DESIGN CONCEPTS FOR AN L5 SWX MISSION
Angelos Vourlidas
SSD/Naval Research Laboratory,
USA
How strong?
When/where
will it hit?
Hurricane prediction without
geosync satellites
Hurricane prediction with geosync satellites
How strong?
When/where
will it hit?
Space Weather prediction with satellite at L5*
Space Weather prediction
without satellite at L5
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WHY DO WE CARE ABOUT SPACE WEATHER?
• Geomagnetic storms are recognized as one of only two future global risks for mankind.
• Improved prediction of CME arrival is is essential for protection.
Global effects of Geostorms. (from 2013 OECD report
on Future Global Shocks).
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WHAT IS THE L5 MISSION CONCEPT?
Deploy a suite of imaging + in-situ instruments
at L5 to study the Sun-Earth interaction and
monitor Space Weather.
Variety of obits to choose from:
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Stationary at L5 (60° from Earth).
Tight orbit around L5 (~ 1000’s km around L5).
Loose orbit around L5 (40°-- 90° from Earth).
…
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HISTORY OF THE L5 CONCEPT
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2005: JAXA studies an L5 mission concept (Akioka et al., J. CRL)
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2009-2010: STEREO crossed L4/L5 points.
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Followed several CMEs to Earth. Demonstrated SWx potential from L5.
2010: Two White Papers submitted during Heliophysics Decadal Survey Call
(Vourlidas et al, Gopalswamy et al).
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Their largest rocket is capable of L5 insertion.
Selected for further study by Heliophysics subpanel
L5 mission features prominently in the Decadal Report (Sect. 7).
2011: Small Workshop on Future Heliospheric Imagers (hosted by Air Force)
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L5 discussed extensively. Is it an OPS or RESearch mission?
NASA most likely sponsor. Research mission focused on the life of Flux Ropes.
• Recent LWS TR&T opportunity is encouraging.
WHY GO TO THE L5 LAGRANGIAN POINT?
Benefits of an L5 viewpoint:
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Full view of the Sun-Earth heliosphere.
Advance view of the solar side to rotate towards Earth.
Advance measurement of solar irradiance.
Advance sampling of solar wind before it reaches Earth.
Continuous quadrature between L5 and L1.
60º
DSCVR
L5 is an ideal location for addressing high priority science issues in SWx prediction, including:
• Emergence of Active Regions (Helioseismology).
• Improved Solar Wind Models (Magnetograms across 60% of the Sun).
• CME/CIR/Solar Wind Interactions (Coronagraphy-Imaging from an exceptional viewpoint).
• Improved Research-to-Operations Procedures (R2O pathfinder).
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WHYLL5?
– SPACE
WEATHER
= Nimbus
program for terrestrial weather
5 mission
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Ideal location for Space Weather studies
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> 4-day warning for recurrent disturbances (e.g., CIRs, Irradiance variations).
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> 4-day warning of coronal activity (e.g., flux emergence, streamer inflation).
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Earth-directed CMEs/solar wind lie on Thomson Surface
 maximum sensitivity for white light obs.
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60% - 75% instantaneous photospheric field coverage (improved boundary conditions for
Heliospheric models, e.g, ENLIL, SWMF, etc).
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In-situ measurements of CIRs BEFORE they hit Earth.
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Vourlidas & Howard 2006; Vourlidas 2009; Vourlidas
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et al 2014
FEASIBLE: WE HAVE ALREADY BEEN AT L5
(OBSERVATIONS FROM STEREOB)
View from L4
From L5 (and L4) it is straightforward to
measure and follow CMEs & CIRs
from the Sun to Earth.
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View from L5
STEREO Facts:
• 480 kps telemetry.
• 5 telescopes.
• 55 Kg payload.
• ~4x improvement in CME time-ofarrival prediction (6 -8ßvs. 24
hours).
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IMPROVED SWX PREDICTIONS FROM OFF SUNEARTH LINE OBSERVATIONS
Example: Time-of-arrival accuracy +/-6 hours for 78% of events
L1-only
measurements!
• Orange: fit in LASCO (< 30R)
• Purple: 2nd order fit (> 50R)
• Blue: 1st order fit (> 50R)
Best Results:
Linear fit on H-t data > 50 Rs
(Colaninno et al 2013, JGR, 118, 6866)
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HOW TO IMPLEMENT THE L5 MISSION
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STEREO+: Single s/c with STEREO imagers + magnetograph.
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Straightforward. Requires V551 or Falcon-9heavy. Less than <$500M
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Advocated in the 2013 Solar Physics Decadal Survey (USA)
Fractionated L5: instruments on individual CubeSats using Solar Sails.
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Distributed in-situ observations along Earth-L5 orbit.
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Cheaper (but it needs to be studied)
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Innovative. Will enable other mission concepts based on solar sails (e.g., Geostorm).
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Telemetry, power, launch opportunity challenges.
L5 Flock: Imaging instruments on regular (but small) s/c. In-situ instruments on
CubeSats flying in flock-formation.
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Best of both worlds (possibly).
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Cheaper than STEREO+. Simplifies s/c instrument integration (EMI/EMC, FOVs, etc)
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No power or telemetry issues.
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The Decadal Survey Concept: The L5 Observer
A Mission to the Sun-Earth L5 Point for Heliophysics & Space Weather Research
Science Objectives:
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Origins and evolution of the Earth-bound solar wind.
Longitudinal evolution of the tachocline.
Follow the emergence of fluxropes from the interior to Earth.
Understand solar wind-CME interactions.
Accurate Time-of-Arrival CME forecasts.
~4-day warning of recurrent disturbances, irradiance variations.
Relevance to Heliophysics Goals:
• Goal 1: Determine the origins of the Sun’s activity and predict
the variations of the space environment.
• SH-1: Understand how the Sun generates the magnetic field
• SH-3: Determine how magnetic energy is stored and
explosively released and how the resulting disturbances
propagate through the heliosphere
• Goal 4: Discover and characterize fundamental processes
within the heliosphere and throughout the universe
Mission Implementation Description:
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No. of s/c: single or multiple cube-sat fleet
3-axis stabilized s/c at orbit around L5.
No of instruments: 6 remote, 3 in-situ. TRL6+
S/c resources: ~100 Kg, ~140 W, ~300 kbps.
Measurement Strategy:
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Enabling and Enhancing Technology Development:
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Launcher cost and availability.
DSN improvements for increased downlink volume from L5.
All technologies at TRL 6 or higher for single satellite
For cube-sat then need a cluster of miniaturized s/c dedicated
to observation type with intra s/c communication for downlink..
Need miniaturized optical designs.
Surface & Interior Flows “stereo” helioseismology.
180⁰ instantaneous coverage of the phot. magnetic field .
Enhancing Pre-mission R&A:
Coronal imaging in EUV & visible.
• Helioseismology from two viewpoints.
Heliospheric imaging from 15 Rs to 1 AU.
• Propagation & interaction of CMEs with SW
Composition of Earth-directed solar wind (UV spectroscopy).
Imaging of HXR looptop sources.
In-situ magnetic field, wind, SEPs.
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STEREO
NEW
A STRAWMAN L5 PAYLOAD BASED ON STEREO
HARDWARE
Instrument
Measurements
FOV
Resolution
Magnetic / Doppler Imager
Photospheric B, V
Full disk
2”
Full Disk
2”
OVI dblt, CIII, Lyβ-γ, ArXII,
SiXII , FeX-XII, XVIII
4Rs slits at
1.7 & 2.5 Rs
<10”
Slit/Slot Spectral Imager
170-210 Å
400” x 20”
1”
EUV Imager
171, 195, 284, 304 Å
0 – 2 Rs
2”
White-light Coronagraph /Imager
Coronal Imaging
2 – 15 Rs
30”
Heliospheric Imager
Heliospheric Imaging
15 – 215 Rs
2’
Low-frequency Radio Telescope
Dynamic spectrum
1 – 100 Rs
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Solar Wind Plasma Instrument
Plasma parameters
In situ
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Solar Wind Magnetometer
Magnetic field
In situ
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Energetic Particle Detector
SEP intensity
In situ
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Hard X-ray Imager
Off-limb Spectrometer
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4-150 KeV,
1 Kev resolution
970 – 1040 Å
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JPL CONCEPT: A Fractionated Space Weather Base At L5 Using
Cubesats And Solar Sails (Liewer et al,, 3rd Int. Symp. On Solar Sailing )
• Concept envisions a string of CubeSats travelling to L5 at any given time.
Multipoint in-situ coverage.
• Based on NIAC study; 6U (2U for Sail, 1.5-2U for instrument).
• Limited downlink capabilities for cubesats.
• Ideal for Solar Sail and in-situ payloads.
• NRL contribution: HI and COR at station in L5.
• OPERATIONAL focus.
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L5 SOLAR-SAIL CUBESAT DESIGN-DEPLOYED
Thanks to P. Liewer and the JPL team
Concerns with Current CubeSats:
• Cheap means Cheap!
• Low reliability and performance.
• Not Research grade. Educational systems, effectively,
• Low orbits unsuitable for solar monitoring.
Requirement for Research-Grade (interplanetary)
CubeSats:
• Rad-hard electronics
• Better pointing
• Higher power
• Higher telemetry
• Quality Assurance
• Higher $ cost!!
Proposed Mission - Pre-Decisional – for Planning and
Discussion Purposes Only
Copyright 2014 California Institute of Technology. Government
sponsorship acknowledged.
The “FLOCK” CONCEPT:
A “Hybrid” Space Weather Base at L5 using
“Flock” Formation (Small Sat + CubeSats)
1000 Km
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Use a medium-size satellite (mothership) to host imaging instruments + CubeSats
for in-situ payload in flock formation.
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Advantages :
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Spinning cubesats + Sun-pointed mothership optimize science for both types.
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Cubesats downlink to mothership. Mothership to Earth via normal S/Ka, etc. Removes
downlink restriction (> 500 Kbps from L5).
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Flock formation easy to achieve at L5 (stable orbits).
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In-situ can be sent via solar sails or launched from mothership and fly in formation to L5.
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Reduced lift mass reqs for mothership.
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Imaging instrumentation: Magnetograph, EUV (to 2 Rs), COR or HI (to 1AU).
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SUMMARY
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Call to Action: We must improve the SWx infrastructure ( Recommendation).
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Can only be accomplished with an International Effort.
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SWx affects us all.
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Very constrained space budgets in several space-faring countries.
Create a SWx Sentinel Network (Recommendation)
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L5 is clearly the first place to send a SWx Sentinel.
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Several concepts with varying complexity and research-to-ops (R2O) balance.
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Develop Sentinel network in manageable steps ( L1L5L3L4, elsewhere).
Possibly the first R2O mission concept in Heliophysics (Recommendation).
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Trailblazing and hence many issues to be resolved.
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Initially RESEARCH mission (e.g., NASA) switching to OPERATIONAL (e.g. NOAA) after
primary objectives are met (2-4 years).
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WHAT’S NEXT?
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Suggestions and Ideas for Discussion:
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Organize a meeting to define Space Weather Requirements for L5 mission and/or a
Sentinel Network.
• Under the auspices of CONPUOS/ILWS?
• To define Minimum reqs for Basic research. Minimum reqs for Ops research.
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Invest in miniaturizing telescopes for CubeSat/MiniSat deployment.
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Invest in training the next generation of R2O heliophysicists.
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BACKUP SLIDES
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AN L5 MISSION IS FEASIBLE
Sample ΔV calculations (from Lo, Llano, & Hintz 2010)
NOTE:
1. Easier transfer to L5
(compared to L4).
2. Both large and small orbit
amplitudes are feasible
3. Both fast and slow flight
times to LOI.
Preferred Orbit
Col 1: L4 or L5 orbits. Col 2: Major amplitude of the periodic orbit. Col 3: Transfer Orbit Arrival; time from injection from Earth.
Col 4: Time Of Science between the TOA and the insertion into the Libration point. Col 5: Time of Flight (TOF= TOA+TOS).
Col 6: Injection ΔV from Earth orbit into the transfer orbit. Col 7: LOI ΔV. Col 8: Total ΔV.
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WHY L5 OBSERVATIONS ARE SO IMPORTANT?
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From Dr. Kent Miller’s 5/8/13 presentation at AFOSR
WHY INCLUDE HELIOSEISMOLOGY ON AN L 5
MISSION?
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Simultaneous helioseismic observations (Earth + L 5)
detect both ends of long, deep wave raypaths. Such
rays penetrate to the tachocline.
Earth
By measuring travel times along such raypaths, the
thermal anomalies and flows in the tachocline will be
resolved in longitude for the first time.
L5
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The resolution will be about 0.1 R s, resolving
azimuthal variations up to
about wavenumber m=30.
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‘HURRICANE’ SEASON : MARCH 2012
• Low sunspot numbers DO NOT imply weak activity.
• An intense episode of solar activity began on 2 March 2012 with the emergence of sunspot AR1429.
• In 2 weeks, AR1429 fired off more than 50 flares, (3 of them X‐class, the most powerful type).
• By the time it decayed, it had done a 360‐degree pirouette in heliographic longitude, hitting every
spacecraft and planet in the solar system at least once with either a coronal mass ejection or a burst of
radiation. This extraordinary series of solar storms, referred to as the “St. Patrick’s Day storms” caused
reboots and data outages on as many as 15 NASA spacecraft .
NASA/ESA need
interplanetary space weather
forecasting.
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LIMB SPECTROSCOPY FROM L 5 CAN OBTAIN ENERGETICS, SHOCK
PROPERTIES OF THE SAME CME EVENT WHOSE SOURCE AND ICME
ARE OBSERVED AT L 1.
Elevated Fe and O charge states in ICME
(Lepri et al. 2001)
UVCS slit
Time evolution of Fe XVIII
emission in the CS
L1 view
Fe Charge
Thermal/non-thermal heating, inflow in CME
current sheet
(Ciaravella & Raymond 2010)
Shock broadening of
O VI 1032/1037 lines
Reconnection rate from motion of flare
ribbons (Qiu et al. 2004)
L5 view
CME shock parameters
(Mancuso et al 2002)
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IT IS STILL UNCLEAR WHETHER ENERGETIC
PARTICLES ARE ACCELERATED IN FLARES OR
CMES
Electron beams heating the chromosphere and generating the SXR flare originate
high in the corona (at the HXR looptop source) .
HXR looptop sources seem to lie at the boundary of CME fluxrope and flaring loops.
HXR looptop sources are much fainter that their footpoints. Observed only when
footpoints are occulted.
THE PROBLEM:
• Observed HXR looptop emission requires huge
amounts of accelerated electrons
(1033 electrons; Krucker et al 2010).
• The corona is very tenuous.
• What is the acceleration mechanism?!
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L5 IS UNIQUE FOR IMAGING THE HXR SOURCES
OF GEO-EFFECTIVE SEP EVENTS
• Bright footpoint emission from L1-connected
flares is occulted from L5.
• L1 assets observe the source region of the flare.
• L5 s/c observes both the HXR looptop sources
and the SEPs.
• Especially powerful when combined with radio
imaging from Earth (FASR).
Example with STEREO-B & RHESSI observations
of 12/31/2007 CME.
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