1. THEMIS MISSION PDRMISSION DESIGN- 1 UCB, November 12-14, 2003 Mission Design Dr. Sabine Frey University of California - Berkeley

2. THEMIS MISSION PDRMISSION DESIGN- 2 UCB, November 12-14, 2003 Mission Design Overview Orbit Requirements Orbit Design Mission Orbits Orbit Placement Maneuver Planning Eclipse Duration Conjunction Analysis Delta V Budget, P1 Status and Next Steps

3. THEMIS MISSION PDRMISSION DESIGN- 3 UCB, November 12-14, 2003 Orbit requirement Orbit Requirements to Accomplish Science Objectives Five probes in 1-, 2-, and 4-day orbits at strategically-selected apogee distances to act as timing monitors and in situ platforms for diagnostic plasma and fields measurements. Space segment coordinated in space and time with Ground Based Observatories (GBO’s) to form a constellation capable of determining the order of events within a substorm. Probes are placed in science orbits prior to first tail observation season, and orbital phases are adjusted periodically (period tweaks) to optimize amount and quality of conjunction time. Inclination of outer probes (P1-2) is restored prior to second-year tail observation season to counteract drift due to orbital perturbations. Main drivers for orbit design to meet science objectives and mission requirements Eclipse durations < 180min [pick appropriate RAP and inclination] Conjunctions with GBO’s [Pick sidereal day period multiples] Conjunctions with plasma sheet [pick appropriate tail center geotail epoch, RAP and inclination] Ensure re-entry within 25 years [perform end-of-mission maneuvers] Maneuvers shall meet delta-V of 566m/s+15% contingency (TBC) (RAP-Right Ascension of Perigee, fixed for target epoch )

4. THEMIS MISSION PDRMISSION DESIGN- 4 UCB, November 12-14, 2003 A Compromise Between Shadows and Conjunctions Orbit Design 1 Minimum shadows: December 21 Maximum conjunctions: March 21

5. THEMIS MISSION PDRMISSION DESIGN- 5 UCB, November 12-14, 2003 Orbit Design 2 Selection of Tail Epoch: Shadows Parametric study on shadows for INC=5…15deg relative to center tail elements (here shown for inc=15deg):

6. THEMIS MISSION PDRMISSION DESIGN- 6 UCB, November 12-14, 2003 Parametric study on conjunctions relative to center tail elements: Orbit Design 3 Selection of Tail Epoch: Conjunctions

7. THEMIS MISSION PDRMISSION DESIGN- 7 UCB, November 12-14, 2003 From CSR: Targeted center geotail (wedding season) to be Feb-21 +/- 1 week Orbit Design 4 Selection of Tail Epoch

8. THEMIS MISSION PDRMISSION DESIGN- 8 UCB, November 12-14, 2003 Orbit Design 5 Software Tools for Orbit Generation: Since 1998 the THEMIS team has been using the following tools for maneuver planning, science optimization,  V analysis and RCS sizing: Excel spreadsheet (UCB/Swales) Perigee/apogee/inclination changes RAAN, APR, INC drifts due to J2 terms RAP drift for season selection Raise, maintenance and replacement strategy  V margin, mass margin GTDS (UCB/GSFC) Workhorse of spreadsheet result validation Includes all appropriate perturbation terms (lunar, solar, drag, etc) Shadow and conjunction parametric studies & forward analyses Geometric and gravity effect assessment, and realistic RCS performance assessment GMAN (UCB/GSFC) Realistic RCS, ACS validation at the thruster pulse level (includes reors) Final validation of mass and deltaV estimates Leads to Mission Operations command generation

9. THEMIS MISSION PDRMISSION DESIGN- 9 UCB, November 12-14, 2003 REQUIREMENT M-13. THEMIS Probes shall be launched into a transfer orbit with the following characteristics: apogee 12 +/- 0.38 Re; perigee 1.1 +/- 0.5Re ; inclination 9 +/- 0.5°; RAAN of 330 +/- 7 deg; and argument of perigee of 0 +/-5 deg (all parameters TBR) M-14. The THEMIS probes shall ascend to the following approximate science orbits prior to the first- year tail observation season: 1.5x30.9 Re, 7deg inclination (P1); 1.2x19.8 Re, 7deg inclination (P2); 1.2x12.0 Re, 9deg inclination (P3, P4); and 1.4x10.0 Re, 9deg inclination (P5). P Orbital Period Orbit Geometry Prior to First Year Tail Season 14 d1.500 x 31.645 Re at 7.0° 22 d1.168 x 19.770 Re at 7.0° 31 d1.200 x 12.019 Re at 9.0° 41 d1.200 x 12.019 Re at 9.0° 54 / 5 d1.350 x 10.042 Re at 9.0° Mission Orbits 1 Results from orbit design study Center geotail epoch, RAP, Inclination : February 21 (WD), 330 deg, 7 deg Geotail observation season: December to April (RAP-Right Ascension of Perigee, fixed for target epoch )

10. THEMIS MISSION PDRMISSION DESIGN- 10 UCB, November 12-14, 2003 Mission Orbits 2 Ground Based Observatory in North America CCA

11. THEMIS MISSION PDRMISSION DESIGN- 11 UCB, November 12-14, 2003 REQUIREMENTDESIGN M-9. THEMIS shall perform science observations with identical probes in multiple period, near- equatorial orbits (five probes required for baseline science). Compliance. Orbit design,placement, and in season maneuvers obtain and maintain conjunctions. M-11. The THEMIS probe conjunctions shall be coordinated with ground-based observations during prime geotail season Compliance. Apogee passes of inner probes are locked over geographic range of ground-based observatories (GBO) in North America (CCA) Orbit Placement 1 Orbit Placement Entire Mission: Launch, Early Orbit, and Initial Science Orbit First Year Tail In-Season Maneuvers Flank and Dayside Second Year Tail Alignment, In-Season Maneuvers Flank and Dayside Third Year- Extended Mission conjunction w/ MMS End of Mission Orbit Placement Through First Tail Season: P3 Reference placement first year tail season Select parking orbit to catch up with CCA Crude lock over CCA Fine tune lock over CCA before deployment P4 Same as P3 delta mean anomaly at apogee:approximate 10 deg Maneuvers at least one orbit apart Catch Up With CCA By Various Parking Orbits 02:0002:00 Apogee chg Perigee up

12. THEMIS MISSION PDRMISSION DESIGN- 12 UCB, November 12-14, 2003 Orbit Placement 2 Orbit Placement Through First tail season P 1,2 Start with stable, low inclination orbit. Late apogee raise to reduce differential precession Final alignment with P3, P4 before EFI deployment before first in-season maneuver P 5 Early raise to final perigee Lower to final period to recur once per 4 days REQUIREMENTDESIGN M-15. Upon ascent, and twice during the first- and second-year tail observation seasons, the orbital phase of P1 and P2 shall be adjusted to optimize the amount and quality of conjunctions. Compliance. Late raise of P1,P2 apogees to reduce differential precession between inner and outer probes but before deployment. In-season maneuver

13. THEMIS MISSION PDRMISSION DESIGN- 13 UCB, November 12-14, 2003 P1, P2 Relative to WD First Year Tail Season WD-120-4 d 1 st Apogee RaiseM1a WD-120 d 1 st Perigee RaiseM2a WD- 90-4 d 2 nd Perigee Raise, Incl. RaiseM2b WD- 90 d 2 nd Apogee RaiseM1b WD- 60 d 1 st Period TweakM3 WD- 24 d 2 nd Period TweakM4 WD +24 d 3 rd Period TweakM5 WD+ 60 Drift into Dayside Maneuver Planning WD-90d WD-60d WD-24d WD+24d WD+60d Selected Orbits P1,P3 LD+5 Orbits Target perigee, lower Inclination P1,P2 M0b LD+10 Orbits Target Apogee P3 M01 LD+10+n Orbits Target Apogee P4 M01 LD+15 Orbits Raise Perigee, Lower Inclination P3 M02 LD+ 15+n Orbits Raise Perigee, Lower Inclination P4 M02 (LD-Launch day, n-days) ( WD-’Wedding Day’ center geotail epoch) Maneuver Plan: P1,2 Early orbits and P 3,4 Initial Science Orbits

14. THEMIS MISSION PDRMISSION DESIGN- 14 UCB, November 12-14, 2003 REQUIREMENTDESIGN M-16. The selected date of tail observation season shall satisfy the requirement for eclipse duration (<180 minutes) Compliance. Shadow analysis shows longest shadow at 163 minutes. Shadow Analysis Earth and Lunar shadows Two Methods compared Shadow entry/exit Condition = %50 of Full Sunlight, extended object, cone shape, Geoid,atmosphere Determining partial and total eclipses, extended objects, cone shape Time Frame: 2007-Jun-02 P1, P2 2007-Apr-24 P3, P4, P5 THEMIS ProbeLongest ShadowTotal NumberTotal shadowsShortest Gap 1163 min371885 min1903 min 2147 min1345286 min 559 min 3137 min1527085 min1305 min 4137 min1527089 min1305 min 5117 min1517456min1036 min Eclipse Duration 1

15. THEMIS MISSION PDRMISSION DESIGN- 15 UCB, November 12-14, 2003 Eclipse Duration 2

16. THEMIS MISSION PDRMISSION DESIGN- 16 UCB, November 12-14, 2003 REQUIREMENTDESIGN M-12. The selected orbital plan shall achieve greater than 188 hours of five-probe conjunctions per year during the prime tail observation season (September to April) Compliance. Conjunction Analysis. The number of hours of conjunctions required to satisfy the L1 requirements takes into account the typical spatial extent and location of the substorm event, proximity required to detect the event, and the average rate of substorm occurrence. Satisfaction of the conjunction requirement is established via orbit simulation using GTDS and a neutral sheet model. A Conjunction satisfies the following criteria: - Four probes within 2 Re in Ygsm. - Inner probes within 2 Re of model neutral sheet. - Outer probes within 5 Re of model neutral sheet. Conjunction Analysis 1 Conjunction Example: GSM Criteria dY<2Re Orbits in GEI Coordinates:x,y Wd +24 days P1P2P3

17. THEMIS MISSION PDRMISSION DESIGN- 17 UCB, November 12-14, 2003 Conjunction Analysis 2 dawnsideduskside midnight Conjunction Estimation Example: GSM x,y plane Wd-60 to Wd -24 Wd+24 to Wd -24 Wd-24 to Wd +24

18. THEMIS MISSION PDRMISSION DESIGN- 18 UCB, November 12-14, 2003 REQUIREMENTDESIGN M-17. All probes shall perform end-of-mission maneuvers to place themselves in orbits that ensure re-entry within 25 years. Compliance. Re-entry maneuver accounted for in delta-V Budget Re-Entry P1,2 have periods adjusted to bring them into Lunar resonance. P3,4,5 have perigees lowered to initial injection perigee to increase drag and decrease lifetime. PCA orbit (injection orbit) has lifetime less than 10 years. Delta-V budget (P-5 example)

19. THEMIS MISSION PDRMISSION DESIGN- 19 UCB, November 12-14, 2003 Delta V Budget: Example of P1 Assumptions for Maneuver Calculator (MC): Latest (September 2003) bus and instrument predicted mass Arde tank size (procurement commenced) 5N thrusters (RCS procurement commenced) P1 total first geotail delta V= 0.456 km/s MC estimate of delta V= 0.411 km/s Projected mission total delta V= 0.611 km/s MC mission total delta V= 0.566 km/s

20. THEMIS MISSION PDRMISSION DESIGN- 20 UCB, November 12-14, 2003 Mission Design Flow

21. THEMIS MISSION PDRMISSION DESIGN- 21 UCB, November 12-14, 2003 Status and Future Work Status Simulation of Orbit Placements for P1, P2, P3, P4, P5 through first tail season in high precision mode to accomplish Shadows < 180min Conjunctions with Canada Feasible maneuver schedule Verify delta V Budget for perturbations included Future Work Improve conjunctions with plasma sheet - in progress Finish Dayside and second year mission Verify and implement maneuver scenarios with GMAN - in progress Maneuver performance verification and if necessary correction Study effects by change of launch day - in progress Replacement scenarios delta V Budget with attitude maneuver Re-iterate according to Mission Design Flow Chart to improve flexibility in parameter selection, to optimize ground contact and maneuver schedule –in progress

22. THEMIS MISSION PDRMISSION DESIGN- 22 UCB, November 12-14, 2003 Back Up

23. THEMIS MISSION PDRMISSION DESIGN- 23 UCB, November 12-14, 2003 Orbit Placement back up Geographic Longitude of P3 at Apogee Parking - Intermediate - Science Orbits

24. THEMIS MISSION PDRMISSION DESIGN- 24 UCB, November 12-14, 2003 Maneuver Planning back up Schedule P2 Through 1 st Tail Season ID UT dV [km/s] n1 n2 ; M1a_P2 2006-Oct-22 06:41:34.31 0.08235 006 006 ; M2a_P2 2006-Oct-24 07:04:34.31 0.00426 060 054 ; M0b_P2 2006-Aug-27 17:09:34.31 0.07773 061 001 ; M2b_P2 2006-Nov-18 20:52:04.31 0.08959 080 019 ; M1b_P2 2006-Nov-23 13:57:34.31 0.08639 083 003 ; M03_P2 2006-Dec-20 23:29:34.31 0.00156 097 014 ; M04_P2 2007-Jan-29 09:55:34.31 0.00009 116 020 ; M05_P2 2007-Mar-15 18:08:04.31 0.00191 138 023 ; P2 total dV= 0.34388931 ; MC estimate of dV= 0.34300000 ; Projected mission total dV= 0.43588932 ; MC mission total dV= 0.435000 (n2- orbits after last maneuver) (n1-orbits after LD)

25. THEMIS MISSION PDRMISSION DESIGN- 25 UCB, November 12-14, 2003 Maneuver Summary back up MID UT dV dD Purpose ; M00_PP 2006-Aug-21 14:14:34.31 0.00000 0.500 Release ; M0b_P1 2006-Aug-26 16:40:34.31 0.03009 5.101 INCLINATION dn, PERIGEE chg ; M0b_P2 2006-Aug-27 17:09:34.31 0.07773 1.020 INCLINATION dn, PERIGEE chg ; M01_P3 2006-Sep-01 07:20:04.31 0.01079 4.591 APOGEE chg ; M01_P4 2006-Sep-02 07:49:04.31 0.01078 1.020 APOGEE chg ; M01_P5 2006-Sep-03 08:18:04.31 0.00473 1.020 APOGEE chg ; M02_P5 2006-Sep-05 22:27:04.31 0.08590 2.590 PERIGEE up, INCLINATION dn ; M02_P3 2006-Sep-06 16:54:04.31 0.03600 0.769 PERIGEE up, INCLINATION dn ; M02_P4 2006-Sep-07 18:02:04.31 0.03633 1.047 PERIGEE up, INCLINATION dn ; M1a_P1 2006-Oct-21 06:24:34.31 0.08156 43.516 APOGEE up ; M1a_P2 2006-Oct-22 06:41:34.31 0.08235 1.012 APOGEE up ; M2a_P2 2006-Oct-24 07:04:34.31 0.00426 2.016 PERIGEE up ; M2a_P1 2006-Oct-24 15:02:34.31 0.00386 0.332 PERIGEE up P1,2 Early orbits and P 3,4 Initial Science Orbits

26. THEMIS MISSION PDRMISSION DESIGN- 26 UCB, November 12-14, 2003 Maneuver Planning backup Schedule P3,P4 Through 1 st Tail Season ID dV [km/s] n1 n2 ; M01_P3 2006-Sep-01 07:20:04.31 0.01079 011 011 ; M02_P3 2006-Sep-06 16:54:04.31 0.03600 016 005 ; P3 total dV= 0.046791709 ; MC estimate of dV= 0.051000000 ; Projected mission total dV= 0.51979171 ; MC mission total dV= 0.52400000 ; M01_P4 2006-Sep-02 07:49:04.31 0.01078 012 012 ; M02_P4 2006-Sep-07 18:02:04.31 0.03633 017 005 ; P4 total dV= 0.047109795 ; MC estimate of dV= 0.051000000 ; Projected mission total dV= 0.52010980 ; MC mission total dV= 0.52400000

27. THEMIS MISSION PDRMISSION DESIGN- 27 UCB, November 12-14, 2003 Maneuver Planning Schedule P5 Through 1 st Tail Season ID UT dV [km/s] n1 n2 ; M01_P5 2006-Sep-03 08:18:04.31 0.00473 013 013 ; M02_P5 2006-Sep-05 22:27:04.31 0.08590 015 015 ; M03_P5 2006-Dec-22 21:43:04.31 0.10730 118 118 ; P5 total dV= 0.19793251 ; MC estimate of dV= 0.19500000 ; Projected mission total dV= 0.55993251 ; MC mission total dV= 0.55700000 (n2- orbits after last maneuver) (n1-orbits after LD)

28. THEMIS MISSION PDRMISSION DESIGN- 28 UCB, November 12-14, 2003 Maneuver Planning back up MID UT dV dD Purpose ; M2b_P2 2006-Nov-18 20:52:04.31 0.08959 25.243 PERIGEE up, INCLINATION up ; M2b_P1 2006-Nov-19 04:42:04.31 0.13107 0.326 PERIGEE up, INCLINATION up ; M1b_P2 2006-Nov-23 13:57:34.31 0.08639 4.386 APOGEE up ; M1b_P1 2006-Nov-24 01:16:34.31 0.20310 0.472 APOGEE up ; M03_P2 2006-Dec-20 23:29:34.31 0.00156 26.926 APOGEE chg ; M03_P1 2006-Dec-22 20:17:34.31 0.00363 1.867 APOGEE chg ; M03_P5 2006-Dec-22 21:43:04.31 0.10730 0.059 Apogee chg ; M04_P2 2007-Jan-29 09:55:34.31 0.00009 37.509 APOGEE chg ; M04_P1 2007-Jan-30 13:07:34.31 0.00154 1.133 APOGEE chg ; M05_P2 2007-Mar-15 18:08:04.31 0.00191 44.209 APOGEE chg ; M05_P1 2007-Mar-17 18:47:04.31 0.00104 2.027 APOGEE chg P1, P2 Maneuver Schedule in intervals relative to WD First Year Tail Season

29. THEMIS MISSION PDRMISSION DESIGN- 29 UCB, November 12-14, 2003 P2 Eclipse Duration back up

30. THEMIS MISSION PDRMISSION DESIGN- 30 UCB, November 12-14, 2003 P3 Eclipse Duration back up

31. THEMIS MISSION PDRMISSION DESIGN- 31 UCB, November 12-14, 2003 P4 Eclipse Duration back up

32. THEMIS MISSION PDRMISSION DESIGN- 32 UCB, November 12-14, 2003 P5 Eclipse Duration backup