Solar Probe Plus: Humanity's First Visit to Our Star - Solar Probe Plus A NASA Mission to Touch the Sun
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Solar Probe Plus
A NASA Mission to Touch the Sun
Solar Probe Plus:
Humanity’s First Visit
to Our Star
Nicola J. Fox, N.E. Raouafi, R. Decker, S. Bale,
R. Howard, J.C. Kasper, D. McComas, M. Velli.
Solar Probe Plus Project Scientist
Nicky.Fox@jhuapl.edu
A Brief History of the Solar Wind 1859: Richard C. Carrington first discovered Hα flare, which was followed by the strongest geomagnetic storm in recorded history. He suggested a connection between solar flares & geomagnetic activity. 1910: British astrophysicist Arthur Eddington suggested the existence of a solar wind, without naming it, in a footnote to an article on Comet Morehouse. 1916: Norwegian physicist Kristian Birkeland suggested that the solar wind was composed of both ions and electrons. 1930s: scientists inferred from eclipse observations that the the solar corona must be > a million degree hot through observations of emissions from highly ionized ions. Mid-1950s: British mathematician Sydney Chapman calculated the properties of a gas at such a temperature and determined it was such a superb conductor of heat that it must extend way out into space, beyond the orbit of Earth. Also in the 1950s: German scientist Ludwig Biermann postulated that the anti-solar orientation of comet tails results from a steady stream of particles emitted by the Sun. 1958: Eugene Parker developed the theory of hot coronal plasma evolving into what he termed the "solar wind”. 1962: Marsha Neugebauer and Conway Snyder confirmed the existence of the solar wind through in-situ measurements. IUGG Solar Probe Plus
How is the Corona Heated?
Reference:
Cranmer & van Ballegooijen, ApJ, 2005
SPP
Electrons and different ion species are heated differently; theoretical work has
shown that single‐fluid theories are clearly not sufficient to explain this.
SPP will provide measurements in the region of space where observations are
most needed
SPP will bridge the measurement gap between the low corona (i.e.,
spectroscopic observations (SOHO/SUMER & UVCS) and heliospheric in‐situ
measurements from Helios.
IUGG Solar Probe Plus
How is the Solar Wind Accelerated?
‘Alfvén point’: Within this point, the magnetic energy density dominates, and
the gas is forced to flow along the field lines. Beyond this point, kinetic energy
acquired by the flowing gas prevails and the field is forced to follow the flow.
In a magnetized plasma, the Alfvén point (colored circles in the figure below)
determines radial extent of the lower (sub‐Alfvénic) corona
Reference:
Kasper et al. 2010,
SWEAP Proposal
It is important to measure the solar wind as close to the solar surface (below the
Alfven critical point) as possible while it is still undergoing most of its
acceleration.
IUGG Solar Probe Plus
50 years into the space age and we still don’t
understand the corona and solar wind
The concept for a “Solar Probe” dates back to
“Simpson’s Committee” of the Space Science
Board (National Academy of Sciences, 24 October
1958)
‒ The need for extraordinary knowledge of Sun from
remote observations, theory, and modeling to
answer the questions:
– Why is the solar corona so much hotter than the
photosphere?
– How is the solar wind accelerated?
The answers to these questions can be obtained
only through in-situ measurements of the solar
wind down in the corona and been of top priority in
multiple Roadmaps and Decadal Surveys.
IUGG Solar Probe Plus
SPP Over-arching Science Objective To determine the structure and dynamics of the Sun’s coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what mechanisms accelerate and transport energetic particles. IUGG Solar Probe Plus
Spacecraft Overview
NASA selected instrument suites
685 kg max launch wet mass
Reference Dimensions:
S/C height: 3 m
TPS max diameter: 2.3 m
S/C bus diameter: 1 m
C-C Thermal protection system
Hexagonal prism s/c bus configuration
Actively cooled solar arrays
388 W electrical power at encounter
Solar array total area: 1.55 m2
Radiator area under TPS: 4 m2
0.6 m HGA, 34 W TWTA Ka-band science DL
Science downlink rate: 167 kb/s at 1AU
Blowdown monoprop hydrazine propulsion
Wheels for attitude control
IUGG Solar Probe Plus
Reference Mission: Launch and Mission
Design Overview
Launch 1st Min Launch
Dates: Jul 31 – Aug 19, 2018 (20 Perihelion 7/31/2018
days) at 9.86 RS
12/19/2024
Max. Launch C3: 154 km2/s2
Delta IV-Heavy with Upper Stage
Trajectory Design
24 Orbits
7 Venus gravity assist flybys Sun
Final Solar Orbits
Closest approach: 9.86 Rsun (3.83 Mercury
million miles)
Venus
Speed ~450,000 miles per hour
(~125 miles per second) Earth
Orbit period: 88 days
Mission duration: 6 yrs, 11 months 1st Perihelion
at 35.7 RS
11/1/2018
IUGG Solar Probe Plus
SPP Rapidly Explores the Inner
Heliosphere
Orbit # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Period (d) 168 150 150 140 121 112 107 102 102 100 96 96 96 96 96 96 96 92 92 92 87 88 88 88
A1
A2 A3 A4
Venus Flyby
A5
A6 A7
A8 A9 A10
A11 A12 A13 A14 A15 A16 A17 A18 A19 A20 A21 A22 A23 A24 A25
P1 P2 P3
P4 P5
P6 P7
P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18 P19 P20 P21 P22 P23 P24
Max solar distance is 1.018 AU, and min solar distance is 0.04587 AU (9.86 RS)
1st perihelion (0.16 AU) 3 months after launch; 19 passes below 20 Rs
Perihelia gradually decreases. Science measurements will commence at the first Perihelion
IUGG Solar Probe Plus
Reference Vehicle: Concept of Operations IUGG Solar Probe Plus
Reference Vehicle:
Anti-Ram Facing View
SWEAP PI
Justin Kasper
University of Michigan
At closest approach, the
front the heat shield will be
at 1,400°C (2500 oF), but
the payload will be near
room temperature
IUGG Solar Probe PlusReference Vehicle:
Ram Facing View
FIELDS PI
Stuart Bale (UC, Berkeley)
ISIS PI
David McComas
(Southwest Research Inst.)
WISPR PI
Russ Howard
(Naval Research Lab)
IUGG Solar Probe PlusSolar Probe Plus Science
Investigations (1/5)
Solar Wind Electrons Alphas and
Solar Probe Cup (SPC)
Protons (SWEAP) Investigation: This
2 Solar Probe ANalyzers (SPAN)
investigation will count the most
abundant particles in the solar wind ‐‐
SPC
electrons, protons and helium ions ‐‐ and
measure their properties such as SPAN-B SPAN-A+
velocity, density, and temperature.
SWEAP Investigation
SWEAP PI
Prof. Justin Kasper
University of Michigan/ Smithsonian
Astrophysics Observatory
IUGG Solar Probe PlusSolar Probe Plus Science
Investigations (2/5)
Fields Experiment (FIELDS): FIELDS Investigation
This investigation will make V1‐V4 electric antennas
‐ Five voltage sensors
‐ Two Fluxgate magnetometers
direct measurements of ‐ One search‐coil magnetometer
‐ Main Electronics Package
electric and magnetic fields
and waves, Poynting flux,
absolute plasma density and MAGi, MAGo
electron temperature, SCM
spacecraft floating potential
and density fluctuations, and V1‐V4 electric antennas V5 electric antenna
radio emissions.
FIELDS PI
Prof. Stuart Bale
University of California, Berkeley
IUGG Solar Probe Plusolar Probe Plus Science
vestigations (3/5)
grated Science Investigation of the
High energy Energetic Particle Instrument (EPI‐Hi)
(ISIS): This investigation makes Low energy Energetic Particle Instrument (EPI‐Lo)
rvations of energetic electrons,
EPI-Lo 8 Sensor
ons and heavy ions that are Wedges
lerated to high energies (10s of keV
00 MeV) in the Sun's atmosphere
nner heliosphere, and correlates LET1
m with solar wind and coronal HET
tures.
ISIS
Bracket
EPI-Hi LET2
ISIS Investigation
ISIS PIolar Probe Plus Science
vestigations (4/5)
e‐field Imager for Solar PRobe
PR): These telescopes will take images White light imager
e solar corona and inner heliosphere.
experiment will also provide images of Inner Telescope
olar wind, shocks and other structures Outer Telescope
ey approach and pass the spacecraft.
nvestigation complements the other
uments on the spacecraft providing
t measurements by imaging the
ma the other instruments sample.
WISPR Investigation
WISPR PI
Dr. Russell Howardervations from 10‐20 Rs are required
chieve the SPP Science Objectives
oronal magnetic
ructure still channels
he flow and determines
Solar Orbiter
ngular momentum loss
Waves, turbulence
rongest
emperature maximum
ollisional‐Collisionless
ransition
Magnetic–KineticP Level‐1 Science Objectives
• Trace the flow of energy that heats the
corona and accelerates the solar wind
• Determine the structure and dynamics
of the magnetic fields at the sources of
the fast and slow solar wind
• Determine what mechanisms accelerate
and transport energetic particles
There are three detailed science sub‐questions
stemming from each of these objectives.ailed Science Sub‐Questions
Example: 1st Science Objective IUGG Solar Probe Plus
Example: 1st Science Objective
Observation Strategy
• SPP, with 75 hrs inside 12 Rs /400 inside 15 Rs (sub‐Alfvénic), will
measure more than 20 hrs (SPP Participation
• 31 institutions participate in SPP science teams
• 23 in the US, 8 foreign
• 17 educational, 5 non‐profit, 8 government labs
• 106 science team members
• 69 PIs and Co‐Is
• 37 additional scientists
• Next generation graduate students and post‐docs
IUGG Solar Probe PlusOpportunity for World‐Wide Community
to Collaborate in SPP!
• Full‐disk magnetograms of the photosphere and chromosphere
• Solar Orbiter, NSO Mount Wilson Observatory, GONG, Wilcox Solar Observatory, SDO, SOHO
• High‐resolution spectro‐polarimetry and imaging spectroscopy of dynamic solar
atmosphere (photosphere to corona)
• Solar Orbiter, ATST; GREGOR; NJIT’s Big Bear Solar Observatory New Solar Telescope (NST),
• Coronagraph observations
• Solar Orbiter, MLSO White light coronagraph, STEREO, SOHO
• UV/X‐ray imaging and spectroscopy
• Solar Orbiter, SDO, IRIS, SOHO
• In‐situ solar wind measurements
• Solar Orbiter, SOHO, ACE, DSCVR, STEREO
• Radio observations
• VLA, Green Bank Solar Radio Burst Spectrometer, Nançay radioheliograph, Nobeyama
Radioheliograph; Owens Valley Solar Array, Siberian Solar Radiotelescope; Atacama Large
Millimeter Array, FASR
• Interplanetary scintillation for tomography of solar wind and ICMEs;
• Differential Faraday rotation of background sources constraining magnetic field strength of outer
corona and SW. –EISCAT, LWA, MWA, ORT
IUGG Solar Probe PlusPhysics of the Corona:
Making The Link - Summary
• Solar Probe Plus provides:
– Statistical survey of outer corona
– 1st perihelion (0.16 AU 0r ~15 million miles) 3 months after launch
– Closest approach below 10 Rs (0.04 AU or 4 million miles)
– Excellent sampling of all types of solar wind
– Measurements from within the region where all the action happens
– Particle measurements from the lowest energy plasma through the most
energetic particles associated with solar flares
– Measurements of plasma waves that enable energy and momentum
flow
– Coronal imaging “from the inside out” bridges local to global scales by
providing the context
0Action Region 20 40 60 80 100
IUGG Solar Probe PlusSPP Conclusions
• Solar Probe Plus will be an extraordinary and historic mission, exploring what
is arguably the last region of the solar system to be visited by a spacecraft,
the Sun’s corona.
• SPP will repeatedly sample the near‐Sun environment, revolutionizing our
knowledge and understanding of coronal heating and of the origin and
evolution of the solar wind and answering critical questions in heliophysics
that have been ranked as top priorities for decades.
• By making direct, in‐situ measurements of the region where some of the
most hazardous solar energetic particles are energized, SPP will make a
fundamental contribution to our ability to characterize and forecast the
radiation environment in which future space explorers will work and live.
• Fantastic mission of discovery to the Sun
• Only opportunity to understand basic plasma physics mechanisms where the
magnetic field dominates
• Trace the flow of energy that heats the corona and accelerates the solar wind
• Determine structure and dynamics of the B fields at sources of the fast & slow
solar wind
• Determine what mechanisms accelerate and transport energetic particles
• Great collaborative opportunities
IUGG Solar Probe PlusIt has been 50+ years since the Solar
Probe Concept was introduced. . .
We are on our way!olar Probe Plus
ASA Mission to Touch the Sun
Back-uprmine the structure and dynamics of the ma and magnetic fields at the sources of olar wind ow does the magnetic field in the solar wind source regions onnect to the photosphere and the heliosphere? Potential Field Source Surface models show that the magnetic field expansion up to the source‐surface plays a crucial role in determining global solar wind outflow properties, including the terminal velocity, which is inversely correlated to the expansion factor itself. re the sources of the solar wind steady or intermittent? To date it has not been possible to determine the origin and variability of the fast solar wind as connections between solar events and high‐speed wind features have not been adequately measured. ow do the observed structures in the corona evolve into the olar wind? Structures emanating from active regions and coronal holes can be traced to several solar radii above the solar surface, but it is unclear how they evolve into the solar wind. Their respective contributions to the solar wind has proven to be hard to quantify from distant (e.g., 1 AU)
rmine the structure and dynamics of the netic fields at the sources of the solar xtended measurements of equatorial extensions of high‐ titude coronal holes as well as equatorial coronal holes. peeds of 110 km/s for perihelia at 20 Rs and ~190 km/s below 0 Rs— allows sampling of the structures, such as plumes, inside he equatorial extensions of the coronal holes. t a radial distance of ~31.5 Rs, there are two periods (one bound, one outbound) where Solar Probe Plus will be in quasi‐ orotation and will cross a given longitudinal sector slowly. In hese intervals, the spacecraft will be able to sample the solar ind for significant radial distances along a field line before oving across the sector. olar Probe Plus, orbiting in the ecliptic, will remain inside the reamer belt for a significant fraction of the 3 encounters inside
rmine what mechanisms accelerate transport energetic particles hat are the roles of shocks, reconnection, waves, and turbulence in the celeration of energetic particles? Identifying the specific SEP acceleration process is a fundamental goal for the SPP mission. Measurements made near SEP acceleration sites will reduce uncertainties due to modifications of angular distributions by propagation and thus provide the timing needed to differentiate specific acceleration processes. hat are the source populations and physical conditions necessary for nergetic particle acceleration? Continuous monitoring of the intensity and composition of suprathermal seed particles in the high corona and inner heliosphere (along with the plasma conditions) are needed to constrain the physical conditions necessary for particle acceleration, their intensity, energy spectrum, and composition. ow are energetic particles transported in the corona and heliosphere? Good pitch‐angle coverage during the observation of these small events close to the Sun is necessary to determine whether the longitudinal spreading of SEP events is due to a direct magnetic connection to the particle source or because of other transport mechanism(s) (e.g., cross‐field diffusion).
rmine what mechanisms accelerate transport energetic particles ong observing times in the inner heliosphere enable extensive ampling of shocks and particle acceleration and transport rocesses. apid scans in longitude allow direct exploration of the spatial xtent of particle acceleration sites olar Probe Plus, orbiting in the ecliptic, will remain inside the reamer belt for a significant fraction of the 3 encounters inside 0 Rs (15 hrs) and the previous 5 below 12 Rs (50 hrs). xtensive radial exploration of the inner heliosphere will clarify he origin of the “ubiquitous” power‐law supra‐thermal tails. addition, the synergy of SEP measurements from SPP and 1 U spacecraft will help constrain the role of cross‐field transport
rticipating Organizations
lifornia Institute of Technology • Royal Observatory of Belgium
ntre Spatiale de Liege, BELSPO • Smithsonian Astrophysical
rvard University Observatory
perial College • Southwest Research Institute
t Propulsion Laboratory • Swedish Institute of Space Physics
hns Hopkins University / APL • University of Alabama, Huntsville
boratoire d'Astrophysique de • University of Arizona
arseille - CNRS • University of California, Berkeley
s Alamos National Laboratory • University of Chicago
assachusetts Institute of • University of Colorado, Boulder
chnology • University of Delaware
ax Planck Institute for Solar System • University of Gottingen - DLR
udies - DLR
• University of Maryland, College Park
ASA Goddard Space Flight Center
• University of Michigan
ASA Marshall Space Flight Center
• University of Minnesota
val Research Laboratory
• University of New Hampshire
ris Observatory LESIA-CNRSar Probe Plus Timeline ssion Confirmation: March 14 tical Design Review (CDR): rch 2015 unch: July 2018 on Delta IV‐ avy with Upper Stage st perihelion (r = 34 Rs): tober 2018 st perihelion with r < 10 Rs: cember 2024
icle Instrument capabilities meet
el 1 requirements with margin
Particle Sensors
SWEAP/SPAN
SWEAP-SPAN
SWEAP/SPC
ons SWEAP-SPC ISIS/EPI-Lo
ISIS-EPI-Lo ISIS/EPI-Hi
L1 Requirement ISIS-EPI-Hi
SWEAP-SPAN
ons SWEAP-SPC
ISIS-EPI-Lo
ISIS-EPI-Hi
SWEAP-SPAN
m SWEAP-SPC
ISIS-EPI-Lo
ISIS-EPI-Hi
s ISIS-EPI-Lo
ISIS-EPI-Hids & Waves Instrument capabilities
t Level 1 requirements with margin
gnetic FIELDS FGM L1 Requirement
gnetic FIELDS SCM
ectric FIELDS EFI
asma
aves Fields & Waves FIELDS PWI
Sensors
FIELDS/FGM
adio FIELDS/SCM FIELDS PWI
FIELDS/EFI
ermal FIELDS/PWI
e FIELDS PWI
~DC 10Hz 1kHz 1MHzds and Waves Measurement Tables
Measurement Dynamic Range Cadence Bandwidth
Magnetic Field 140 dB 100k vectors/s DC - 50 kHz
Electric Field 140 dB 2M vectors/s DC - 1 MHz
Plasma Waves 140 dB 1 spectrum/s ~ 5 Hz - 1 MHz
Quasi-Thermal 100 dB for QTN 1 spectrum/4 s QTN 10-2500 kHz QTN
Noise/Radio 80 dB for radio 1 spectrum/16 s radio 1-16 MHz radio
Meas. Energy Energy FOV Ang. VDF Mass Res.(3)
range(1) Res. Res.(2) cadence
Thermal 10 eV – < 20% nadir and ram 10ox25o 1 Hz d(m/q)/(m/q)
Ions 20 keV directions < 25%
Thermal 5 eV – < 20% > 75% of the 10ox10o 1 Hz n/a
Electrons 20 keV skyrmal Particle Measurement
uirements Tables
seline
Meas. Energy Energy FOV Ang. VDF Mass Res.(3)
range(1) Res. Res.(2) cadence
Thermal 10 eV – < 20% nadir and ram 10ox25o 1 Hz d(m/q)/(m/q)
Ions 20 keV directions < 25%
Thermal 5 eV – < 20% > 75% of the 10ox10o 1 Hz n/a
Electrons 20 keV sky
reshold
Meas. Energy Energy FOV Ang. VDF Mass Res.(3)
range(1) Res. Res.(2) cadence
Thermal 100 eV – < 30% nadir and ram 20ox25o 1 Hz None
Ions 10 keV directions
Thermal 5 eV – 2 < 30% > 65% of the 20ox20o 1 Hz n/a
Electrons keV sky
rgy range not required in all directionsite Light Baseline Measurement
quirements Tables
Meas. Cadence FOV Inner Spatial Photometric
FOV res. sensitivity
bound. (SNR/pixel)
Visible ≤16.5 min ≥76° radial x ≥20° ≤ 14° ≤ 6.4 ≥ 20
Broadband transverse at 14° arcmin
elongation to ≥44°
transverse at 90°
elongation
Meas. Energy range Highest FOV (3) Angular Composition
(1) cadence (2) sector (4)
Energetic ≥1.5 decade in ≤10 sec ≥π/4 sr in sunward vs n/a
electrons the range from sunward & anti-
0.02 - 6 MeV anti-sunward sunward
hemispheres
Energetic ≥2 decades in ≤10s, ≥π/4 sr in sunward vs protons, heavy
protons the range from protons; 1 sunward & anti- ion groups
and heavy 0.02 to 100 min, ion anti-sunward sunward (He, CNO,ergetic Particle Measurement
quirements Tables
seline
Meas. Energy Highest FOV (3) Angular Composition
range (1) cadence sector (4)
(2)
Energetic ≤0.05 to≤1 sec ≥π/2 sr in sunward ≤45° n/a
electrons ≥3 MeV (select & anti-sunward sectors
rates) hemispheres
Energetic ≤0.05 to ≤5 sec ≥π/2 sr in sunward ≤30° at least H, He,
protons and ≥50 (selected & anti-sunward sectors 3He, C, O, Ne,
heavy ions MeV/nuc rates) hemispheres Mg, Si, Fe
reshold
Meas. Energy range Highest FOV (3) Angular Composition
(1) cadence (2) sector (4)
Energetic ≥1.5 decade in ≤10 sec ≥π/4 sr in sunward vs n/a
electrons the range from sunward & anti-
0.02 - 6 MeV anti-sunward sunward
hemispheres
Energetic ≥2 decades in ≤10s, ≥π/4 sr in sunward vs protons, heavyP High Level Organizational Chart
NASA
Science Mission Directorate
Heliophysics Division
Director: S. Clarke
Program Scientist: M. Guhathakurta
Program Executive: J. Lee
GSFC LWS Program Office APL/SES Management
Program Manager: N. Chrissotimos
PM for APL Projects: M. Goans
Mission Scientist: A. Szabo
HELIOSPP – JPL*
PI: M. Velli, Obs Sci
Solar Probe Plus Project Office Project SAM: L. Becker
Project Manager: A. Driesman
EPO EV Manager: H. Hunter
Deputy Project Manager: P. Hill
D. Turney Planning Manager: C. Battista
Deputy PM for Instruments: K. Cooper
Production Planning Mgr: C. Battista Financial Manager: S. Diamond
ISIS – SwRI
R – NRL* PI: D. McComas Mission System Project Scientist
Howard PM: S. Weidner Engineer N. Fox
Plunkett MSE: J. Kinnison
DMSE: M. Lockwood
FIELDS – UCBker’s ‘solar wind’ model - 1958 Sun's corona is strongly attracted by solar gravity, but it is such a good ductor of heat that it is still very hot at large distances. Since gravity kens as distance from the Sun increases, the outer coronal atmosphere pes supersonically into interstellar space. weakening effect of the A ‘solar wind’ is accelerated from the corona ity has the same effect on odynamic flow as a de Laval le (or jet engine): it incites nsition from subsonic to ersonic flow. uires energy input at the . kTph is not nearly enough! uires non‐thermal energy predicts a critical point
e solar wind is heated continuously s spacecraft urements from 0.3 U ger spacecraft urements outward /r batic cooling cts a much more decay ires continuous, buted energy input
Waves/turbulence vs reconnection
otpoint shuffling of open Reconnection injects
d lines generates Alfvén energy from closed field
ves. Waves propagate regions
(Cranmer cartoon)
ward and dampere are we today? e corona requires a non-thermal source of heat A sufficiently heated corona will expand super-sonically and super- Alfvénically to form a ‘solar wind’ The expanding solar wind requires additional heating e large coronal magnetic energy density is a sufficient energy source. s is our ‘dark energy’. But problems remain: How are the magnetic fields created and transported How is the magnetic energy converted to thermal energy: magnetic reconnection, shocks, waves and turbulence What is the role of ambipolar electric fields?
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