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Taken from the Charter:   At the Senior Review of April 2013, the THEMIS team proposed a repurposing of the mission in order to enhance the science coordination and output from the Heliophysics System Observatory (HSO).  Specifically, it was proposed to align three THEMIS probes with the MMS constellation to form a large-scale tetrahedron along ion inertial to MHD lengths with THEMIS probes comprising three vertices of that tetrahedron and the MMS constellation at the fourth. This configuration will enable THEMIS to provide contextual information as well as explore ion physics at the same time that the four MMS spacecraft study electron kinetics within the reconnection region on the dayside of the magnetosphere. The Senior Review panel was enthusiastic about this concept and ranked it very highly in terms of overall scientific merit and potential contribution to the HSO.  NASA Heliophysics and SMD management decided to support the THEMIS request and fund the repositioning of three of its probes. Beginning September 25, 2013 and into October, THEMIS performed all maneuvers to accelerate its line of apsides drift towards the launch elements of MMS as was known at that time.  The working group is charged with exploring options for orbital alignments and coordinating measurements under various realistic MMS launch scenarios as they become apparent or necessary. 

MMS-THEMIS Working Group Telecon:

Tuesday April 29th, 4pm AND Thursday noontime MMS SWG Telecon

MMS-THEMIS Working Group Telecon:

Tuesday April 8th, 4pm


Draft of Whitepaper

  • whitepaper will be drafted and HQ briefed regardless of the content of the recommendations
  • current draft summarizes the factual information gathered so far, please review and improve
  • primary topic for today's telecon:    outline of the white paper,  the recommendations


Week of Mar 31:  Additional work in preparation for MMS SWG Telecon on Friday, April 4.  Cindy Russell added ephemeris files at Data are at 1 minute resolution and in ascii (.txt), compressed (.Z), gzip (.gz) formats. In addition there are files for both state vectors (gei) and orbital elements.  SWG Telecon on Friday, April 4th, MMS is preparing to take the next steps-- see agenda and notes below.  HQ set schedule toward DPMC/APMC that will address MMS resource issues for March 2015 launch.

Tai Phan supplied information from the Decadal Survey re the Cross Scale Mission. In the Decadal Survey book, on Page 232, third paragraph, there is a discussion of cross-scale physics of reconnection beyond MMS. On page 252, under "International Partnerships" there is a discussion of a future Cross-Scale mission.  The "Solar Wind-Magnetosphere Interactions" panel led by Michelle Thomsen supplied more expanded versions of these materials to the Steering committee: language on international partnership, language that includes cross-scale physics of reconnection.

Fuselier/Petrinec charts re MMS magnetopause/neutral sheet encounters

 Petrinec timeline chart

Week of Mar 24:  MMS SWT/SWG Meeting.   Updated presentations from Conrad Schiff and Vassilis Angelopoulos.   Launch date nominally settling on March 11, 2015.  Vassilis circulated launch elements for the March 15 MMS-THEMIS coordinated orbit, Fuselier will do his analysis on these ephemeris files for direct comparison to the nominal March 15 MMS orbit.  Conrad circulated a direct side-by-side, apples-to-apples  comparison of the timelines and sequence of events.  Burch wrote an email on the next steps for MMS.

Cindy Russell posted another file (mms_LD0315_RAAN76_RAP255_6_LT18_gei.txt) in ascii format. It contains state vectors for the mms mission and is located at:

Week of Mar 17:  Vassilis Angelopoulos circulated the final version of his initial work to document the movement of the two missions and to provide examples/options of what we might do to coordinate the two missions.  Brent Robertson investigated the schedule by which this work would need to be completed, see notes below but the answer is within 2 months.  Working group telecon focused on an optimized options 2/3d, and optimizer spreadsheet.   FDOA worked further to verify the Themis team analysis.

Week of Mar 10: Vassilis Angelopoulos and his team further documented the movement of the two missions and provided examples/options of what we might do to coordinate the two missions.  Version 6 is the latest.    Communication to the MMS Project and NASA HQ, ensuring all are aware of the effort and that we are all on the same page.  Thanks to Craig Tooley for ensuring the MMS team knows how to place this work in the context of their present work.  Mel Goldstein provided information on the position of Cluster in the future, see March 11 telecon for notes on that.   Held Status Telecon on March 11

Week of Mar 3:  Much work by Angelopoulos, Moore, Williams, and the THEMIS team on the initial options identified.  Telecon on March 6 for subgroup of folks working the options.  No telecon notes or agenda published; reviewed Angelopoulos initial cut at options, version 3.4.  Added Pete Spidaliere to the email list.

Week of Feb 24: The MMS science team has been asked to consider the impacts of a launch date that would fall within a 30 day window beginning late Feb. 2015.  Within this window, which dates are technically acceptable and have optimal science opportunity.  Kickoff telecon of the group on February 25.  Availability for other dates at

Vassilis Angelopoulos circulated first cut at options:  email summary, powerpoint charts

Trevor Williams circulated MIWG slides and further information on the "spring-like" launch windows:  email, powerpoint charts

How much extra time must be added to the mission before the start of Phase 1 science for the "Spring-like" launch windows.

(1) Feb. 20, 2015: 2.2 months for launch at window open; 2.4 months for launch at window close.

(2) Mar. 5, 2015: 1.7 months for launch at window open; 2.0 months for launch at window close.

(3) Mar. 20, 2015: 1.2 months for launch at window open; 1.5 months for launch at window close.

Each additional day that we bring launch earlier adds about an extra day to the mission duration.  In other words, the dayside passes, nightside pass and end of mission always fall on essentially unchanged dates.

Tom Moore circulated chart showing that the "spring-like" launch option has the potential to bring the missions into alignment within a reasonable period of time: email summary, powerpoint chart

Requested: It would be nice to be able to know the various options as function of launch time and compare them with nominal. Do we have a list of nominal LTs at launch for MMS, for May 7th, Jul. 7th, Sep. 7th that we can use for the table on P8 of the PPT Vassilis sent out? (For example for Mar. 7th I assumed 5LT, per your charts). This will help establish a trend of how the various options evolve in time. Also do the launch scenarios on Feb/Mar 2015 at 15LT (Option2/3) would violate shadows?  Is that true and if yes, is that due to early orbit shadows or tail season shadows?

Week of Feb 17: Establish working group and set kickoff telecon.  One-on-one discussions to set telecon agenda, gather information produced to date, establish scope of effort for near term and far term.

Week of Feb 10: The intention this week is to work individually with the mission PIs, PSs and the MMS Project Manger to work the membership list and gather suggestions for our approach.  A kickoff telecon will be held in the week or so after the Yosemite meeting concludes


Background Materials:


Telecon/Meeting Archive:

MMS SWG Telecon:

Friday April 4th, 3pm

Burch: Introduction, goal for the telecon


All: Discussion on questions left from SWG meeting in Iowa

  • The 6-month longer wait before Phase 1A can begin. This would be partly mitigated by Phase 0A if we can finish commissioning on time and have high-quality tetrahedrons while still maintaining sufficient propellant reserves. This also adds to the HV801 on-time, so it may be that FPI would have to be OFF during Phase 0X.
  • What is the neutral-sheet dwell time as compared to that for the nominal mission. We would not want to see a significant decrease.
  • How does the extra propellant usage affect our chances for a second tail pass, which several people are very interested in.

Burch:  Reach a SWG decision or identify what further information will be needed to decide.

All:  Advice to the PI in anticipation of the upcoming MMS-THEMIS Working Group Telecon.

Thursday, March 27: SWG Discussion

Information Updates:

  1. Conrad:  comparison of the timelines and sequence of events
  2. Conrad:  summarize what is currently known re formation flying versus fuel usage

Further Study / Decision Timeline:

  1. Now:  SWG Discussion - go/no-go on further work to be performed to inform final decision
  2. Next week:  Mission subsystems polled for impacts/risks, including instrument teams
  3. Next week:  Telecon on Tuesday – comparison of March 15 nominal launch vs March 15 MMS-THEMIS coordinated launch
  4. Within a month:  actionable information gathered for final decision - launch elements, impacts/risks, operations plan
  5. Six weeks:  deadline for delivery to ULA of any changes to nominal launch elements

Preliminary assessments of Technical Risk:

  • Mission Risk: Craig Tooley
  • Mission Risk: Brent Robertson
  • Mission Risk:  Pete Spidaliere
  • HPCA:  Stephen Fuselier
  • Fields:  Roy Torbert
  • EPD:  Barry Mauk
  • FPI:  Craig Pollock
  • ASPOC:  Rumi Nakamura

Open for Discussion - led by Jim Burch

Tuesday, March 17 Telecon

  • Brent Robertson:  News on the MMS Launch Date?
  • Brent Robertson investigated the schedule by which this work would need to be completed in order for ULA to complete their necessary work before launch, and later will investigate what additional cost such a late change to the ULA work would incur. This is not trivial as it involves not only launch and launch vehicle considerations but also the full complement of range and communication assets that support a launch.

    • Notes from Brent:  – as requested at the last MMS-THEMIS working group tag-up, I have communicated with both the KSC Launch Services Program and ULA regarding the change in launch target specification required for the current options identified by the MMS / THEMIS working group.  A change in launch target specification at this time would represent significant increased work for KSC / ULA to produce additional products necessary for rocket trajectory / environment assessment and flight software loads.  If the change is enacted in the next 2 months (from L-12 mo to L-10 mo) the cost is estimated to be on the order of $1,000K.  The cost would escalate into the multi-million dollar range from L-10 mo to L-6 mo and there would be some schedule risk of impact to the MMS launch date.  After L-6 mo, a change in launch target specification would not be possible without impacting the MMS launch date.

    • Followup from Vassilis:  Might be any reprieve from costs of looking at the elements AOP~183, RAAN~72 (window center)? The variation of these elements over the month is very small (see p.8 of powerpoint or the table in the excel sheet). They range from Feb20 to Mar22 from AOP = 180 to 186 and from RAAN=77 to 67 (this is due to the time of launch). All other elements should be the same as nominal to zeroth order. This orbit is such that it is dawn-dusk (apogee towards dusk), inclined about the major axis and should have little shadows so must be very benign. I hope the launch sequence is as benign as it seems. Since the launch vehicle just gave MMS a new launch date to consider, it is natural for new launch elements to arise -- perhaps an effort can be made to cover the cost of looking at these under nominal runs, if a decision is made quickly.

  • Trevor Williams and Vassilis Angelopoulos met to explore the options to identify actionable solution space for consideration.  Notes from Conrad:

1)  Vassilis and MMS Flight Dynamics (FD)  met Thursday March 13 to discuss how to proceed.

2)  MMS FD modeling on option 1 using SWM76 agrees very well with the detailed numerical simulations performed by the THEMIS team and so any concerns about modeling differences are retired for this option.

3)  MMS FD has a prototype version of SWM76 for Option 2/3 (really just one option with two minor variations on the theme)

4)  The THEMIS team is expecting to close out their preliminary runs on Tuesday for options 1 & 2/3.

5)  MMS FD will compare SWM76 results with the results from item 4).  I expect that there will be good agreement, as in option 1, but since the flight physics is somewhat different some differences may need to resolved.

6)  I will merge the data and produce slides and an accompanying pros/cons chart - this package will be ready for me to present at the SWT on the 25th.

7) At the SWT there should be enough expertise to decide if more analysis is warranted.  We should have enough people at the SWT to comment on 1) science merits and risks, 2) engineering risks and costs, 3) commissioning logisitics, and 4) operations.  These discussions should include a splinter on ATOX with the aim to determine how soon we really need to perform perigee raising (impacts commissioning and therefore impacts the risk associated with options 1 & 2/3) and how low in perigee altitude we really can go (perigee altitude acts a 'knob' that can be turned to take error in the MMS to THEMIS phasing).

8) Detailed feasibility analysis can follow if the outcome on 7) is favorable.  Assuming that SWM76 is validated at this point, the flight dynamics will not be a bottle neck (SWM76 is very fast)  and the remaining work will be standard systems engineering and detailed discussions.  The corresponding Launch Vehicle targets will naturally be generated and we should have a new LV target spec out within the 2 months discussed by Brent.  That said, a possible sticking point with ULA might be the type of coast solution that results from the range of argument of perigees but let's burn that bridge when we come to it.


  • FOCUS FOR THIS TELECON --> Powerpoint for Discussion, and optimizer spreadsheet. Also,a PDF showing plots of MMS neutral sheet conjunctions for Phase0x.   Focus is on the optimization of "option 3" and to quickly provide information to settle the potential ULA cost issue.  Notes from the emails:  Vassilis Angelopoulos and his team have through further about what to do about retaining flexibility to overcome launch dispersions and avoid RAAN steering. Another approach can be to make the perigee raise on THEMIS late, after the MMS placement elements are known. Then by adjusting the time of raise we can optimize the steering of  THEMIS ahead or behind in RAP and make it meet MMS in orbit. However, this means THEMIS must keep drifting at a faster rate (which is acquired after last Fall’s perigee reduction maneuvers), which in turn could mean MMS would have to launch even later in LT, at 18LT.  This adds another month to the mission. The advantages are high flexibility in orbit for optimal matching, plus an extra month of dayside 0 (Phase0) prime MMS observations with the full 4 mo of commissioning.  Lowering MMS perigee through Phase1a-Phase1b would help a lot (the further down MMS goes the better the matching for less fuel from THEMIS and better joint observations during extended phase – right now THEMIS is spending all its got) but this further optimization is not required.  Comments are encouraged!  Write to Vassilis/Travor/Conrad directly or to the full email list as appropriate.


  • Schedule for discussion at MMS SWT/SWG in Iowa?


  • Reminder from Trevor on MMS eclipse constraints as relaxed for the Winter block:  MMS defines eclipse durations as umbra plus one-half penumbra time. 
  1. No eclipse longer than 3.00 hr in the first two weeks.
  2. No eclipse longer than 4.50 hr at any time in the mission.  (This is often referred to as the "Phase 2b" eclipse limit, because it is not possible to achieve an eclipse of 4.50 hr on the Phase 1 orbit, rather it applies throughout the nominal mission.)

Tuesday, March 11 Telecon

At our last telecon, we said we'd set a new telecon date once some good progress had been made on the initial options suggested.  There has been progress although not to the extent we're ready to have a full in-depth discussion of the details or to make any recommendations. To keep everyone informed, we'll hold a telecon March 11 at 4pm to brief folks on the progress made to date and to answer any questions.  The information at this 4pm telecon will be identical to that presented in the March 11 MMS SODAWG telecon at 11pm Eastern. And will probably be identical to that briefed by Vassilis last Thursday at 1pm.  With so many opportunities to view the briefing, I'm hopeful that  folks can't help but be informed.

  • Vassilis Angelopoulos:  Exploring options, whether likely or unlikely to be approved for implementation is a good thing at this point in time. 
  • Version 5 is the latest! Two dimensional plots for Option#1 have been attached now (p6). The 2D plots for Option#2 are still under work, but the 1D plots provide sufficient insight (will provide them after telecon when ready).

Also, interesting will be the position of Cluster in the future Andrew Fazakerley provided information to illustrate observation possibilities in 2018 and 2020, highlights include:

  • (i) revisits of the Northern Cusp, now crossing in MLT rather than in latitudinal cuts as in the early mission;once again making the point that no other mission is doing high latitude observations in the magnetosphere
  • (ii) revisits of the magnetotail 15-15 Re downtail (chance to see more reconnection events at those distances)
  • (iii) crossings of the inner magnetosphere magnetic equator around geostationary distance


  • Trevor Williams and Vassilis Angelopoulos will continue to explore the options to identify an actionable solution space for consideration
  • Brent Robertson will investigate the schedule by which this work would need to be completed in order for ULA to complete their necessary work before launch, and later will investigate what additional cost such a late change to the ULA work would incur. This is not trivial as it involves not only launch and launch vehicle considerations but also the full complement of range and communication assets that support a launch. 

Tuesday, February 25 Telecon

1. Logistics for working group, scope of work, background materials, email list – Barbara Giles

    • Distinguished authors for white paper / recommendations:  Burch, Angelopoulos, Moore, Sibeck, Torbert, Phan, Fuselier, Tooley, Schiff, Knapp, Burns + Giles, Klumpar, Talaat

2. Overview of MMS information to date – Tom Moore

3. Overview of THEMIS information to date – Vassilis Angelopoulos

    • Vassilis reviewed where THEMIS is at the moment.  In the summer of last year, performed maneuvers to change the line of apsides and reduce perigee to better align with the anticipated position of the MMS constellation.  Separation of line of apsides is chanages by approx 1 deg per day from the nominal late October launch date.  That is, with a Feb/Mar launch that would place the missions approximately 90 degrees apart.  Vassilis reviewed three potential options that could be explored.

4. Discussion of the implications of the three options Vassilis presented.

    • The additional science that could be achieved by aligning THEMIS and MMS was noted as being highly desirable.
    • There are some scenarios that would require changes to the THEMIS operations or MMS operations or both.  There are scenarios that would require significant changes to the MMS Program Level Requirements and so approval by the DPMC and APMC.  Arguments for that level of change would need to be particularly compelling and weighed against the risk of achieving MMS full mission success, which was noted as being unlikely to be successful.

4. Next steps, including next tagup – All

    • Agreed to flesh out the proposed options and write up the impacts for consideration by the group.
    • Stephen Fuselier and Stephen Petrinec will start their usual MMS analysis for the new launch window; FDOA needs to get orbit information to them
    • The THEMIS team will take the lead on writing the first draft of potential options, FDOA will provide the results of the work performed this week on what appears to be a limited set of options possible within the new 30-day launch window (that is, something along the lines of the "green" spring-like launch illustrated on slide 4 of the launch block briefing shown above).
    • Next tagup is at least two weeks from now; in the meantime will circulate materials by email.


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