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THEMIS Mission Ops Peer Review Mission Design − 1 November 4 2003 THEMIS Mission Design.

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Presentation on theme: "THEMIS Mission Ops Peer Review Mission Design − 1 November 4 2003 THEMIS Mission Design."— Presentation transcript:

1 THEMIS Mission Ops Peer Review Mission Design − 1 November 4 2003 THEMIS Mission Design

2 THEMIS Mission Ops Peer Review Mission Design − 2 November 4 2003 Mission Design  Overview − Mission Requirements − Mission Orbits − Orbit Placement − Maneuver Planning − Delta V Budget − Shadow Analysis − Conjunction Analysis − Status and Next Steps

3 THEMIS Mission Ops Peer Review Mission Design − 3 November 4 2003 Mission Requirements 1 − 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 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.

4 THEMIS Mission Ops Peer Review Mission Design − 4 November 4 2003 Mission Requirements 2  Mission Requirements (in addition to the L1 requirements discussed) − M-2 The THEMIS project shall develop a plan to meet the NASA orbital debris guidelines of re-entry in NASA Safety Standard (NSS) 1740.14 − Compliance: Already accounted for in nominal  V budget − M-25 Each Probe shall be designed to achieve electrical energy balance over an orbit assuming a 30 minute transmitter power on time and a 180 min eclipse. − Compliance: Orbit design avoids orbit elements with long shadows − M-44 Within the schedule cap (<March 2007), the THEMIS launch date shall not be restricted [Restating a L1 requirement]. − Compliance: Bus and orbit design are independent of launch date  Main drivers for orbit design to meet science requirements Shadows < 180min [pick appropriate RAP and inclination] Conjunctions with Canada [Pick sidereal day period multiples] Conjunctions with plasma sheet [pick appropriate RAP and inclination]

5 THEMIS Mission Ops Peer Review Mission Design − 5 November 4 2003 Mission orbits: A compromise between shadows and conjunctions

6 THEMIS Mission Ops Peer Review Mission Design − 6 November 4 2003 Orbits Design #1: Selection of Tail Epoch; shadows  Parametric study on shadows for INC=5…15deg relative to center tail elements (here shown for inc=15deg):

7 THEMIS Mission Ops Peer Review Mission Design − 7 November 4 2003 Orbits Design #2: Selection of Tail Epoch; conjunctions  Parametric study on conjunctions relative to center tail elements:

8 THEMIS Mission Ops Peer Review Mission Design − 8 November 4 2003 Orbits Design #3: Selection of Tail Epoch  From CSR: targeted center tail (wedding season) to be Feb-21 +/- 1 week

9 THEMIS Mission Ops Peer Review Mission Design − 9 November 4 2003 Orbits Design #4: Orbit finalization (pre-PDR) − The THEMIS probes shall be launched into a transfer orbit with the following characteristics: − Apogee radius: 12 +/- 0.38 Re. − Perigee radius: 1.1 +/- 0.5 Re. − Inclination: 9 +/- 0.5 degrees. − RAAN: 330 +/- 7 degrees optimizes Feb 21 configuration − APER: 0 +/- 5 degrees − The THEMIS probes shall ascend to the following approximate science orbits prior to first-year tail observation season: − P1:1.5x30.9-Re, 7-deg INCL. − P2:1.2x19.8-Re, 7-deg INCL. − P3,4:1.2x12.1-Re, 4-deg INCL. − P5:1.1x9.8-Re, 9-deg INCL (18-hr period). − P5 apogee raised to 13.2-Re (27-hr period) after tail season (1 st day-side) and then reduced again to 12.1 Re (same as P3,P4) for second year tail. The relative APER change due to the inclination difference separates the orbit plane of P5 from that of P3/P4 along Z. This adheres to the requirement to measure plasma sheet with Z- separated probes.

10 THEMIS Mission Ops Peer Review Mission Design − 10 November 4 2003 Mission Orbits PCA1.100 x 12.103 Re at 9.0° ProbeOrbital PeriodOrbit 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° 5 Re / div

11 THEMIS Mission Ops Peer Review Mission Design − 11 November 4 2003 Mission Design Flow

12 THEMIS Mission Ops Peer Review Mission Design − 12 November 4 2003 Maneuver Planning Software Tools  Since 1998 the THEMIS team has been using the following tools for maneuver planning, science optimization,  V analysis and RCS sizing: − Excell 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 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

13 THEMIS Mission Ops Peer Review Mission Design − 13 November 4 2003 Orbit Placement  Orbit Placement Entire Mission Initial Science Orbit First Year Tail In-Season Maneuvers Flank and Dayside Second Year Tail Alignment and In-Season Maneuvers Launch and Early Orbit Flank and Dayside Third Year- Extended Mission conjunction with MMS End of Mission

14 THEMIS Mission Ops Peer Review Mission Design − 14 November 4 2003 Orbit Placement  Orbit Placement Through 1 st 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 dMA(apogee)=10 degree Maneuvers one orbit apart

15 THEMIS Mission Ops Peer Review Mission Design − 15 November 4 2003 Orbit Placement Central Canada (CCA)

16 THEMIS Mission Ops Peer Review Mission Design − 16 November 4 2003 Orbit Placement UT Catch Up With CCA By Various Parking Orbits 10:00 02:00 18:00 02:0002:00 02:00 10:00 Release Apogee chg Perigee up

17 THEMIS Mission Ops Peer Review Mission Design − 17 November 4 2003 Orbit Placement Geographic Longitude of P3 at Apogee Parking - Intermediate - Science Orbits

18 THEMIS Mission Ops Peer Review Mission Design − 18 November 4 2003 Orbit Placement  Orbit Placement Through 1 st Tail season P1,2 Start with stable, low inclination orbit Late apogee raise to reduce differential precession Final alignment with P3, P4 before EFI deployment P5 Early raise to final perigee Lower to final period to recur once per 4 days Final alignment with P3, P4 before EFI deployment

19 THEMIS Mission Ops Peer Review Mission Design − 19 November 4 2003 Maneuver Planning P1,2 Early orbits and P 3,4 Initial Science Orbits 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

20 THEMIS Mission Ops Peer Review Mission Design − 20 November 4 2003 Maneuver Planning 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 ( M1b,3-5 below): M M3 M4 M5 b P1,P3

21 THEMIS Mission Ops Peer Review Mission Design − 21 November 4 2003 Maneuver Planning P1, P2 Maneuver Schedule in intervals 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, Inclination 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 WD-’Wedding Day’ tail center

22 THEMIS Mission Ops Peer Review Mission Design − 22 November 4 2003 Maneuver Planning After 1 st Tail season and second year (preliminary) WD+m d Apogee change for Dayside Alignment WD-90 to WD+24 Tail Season Maneuver Sequence with Inclination and Perigee adjustment 2 nd Dayside Season Alignment

23 THEMIS Mission Ops Peer Review Mission Design − 23 November 4 2003 Maneuver Planning Preliminary Summary with no splitting of Large Maneuver Through 1 st tail Season : 23 Maneuver Through 2 nd tail Season : Minimum of 17 Maneuver Through 2 nd Tail season: Minimum of 5 Maneuver  Re-Entry maneuver : 10

24 THEMIS Mission Ops Peer Review Mission Design − 24 November 4 2003 Maneuver Planning Schedule P1 Through 1 st Tail Saeson ID UT dV[km/s] n1 n2 ; M0b_P1 2006-Aug-26 16:40:34.31 0.03009 005 005 ; M1a_P1 2006-Oct-21 06:24:34.31 0.08156 059 054 ; M2a_P1 2006-Oct-24 15:02:34.31 0.00386 061 002 ; M2b_P1 2006-Nov-19 04:42:04.31 0.13107 080 019 ; M1b_P1 2006-Nov-24 01:16:34.31 0.20310 083 003 ; M03_P1 2006-Dec-22 20:17:34.31 0.00363 091 008 ; M04_P1 2007-Jan-30 13:07:34.31 0.00154 101 011 ; M05_P1 2007-Mar-17 18:47:04.31 0.00104 113 013 P1 total dV= 0.45589349 MC estimate of dV= 0.41100000 Projected mission total dV= 0.61089349 (n2- orbits after last maneuver) MC mission total dV= 0.56600000 (n1-orbits after LD)

25 THEMIS Mission Ops Peer Review Mission Design − 25 November 4 2003 Maneuver Planning Schedule P2 Through 1 st Tail Saeson 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)

26 THEMIS Mission Ops Peer Review Mission Design − 26 November 4 2003 Maneuver Planning Schedule P3,P4 Through 1 st Tail Saeson ID UT 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 Ops Peer Review Mission Design − 27 November 4 2003 Maneuver Planning Schedule P3 Through 1 st Tail Saeson 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 Ops Peer Review Mission Design − 28 November 4 2003 Maneuver Planning 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 Ops Peer Review Mission Design − 29 November 4 2003 Maneuver Summary 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

30 THEMIS Mission Ops Peer Review Mission Design − 30 November 4 2003 Example of Delta V Budget: P1  Assumptions: − Latest (September 2003) bus and instrument predicted mass − Arde tank size (procurement commenced) − 5N thrusters (RCS procurement commenced)

31 THEMIS Mission Ops Peer Review Mission Design − 31 November 4 2003 DV propellant margin

32 THEMIS Mission Ops Peer Review Mission Design − 32 November 4 2003 Shadow Analysis  Shadow Analysis THEMIS Probe Longest Shadow Total NumberTotal shadowsShortest Gap 1163 min371885 min1903 min 2147 min1345286 min 559 min 3137 min1527085 min1305 min 4137 min1527089 min1305 min 5117 min1517456min1036 min Earth and Lunar shadows Two Methods compared Shadow entry/exit Condition = %50 of Full Sunlight Determining partial and total eclipses Time Frame: Till 2007-Jun-02 P1, P2 2007-Apr-24 P3, P4, P5

33 THEMIS Mission Ops Peer Review Mission Design − 33 November 4 2003 P1 Shadow Analysis

34 THEMIS Mission Ops Peer Review Mission Design − 34 November 4 2003 P2 Shadow Analysis

35 THEMIS Mission Ops Peer Review Mission Design − 35 November 4 2003 P3 Shadow Analysis

36 THEMIS Mission Ops Peer Review Mission Design − 36 November 4 2003 P4 Shadow Analysis

37 THEMIS Mission Ops Peer Review Mission Design − 37 November 4 2003 P5 Shadow Analysis

38 THEMIS Mission Ops Peer Review Mission Design − 38 November 4 2003  Conjunction Analysis The selected orbital plan shall achieve greater than 188 hours of four-probe conjunctions during the prime tail observation season (September to April). –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

39 THEMIS Mission Ops Peer Review Mission Design − 39 November 4 2003 Conjunction Analysis Alignment of P1, P2, P3 at WD –24 d GSM Criteria dY<2Re Orbits in GEI Coordinates

40 THEMIS Mission Ops Peer Review Mission Design − 40 November 4 2003 Conjunction Estimation Example dawnside duskside midnight

41 THEMIS Mission Ops Peer Review Mission Design − 41 November 4 2003 Status and Next Steps 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 Maneuver separation Verify dV Budget for perturbation included Next Steps Improve Conjunctions with plasma sheet in progress Finish Dayside and 2 nd Year Mission Verify maneuver Scenarios with GMAN in progress Implementing Maneuver simulation Replacement Scenarios Re-Iterate to optimize according to Mission Design Flow Chart Ground Contact analysis and maneuver Schedule dV Budget with attitude Maneuver

42 THEMIS Mission Ops Peer Review Mission Design − 42 November 4 2003 Backup slides on P2,3,4,5 and replacement strategy…..

43 THEMIS Mission Ops Peer Review Mission Design − 43 November 4 2003 Example of Delta V Budget: P2

44 THEMIS Mission Ops Peer Review Mission Design − 44 November 4 2003 Example of Delta V Budget: P3

45 THEMIS Mission Ops Peer Review Mission Design − 45 November 4 2003 Example of Delta V Budget: P4

46 THEMIS Mission Ops Peer Review Mission Design − 46 November 4 2003 Example of Delta V Budget: P5

47 THEMIS Mission Ops Peer Review Mission Design − 47 November 4 2003 Replacement strategy: P3->P5

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