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CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
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Transcript of CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUELaboratoire de Physique et Chimie de l'Environnement et de l’Espace
3A, avenue de la Recherche ScientifiqueF-45071 Orléans cedex 02, France
Phone: (33 2) 38 25 52 63; Fax: (33 2) 38 63 12 34; E-mail: [email protected]
EJSM JGO/RPWI Team Meeting, 26-27 Nov. 2009
Mutual Impedance MEasurements, MIME as part of the EJSM JGO/RPWI
Jean Gabriel TROTIGNON and Jean Louis Rauch
LPC2E, CNRS, Université d’Orléans, Orléans, France
EJSM JGO/RPWI Team Meeting, 26-27 Nov. 2009
Mutual Impedance MEasurements, MIME as part of the EJSM JGO/RPWI
Téléphone: (33 2) 38 25 52 63 Secrétariat: (33 2) 38 25 52 64 Télécopie (Fax): (33 2) 38 63 12 34 E-mail: [email protected]
Experiment Objectives
Principle of Measurements
Range of Measurements
Heritage
Instrument
Conclusion
Presentation Outline
Provide reliable/accurate measurements of total plasma density & thermal electron temperature, in Jupiter system environment (solar wind included);
Contribute to the study of the interactions between solar wind & Jupiter’s Magnetosphere, in particular around Ganymède and Callisto;
Give insight into thermal coupling between neutral & charged particles;
Detect plasma boundaries and identify plasma regimes;
JGO/RPWI/MIME Experiment Objectives (1 / 2)
Enable self and/or mutual impedances of LP-PWI and possibly RA-PWI electric antennae to be determined as a function of plasma environment;
Determine the effective length of these antennae (then allow E-field component of waves to be calibrated);
Possibly measure the physical/deployed length of antennae;
Contribute to onboard calibrations of LP-PWI, and maybe SCM and RA-PWI (calibration signal can be delivered)
cross-calibration between sensors.
JGO/RPWI/MIME Experiment Objectives (2 / 2)
MIME Principle of Measurements
A sinusoidal signal of known amplitude & frequency, coming from a current (or voltage) generator, is applied to antenna probe or wire shield, by short pulses (some ms), while induced voltage (or current) is simultaneously measured.
Antenna impedance Z = V / I is a function of frequency & plasma conditions.
Transmitted frequency varies step by step in a frequency bandwidth that includes the plasma frequency expected at Jupiter’s Magnetosphere (Ne proportional to Fpe
2).
Impedance spectra are computed onboard by FFT/DFT algorithms.
Plasma parameters, such as density and electron temperature, are derived from variations of both impedance modulus and phase close to Fpe.
Thermal electron temperature Te shall be determined provided
2 λD < L < a few tens λD ,
where L is the tip-to-tip antenna length and the plasma λD Debye Length
For the total electron density Ne, L must be higher than λD and can be higher than a few tens λD depending on the onboard FFT frequency resolution
Ne can be determined from resonance and/or wave signatures at the plasma frequency Fpe, the upper-hybrid frequency Fuh and Berstein mode frequencies Fqn
As a bonus, the magnetic field strength B can be derived from the electron cyclotron frequency Fce and its gyroharmonics nFce
Ne (cm-3) = Fpe2 (kHz) / 81Fce (Hz) = 28 B (nT)Fuh = (Fpe + Fce)1/2
Fpe (kHz) = 6687 Te1/2 (eV) / λD (cm)
MIME Principle of Measurements (cont’d)
4 March 2005, 22:12:39.14 UT, 0 dB ≡ 0.6 μV Hz1/2
Fpe = 468 kHz = 1.17 Fce Ne = 2,700 cm-3
616 kHz
Fuh896
FQ2
1232
FQ3
1624
FQ4
406 kHz
Fce
266 kHzInterference
812
2Fce1176
3Fce1568
4Fce
2,090 km altitude
MIME Range of Measurements
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUELaboratoire de Physique et Chimie de l'Environnement et de l’Espace
3A, avenue de la Recherche ScientifiqueF-45071 Orléans cedex 02, France
Phone: (33 2) 38 25 52 63; Fax: (33 2) 38 63 12 34; E-mail: [email protected]
Fpe (kHz) Necm-3
10-3 eVλD (cm)
0.01 eVλD (cm)
0.1 eVλD (cm)
1 eVλD (cm)
10 eVλD (cm)
100 eVλD (cm)
0.285 0.001 740 2.35 103 7.4 103 2.35 104 7.42 104 2.35 105
0.705 0.006 300 949 3 103 9.5 103 3 104 9.5 104
1 0.012 210 670 2.1 103 6.7 103 2.1 104 6.7 104
2.1 0.05 100 320 103 3.2 103 104 3.2 104
2.23 0.06 300 950 3 103 9.5 103 3 104
6.7 0.55 100 316 103 3.2 103 104
7 0.6 300 955 3 103 9.6 103
10 1.23 21 67 210 670 2.1 103 6.7 103
21 5.4 100 318 103 3.2 103
22 6 300 960 3 103
67 55 100 316 103
70 60 300 955
100 123.5 2.1 6.7 21 67 210 670
210 540 100 318
220 300
670 5.5 103 100
1 000 1.2 105 0.2 0.67 2.1 6.7 21 67
3 500 1.5 105 0.06 0.2 0.6 2 6 19
9 000 106 0.02 0.07 0.23 0.74 2.35 7.4
Comparison between a 2 x 3 m long antenna (green) and a 2 x 1 m one (yellow);Ne and Te should be measured provided 0.5 cm ≤ λD ≤ 3 m (or 1 m)
Callisto (Gurnett et al., 2000)
Ne ~ 400 cm-3 (180 kHz) at 535 km
> 100 cm-3 (90 kHz) at 500 - 600 km
Iomospheric peak: 7 000 – 17 000 cm-3
(750 – 1200 kHz) at 30-50 km
Ganymede (Gurnett et al., 1996; Eviatar et al., 2001)
Ne ~ 200 – 300 cm-3 (130 – 160 kHz)at 1 000 km
Ne peak 400 - 2 500 cm-3
(180 – 450 kHz)
Expected MIME Range of Measurements
Frequency bandwidth: from a few hundred Hz* up to 3 MHz;
Debye length: from 0.5 cm up to 1-3 m (depending on antenna length);
Total plasma density: 0.01 – 1.5 105 cm-3;
Electron temperature: 0.01 – 100 eV.
The E-field antenna is assumed to be of the order of 2 to 6 m tip-to-tip long(the longer, the better)
* Lower-frequency signals can be produced for sensor calibrations (TBD)
Mutual Impedance Technique Heritage
The mutual/self impedance measurement technique has successfully been used, during nearly three decades, onboard ionospheric rockets and spacecraft (GEOS, VIKING, MARS 96, ROSETTA, and more recently BepiColombo/MMO).
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUELaboratoire de Physique et Chimie de l'Environnement et de l’Espace
3A, avenue de la Recherche ScientifiqueF-45071 Orléans cedex 02, France
Phone: (33 2) 38 25 52 63; Fax: (33 2) 38 63 12 34; E-mail: [email protected]
ROSETTA/RPC/MIP Observations in the Earth’s Plasmasphere
Active: Impedance Modulus
Active: Impedance Phase
Passive: Natural waves
Mutual Impedance Technique Heritage (cont’d)
Numerical Simulations for BepiColombo/MMO
Both the capacitance and the resistance of the MEFISTO antenna exhibit a peak at the plasma frequency (=> density) and a “plateau” below (=> temperature).
Here, Debye length is 5 m, which is a typical value in solar wind close to Mercury (~30 m antenna tip-to-tip length).
Double probe
Double wire-shieldR0 /2
(analytic approx.)
(analytic approx.)
Double probe
Double wire-shield
R0 /2
(analytic approx.)
(analytic approx.)
Double probe
Double wire-shield
Double probe
Doublewire-shield
Mutual Impedance Technique Heritage (cont’d)
MIME Instrument
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUELaboratoire de Physique et Chimie de l'Environnement et de l’Espace
3A, avenue de la Recherche ScientifiqueF-45071 Orléans cedex 02, France
Phone: (33 2) 38 25 52 63; Fax: (33 2) 38 63 12 34; E-mail: [email protected]
Global view of MIME instrument
electricantenna(e)
digital signalgenerator
signal acquisition
ADSP signal analyser(FFT, phase…)
signalcontroller
command word
clock
()
() also to SCM for calibrations (TBD)
Output signals of synthesizer are referenced to ground
Possible Electrical Interface: here AM²P-E to MEFISTO on BepiColombo/MMO
Safety relay
MIME outputswitch
synthesizer
MIME SensorElectronics
E-Field Sensor
Detail of possible interface with E-Field antenna(e) for wire and mutual modes
Electrical Interfaces : MIME to E-Field Antenna(e)
MIME may be composed of the following elements:
• The electronic board hosted in RA (it would allow MIME to be connected to every electric/magnetic sensors);
• Current probes hosted by E-field antenna deployment boxes (as in BepiColombo/MEFISTO ones);
• EGSE including data processing software.
RPWI/MIME Elements
“I " measured by MIME current probe“V " measured by LP/PWI
3 casescurrent injected on LP/PWI spheres,
voltage is measured
voltage injected on boom external shield,
current/voltage is measured
send calibration signal to a selected sensor:
LP/PWI or SCM
• V1 and V2 (2 channels)• V1 - V2 (1 channel)
• I1 and I2 (2 channels)• I1 - I2 (1 channel)• V1 - V2 (1 channel)• I1 - I2 and V1 - V2 (2 channels)
MIME possible working modes
A MIME measurement point contains 3 pieces of information:
• Reference spectrum (no transmission)• Power spectrum• Phase spectrum
from which Ne, Te, antenna impedances… are derived on ground.
Note: to increase SNR, each frequency may be transmitted n times depending on MIME working modes, and averages will
therefore be computed onboard.
MIME Measurement Point Definition
MIME power and mass ressources
Mass: 13 g eachPower consumption: 50 mWSize: 52 mm x 52 mm
Mass: 470 g (1.3 g / cm2)Power consumption: 1.3 W (1.6 W peak)Size: 247 mm x 147 mm
(BepiColombo/MMO/AM2P)
(Rosetta/MIP)
(BepiColombo/AM2P)
Mass: 240 g (0.8 g / cm2)Power consumption: 0.5 W (0.7 W peak)Size: A5
MIME Telemetry Ressources
Survey: 1952 bits / 60 s (33 bits s-1)
Ref. spectrum (passive): 64 frequency bins x 10 bits x 1Power spectrum: 64 frequency bins x 10 bits x 1Phase spectrum: 64 frequency bins x 10 bits x 1HK: 32 bits
Nominal: 6976 bits / 30 s (233 bits s-1)
Ref. spectrum: 96 frequency bins x 12 bits x 2Power spectrum: 96 frequency bins x 12 bits x 2Phase spectrum: 96 frequency bins x 12 bits x 2HK: 64 bits
Burst: 12 352 bits / 10 s (1 235 bits s-1)
Ref. spectrum: 128 frequency bins x 16 bits x 2Power spectrum: 128 frequency bins x 16 bits x 2Phase spectrum: 128 frequency bins x 16 bits x 2HK: 64 bits
E-Field Antenna Occupancy
1 MIME channel
Ref F0 F1 F126 F127
2 MIME channels
F1Ref F0 F126 F127
F1Ref F0 F126 F127
MIME emission 2 times shorter
ORFrequency repeated N times
Frequency repeated N/2 times
Example:
N = 24 (frequency step repetition factor; for a high signal to noise ratio)Frequency sweep = 128 different frequency steps (FFT: 256 samples)3 Frequency bands: 200 Hz – 20 kHz; 2 kHz – 200 kHz; 20 kHz – 2 MHz1 or 2 acquisition channels
Acquisition time (worst case): 855 ms (including time for the plasma to be stabilized)
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUELaboratoire de Physique et Chimie de l'Environnement et de l’Espace
3A, avenue de la Recherche ScientifiqueF-45071 Orléans cedex 02, France
Phone: (33 2) 38 25 52 63; Fax: (33 2) 38 63 12 34; E-mail: [email protected]
Mutual Impedance MEasurements, MIME as part of the EJSM JGO/RPWI
J. G. Trotignon and J. L. Rauch
Conclusion
Thank you, first, for the invitation to participate in this exciting mission;
MIME may definitely contribute to the study of the Jupiter’ magnetosphere, in particular in measuring the electron plasma density and temperature, determining the effective length of electric antennae, helping out with in-flight sensor calibrations.
Application for funding has been submitted to CNES.