Solar Radar and Distributed Multi-static meteor radars ...
Transcript of Solar Radar and Distributed Multi-static meteor radars ...
Solar Radar and Distributed Multi-static meteor radars/receivers
J. L. Chau1, W. Coles2 et al. 1LeibnizInstituteofAtmosphericPhysics–UniversityofRostock,Kühlungsborn,Germany
2UniversityofSanDiego,CA,USA.
Thanks to: Gunter Stober Namir Kassim
Joseph Helmboldt Chris Hall
Masaka Tsutsumi Christoph Jacobi
Quo Vadis Workshop, May 26, 2016, Boulder, CO, USA
Outline SolarRadar:LessonslearnedfromJicamarcaexperiments
MMARIAapproach,acomplementtoafutureGEO-FacilityforMLTstudies Stand-alone AspartofapowerfulVHFradar
Personal“opinions”onwhattoconsider
Solar Radar Bill Coles (UCSD) and Jorge Chau (IAP)
What we learned from the Jicamarca Experiment:
1. The echo was much weaker (>10dB) than expected so we will need more power delivered to the Sun.
2. The solar noise was much stronger than expected. It comes from compact noise bursts, so we will need spatial
resolution to observe between noise bursts.
Solar noise Feb 10 -15, 2004, at 50 MHz integrated over entire discsolar activity was “low” to “very low” during entire period
the quiet Sun is the lower envelope
BW=1MHz; T=1s σP=0.013dB
expected echo is ≈10σP of quiet Sun (after decoding)
RCP 2004/2/10 LCP 2004/2/10
CAL
LCP 2004/2/11 LCP 2004/2/12
Four examples of delay-Doppler maps during quiet periods
1. Since the echo is > 10 dB weaker, we will need to deliver 10 dB more power to the Sun - roughly 1 MW CW and the transmitter beam width must be roughly 1 degree. This implies a filled aperture > 60 wavelengths in diameter, comparable to JRO in fact.
2. We want to be able to observe the Sun more than 1000 s per day, so we will have to track the Sun. This implies that the elements in the transmitter array will need independent phase control.
3. The solar noise increased 30dB during a strong earthward CME - exactly what we want to detect. So the receiver must be able to resolve out solar noise bursts with a dynamic range of about 30dB. This will also require spatial resolution < 0.05 degree, which implies a thin array >1200 wavelengths in diameter.
Implications for a new solar radar system
Transmitter Design• It is almost certainly cost-effective to use an array and very likely cost-effective to put a
power amplifier on each linear element of the array. • The size of the array must be 60 λ in diameter so the number of elements Ne depends on
the element spacing. • The element spacing (in λ) depends on the scan angle, so the spacing may have to be λ/
2 E-W, but might be relaxed somewhat N-S. So Ne ≲ 11300. • Regular spacing is probably most efficient as we would then transmit equal power from
each element. A hexagonal arrangement is likely preferred. • More elements increases the cost, but decreases the power requirement for each power
amplifier, so the cost is < linear with the number of elements. • Small power amplifiers can be made broad band (28 to 53 MHz?), and flexibility in
transmitting frequency would be very useful for known applications. It would also, perhaps, permit unforeseen applications.
• It is probably efficient to put an intelligent transmitter controller on each element, which would require only a clock signal and a digital link, perhaps ethernet or even WiFi, to be distributed to each element.
• With independent control of each element we could transmit multiple beams in different directions with different power levels, different codes, and even different frequencies, provided only that the total transmitted power/element is respected.
• It would be valuable to be able to receive with the same antenna. With distributed power amplification the T/R switch should be relatively simple to design. In addition to receiving and analyzing an echo for scientific purposes, the echo can also be used for calibration of the array.
Other considerations
• Transmitter (cont) • CW Broadband, able to work on pulsed mode. • Linear, circular, elliptical polarizations. • Broadband antenna element for transmission. Modified LOFAR LB or LWA?
• Array calibration • Radio sources (e.g., Cygnus A, Cassiopeia, Hydra) • Use of drones (reflectors or radio beacons).
ImprovedMLTwindmeasurements:
MMARIAapproach(Multi-static,Multi-FrequencyMeteorRadar)
J.Chau,G.Stober,J.Vierinen,etal.
[see Stober and Chau, RS, 2015, Vierinen et al., 2016]
MMARIA:Multi-static,Multi-frequency,Multi-transmitter
Northern Norway Northern Germany
Andenes,Trømso,Kiruna, Sodankyla,Trondheim, Alta, Svalbard
Juliusruh, Collm, Kborn
MMARIAApproach:Advantages
Improvement Relevance
(1)Increasednumberofdetections
Bettertimeandaltituderesolution
(2)ObservationoflargereffectiveBraggwavelengths
Higheraltitudecoverage
(3)Multipleobservinganglesofcommonvolume
Extractionofparameterslikerelativevorticity,horizontaldivergence,shear,stretching,…
(1)and(3) ImprovedeterminationofGWparametersinbothtimeandspace(3D)
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From: 14-Mar-2016, to: 20-Mar-2016
ExamplefromsimultaneousPulsedandSpread-spectrumCampaign
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Only P
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Rx 2
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Four links: • Pulsed – Rx1 • Pulsed – Rx2 • CW1 – Rx2 • CW2 – Rx2 Transmission in the same frequency! Only 400 W CW Power on each CW link (compared to 1.2 kW avg – Pulsed).
ExamplefromAndenes-Tromso
Climatology
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Composite over Andenes-Tromso (69.4N)
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MMARIAandSolarRadar/Radio Asolarradarwouldbeasuperb“all-in-one”meteorradar: Head-echoes:Meteormass,Meteorpopulations,etc. Non-specular:Higheraltitudewinds,plasmaphysics
Specularechoes:MMARIAwindfieldswithin300-700kmradius(forallpracticalpurposes,asolarradarwouldbean“all-sky”illuminator).
TechnicalRequirements: Multi-staticcapabilities
“Knowledge”oftransmittingsequence.
• Solar VHF receivers are excellent for MMARIA applications, either receiving solar radar signals or receiving other existing transmitters (FM, TV, existing meteor radars, etc.).
• Technical Requirement: Access to few (5-7) closely spaced antennas in parallel to any solar/astronomical application. We are currently evaluating such possibility with LOFAR.
Personal“opinions”onwhattoconsider TheUSspacesciencecommunityneedsabettercoordination(orintegration)betweenNSFGeospaceandNSFAstronomyonsolar-relatedresearch.Similarly,abettercoordinationbetweenNASAandNSFGeospace(e.g.,wouldGeospacecubesatsbeagoodideaforanNSF-MREFC?)
ThenextGeospaceNSF-MREFC? DASI-like“small/large”instrumentsorsingleLargefacility(andclustered
instrumentation)? DASIisnotjustaboutresources,nationalandinternationalcollaborationiscrucial.
Transformationalscienceand/orService? Afacilitywithasignificantbettercapability,oranetworkof“standard”instrumentswith24/7capabilities(analogywithOcean,ashiporbuoys?).
Towardsresearchortowardsoperations.
OneGiantfacilityoraGiantUmbrellaofsmallersystems?
Ionosphere Forcing
[adapted from Marchavilas, 2007]
Ionosphere
Solar/Magnetospheric forcing, e.g.,
geomagnetic storms
Tropospheric/Stratospheric forcing, e.g., planetary
waves, tides, GWs
Ionosphere Lower
atmosphere
Sun Earth Magnetosphere
Mesosphericwindsandshears
Meteor winds from 3 days
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ExamplefromAndenes-TrømsoSelectedClimatologicalProfiles
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Tempora l cu ts over Andenes-Tromso (69.4N)