determine *in-situ* the
distribution, composition and dynamics of dust particles in the near-Sun
heliosphere in and out of the ecliptic. The spatial distribution of
particles with masses ranging between 10^-16^ g and 10^-6^ g will be
determined. DUD will

-   help outlining the extent of the dust-free zone around the Sun,

-   find out the sources of dust, e.g. from Sun-grazing comets,

-   unravel the role played by near-Sun dust for pick-up ions,

-   deliver data relevant for an understanding of proto-planetary discs.

**Instrument concept**

The science objectives can be met with an instrument of, e.g., Giotto
heritage. The minimal dust experiment may consist of a multiple sensor
assembly, with each sensor looking in a different direction to resolve
incidence angles. A low-mass dust-detecting element could look as
sketched in Fig 8.3. The dust particles enter the detector through a
thin aluminium foil and evaporate during impact on a gold target. A set
of wires in front of the target plate collects the produced ions. The
signal is analysed to deduce the mass and possibly speed of the dust
particle.

![](media/image3.png){width="6.072916666666667in" height="2.4375in"}

Fig.8.3: Instrument design of DUD **to be improved by BF**

Full chemical analysis and mass resolution of the important elements H,
C, N, O of carbonaceous material and the metals like Na, Mg, Al, Si, Ca
and Fe contained in chondritic silicates is desirable but may require a
more sophisticated design.

###### 

###### Resources and requirements

Two identical detector units should be located on the sides of the
spacecraft body, one looking 90 degrees off the spacecraft-sun line in
the orbital plane to measure the near-ecliptic dust particles, the other
one in the direction perpendicular to the orbital plane in order to
measure dust particles in orbits highly inclined to the ecliptic. The
FOV of each sensor is ± 80°.

The mass of each sensor is 0.5 kg, consumes a power of 0.3 W and has a
volume of 1200 cm^3^. The average bitrate will not exceed 50 b/s. The
DPU should

be shared with other particle instruments.

####### 

####### 

####### Instrument summary

+---------------+------------+------------+-------------+------------+
| *             | **Mass**   | **Power**  | **Volume    | **Data     |
| *Instrument** |            |            | (cm^3^)**   | rate       |
|               | **(kg)**   | **(W)**    |             | (b/s)**    |
+---------------+------------+------------+-------------+------------+
| DUD           | 1          | 0.6        | 2400        | 50         |
+---------------+------------+------------+-------------+------------+

**8.2.7 Neutral Particle Detector (NPD)**

## Scientific drivers

The L line of neutral hydrogen is used in spectroscopic observations on
SOHO to determine the solar wind velocity profile in the corona up to
several solar radii. The NPD on the Solar Orbiter will measure primarily
neutral hydrogen atoms and thus render possible the detection of the
interplanetary \"neutral solar wind\". The instrument should detect
neutral atoms in the typical solar-wind and supra-thermal velocity range
between about 350 and 5000 km/s.

The neutral atom flux is expected to be about 100-1000 atoms cm^-2^
s^-1^ at 0.21 AU, but it could be up to 10^6^ atoms cm^-2^ s^-1^ in a
CME. The NPD will also measure energetic neutral atoms emitted from
various coronal sources, and thus enable images of these coronal
emission regions to be constructed from rays of neutral atoms with
different velocities.

**Instrument concept**

Neutral atom detectors have been flown on SOHO, Cassini and IMAGE.
Time-of-flight instruments are for example flown on Ulysses, SOHO and
ACE.

As a baseline, the instrument parameters of the NPD on the Solar Orbiter
could be: Energy/mass range: 0.6 to 100 keV/nucleon, moderate velocity
resolution; mass resolution is a secondary objective. The field of view
(for the imaging capability) of the NPD should be centred at about 17°
off the spacecraft-Sun-centre line .

The instrument entrance system must block radiation emerging from the
solar disk. The UV scattered in the solar corona, i.e. L, must be
suppressed by a factor of more than 10^-10^. The entrance system must
reduce ions and electrons of the solar wind plasma by a factor of about
10^-8^ while transmitting neutral atoms.

## A feasible neutral atom detector (see Fig. 8.4) may consist of two sections: the first compartment accommodates the baffle plates keeping out solar UV and the deflection unit for keeping off unwanted charged particles. The second section contains a time-of-flight (TOF) double-coincidence detector. Between the two sections is the pinhole/slit that defines the optical properties of the neutral atom detector. 

The direct solar radiation is blocked by a collimator. For the
suppression of scattered light within the collimator, the plates are
covered with sawtooth-like structures. The collimator consists of,
alternatively positive and negative, high-voltage biased plates and
therefore acts as a charged-particle deflector. The collimator plate
length, distance and potential determine the cut-off of the
charged-particle transmission (about 100 keV/q). L light is transmitted
through the collimator. The grid in front of the pinhole reflects the
UV. The grid consists of 2 gratings with a grating constant matching the
L peak. The grids are more transparent for particles than for UV photons
(ratio up to 10^5^ per grating, in dependence on the UV wavelength).

The neutral atoms pass through the pinhole (or slit) and a 0.5 to 1.1
g/cm^2^ carbon foil. As they pass the carbon foil, they release
secondary electrons which are accelerated towards a START MCP
(multi-channel plate). The atoms travel through a 3-cm-wide TOF drift
region and hit the rear STOP MCP. The time of flight for 1 keV/n-100
keV/n atoms is about 8 to 80 ns. The position resolution is 1-D for the
START MCP and 2-D for the STOP MCP. The flight pass of the neutral atom
can be calculated from these measurements by an inversion of the
instrument function. The detector determines the velocity
(energy/nucleon) and the flight pass (imaging) of the neutral atoms.

![](media/image4.png){width="4.825in" height="3.1006944444444446in"}

Figure 8.4: Instrument schematics of the Neutral Particle Detector.

## 

## Resources and requirements

The NPD can be built for a mass of 1 kg. The power consumption is 2 W.
The required telemetry rate is less than 0.5 kb/s. It is envisaged to
use a common DPU and to share the mechanical structure with the SWA. The
FOV has to be 17° off the S/C - Sun line because of the typical 10°
aberration of a 1 keV hydrogen atom travelling at solar wind speed.

**Instrument summary**

+---------------+------------+------------+-------------+------------+
| *             | **Mass**   | **Power**  | **Volume    | **Data     |
| *Instrument** |            |            | (cm^3^)**   | rate       |
|               | **(kg)**   | **(W)**    |             | (bps)**    |
+---------------+------------+------------+-------------+------------+
| NPD           | 1.00       | 2.00       | 2000        | 500        |
+---------------+------------+------------+-------------+------------+

**8.2.8 Neutron Detector (NED)**

**Scientific drivers**

Solar neutrons (and rays) are a by-product of solar flares due to
spallation reactions between energetic protons and particles. The
overwhelming majority of these neutrons are thermalised within minutes
and later absorbed by hydrogen to form deuterium and the well known 2.2
MeV line. Some neutrons, however, escape into space and can eventually
be detected (before they decay with a half-life of 619.9 s) by a sensor
located in close proximity to the Sun. The temporal correlation of
neutron fluxes with solar energetic particle fluxes and with optical
observations in the EUV provides crucial information on the solar
particle acceleration process, which is inaccessible by other means.

The advantage of neutrons over charged particles not being delayed by
travel along complicated paths through magnetic fields will allow an
unambiguous temporal correlation with optical observations of features
of flares in different energy ranges.

Incorporation of NED on the Solar Orbiter which offers routine
monitoring of neutron fluxes and, optionally, rays will be a "first" in
solar science. A major contribution to the solar ray flux stems from the
2.2 MeV line, which is due to the reaction of thermal neutrons with
protons to form deuterium. Hence, the ray detector registering "extinct"
solar neutrons would ideally complement the neutron detector, which is
to record "life" neutrons in situ.

**Instrument concept**

Following the design of the instrument proposed for the Solar Probe the
heart of the suggested NED instrument consists of a cell with thin (\<10
m) thorium foils. With a cross section of typically 100 mbarn (at
energies above 1 MeV) an efficiency of 10^-5^ for producing fission
fragments - to be detected in a pulse ionisation chamber - can be
achieved. The anti-coincidence chamber surrounding the sensitive volume
contains a counting gas, e.g. methane or argon, and energetic particles
which might produce false counts in the ionisation chamber will be
detected with an efficiency of close to 100%. The angular resolution of
the NED will not be sufficient to map individual features on the solar
surface.

Optionally, incorporation of a facility to monitor solar rays into the
experiment would greatly enhance the scientific return.

Planetary flybys could be used to block the solar neutron flux and to
determine the intrinsic background rate of the spacecraft. Further
information, also on the average energy of solar neutrons will be gained
by comparison of long time averages of the neutron flux at different
solar distances.

**Resources and requirements**

The main concern with NED will be to minimise the energetic particle
background in the sensor cell. On one hand the anti-coincidence cell
should be as efficient as possible to prevent false coincidences, on the
other hand, the location of the sensor within the payload has to be
chosen such that as to keep the particle radiation level at a minimum.

![](media/image5.png){width="5.622222222222222in"
height="3.6618055555555555in"}

Fig. 8.5 Schematics of the NED sensor

**Instrument summary**

+------------------+-----------+-----------+-------------+------------+
| **Instrument**   | **Mass**  | **Power** | **Volume    | **Data     |
|                  |           |           | \[cm^3^\]** | rate       |
|                  | *         | **\[W\]** |             | \[b/s\]**  |
|                  | *\[kg\]** |           |             |            |
+------------------+-----------+-----------+-------------+------------+
| **NED**          | 1         | 1         | 1000        | 100        |
+------------------+-----------+-----------+-------------+------------+
| **NED+ ^\*)^**   | 2         | 1.5       | 2000        | 150        |
+------------------+-----------+-----------+-------------+------------+
| **^\*)^**        |           |           |             |            |
| Version          |           |           |             |            |
| including ray    |           |           |             |            |
| detection        |           |           |             |            |
| facility         |           |           |             |            |
+------------------+-----------+-----------+-------------+------------+

**8.2.8 Heliospheric instrument summary**

+-----------+----+--------+--------+-----+-----------+-----+--------+
| Name      | A  | Measur | Spe    | M   | Size      | Po  | Tel    |
|           | cr | e-ment | cifica | ass |           | wer | emetry |
|           | o- |        | -tions |     | cm x cm x |     |        |
|           |    |        |        | kg  | cm        | W   | kb/s   |
|           | n  |        |        |     |           |     |        |
|           | ym |        |        |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+
| Solar     | S  | T      | 0-30   | 6   | 20 x 20 x | 5   | 5      |
| Wind      | WA | hermal | keV/Q; |     | 20        |     |        |
|           |    |        |        |     |           |     |        |
| Plasma    |    | ions   | 0-10   |     |           |     |        |
|           |    |        | keV    |     |           |     |        |
| Analyser  |    | and    |        |     |           |     |        |
|           |    | ele    |        |     |           |     |        |
|           |    | ctrons |        |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+
| Radio and | R  | AC     | V/m -  | 10  | 15 x 20 x | 7.5 | 5      |
|           | PW | el     | V/m    |     | 30        |     |        |
| Plasma    |    | ectric |        |     |           |     |        |
|           |    |        | 0      |     | (el       |     |        |
| Wave      |    | and    | .1nT - |     | ectronics |     |        |
| Analyser  |    | ma     | T      |     | box)      |     |        |
|           |    | gnetic |        |     |           |     |        |
|           |    | fields |        |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+
| Magn      | M  | DC     | to 500 | 1   | 10 x 10 x | 1   | 0.5    |
| eto-meter | AG | ma     | Hz     |     | 10        |     |        |
|           |    | gnetic |        |     |           |     |        |
|           |    | field  |        |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+
| Energetic | E  | Solar  | Ions   | 4   | 10 x 20 x | 3   | 2      |
| Particle  | PD | and    | and    |     | 20        |     |        |
| Detector  |    | cosm   | ele    |     |           |     |        |
|           |    | ic-ray | ctrons |     |           |     |        |
|           |    | par    | .01-10 |     |           |     |        |
|           |    | ticles | MeV    |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+
| Neutral   | N  | N      | 0.6 -  | 1   | 10 x 10 x | 2   | 0.5    |
| Particle  | PD | eutral | 100    |     | 20        |     |        |
| Detector  |    | hy     | keV    |     |           |     |        |
|           |    | drogen |        |     |           |     |        |
|           |    | and    |        |     |           |     |        |
|           |    |        |        |     |           |     |        |
|           |    | atoms  |        |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+
| Dust      | D  | In     | Mass   | 2   | 10 x 10 x | 1   | 0.5    |
| Detector  | UD | terpla | (g):   |     | 10        |     |        |
|           |    | netary |        |     |           |     |        |
|           |    |        | 10     |     |           |     |        |
|           |    | dust   | ^-16^- |     |           |     |        |
|           |    | par    | 10^-6^ |     |           |     |        |
|           |    | ticles |        |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+
| Radio     | C  | Wind   | X-band | (   | 5 x 5 x 5 | 3   | 0      |
|           | RS | d      |        | USO |           |     |        |
| Sounding  |    | ensity | K      | 20  |           |     |        |
|           |    |        | a-band | 0g) |           |     |        |
|           |    | and    |        |     |           |     |        |
|           |    | ve     |        |     |           |     |        |
|           |    | locity |        |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+
| Neutron   | N  | Solar  | e      | 1   | 10 x 10 x | 1   | 0.2    |
| detector  | ED |        | \>1MeV |     | 10        |     |        |
|           |    | ne     |        |     |           |     |        |
|           |    | utrons |        |     |           |     |        |
+-----------+----+--------+--------+-----+-----------+-----+--------+

**Table 8.6: *In-situ* heliospheric instrumentation**