1 / 35

Mission Design Status

Mission Design Status. THEMIS - History of Events and Macroscale Interactions during Substorms - Overview Orbit Placement Conjunctions Shadows Delta-V Budget Operational Aspects Status and Next Work. P1. P5. P2. P3. P4. GBO.

lois-crawford
Download Presentation

Mission Design Status

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mission Design Status • THEMIS - History of Events and Macroscale Interactions during Substorms - • Overview • Orbit Placement • Conjunctions • Shadows • Delta-V Budget • Operational Aspects • Status and Next Work

  2. P1 P5 P2 P3 P4 GBO Orbit Placement 1 Onset and evolution of magnetospheric substorms Launch August 2006 In Tail (midnight) on February 21, 2007/2008

  3. GROUND OBSERVATORIES • About 20 stations with magnetometer and allsky imagers • Located in North America along auroral oval (red markings are substorm onsets observed by IMAGE-FUV Courtesy H.Frey, UCB

  4. Orbit Placement 2 Maneuver Plan: A 5 probe, single launch vehicle (Delta 2925) mission About 20 ground observatories in North America (GBO) P1, P2, P5 Intermediate Orbits P3, P4 Final Science Orbits LD Target Parking Orbit (MC) 1.10re 12.10re 9 deg LD+5/6 Orbits Target perigee, lower Inclination P1, P2 M0b 24.5h 1.10re 12.33re 7/4deg LD+10 Orbits Target Apogee P3 M01 23.7h 1.10re 12.02re 8.8deg LD+10+n Orbits Target Apogee P4 M01 23.7h 1.10re 12.02re 8.8deg LD+10+n+1 Orbits Intermediate Apogee P5 M1a 25.7h 1.10re 12.74re 8.8deg LD+10+n+3 Orbits Raise Perigee, adjust inclination P5 M02 26.3h 1.39re 12.74re 9.0deg LD+15 Orbits Raise Perigee, Lower Inclination P3 M02 23.9h 1.20re 12.02re 9.0deg LD+15+n Orbits Raise Perigee, Lower Inclination P4 M02 23.9h 1.20re 12.02re 9.0deg (LD-Launch day, n-orbits)

  5. Orbit Placement 3 • WD-120-4 d 1st Apogee Raise P1,P2 M1a 32.3h 1.14re 15.00re 6.4deg • 32.6h 1.14re 15.00re 3.4deg • WD-120 d 1st Perigee Raise P1,P2 M2a 32.3h 1.15re 15.00re 6.4deg • 32.3h 1.15re 15.00re 3.4deg • WD- 90-4 d 2nd Perigee Raise, Incl. Raise P1,P2 M2b 33.3h 1.50re 15.00re 12.9deg • 32.3h 1.17re 15.00re 10.4deg • WD- 90 d 2nd Apogee Raise P1,P2 M1b 92.6h 1.50re 30.94re 12.8deg • 46.9h 1.16re 19.67re 10.4deg • WD- 60 d 1st Period Tweak P1,P2 M3 94.3h 1.50re 31.13re 10.8deg • 47.8h 1.16re 19.82re 9.7deg • WD- 24 d 2nd Period Tweak P1,P2 M4 91.5h 1.36re 30.96re 7.6deg • 47.8h 1.12re 19.85re 8.4deg • WD +24 d 3rd Period Tweak P1,P2 M5 95.2h 1.48re 31.71re 5.4deg • 47.6h 1.13re 19.78re 6.9deg • WD- 60 d 2nd Apogee Change P5 M1b 19.1h 1.39re 10.01re 7.9deg • WD+ 60 Drift into Dayside P1, P2, P5 Relative to WD First Year Tail Season (WD-’Wedding Day’ center geotail epoch)

  6. Orbit Placement 4 Orbit Evolution Through First Tail Season

  7. Orbit Placement 5 Catch Up With CCA By Various Parking Orbits UT 10:00 Perigee up 02:00 Apogee chg 18:00 Release 18:00 02:00 02:00 10:00

  8. Orbit Placements 6 Conjunction with GBO’s P3,4,5

  9. Conjunctions 1 • THEMIS’ goal: study >10 substorms • w/ 4- or 5–probe alignments along x • Requirement: 188h, over CCA* • Conditions (GSM –Coordinates) • dYPn<±2RE • dZ3,4/NS<±2RE; dZ1,2/NS<±5RE • Estimation: 40+95+105=240h • Forwardrun*: 36+51+126=213h M5, Dusk, 99-125h M3, Dawn, 20-35h M4, Midn, 30-50h

  10. Conjunctions 2 Conjunctions hours hard limits dz12=10Re Current Approach: WD –n sidereal days FA M3 M4 M5 -88,-60,-24,24 22+40+100=162 40+114+100=254 -88,-60,-24,24 * 22+43+102=166 39+113+127=279 -88,-60,-24,16 * 22+33+127=181 -88,-60,-48,16 35+51+126=213 -92,-64,-48,16 43+49+ 99=191 *different times

  11. Conjunctions 3 • Two Alternative Approaches • incl12=4,aper ->180, no rise of inclination by Maneuver hence shadows >180 min • -88,-60,-24,24 42+92+102=236 55+111+102=268 • -88,-60,-24,24* 43+95+130=267 • Shadow avoidance maneuver tbd • Launch with raan=323 to get lower aper ;tbd • Extending GBO-range , widen midnight constraint • Extend GBO range by ~30 to the east (most effective) and west to use • Currently obtained conjunctions adds 20 to 30 h. • 166->196, 181->208, 213->235 • Summary • Current aper of 70deg does not allow pre-midnight conjunctions • Soft dz limits (10RE) adds conjunction orbits mostly in midnight • Shifting M4 out of good conjunction orbits preserves conjunction • Rescheduling M3,M4 not unlimited • Low inclination , resulting in aper ~180 sufficiently improves conjunctions in midnight • FA- Final ascent, M3,M4,M5-Tweak maneuver, * release time changed slightly

  12. Shadows 1

  13. Eclipse Examples P1,2,3 Corrupted aspect ratio Corrupted aspect ratio

  14. Conjunction with GBO’s

  15. Delta-V Budget First Season Impulsive M1 to M5 162h 181h 213h <100h P1 total dV= 0.46646123 0.46615421 0.46546704 0.45589349 MC estimate of dV= 0.41100000 km/s deviation by MC : -13.5% -13.4% -13.2% -10.9% P2 total dV= 0.34509983 0.34542122 0.34577527 0.34388931 MC estimate of dV= 0.34300000 km/s deviation by MC: -0.6% -0.7% -0.8% -0.6% P3 total dV= 0.04660430 0.04732671 0.046604238 0.046791709 MC estimate of dV= 0.05100000 km/s deviation by MC: 8.6% 7.2% 8.6% 8.0% P4 total dV= 0.046909579 0.047701821 0.046909952 0.046791709 MC estimate of dV= 0.051000000 km/s deviation by MC: 8.0% 6.5% 8.05 8.0% P5 total dV= 0.21654378 0.19793251 MC estimate of dV= 0.19500000 km/s deviation by MC: -11.0% -1.5% MC= Maneuver Calculator

  16. Conjunction Overview Conjunctions hours hard limits dz12=10Re Current Approach: WD –n sidereal days FA M3 M4 M5 -88,-60,-24,24 22+40+100=162 40+114+100=254 -88,-60,-24,24 * 22+43+102=166 39+113+127=279 -88,-60,-24,16 * 22+33+127=181 -88,-60,-48,16 35+51+126=213 -92,-64,-48,16 43+49+ 99=191 * different times

  17. Impacts on Delta-V Improve Conjunctions by Rescheduling Tweak Maneuvers: M @WD hard P1 dV [m/s] change in dV sum MC 189 5.0 5.0 5.0 -21 2.1 1.6 - 0.7 -18.0 -88,-60,-24,24 22+43+102=166 210 2.9 3.4 5.7 - - - - - -88,-60,-24,16 22+33+127=181 210 2.9 4.1 6.1 0 0.0 0.7 0.4 1.1 -88,-60,-48,16 35+51+126=213 211 4.2 3.9 4.8 1 1.3 0.5 -0.8 2.0 -92,-64,-48,16 43+49+ 99=191 233 4.2 5.7 6.8 22 1.3 2.3 1.1 26.7 Catch up with Central Canada: Ra can go up a few tenth of an Re Final Ascend to Meet Min-Shadow, 1st Alignment by Raise of Inclination, Ra: MC P1 11 deg, 30.94 Re ; P2 9 deg, 19.76 Re P1 13 deg, 31.20 Re dV +25 m/s ;P2 10 deg 19.72 Re dV +11 m/s Vary Time First Alignment M (WD-90,-88,-74): Ra varies by 1-2 Re, must be undone to get appropriate period for P1 using ~15m/s Into Dayside Adjustment:Forwardrun/MC target P1 2007-Jun-02 6.5/7.0 deg 94.8h 1.8/1.5 Re 31.2/31.0 Re 7,1.5,31.4 ~MC P2 2007-May-31 6.3/7.0 deg 47.5h 1.3/1.2 Re 19.6/19.9 Re 7,1.2,19.8 ~MC P3 2007-Apr- 24 7.0/9.0 deg 23.9h 1.2/1.2 Re 12.0/12.0 Re 4,1.8,12.0 <MC

  18. Operational Aspects 1 • Maneuver Planning Driven by: • Science requirements • Shadow length • Delta-V • ‘Logistic’ • deployment after final ascent • time for instrument commissioning • time for Orbit determination • man power for 5 probes • min-time between M of same probe: 1Orbit • abs. min-time between M different probes: 8h • reduce emergency situation

  19. Operational Aspects 2 P1,2 Early orbits and P 3,4 Initial Science Orbits MID UT dV/(km/s) days Purpose ; M00_PP 2006-Aug-21 14:15:06 0.00000 0.500 Release ; M0b_P1 2006-Aug-26 16:46:06 0.03008 5.105 INCL dn, PERIGEE chg ; M0b_P2 2006-Aug-27 17:16:06 0.07769 1.021 INCL dn, PERIGEE chg ; M01_P3 2006-Sep-01 07:31:36 0.01063 4.594 APOGEE chg ; M01_P4 2006-Sep-02 08:01:36 0.01059 1.021 APOGEE chg ; M01_P5 2006-Sep-03 08:31:36 0.01409 1.021 APOGEE chg ; M02_P5 2006-Sep-06 00:41:06 0.08418 2.673 PERIGEE up, INCL dn ; M02_P3 2006-Sep-06 17:05:36 0.03598 0.684 PERIGEE up, INCL dn ; M02_P4 2006-Sep-07 18:14:36 0.03632 1.048 PERIGEE up, INCL dn ; M1a_P1 2006-Oct-23 08:26:06 0.07813 45.59 APOGEE up ; M1a_P2 2006-Oct-24 08:44:06 0.07917 1.012 APOGEE up ; M2a_P2 2006-Oct-26 09:07:36 0.00445 2.016 PERIGEE up ; M2a_P1 2006-Oct-26 17:05:36 0.00433 0.332 PERIGEE up ; M2b_P2 2006-Nov-20 23:02:36 0.08934 25.25 PERIGEE up, INCL up ; M2b_P1 2006-Nov-21 06:58:06 0.13067 0.330 PERIGEE up, INCL up

  20. Operational Aspects 3 P1, P2 Maneuver Schedule in intervals relative to WD First Year Tail Season MID UT dV /(km/s) days Purpose ; M1b_P2 2006-Nov-25 16:09:36 0.09040 4.383 APOGEE up ; M1b_P1 2006-Nov-26 03:35 06 0.21164 0.476 APOGEE :up ; M03_P2 2006-Dec-21 01:14:36 0.00223 24.90 APOGEE chg ; M03_P5 2006-Dec-22 00:49:06 0.11828 0.982 APOCHE chg ; M03_P1 2006-Dec-22 23:04:06 0.00250 0.927 APOGEE chg ; M04_P2 2007-Jan-29 11:57:06 0.00030 37.537 APOGEE chg ; M04_P1 2007-Jan-30 23:11:06 0.00347 1.468 APOGEE chg ; M05_P2 2007-Mar-15 19:12:36 0.00152 43.83 APOGEE chg ; M05_P1 2007-Mar-17 18:15:06 0.00565 1.960 APOGEE chg

  21. Status and Next Work • Status • Simulation of Orbit Placements for P1, P2, P3, P4, P5 through first tail season in high precision mode to accomplish meeting shadow and conjunction requirement with feasible maneuver schedule and verifying delta-V budget. • Next Work • Finish Dayside and second year mission • Optimize Conjunctions • Study effects by change of launch day - • Verify and implement maneuver scenarios with GTDS,GMAN • Maneuver performance verification and if necessary correction • Implement launch trajectory • Replacement scenarios • Reentry

  22. Back Ups

  23. Alternative Approach Lower Inclination for P1,P2 Without Later Raise of Inclination

  24. MISSION DESIGN FLOW • Software Tools for Orbit Generation, maneuver planning, • science optimization, DV analysis: • Excel spreadsheet • (UCB/Swales) • RAAN, APR, INC drifts due to J2 terms • GTDS (GSFC) • Includes all appropriate perturbation terms (lunar, solar, drag, etc) • - GMAN (GSFC) • -Leads to Mission Operations command generation

  25. Orbit Design Software • Software Tools for Orbit Generation: Since 1998 the THEMIS team has been using the following tools for maneuver planning, science optimization, DV 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 • DV 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

  26. 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)

  27. 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 deploymentbefore first • in-season maneuver • Three in-season maneuvers • P 5 • Early raise to final perigee • Lower to final period to recur • once per 4 days late Fault Tolerance, Redundancy: Replacement Strategy 4 Probes are required for Mission: P1, P2, P3, P4 5th probe: Replacement reserve otherwise enhancing science Probe placement decision: State of health checkouts, failure mode analysis Replacement process: PI decision , consulting team Criteria: Minimum science mission Failure tree analysis 1-2 weeks: Failure verification and diagnostic, preparation of execution Critical operation: replacing outer probes in final orbit, worst case P1 Replacing probe: p3, p4 nominal replacement probes First year: P1 by un-deployed P5 ; until 1st in-season maneuver P1 by deployed P3 and P5->P3; until 2nd in-season maneuver or after judgment until center geotail epoch Implications and Requirements: 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 P 1,P 2 final check outs

  28. Replacement Strategy: P3->P5

  29. Example of Delta V Budget: P2

  30. 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

  31. Example of Delta V Budget: P3

  32. Example of Delta V Budget: P4

  33. Example of Delta V Budget: P5

  34. SHADOW ANALYSIS • Shadow Analysis Methods: • 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 • Example Time Frame: 2007-Jun-02 P1, P2 • 2007-Apr-24 P3, P4, P5

  35. CONJUNCTION THEMIS’ goal: study >10 substorms w/ 4- or 5–probe alignments along X . Requirement: 188h of conjunctions. Duskside 105h • Conjunction Conditions in GSM coordinates • dYPn<±2RE; dZ3,4/NS<±2RE; dZ3,4/NS<±5R • Estimation Example: 40+95+105=240h • Computation includes lunar, solar, drag, J2 terms Wd+24 to Wd +60 Midnight 95h Wd-60 to Wd -24 Dawnside 40h Wd-24 to Wd +24

More Related