THEMIS FDMO Review Mission Design Update − 1 October 5, 2004 Mission Design Update Sabine Frey

THEMIS FDMO Review Mission Design Update − 2 October 5, 2004 Mission Design Update Overview Mission Requirements Changes Since MPDR Mission Science and Design Orbit Design Mission Plan Orbit Placement Orbit Evolution of Ascent Delta V of Placement Mission Design Status Shadow Conjunctions Design Software Next Work

THEMIS FDMO Review Mission Design Update − 3 October 5, 2004 Mission Requirements 1 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). M-12. The selected orbital plan shall achieve greater than 188 hours of four-probe conjunctions during the prime tail observation season (September to April). Compliance. Orbit design and in season maneuvers. M-13. THEMIS Probes shall be launched into a 3rd stage target orbit with the following characteristics: apogee km; perigee 305 km; inclination 9.5 deg; Target RAAN; and argument of perigee of 0 deg. (Injection errors are: perigee ±10 km; perigee velocity ± 66 m/s; inclination: ± 0.24 deg; apogee ± 7400 km) (all parameters TBR). Compliance. System Change Notice redefined orbit with lower perigee.

THEMIS FDMO Review Mission Design Update − 4 October 5, 2004 REQUIREMENTDESIGN 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, 9 deg inclination (P3, P4); and 1.4x10.0 Re, 9 deg inclination P5). Compliance. Ascent maneuver scenario. 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. Raise of P1,P2 apogees prior to deployment. In-season maneuver. M-17. All probes shall perform end-of-mission maneuvers to place themselves in orbits that ensure re-entry within 25 years. Compliance. PCA (injection orbit ) has life time less than 10 years. Re-entry maneuver accounted for in delta-V budget. Mission Requirements 2

THEMIS FDMO Review Mission Design Update − 5 October 5, 2004 Changes since MPDR Changes in Orbit Design with Effect on Delta V, Conjunctions: Launch into lower perigee Launch two months later Higher perigee for P3,P4 for 2 nd yr now from 1st yr

THEMIS FDMO Review Mission Design Update − 6 October 5, 2004 Mission Science and Design Observation seasons :WD +/-2 month Tail 1 Jan * - Apr WD Jan Apr WD Day1 Jun Oct WD Tail 2 Jan May WD Day2 Jul Nov WD (RAP-Right Ascension of Perigee, fixed for target epoch) Eclipse durations < 180 min Conjunctions with GBO’s Conjunctions with plasma sheet, RAP and inclination tail center epoch Ensure re-entry within 25 years [perform end-of-mission maneuvers] Maneuvers shall meet Delta-V of 628 m/s +15% contingency Parameter study for CSR Center tail epoch: Feb (WD) RAP, inclination at WD 330 deg, 7 deg Tail observation season: December to April Orbit Design - A Compromise Between

THEMIS FDMO Review Mission Design Update − 7 October 5, 2004 Orbit Design 1 P5 P2 P1 GBO P3 P4 P Orbital Period Orbit Geometry Prior to First Year Tail Season (B5.2) 14 d x Re at 7.0° 22 d1.168 x Re at 7.0° 31 d1.600 x Re at 4.0° 41 d1.600 x Re at 4.0° 54 / 5 d1.350 x Re at 9.0° In Tail (midnight) on February WD, 2007/2008 Launch October 2006 Onset and Evolution of Magnetospheric Substorms

THEMIS FDMO Review Mission Design Update − 8 October 5, 2004 Ground Based Observatories Courtesy H.Frey, UCB 20 stations with magnetometer and all sky imagers Located in North America along auroral oval (red markings are substorm onsets observed by IMAGE-FUV) Tail season time constraint: 00:00 to 12:00 UT MLT 00 UT MLT 12 UT GBO Range Orbit Design 2

THEMIS FDMO Review Mission Design Update − 9 October 5, 2004 Mission Plan 1 Orbit Placement Entire Mission: Launch Oct 21, 2006 (LD) ; 40 min window Early checkout and assignment 26 days Probe placement into initial science orbit LD+26d until WD-25d Ascent, inclination adjustments probes P1,P2, P3, P4 ASAP Ascent, inclination raise of probe P5 T P5 = 4/5 × T P3 Tail 1 in-season maneuvers: Apogee adjustments for alignment of P1,P2, P3, P4 2 tweaks Repeat for following seasons: Readjust P3, P4 Stay over CCA Varying period of P5 T P5 = [8/7;1;8/9] × T P3 In-season maneuvers: Apogee adjustments for alignment P1,P2, P3, P4 3 tweaks Third year - Extended mission conjunction w/ Cluster End of mission Re-Entry

THEMIS FDMO Review Mission Design Update − 10 October 5, 2004 Mission Plan 2 Launch Constraint Issue: Potentially long shadows - delay launch until shadows are avoided Readiness for first year tail season Operational Aspects: Time for orbit determination, minimum=1d /w 3 stations Logistics to manage five probes Robust schedule to allow for contingencies Operational Time Constraints and Aspects: 5 days State of health checks prior to first placement maneuver 26 days of early check ending with probe assignment Maneuvers here after are probe specific Deployment and finishing commissioning after final ascent Attitude reorientation to upside down at final ascent, alignment 20+5 days outer ascent merged with inner probe commissioning 20+5 days EFI deployment on P1,P2 Replacement Strategy: (5th Probe: Replacement reserve in 1 st year) Prior to Deployment: P5 to replace outer probes; after P3, P4

THEMIS FDMO Review Mission Design Update − 11 October 5, 2004 Mission Plan 3

THEMIS FDMO Review Mission Design Update − 12 October 5, 2004 Orbit Placement Catch Up With CCA By Various Parking Orbits Apogee up Perigee up P1,2 Raise Apogee to lower Aper drift Later ascent to final apogee Alignment with P3,4 EFI deployment In-season maneuver Launch to First Tail Season P3,4 Reference placement Parking orbit to catch up with CCA dMA=10 deg. separation P3-P4 at apogee P5 Reduce final period to recur once per 4 days later Perigee up GBO FOV

THEMIS FDMO Review Mission Design Update − 13 October 5, 2004 Orbit Evolution of Ascent Prior to science season

THEMIS FDMO Review Mission Design Update − 14 October 5, 2004 Mission Design Status 1 Status LD Oct 21: (Sep 2004) LV-RAAN 322: Two years LV-RAAN 312: Two years LV-RAAN 308: Two years LV-RAAN 304: Tail season 1 LV-RAAN 302: Tail season 1 LV-RAAN 312 disp.P1: Tail 1 LD Nov 21: (Aug 2004) 322,312,302 : Tail season 1 DESIGN FLOW

THEMIS FDMO Review Mission Design Update − 15 October 5, 2004 Mission Design Status 2 LV-raan /04: LD 08/ /04: LD 10/06 210,280,260, /04: LD 10/06 80,120,160,230 < /04: LD 10/06 195,290,160, , *,470*,430,430,695 *estimate for P1,P2 re-entry 5 m/s LV-raan /04: LD10/06 198,235,168, , *,425*,430,430,595 LV-raan 308 LD10/06 200,320,186, ,183^ 720*,415*,430,430,616 *estimate for P1,P2 re-entry 15 m/s Date Launch Conjunctions [h] Shadows T2 total dV [m/s] mm/yy mm/yy T1,D1,T2,D2 P1,P5 [min] P1,P2,P3,P4,P5 ^ low inclination in Tail1

THEMIS FDMO Review Mission Design Update − 16 October 5, 2004 Mission Design Status T = ,143,128,127, D =290 30, 70, 70, 70, T = ,163,186,186, ;250 D =230 80, 64, 27, 27, T = ,126,101,102, D =235 68, 92, 91, 92, T = ,180,172,174, ;272 D =309 70, 40, 20, 20, T = ,100, 90, 90, D =320 60, 80, 80, 80, T = ,168,164,166,183^ 690;256 D =340 44, 64, 73, 27, ^ low inclination in Tail2 LV-raan Conjunctions [h] Shadows [min] P1-dV ;T2 shadow [degree] tweak1+tweak2+tweak3 P1,P2,P3,P4,P5 [m/s] avoidance Season

THEMIS FDMO Review Mission Design Update − 17 October 5, 2004 Delta V of Placement 1 Delta-V [m/s] from Impulsive Placement Maneuvers P1 Ascent, Alignment, Tweaks Tail Season 1 Different Scenarios LD 10/21/06 LV-raan a 312-b 312-b-disp. 308-a Perigee up Apogee up Apogee up Apogee up Peri. Up, Incl Alignment Tweak Tweak Total T a,312-b different references for tweaks (312-conjunctions: 198h,211h) Disp> lower perigee, apogee, higher inclination

THEMIS FDMO Review Mission Design Update − 18 October 5, 2004 Delta V of Placement 2 Delta-V [m/s] from Impulsive Placement Maneuvers P1 Ascent, Alignment, Tweaks Tail Season 1 Different Launch Day LD 10/21/06 LD 11/21/06 LV-raan Perigee up Apogee up Apogee up Apogee up Peri. Up, Incl Alignment Tweak Tweak Total T

THEMIS FDMO Review Mission Design Update − 19 October 5, 2004 Shadow Analysis Methods: Earth and Lunar Shadows Two Methods Compared Shadow entry/exit condition = 99% of full sunlight, extended object, overlapping circles, Geoid, atmosphere Determining partial and total eclipses, extended objects, cone shape Time Frame: Entire two year mission Long shadows > 90 min THEMIS Probe Longest Shadow Raan 312 Number of long Shadows 1172 min min min min min20 Shadows Tail season 2 nd year: ~ dV* P1 shadow Raan m/s 180 min 240 m/s 190 min 230 m/s 220 min Raan m/s 180 min 270 m/s 170 min Raan m/s 180 min * Shadow avoidance Maneuver Shadows: penumbra to penumbra

THEMIS FDMO Review Mission Design Update − 20 October 5, 2004 P3, P4, P5 Apogee Passes over CCA Conjunctions 1 THEMIS’ goal: study >10 substorms with 4- or 5-probe alignments along x Requirement: 188 h, over CCA* Conditions (GSM –Coordinates) –dY Pn <±2R E –dZ 3,4/NS <±2R E; dZ 1,2/NS <±5R E Conjunctions with plasma sheet model by orbit simulations from launch forward: LV-raan Tail season 1: 195h 198h 200h Dayside1: 290h 235h 320h Tail season 2: 160h 168h 186h Dayside2: 230h 309h 340h

THEMIS FDMO Review Mission Design Update − 21 October 5, 2004 Conjunctions 2 Day 1 Tail1 Season 1 Tweak 1,2 Season 2 Tweak 1,2,3 GSM:xy xz planes

THEMIS FDMO Review Mission Design Update − 22 October 5, 2004 Conjunctions 3 Day2 Tail2

THEMIS FDMO Review Mission Design Update − 23 October 5, 2004 Orbit Design Software Software Tools for Orbit Generation: Since 1998 the THEMIS team has been using the following tools for maneuver planning, science optimization, delta 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  Delta V margin, mass margin GTDS (GSFC) Plus IDL Code (UCB) –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, and realistic RCS performance assessment GMAN (GSFC) Plus IDL Code (UCB) –Realistic RCS, ACS validation at the thruster pulse level (includes re-ors) –Final validation of mass and delta V estimates Freeflyer (AI Solutions) - Verification of mission design - Maneuver planning

THEMIS FDMO Review Mission Design Update − 24 October 5, 2004 Next Work Verification Improve delta-V budget Complete Launch Window Stability analysis Optimize Conjunctions Complete Launch Vehicle Dispersion analysis Various Probe Assignment scenarios Implement Maneuver Trajectory Probe Replacement scenarios

THEMIS FDMO Review Mission Design Update − 25 October 5, 2004 Back-up Slides

THEMIS FDMO Review Mission Design Update − 26 October 5, 2004 Shadows 2

THEMIS FDMO Review Mission Design Update − 27 October 5, 2004 Shadows 3

THEMIS FDMO Review Mission Design Update − 28 October 5, 2004 Shadows 4

THEMIS FDMO Review Mission Design Update − 29 October 5, 2004 Shadows 5

THEMIS FDMO Review Mission Design Update − 30 October 5, 2004 Eclipse Examples P1, P2, P3 Changed aspect ratio

THEMIS FDMO Review Mission Design Update − 31 October 5, 2004 Orbit Evolution Dayside 1

THEMIS FDMO Review Mission Design Update − 32 October 5, 2004 Orbit Evolution Tail Season 2

THEMIS FDMO Review Mission Design Update − 33 October 5, 2004 Orbit Evolution Dayside 2

THEMIS FDMO Review Mission Design Update − 34 October 5, 2004 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. B5.2

THEMIS FDMO Review Mission Design Update − 35 October 5, 2004 Feb : Targeted center geotail (WD) Eclipse durations < 180 min [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 628 m/s +15% contingency (RAP-Right Ascension of Perigee, fixed for target epoch ) Main drivers for orbit design to meet science objectives and mission requirements Orbit Design 6 SELECTION OF TAIL EPOCH

THEMIS FDMO Review Mission Design Update − 36 October 5, 2004 Parametric study on conjunctions relative to center tail elements: Orbit Design 3 Selection of Tail Epoch: Conjunctions

THEMIS FDMO Review Mission Design Update − 37 October 5, 2004 Orbit Design 2 Parametric study on shadows for INC=5…15deg relative to center tail elements (here shown for inc=15deg): Selection of Tail Epoch: Shadows

THEMIS FDMO Review Mission Design Update − 38 October 5, 2004 Replacement Strategy 1 Implications for Orbit Placement: Part of delta V budget Instrument check out: Before deployment of electric field antennas Deployment of electric field antennas : Final orbit Instrument diagnostic modes P5 final placement and deployment after P1, P2 final check outs Fault Tolerance, Redundancy: Replacement Strategy 4 Probes are required for mission: P1, P2, P3, P4 5th Probe: Replacement reserve, otherwise enhancing science Nominal Candidates: P3, P4 replace outer probes Prior to Deployment: P5 to replace outer probes

THEMIS FDMO Review Mission Design Update − 39 October 5, 2004 Replacement Strategy 2