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THEMIS Orbit Updates Prior to Second Tail Season 2008/2009

THEMIS Orbit Updates Prior to Second Tail Season 2008/2009 S.Frey, V.Angelopoulos, M. Bester, H.Frey University of California - Berkeley. Overview. Overview Introduction THEMIS Orbits 2008/2009 Tail Season Conjunctions Inner Probe Conjunctions THEMIS-Cluster Conjunctions.

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THEMIS Orbit Updates Prior to Second Tail Season 2008/2009

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  1. THEMIS Orbit Updates • Prior to • Second Tail Season • 2008/2009 • S.Frey, V.Angelopoulos, M. Bester, H.Frey • University of California - Berkeley

  2. Overview • Overview • Introduction • THEMIS Orbits 2008/2009 • Tail Season Conjunctions • Inner Probe Conjunctions • THEMIS-Cluster Conjunctions

  3. Introduction • THEMIS Nominal Mission • Launch February 17, 2007 • Coast Phase Mar, 2007-Sep, 2007 String-of-Pearls, T= 31h • Placement Into THEMIS Constellation Sep, 2007 – Nov, 2007 • Tail Season 1 Dec, 2007 - Apr, 2008 WD Feb-02-2008 • Dayside 1 Jun, 2008 - Oct, 2008 WD Aug-03-2008 • Substorm Observations Tail1: • Within 12 h of conjunctions over the GBOs on average 5 substorm events have been observed • However P1,P2 (outer probes) were only occasionally within 1 Re to neutral sheet (NS) • Of those times near the NS P1, P2 observed NS signatures for about 60% of the substorms • UPCOMING Seasons With Modifications • Tail Season 2 Dec, 2008 - Apr, 2009 WD Feb-07-2009 •  Bringing outer probes closer to neutral sheet • Dayside 2 Jun, 2009 - Aug, 2009 WD Aug-10-2009  Shortened to start ARTEMIS ascent for P1,P2

  4. WD+60d WD WD-60d WD-60d WD Period [h] Period [h] P1 P2 P3 P4P5 Days since 04-09-2009 Days since 10-03-2008 Inclination Arg.of Perigee THEMIS Orbits 2008/2009 • Dayside 2 (short) • WD 08-10-2009 • WD-60d 06-11-2009 • WD-24d 07-17-2009 • Setup: 17 Maneuvers • Day2: 3 Tweaks • Tail Season 2 • WD 02-07-2009 • WD- 60d 12-09-2008 • WD+60d 04-08-2009 • Setup: 17 Maneuvers • Tail2: 6 Tweaks ARTEMIS Ascent: P1 08-01-2009 P2 07-01-2009

  5. 01-13-2008 - 02-26-2008 01-17-2009 - 03-03-2009 Tail Season Conjunctions 1 • Tail 1 2007/2008 NS-target : • dzNS<5 (2) Re outer probes (inner) • Tail 2 2008/2009 NS-targets all probes: • dzNS<2 Re for most of the12h • dzNS<1 Re focused at midnight interval • Compromise: • Less quantity more quality • Longer shadows up to 4h for P1 • Limiting parameters: • Inclination • Argument of perigee • Results x<-10 Re, dy<2 Re, • 4 probes ~ 5 probes: • dzNS < 1 Re: 30h+ 63h+10h=103h • dzNS < 2 Re: 43h+ 95h+37h=175h • Nominal criteria: 63h+100h+93h=256h Distances to NS at dy<2Re

  6. Distances to Neutral Sheet Along Orbits Centered at WD: 01-17-2009 – 03-03-2009 dzNS [Re] Time [d] dzNS [Re] Y-GSM [Re] dzNS [Re] X-GSM [Re] P1PB P2PC Blue: Conjunctions dzNS<5 Re, dy<2 Re Yellow: -2 Re<dzNS<2 Re Tail Season Conjunctions 2

  7. 08-03-2008 08-27-2008 03-25-2008 02-26-2008 02-07-2009 03-07-2009 08-10-2009 09-03-2009 Inner Probe Conjunctions • Tail season 1: TP5 = 4/5*TP34 • 5-probe conjunctions – every 4 days • Dayside 1: TP5 = 8/9*TP34 • 5-probe conjunctions – every 8 days • Tail season 2: TP5 = TP34 • 5-probe conjunctions – every 4 days • Dayside 2: TP5 = 8/7*TP34 • 5-probe conjunctions – every 8 days

  8. THEMIS-Cluster Conjunctions THEMIS TAIL Center Epoch (WD) 2009 CLUSTER THEMIS P1PB THEMIS P3PD CLUSTER in CUSP 2008/10 -2008/12

  9. THEMIS 2012

  10. Back-UP slides

  11. Tail 2008/2009 WD+60d Apr -08 WD+24d Mar-03 WD Feb-07 WD-24d Jan-14 WD-60d Dec09

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