themis mission pdrmission design- 1 ucb, november 12-14, 2003 mission design dr. sabine frey...

THEMIS MISSION PDR MISSION DESIGN-1 UCB, November 12-14, 2003

Mission DesignDr. Sabine Frey

University of California - Berkeley


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


Orbit requirementOrbit 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 )


A Compromise Between Shadows and Conjunctions

Orbit Design 1

Minimum shadows: December 21

Maximum conjunctions: March 21


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):


Parametric study on conjunctions relative to center tail elements:

Orbit Design 3Selection of Tail Epoch: Conjunctions


From CSR: Targeted center geotail (wedding season) to be Feb-21 +/- 1 week

Orbit Design 4Selection of Tail Epoch


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


REQUIREMENT REQUIREMENTM-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

1 4 d 1.500 x 31.645 Re at 7.0°

2 2 d 1.168 x 19.770 Re at 7.0°

3 1 d 1.200 x 12.019 Re at 9.0°

4 1 d 1.200 x 12.019 Re at 9.0°

5 4 / 5 d 1.350 x 10.042 Re at 9.0°

Mission Orbits 1

Results from orbit design studyCenter geotail epoch, RAP, Inclination : February 21 (WD), 330 deg, 7 degGeotail observation season: December to April(RAP-Right Ascension of Perigee, fixed for target epoch )


Mission Orbits 2

Ground Based Observatory in North America

CCA


REQUIREMENT DESIGNM-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 MissionOrbit 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 deploymentP4 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

02:00

Apogee chg

Perigee up


Orbit Placement 2

Orbit Placement Through First tail seasonP 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

maneuverP 5 • Early raise to final perigee• Lower to final period to recur once per 4 days

REQUIREMENT DESIGNM-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


P1, P2 Relative to WD First Year Tail Season WD-120-4 d 1st Apogee Raise M1a

WD-120 d 1st Perigee Raise M2a

WD- 90-4 d 2nd Perigee Raise, Incl. Raise M2b

WD- 90 d 2nd Apogee Raise M1b

WD- 60 d 1st Period Tweak M3

WD- 24 d 2nd Period Tweak M4

WD +24 d 3rd Period Tweak M5

WD+ 60 Drift into Dayside

Maneuver Planning

WD-90dWD-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


REQUIREMENT DESIGNM-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 Probe Longest Shadow Total Number Total shadows Shortest Gap

1 163 min 37 1885 min 1903 min

2 147 min 134 5286 min 559 min

3 137 min 152 7085 min 1305 min

4 137 min 152 7089 min 1305 min

5 117 min 151 7456min 1036 min

Eclipse Duration 1


Eclipse Duration 2


REQUIREMENT DESIGNM-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<2ReOrbits in GEI Coordinates:x,y

Wd +24 days

P1 P2 P3


Conjunction Analysis 2

dawnside duskside

midnight

Conjunction Estimation Example: GSM x,y plane

Wd-60 to Wd -24

Wd+24 to Wd -24

Wd-24 to Wd +24


REQUIREMENT DESIGNM-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)

Target Parking Orbit 12.101 1.100 0.927 10.199 9.000 86.492 August 21, 2006Launch Vehicle Dispersions 12.478 1.099 0.900 10.216 9.500 0.0 86.492 August 21, 2006Inclination Lower, Perigee Raise and ma Placement 12.478 1.350 0.988 9.134 9.000 0.089 25.0 82.879 August 21, 2006Lower period to 4/5 TP3,4 to recur once per 4 days 10.042 1.350 1.214 9.028 9.000 0.106 28.6 78.751 December 23, 2006Increase period to 8/7 TP3,4 for dayside 13.100 1.350 0.943 9.155 9.000 0.128 32.5 74.068 April 22, 2007

Prg raise to minimize diff. rap; target 1st yr day 13.100 1.350 0.943 9.155 9.000 0.000 0.0 74.068 April 22, 2007ma target 2nd yr tail 13.100 1.350 0.943 9.155 9.000 0.000 0.0 74.068 December 6, 2007ma plcmnt and period to TP3,4's for 2nd year tail 11.869 1.350 1.036 9.111 9.000 0.044 10.8 72.516 January 3, 2008Decrease period to 8/9 TP3,4 for 2nd yr dayside 10.871 1.350 1.126 9.069 9.000 0.042 10.2 71.052 May 2, 2008

Re-entry maneuver (prg change) 10.871 1.100 1.027 10.151 9.000 0.099 22.9 67.747 November 2, 2008Re-entry maneuver (apg change) 12.146 1.100 0.924 10.200 9.000 0.049 11.0 66.160 November 2, 2008

dVtotal= 0.557 Final mass= 66.160 November 2, 2008

DateManeuver Title Ra [Re] Rp [Re]Va

[km/s] Vp [km/s] Inc [deg]Current Mass (base loading)

Burn Duration dV(km/s)


Delta V Budget: Example of P1

Target Parking Orbit 12.101 1.100 0.927 10.199 9.000 86.846 August 21, 2006Launch Vehicle Dispersions 11.725 1.099 0.955 10.190 9.500 0.0 86.846 August 21, 2006Stabilize dispersion, inc lower for aper reduction 11.725 1.100 0.956 10.185 7.000 0.042 11.9 85.122 August 21, 2006Intermediate Apogee Raise 15.000 1.100 0.754 10.282 7.000 0.097 38.8 81.254 November 25, 2006Intermediate Perigee Raise (increase stability) 15.000 1.150 0.770 10.040 7.000 0.016 4.3 80.641 November 25, 2006Final Apogee Raise, period drift 30.943 1.150 0.380 10.230 7.000 0.189 48.7 73.621 November 25, 2006Final Prg/Inc. Raise, period targeting 30.943 1.500 0.432 8.909 10.858 0.058 14.1 71.581 December 23, 2006Period Tweak #1 31.645 1.500 0.423 8.91333 7.000 0.005 1.1 71.424 January 28, 2007Period Tweak #2 30.943 1.500 0.432 8.909 7.000 0.005 1.1 71.268 March 17, 2007Optimize for 1st yr dayside observations 31.412 1.500 0.426 8.912 7.000 0.003 0.7 71.162 June 29, 2007Inc. & prg. Adjust.; Drift to Minimum W-Day Shadow 31.412 1.814 0.466 8.067 23.000 0.130 30.0 66.842 December 6, 2007Placement starting 2nd yr tail conjunctions 30.943 1.500 0.432 8.909 7.000 0.003 0.7 66.743 January 3, 2008Period Tweak #1 31.645 1.500 0.423 8.913 7.000 0.005 1.0 66.597 February 8, 2008Period Tweak #2 30.943 1.500 0.432 8.909 7.000 0.005 1.0 66.450 March 27, 2008Optimize for 2nd yr dayside observations 31.412 1.500 0.426 8.912 7.000 0.003 0.7 66.352 July 5, 2008Re-entry maneuver; begin Phase F data collection 31.877 1.500 0.419 8.915 7.000 0.006 1.3 66.160 January 0, 1900

dVtotal= 0.566 Final mass= 66.160

DateManeuver TitleBurn

Duration Ra [Re] Rp [Re] Inc [deg] dV(km/s)Va

[km/s] Vp [km/s]Current Mass (base loading)

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/sProjected mission total delta V= 0.611 km/s MC mission total delta V= 0.566 km/s


Mission Design Flow


Status and Future Work

StatusSimulation 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 includedFuture 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


Back Up


Orbit Placement back up

Geographic Longitude of P3 at Apogee

Parking - Intermediate - Science Orbits


Maneuver Planning back up

Schedule P2 Through 1st 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)


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


Maneuver Planning backup

Schedule P3,P4 Through 1st 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


Maneuver Planning

Schedule P5 Through 1st 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)


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


P2 Eclipse Duration back up


P5 Eclipse Duration backup

themis mission pdrmission design- 1 ucb, november 12-14, 2003 mission design dr. sabine frey...

Documents