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Langmuir Probe

Langmuir Probe. Atelier magnetosphere de Jupiter et de Ganymede Jean-Pierre Lebreton ESA/ESTEC ( -31/08/2011) LPC2E. Principe de la Sonde de Lagmuir.

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Langmuir Probe

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  1. Langmuir Probe Atelier magnetosphere de Jupiter et de Ganymede Jean-Pierre Lebreton ESA/ESTEC ( -31/08/2011) LPC2E

  2. Principe de la Sonde de Lagmuir • Electrode (sphere, cylindre, etc..) connectee a une source de polarisation variable (± 5 V a ± 100 V). La courbe I-V renseigne sur les parametres suvants: • Densite electronique (1e-3 a 1e6 /cm3) • Temperature electronique (0.01 a 20 eV) • Potentiel du satellite (± 50 V ) • Sous certaines conditions • Vitesse des ions • Identification de +sieurs populations (ions ou electrons) • Instrument simple a mettre en oeuvre mais interpretation de la courbe I-V parfois delicate mais riche en information (Cassini LP). • Calibration et x-calibration essentielles • Instrument “actif” donc generateur de perturbations (Demeter)

  3. Courbe I-V (1): Ions froids, 20eV

  4. Courbe I-V (2): ions maxwelliens

  5. Types de SDL (senseurs) • Sphere: la Suedoise • Reference Cassini (Wahlund et al.) • SondeCylindrique: Needle LP, la Norvegienne • Nouveau concept (valide en labo (ESTEC), et en volfusee). Avec 2 electrodes a polarisation fixe (>> Vp), on obtientdirectement Ne (sans connaitreTe) et sa variation a qques kHz (metres). • SondeSegmentee: la francaise • Demeter: Lebreton et al.; Proba-2: Travnicek et al.

  6. ISL Langmuir Probes ball diameter 4 cm six surface sectors of diameter 1 cm LP - 2 1 Hz sweep frequency, [-7.38 .. 7.62 V] 128 sweep points  8 ms time steps. Different modes: -ISL1-1, LP1 sweep -ISL1-2, LP1 offset sweep -ISL1-3, LP1 vs. LP2 -ISL2, LP2 & LP1 sweep -ISL3, surface control LP - 1 diameter 3 mm length 5 cm

  7. Proba-2 SDLP PS: Face Avant PS: face arriere

  8. Contraintes • Accommodation: • Hors gaine, hors sillage • Bras de +sieurs metres • Positionnement possible en bout de PS (mais avec fortes contraintes sur cablage). • Contamination de surface/decontamination en vol (Polar ±100/100 V pendant 1 hr); recontamination immediate (survol de Titan, Encelade a l’etude, Ganymede ?, Callisto ?). • Instrument actif: Perturbation des autres instruments (E-field) et du pot. du satellite; • operation synchronisee

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