1. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 1 UNH, Sep 23-26, 2008 THEMIS Orbit Updates Prior to Second Tail Season 2008/2009 S.Frey, V.Angelopoulos, M. Bester, H.Frey University of California - Berkeley

2. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 2 UNH, Sep 23-26, 2008 Overview Introduction THEMIS Orbits 2008/2009 Tail Season Conjunctions Inner Probe Conjunctions THEMIS-Cluster Conjunctions Overview

3. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 3 UNH, Sep 23-26, 2008 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. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 4 UNH, Sep 23-26, 2008 WD+60d WD WD-60d WD P1 P2 P3 P4 P5 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 Period [h] Days since 10-03-2008 Period [h] Days since 04-09-2009 Inclination Arg.of Perigee ARTEMIS Ascent: P1 08-01-2009 P2 07-01-2009

5. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 5 UNH, Sep 23-26, 2008 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 01-17-2009 - 03-03-2009 01-13-2008 - 02-26-2008 Distances to NS at dy<2Re

6. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 6 UNH, Sep 23-26, 2008 Tail Season Conjunctions 2 dzNS [Re] Time [d] Y-GSM [Re] X-GSM [Re] dzNS [Re] P1PB P2PC Blue: Conjunctions dzNS<5 Re, dy<2 Re Yellow: -2 Re<dzNS<2 Re Distances to Neutral Sheet Along Orbits Centered at WD: 01-17-2009 – 03-03-2009

7. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 7 UNH, Sep 23-26, 2008 Inner Probe Conjunctions Tail season 1: T P5 = 4/5*T P34 5-probe conjunctions – every 4 days Dayside 1: T P5 = 8/9*T P34 5-probe conjunctions – every 8 days Tail season 2: T P5 = T P34 5-probe conjunctions – every 4 days Dayside 2: T P5 = 8/7*T P34 5-probe conjunctions – every 8 days 03-07-2009 03-25-2008 02-26-2008 02-07-2009 08-03-2008 08-10-200909-03-2009 08-27-2008

8. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 8 UNH, Sep 23-26, 2008 THEMIS-Cluster Conjunctions THEMIS TAIL Center Epoch (WD) 2009 CLUSTER in CUSP 2008/10 -2008/12 CLUSTER THEMIS P1PB THEMIS P3PD

9. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 9 UNH, Sep 23-26, 2008 THEMIS 2012

10. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 10 UNH, Sep 23-26, 2008 Back-UP slides

11. 1st Joint Cluster-THEMIS Workshop THEMIS Orbit Updates - 11 UNH, Sep 23-26, 2008 Tail 2008/2009 WD+60d Apr -08 WD+24d Mar-03 WD Feb-07 WD-24d Jan-14 WD-60d Dec09