THEMIS SCIENCE

1

• THEMIS SCIENCE
• WORKING TEAM MEETING
• Tail 1 Conjunctions
• Sabine Frey
• University of California - Berkeley

2
Overview

• Overview
• Tail Season Schedule
• Conjunction Criteria
• Orbit Evolution
• Conjunctions Tail1 2008/2009
• - In Space
• - Geographic

3
Tail Season Schedule 1
First Tail Season Winter 2007/2008
2007-11-06 alignments P1,P2 v
2007-12-04 1st tweaks P1,P2 v
912h Dawn conjunctions
2008-01-09 2nd tweaks P1,P2
1212h Midnight conj.
2008-02-26 3rd tweaks P1,P2
912h Dusk conjunctions
2008-04-02
WD-88d
WD-60d
WD-24d
Center Epoch, WD of season 2008-02-02
WD24d
WD60d
4
Tail Season Schedule 2
WD60d
THEMIS Orbits First Year
Dusk Flanks
Tail season
Dusk
Dawn Flanks
Dayside
WD
Conjunction Intervals 0030-1230 UTC Dawn
2007-Dec-08 2008-Jan-09 9 Orbits Midnight 2008-
Jan-09 2008-Feb-29 12 Orbits Dusk 2008-Feb-29
2008-Apr-02 9 Orbits
Midnight
Dawn
WD-60d
5
Conjunction Criteria
C1 C2 C3

• Inter probe separation
• dYGSMPn lt 2 RE
• Probe to neutral sheet
• dZ3,4/NS lt 2 RE
• dZ1,2/NS lt 5 RE
• GBO midnight/noon 6 h

Tail Season 1-Midnight
P1 P2 P3 P5 P4
Observation geometry
Z-GSE Re
Z-GSM
Magnetic Axis, 22 Diurnal Range
5 Re 2 Re
X-GSM
-2 Re -5Re
-30 -20 -10
Ecliptic X-GSE Re
Distance to Neutral Sheet
Equatorial plane
Neutral Sheet (NS)
P1 Orbit Plane
Center Epoch of Tail Season (WD)
6
Orbit Evolution
Inclination
Apogee
7
Conjunctions Tail1 2007/2008 1
WD WD24d
WD-24d WD-60d
C1,3 YGSM XGSM
WD24d WD60d
WD WD-24d
C2,3 dZ XGSM
Mar 08 Feb.
08 Dec 07
Dusk
Midnight Dawn WD60d
WD
WD-60d
Time
8
Conjunctions Tail1 2007/2008 2
Geographic Longitude of Apogee Passes of Inner
Probes
P5 P3 P4
9

• Back-up Slides

10
Neutral Sheet Model
Neutral Sheet Model Verification

• Neutral Sheet (NS) model
• Hammond, 1994
• Hinge point at inner probe
• orbits
• Distance to NS
• dz lt 2 Re for inner probes
• dz lt 5 Re for outer probes
• Compared with Tsyganenko
• Model T96

d
March
Hinge Point Zone
December