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THEMIS SCIENCE WORKING TEAM MEETING Orbit Design Sabine Frey University of California - Berkeley

THEMIS SCIENCE WORKING TEAM MEETING Orbit Design Sabine Frey University of California - Berkeley. Overview. Overview Orbit Design Status Tail and Dayside Orbits Coast Phase Orbits Launch Day Analysis Back-up slides: Orbit evolution, conjunctions, shadows. Orbit Design Status.

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THEMIS SCIENCE WORKING TEAM MEETING Orbit Design Sabine Frey University of California - Berkeley

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  1. THEMIS SCIENCE • WORKING TEAM MEETING • Orbit Design • Sabine Frey • University of California - Berkeley

  2. Overview • Overview • Orbit Design Status • Tail and Dayside Orbits • Coast Phase Orbits • Launch Day Analysis • Back-up slides: Orbit evolution, conjunctions, shadows

  3. Orbit Design Status Launch through 1st Tail Season Checkout Placement EFI 1st tweak 2nd tweak Perigee AXIAL P1-4 Raise 18-25d 19-37d 16-28d 48d 36d Old Concept: LD Oct 19-Nov 19, 2006 WD February 2007 Late Launch Concept: LDs since 11/27/2006 LD LD+n WD-24 WD WD+24 WD+60 LD LD+n 09-07-07 WD-88 WD-60 WD-24 WD WD+24 WD+60 Checkout Coast Phase Placement EFI 1st tweak 2nd tweak 3rd tweak Perigee PerigeeAXIAL P1 EFI P5 Raise EFI P2,3,4SIDE 26d 34d + 200d 65-70d 28d 36d 48d 36d LD shifts are compensated by coast phase ~230d P 2,3,4 mostly side thrust placement P 1, 5 axial thrust placement Additional maneuvers Tail 1: 27 New: Coast Phase Full Tail1 in 2008 Early EFI deploy on P2,3,4 Late EFI deploy on P1,P5 <Conjunctions> >> 200 h, 94h shadows < 180 min <dV> <670m/s

  4. Tail and Dayside Orbits Dusk Bow shock Dusk Flanks Flanks Tail season Magnetopause Dawn Flanks Dayside Center of Tail season Noon Coast phase: LD+60d -08/2007 Placement : 09/2007-11/2007 Tail 1 : WD early Feb 2008 12/2007-04/2008 Dayside 1 : WD early Aug 2008 06/2008-10/2008 Tail 2 : Wd early Feb 2009 12/2008-04/2009 Midnight Center of Dayside Flanks Dawn

  5. Coast Phase Orbits 1 Coast Phase : 1.15 Re x 15.4 Re, 15 deg inclination Approximate probe to probe separation with no particular phasing targets: 05/08 07/05 03/29 08/08 08/31 P1 P2 P5 P3 P4

  6. Coast Phase Orbits 2 Magnetic Foot Prints: End of March 2007 End of June 2007

  7. Launch Day Analysis Launch day period:Feb 15 to May 15, 2007 Accumulated dV Accumulated Conjunctions per season [m/s] per season [h]

  8. Back-up Slides

  9. Orbit Evolution 1st Year

  10. Orbit Evolution 2nd Year

  11. Conjunction Criteria • Inter probe separation • dYPn < ±2RE • Probe to neutral sheet • dZ3,4/NS < ± 2RE • dZ1,2/NS < ± 5 RE • GBO midnight/noon ± 6h Tail Season 2- Midnight Tail Season 1-Midnight P1 P2 P3 P5 P4 P1 P2 P3,P4 P5 Observation geometry Z-GSE] Z-GSM +5 Re +2 Re +5 Re +2 Re Magnetic Axis, 22 Diurnal Range -2 Re -5Re X-GSM -2 Re -5Re -30 -20 -10 Ecliptic X-GSE [Re] Distance to Neutral Sheet (NS) Distance to Neutral Sheet (NS) Equatorial plane Neutral Sheet (NS) P1 Orbit Plane Center Epoch of Tail Season

  12. Conjunction Analysis 2 Neutral Sheet Model Verification • Neutral Sheet (NS) model • Hammond, 1994 • Hinge point at inner probe • orbits • Distance to NS • |dz| < 2 Re for inner probes • |dz| < 5 Re for outer probes • Compared with Tsyganenko • Model T96 d March Hinge Point Zone December

  13. Tails Season Shadows Tail season 1 Tail Season 2

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