1. MMS SWG 27 March 2014 1 MMS SWG –27 March 2014 MMS Mission Design March Launch Comparison (slides for the Telecon on 4 April 2014) Stephen A. Fuselier Southwest 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

2. 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 2

3. 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 R E 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 R E of the Fairfield tail neutral sheet 3 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

4. MMS SWG 27 March 2014 MMS – 15 Mar 2015 launch date Nominal Mission THEMIS Coordination Mission Launch Science Start End Phase 1a Launch Science Start End Phase 0a After phase 0x, the THEMIS coordination mission starts phase 1a, and the mission continues similar to the nominal mission Orbit Precession

5. 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 Science Start End Phase 0a Nominal Mission has no Phase 0a, and therefore no MP crossings

6. 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 Science Start End Phase 0a Phase 1a, 1390 MP crossings Differences are mainly due to the random element in the analysis

7. 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 Science Start End Phase 0a Phase 1b, 1026 MP crossings Both mission end phase 1b early to have time to raise apogee for phase 2b

8. MMS SWG 27 March 2014 8 Phase # of crossings (all IMF) # of X-line encounters (±0.50 R E ) Percentage (±0.50 R E ) 1a 1496 473.1% 1b 1068 161.5% 1a – 1b 2564 632.5% Phase # of crossings (all IMF) # of X-line encounters (±0.50 R E ) Percentage (±0.50 R E ) 0a 390112.8% 1a 1390342.4% 1b 1026302.9% 0a – 1b 2806752.7% 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

9. MMS SWG 27 March 2014 Both missions have similar dwell time near the neutral sheet (299 vs 264 hours), LT coverage is similar 9 MMS – 15 Mar 2015 launch (Phase 2b MP hours within 0.5 RE of the Fairfield 1980 neutral sheet) Nominal Mission THEMIS Coordination Mission

10. MMS SWG 27 March 2014 Orbits were provided beyond the primary mission up through a second pass through the tail 10 MMS – 15 Mar 2015 launch (Extended Mission (1)) Nominal Mission THEMIS Coordination Mission

11. 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) 11 MMS – 15 Mar 2015 launch (Extended Mission (2)) Nominal Mission THEMIS Coordination Mission

12. 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 12

13. 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 13