MMS SWG 27 March 2014 1

MMS SWG –27 March 2014MMS Mission Design

March Launch Comparison(slides for the Telecon on 4 April 2014)

Stephen A. FuselierSouthwest Research Institute

Steven M. Petrinec, Lockheed Martin Advanced Technology Center

Karlheinz J. Trattner LASP

Special thanks to Vassilis and his team for providing the ephem files and to Steve Petrinec for quickly completing the analysis

MMS SWG 27 March 2014

Agenda and Results• Side-by-side comparison of the 15 March 2015 launch

date– Nominal mission– THEMIS coordination mission (using the “Peak” mission”If you don’t want to look at the following slides, here are the results

• Compare the number of diffusion region encounters at the dayside MP– Result: THEMIS coordination has ~400 more magnetopause

encounters, and therefore ~4-8 more diffusion region encounters

• Compare the number of hours near the tail neutral sheet– Result: both missions have similar number of hours

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MMS SWG 27 March 2014

Analysis of 15 March 2015 Launches• Nominal Mission: Orbit Ephem. provided by GSFC Flight

Dynamics – Predicted number of magnetopause crossings for phase 1a, 1b

• Predicted number of diffusion region encounters

– Number of hours within 0.5 RE of the Fairfield tail neutral sheet

• THEMIS coordination mission: Orbit Ephem. provided by Vassilis/UCLA/UCB– 2 different RAANs – picked the “peak” mission (RAAN = 76 deg)– Predicted number of magnetopause crossings for phases 0a, 1a, 1b

• Predicted number of diffusion region encounters

– Number of hours within 0.5 RE of the Fairfield tail neutral sheet

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Steve Petrinec used an identical process to analyze these missions Analysis includes a random element – IMF data from 1 solar cycle prior to the orbits used to determine number of dayside diffusion region encounters

MMS SWG 27 March 2014

MMS – 15 Mar 2015 launch dateNominal Mission THEMIS Coordination Mission

Launch

ScienceStart

End Phase 1a

Launch

ScienceStart

End Phase 0a

After phase 0x, the THEMIS coordination mission starts phase 1a, and the mission continues similar to the nominal mission

OrbitPrecession

MMS SWG 27 March 2014

MMS – 15 Mar 2015 launch date (Phase 0a MP Crossings)Nominal Mission THEMIS Coordination Mission

Phase 0a, 390 MP crossings

ScienceStart

End Phase 0a

Nominal Mission has no Phase 0a, and therefore no MP crossings

MMS SWG 27 March 2014

MMS – 15 Mar 2015 launch date (Phase 1a MP Crossings)Nominal Mission THEMIS Coordination Mission

Phase 1a, 1496 MP crossings

ScienceStart

End Phase 0a

Phase 1a, 1390 MP crossings

Differences are mainly due to the random element in the analysis

MMS SWG 27 March 2014

MMS – 15 Mar 2015 launch date (Phase 1b MP Crossings)Nominal Mission THEMIS Coordination Mission

Phase 1b, 1068 MP crossings

ScienceStart

End Phase 0a

Phase 1b, 1026 MP crossings

Both mission end phase 1b early to have time to raise apogee for phase 2b

MMS SWG 27 March 2014 8

Phase# of

crossings (all IMF)

# of X-line encounters

(±0.50 RE)

Percentage(±0.50 RE)

1a 1496 47 3.1%

1b 1068 16 1.5%

1a – 1b 2564 63 2.5%

Phase# of

crossings (all IMF)

# of X-line encounters

(±0.50 RE)

Percentage(±0.50 RE)

0a 390 11 2.8%

1a 1390 34 2.4%

1b 1026 30 2.9%

0a – 1b 2806 75 2.7%

• The two missions yield similar probabilities of diffusion region encounters• Both missions do a reasonably good job of “targeting” the diffusion

region• The THEMIS Coordination Mission has 12 more predicted diffusion region

encounters• Due to nearly 250 more MP crossings, resulting from the addition of a

phase 0a

MMS – 15 Mar 2015 launch (Diffusion Region Encounters)Nominal Mission THEMIS Coordination Mission

MMS SWG 27 March 2014

• Both missions have similar dwell time near the neutral sheet (299 vs 264 hours), LT coverage is similar

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MMS – 15 Mar 2015 launch (Phase 2b MP hours within 0.5 RE of the Fairfield 1980 neutral sheet)Nominal Mission THEMIS Coordination Mission

MMS SWG 27 March 2014

• Orbits were provided beyond the primary mission up through a second pass through the tail

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MMS – 15 Mar 2015 launch (Extended Mission (1))Nominal Mission THEMIS Coordination Mission

MMS SWG 27 March 2014

• The second pass through the tail is not optimized for neutral sheet encounters– Significantly lower dwell times (119 and 149 hours)

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MMS – 15 Mar 2015 launch (Extended Mission (2))Nominal Mission THEMIS Coordination Mission

MMS SWG 27 March 2014

Conclusions (1)• Side-by-side comparison of the Nominal Mission

and THEMIS Coordination Mission– Similar probabilities of encounter of diffusion region at the

dayside magnetopause– ~250 more magnetopause crossings for the THEMIS

Coordination Mission• ~12 more diffusion region encounters

– Nearly the same dwell time in the tail neutral sheet (299 versus 264 hours, respectively)

– Similar, lower dwell times in the tail neutral sheet for the second tail pass in the extended mission

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MMS SWG 27 March 2014

Conclusions (2)• This comparison for the “Peak” THEMIS Coordination

Mission (RAP=255.6, RAAN=76,AOP=179.6)• Results for the “Center” THEMIS Coordination Mission

(RAP=255.6, RAAN=71.1,AOP=184.5):– 90 diffusion region encounters at dayside– Only 214 hours dwell time near the neutral sheet– Similar, lower numbers (114 hours) for the dwell time in the second

pass

• The “Peak” mission is preferred– Distinctly better dwell time near the tail neutral sheet

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