MMS Extended Mission Formation Change Decision - PowerPoint Presentation

1. MMS Extended Mission Formation Change DecisionApproved at MMS Science Working Group Meeting – April 21, 2023 GuidelinesApproval: (1) MMS EOM extended to 2037Approval: (2) FY24 Formation Change Plan Understanding of Constraints/Options – with notes from SWG offering opportunities for compromiseContext: Solar Cycle – Mission PhasesContext: Proposed by Senior Review 2023Context: Extended Mission Objectives Context: Understanding of Fuel Estimates, to EOMContext: Understanding of Future Eclipse Durations

2. GuidelinesSince the time of the 2020 Senior Review, The MMS Flight Dynamics team has been examining the possibility of altering the flight formation. They established a range of alternatives along with constraints. While MMS scientists can imagine many other equally valuable configurations, the plan approved (1) aligns with the highest priority science objectives proposed to the 2023 Senior Review, (2) is achievable, although some aspects may need compromise, and (3) provides ample time for planning while also assuring completion early in the extended mission so that results can be presented to the FY26 Senior Review.The plan approved should be considered a framework. The MMS Mission Director and flight dynamics team will determine the final details of execution, optimizing specific start/stop dates, orbit-to-orbit separations, drift rates, handling of the eclipse season, etc to ensure safety throughout the campaign. While MMS has been in a String-of-Pearls formation in the past, the MMS PI/PS understand that new constraints may be identified and need to be resolved before implementation.The MMS PI/PS plan to offer compromises on the approved plan rather than press our operations into a greater risk posture. The intent is to maintain a reasonable MMS risk posture while maximizing the scientific output for this 3rd mission extension. Conrad Schiff/Trevor Williams will negotiate any compromises with our PI/PS/MD – in consultation our DPI and SWG science operations and burst leads (Stephen Fuselier, Bob Ergun, Steve Petrinec, Kevin Genestreti). PI/PS/MD have final approval.The final configuration will represent a balance between science traceability and the practical limitations inherent to a mission in flight.Requirements are to finalized with FDOA(DSN) at least 9(6) months in advance of associated maneuvers. We do this not only to minimize risk but also so that our many engineering teams can put all in place as part of their normal 40-hr-week course of business. The new formations then become part of their regular seasonal navigation and formation flying planning/execution. This is how we’ve always managed MMS and this is why these formations were considered to fit within the MMS inguide budget at the time of the 2023 Senior Review proposal.

3. Approval for Refreshed EOM PlanPerigee-raise – already budgeted – to keep above 700 km threshold, 20231. Driven by lunisolar, reentry would naturally occur ~2030. Each MMS should have >63 kg fuel remaining.2. Perigee raises in 2029 and 2030 can delay this reentry indefinitely. 4. Sufficient fuel would be reserved over the lifetime of the mission for the forced reentry, whether that occurs in 2037 or is again postponed through another update of the EOM plan.3. If this is done, the spacecraft do not reenter for as long as the orbits can reliably be propagated (~100 years), violating the 25-year orbital debris mitigation rule. Reentry would be forced; the refreshed EOM plan would schedule reentry at the next dip in perigee in early 2037.MMS has a signed EOM plan that is “re-confirmed” at the time of each Senior Review. The MMS SWG approves the suggested 2029/2030 perigee raises and requests the MOC lead the effort to study and gain approval for a refreshed EOM plan for forced reentry in 2037 that would be submitted at the time of the 2026 Senior Review

4. FY24 Formation Change Plan Approved by SWGoriginators were Fuselier / Ergun / Chasapis / Stawarz Additional notes and preferences:Tai Phan  X-Lines are measured to be between 1 and 3 REMMS4 selected for larger separation because of FPI-DES issue. With half-sky (or half-spin) electron data, analysis is difficult/ambiguous at smaller scales.Slow, gradual separations and unifications are welcome; each orbit at a somewhat wider/smaller separations give measurements at varying scales – more data across a wide range of scales Avoid the need for quick (costly in terms of fuel) adjustmentsPreference for the largest separations in the solar wind during 10A (ideally up to ~104km or more), and smallest separation at the magnetopause during 10B (~100km or less).Solar wind observations preferred on dusk side (10A/B or 9A/B) to avoid foreshock contamination. BBFs tend to be a bit more frequently observed on dusk side tail.Hence the preference to start during tail season and use 9C to get into formation and 10C to recover tetrahedron without time pressure. The FY24 formation change plan consists of seven stages that would be implemented over mission phases 9C to 10C. See graphic depiction in addition to description below:Late dawn flank, begin maneuvers to drift slowly apart (over 1.5-3 months) into log string of pearls, covering range of scales in magnetotail Settle at target A1:[separations of 50/500/5,000 km at 29 RE]; maintain for remainder of nightside magnetosphere and into dusk flank (Contributes to Objectives 1,2,3,4 for magnetotail)In dusk flank, maintain max spacing A1:[80/1500/15,000 km at 15 RE], for Kelvin Helmholtz investigationLate dusk/early dayside, drift to A1:[150/1000/5000 at 29 RE], range of scales for turbulence studies in pristine solar wind (Contributes to Objectives 4,5)Early dayside, begin slow drift (~1 mo) toward A1:[86/860/8600 km at 12 RE]; for multiscale studies of the shock and magnetosheath (Contributes to Objectives 1,2,4,5 for subsolar region)Post-noon, transition to multiscale 2D tetrahedron B1:[86/86/20,000 km at 12 RE] for magnetosheath turbulence studies. (Contributes to Objectives 1,2 for subsolar region)Dawn flank, return to nominal MMS tetrahedronSee slide 9 for nomenclature used in formation plan descriptions

5. 9A: dusk flank – nominal 20km tetrahedron9B: dayside – nominal 20km tetrahedron9C: dawn flank – nominal 20km tetrahedron, start drift into SOP9D: nightside1. drift apart over 1.5-3 mo into A1:SOP, range of scales in magnetotail2. Settle at A1:[50/500/5,000km@29RE], maintain for remainder of tailFY24 – Year 9FY25 – Year 10FY starts w/ dusk flank, proceeding clockwiseY separation in dusk tailDrift apart for range of scales.10A: dusk flank3. drift to max spacing A1:[80/1500/15,000km@15RE], for Kelvin Helmholtz studies4. late dusk, to A1:[150/1000/5000@29RE], turbulence studies in pristine solar wind 10B: dayside5. drift ~1mo to A1:[86/860/8600 km@12 RE]; range of scales shock/magnetosheath6. transition to B1:[86/86/20,000km@12 RE] for magnetosheath turbulence studies10C: dawn flank – 7. return to nominal MMS tetrahedron10D: nightside – nominal 40km tetrahedronKelvin-Helmholtz studiespristine solar windmagnetosheath studies1234567FY24 Formation Change Plan Approved by SWGSee slide 9 for nomenclature used in formation plan descriptions

6. FY24 Formation Change Plan approved by SWGPhaseObservationsScience Obj9D: MagnetotailSlow drift across multiple scales Magnetotail: Examine Transverse structure of the tailTail reconnection: x-point motion, RX jet structure and evolution Dusk side: BBF mesoscale structure observationsSR2023-3 & SR23-4R. Ergun, M. Usanova10A: Dusk FlankMove to largest separation in transition to daysideKelvin-Helmholtz vortex structure: examine cross-scale coupling SR2023-410A-10B: Solar windMax separation, max time in pristine solar windSolar wind: Mesoscale structure of solar wind turbulenceSolar wind current sheet dynamicsEstablish multi-point methods for future heliophysics missionsSR2023-4 & SR2023-5W. Matthaeus, R. Chhiber10B: Magnetosheath and BowshockGradually move to smallest separation for MMS1,2,3. MMS4 stays further away as upstream monitorBowshock:Non-stationary processes in the shock transition regionResponse to solar wind transients – upstream monitoringSimultaneous observ. of different parts of the shock transition regionMagnetosheath:Monitor global magnetosheath dynamics Direct observation of turbulent driving and relaxationEvolution of current sheets & flux ropes through the regionSR2023-4 & SR2023-5I. Gingell, S. Schwartz J. Stawarz, R. Bandyopadhyay, R. Qudsi10B (Subsolar): Magnetopause: Move to smallest separation, MMS4 stays trailingMagnetopause:Onset & evolution of reconnection – impact on EDR physicsRole of compression & magnetic pile up from the sheathMagnetopause response to transient upstream flows SR2023-1 & SR2023-2F. Wilder, K. Genestreti

7. FY24 Formation Change Plan approved by SWGYear-by-Year Summary9 – FY2410 – FY2511 – FY2612 – FY2713 – FY2814 – FY2920km TetrahedronA1: Log string-of-pearls20km Tetrahedron20km Tetrahedron20km Tetrahedron40km Tetrahedron, Transition20km TetrahedronA1: Log string-of-pearlsB1: kinetic+upstream20km Tetrahedron20km Tetrahedron20km Tetrahedron20km Tetrahedron20km Tetrahedron, TransitionTransition, 20-or-40km Tetrahedron20km Tetrahedron20km Tetrahedron20km Tetrahedron20km TetrahedronA1: Log string-of-pearls40km Tetrahedron40km Tetrahedron40km Tetrahedron40km Tetrahedron40km TetrahedronABCD15 – FY3016 – FY3117 – FY3218 – FY3319 – FY3420 – FY35Scheduled EOM, 20-40km Tetrahedron20-40km Tetrahedron20-40km Tetrahedron20-40km Tetrahedron20-40km Tetrahedron20-40km Tetrahedron21 – FY3622 – FY3723 – FY38…XX – EOM20-40km TetrahedronNext Scheduled EOMPhase F or extend EOM via min-maintenance string-of-pearlsDisposal  >25kg fuelNote longer dwell times near neutral sheetAfter FY29 there may, or may not, be sufficient fuel reserves for further formation changes (i.e., more than the initial 3) … depends on success of previous campaigns and state of the payload … to be revisited for the FY29 SR.After FY36 there may, or may not, be sufficient fuel reserves for a few more years of continued tetrahedron formation maintenance … to be revisited in conjunction with updates to the FY37 MMS EOM plan.Further formation change plans are tbd. By early-Phase 9B, SWG should determine whether to repeat this formation starting at Phase 10D or defer this or another formation plan to later years.

8. Understanding of Constraints – OptionsSlow drifts into SOP formation Enable Range of Multiscale SamplingRelative positions of spacecraft shown at successive apogees.First ~radial steps by modified “eclipse-tweaking“ apogee-adjust burns at preceding perigee.Resulting differences in periods cause gradual along-track drifts over tbd time period – in this illustration over a 1-month time period.Final apogee-adjust maneuvers match apogee radii, nulling drift rates.MMS sets its formation requirement at the location of prime science – e.g., apogee for nightside reconnection or ~12 RE for dayside magnetopause, see also tetrahedron "quality factor" in L1 requirements. Quality factor for SOP (to be formulated) allows spacings to vary (e.g., up to +20%), maximizing the formation quality within the region of interest.Drifting Motion into the String-of-PearlsStartAfter ~1-moAfter ~1-moSmallest string-of-pearls spacing at location of prime science as a function of radial distance4/18/20238Other constraints include handling long nightside eclipses and lunar perturbations that can limit max separations (>10,000km) before slight scattering complicates return to our tight tetrahedron.  FY24 and FY25 eclipses are mild and can accommodate 2RE string; future years may require formation to return to 40km tetrahedron for eclipse operations

9. Understanding of Constraints – Options with notes from SWG offering opportunities for compromise4/18/20239(A) Basic strings, including logarithmic string of pearls, possibly w/ wide range of intersatellite spacings. String must lie along orbital velocity vector.VelocityOrbit normalMax 18(50)km @12(29)REMin 83(15)km @ 12(29)REDirect insertion – Max 560(100)km @ 12(29)RE 1-mo drift insertion – Max 5.0(0.9)RE @ 12(29)RE 2-mo drift insertion – Max 10.1(1.8)RE @ 12(29)RE(B) Strings with cross-members. Cross member must lie along orbit normal, not radius, if formation is to persist.A1 is most desirable on dayside as MMS4 becomes upstream monitor on inbound legs of orbitA1, A2 provide monitoring both sides of closely spaced S/CA3, A4 are acceptable and least desirableSpacings are denoted Formation#:[smallest, mid-spacing, longest km @nRE] and typically correspond to [de, di, n*di], which is region dependant.A1B1A3A2Spacecraft are generally interchangeable – MMS4 (blue) to be furthest as often as possible due to half-sky electron observations. Ultimately, flight dynamics team implements as feasible from season-to-season/orbit-to-orbit.A4~Constraints along Orbit Normal and Velocity Vector:B2B1 is most desirable, B2 is acceptable. Note that B1 is ~"promised" in the 2023 Senior Review proposal. Other Type B configurations are possible (i.e., Dumbbell and Kite) and are not under consideration for this FY24 formation change campaign.Note: In the 2023 SR proposal, B1 is referred to as the "multi-scale tetrahedron".

10. Understanding of Constraints – Options ParameterValue if string specified at apogeeValue if string specified at 12 RE (i.e. ~MP)ExplanationMin along-track spacing15 km83 kmSafety at apogee (string closest approach point)Max along-track spacing for direct insertion into string100 km560 kmFuel (~10kg per obs.)Max along-track spacing for drift into string over 1 month (one way)0.9 RE5.0 REFor max apo-change of 0.1 RE (to not corrupt eclipse geometry), all performed by one MMSMax along-track spacing for drift into string over 2 months (one way)1.8 RE10.1 RETightest specified relative tolerance on along-track spacing giving at least 2 weeks between maintenance maneuvers4%4%Driven by effects of differential lunisolar perturbationsTightest specified relative tolerance on along-track spacing giving at least 4 weeks between maintenance maneuvers7%7%Max out-of-plane (OOP) spacing in dumbbell or kite50 km18 kmPrevents perturbations from driving OOP errors above ±5 km in 2 weeks

11. Context: Solar Cycle – Mission PhasesThe NOAA/NASA/ISES Prediction Panel predicted a maximum of 115 in July 2025 – or, 105-125 between Nov 2024 and March 2026. Note that on completion of Phase 11, MMS will have completed a full solar cycle of reconnection observation252423helioforecast.space/solarcycleFY24FY25FY26Dwell time near plasma sheet is modest in FY24, increases in FY25/FY26

12. Context: Proposed by Senior Review 2023Executive Summary“The MMS spacecraft remains in the electron-scale tetrahedron configuration through calendar year 2023, after which we propose changes to the spacecraft configuration. Examples of new configurations include a multi-scale tetrahedron, allowing for simultaneous sampling of adjacent plasma regimes and a logarithmic string-of-pearls formation with separations approximating a geometric series, e.g., 30 km, 650 km, 15,000 km in order to sample electron, ion and MHD scales simultaneously.”4 Technical Implementation4a Observatory Formations“To date, MMS has kept the spacecraft in the tight tetrahedron formation optimal for exploring kinetic-scale reconnection in the magnetotail (avg 40km separation) and for resolving reconnection at the magnetopause crossings that occur approximately half-way to apogee on the outbound and inbound orbit legs (avg 20km separation).The intent is to remain in this formation at least through CY2023, especially as MMS accesses the high-latitude dayside and flank magnetopause, which are important sites for investigating reconnection, particularly in the presence of flow shears.In the FY24-FY26 extended mission, we propose to add “formation change” periods to investigate the cross-scale physics that couple electron-kinetic processes to the surrounding environment in which they occur. Changes to the spacecraft constellation will be executed over many weeks with minimal maneuvers, both to avoid disruption to science data collection and to collect observations over a range of spacecraft distance. “The guideline budget that was provided at the time of the SR supports the proposed payload and mission operations.

13. Context: Proposed by Senior Review 2023“The proposal for the first campaign (nominally in FY24 for ~9 months) is a logarithmic string-of-pearls configuration. Starting with an ion-scale formation ideal for studying the coupling between the ion-kinetic structure of the magnetopause boundary and the electron-kinetic physics of diffusion regions, the formation would evolve to peak separation in the deep magnetotail to provide coverage over a variety of scales ranging from two spacecraft separated by electron-kinetic scales to 5 pairs of spacecraft with ion-to-MHD-scale separations.Minimal development is expected as a similar observing configuration was necessarily adopted during a 1-month period in February 2019 when the MMS apogee was raised from 25 to 29RE. After each formation change period, the intent is to return to the nominal tetrahedron formation. Subsequent formation changes would depend on the scientific success of previous campaigns.The only expendable on the spacecraft is hydrazine with about 116kg left in the fuel tanks of each s/c as of October 2022, which is enough to maintain tetrahedron formations for 20+ years (~1kg/MMS/0.5yr).Fuel reserves support at least three science-focused formation changes (~2-9kg/MMS/formation depending on configuration, timing, and duration), plus a perigee raise (~16kg) to extend the mission beyond 2030, and later the forced reentry (21kg). Small apogee- adjusts are applied ~annually to minimize long duration eclipses.”4b.2 Spacecraft System Status“Delta-V analysis shows MMS can complete a 5-year extended mission with sufficient propellant reserve to meet the 25-year reentry requirement (current predicted Earth reentry ~August 2030). Any fuel not consumed for science campaigns is available for potential mission extensions past the current planned 2030 EOM date. A tentative plan has demonstrated feasibility to delay reentry to 2037, although this is not proposed at this time.” Plan is to update the EOM plan during FY23-24 for submission to 2026 SR.The guideline budget that was provided at the time of the SR supports the proposed payload and mission operations.

14. Context: Extended Mission Objectives

15. Understanding of Fuel Estimates, to EOMFuel Budget to EOM 2030Fuel per S/C (kg)EventDRemainingCurrent fuel {118,116,116,116 kg} (bookkeeping, as of 10/4/2022)--116Tetrahedron formation flight to mid-2023 (0.5 yr @ 2 kg/MMS/yr)1115Perigee-raise to keep above 700 km threshold, 20236109Non-tetrahedral campaigns, 2024-2026 (3 @ 2-9 kg/MMS/yr – Fuel balancing may reduce max used)6-2782Apogee-adjusts (eclipse tweaking), 2025-2027379Tetrahedron formation flight, 2025-2030 reentry (5 yr @ 2 kg/MMS/yr)1069Possible Dodge maneuver/recovery (x 2)267End of mission (EOM) dephasing/disposal265Unusable in tanks/lines at EOM263Remaining usable fuel at End of Mission  2030--63Fuel Budget to EOM 2037Fuel per S/C (kg)EventDRemainingEOM Fuel Reserve(bookkeeping, as of 10/4/2022)--63Perigee-raise 1 to prevent reentry in 2030: late 2029855Perigee-raise 2 to prevent reentry in 2030: early 2030847Perigee-lowering 1 to cause reentry in 2037: Feb. 2036839Perigee-lowering 2 to cause reentry in 2037: Oct. 20361326Apogee-adjusts (eclipse tweaking), 2031-2034422Tetrahedron formation flight, 2031-2037 reentry (6 yr @ 2 kg/MMS/yr)1210Remaining usable fuel at End of Mission  2037--10

16. Understanding of Future Eclipse DurationsApogee and perigee maneuvers also marked

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