THEMIS%20Extended%20Phase

1
THEMIS Extended Phase Summary of THEMIS team
discussions (Please note this is work in
progress)
2
Preamble

• P3,4,5 will be uniquely suited to study
  microphysics at small scale separations
• Equatorial magnetosphere at 9-12 RE was not
  studied by Cluster
• Having explored Rf, fq planes during prime
  mission, THEMIS ready to explore 3rd dimension
  Rq
• Rq plane is optimal three-probe configuration for
  studying currents in the tail and at the
  magnetopause
• Tail Region 9-12RE is unique to substorms
• Auroras and substorm onset currents map there
• Region is important for MI coupling during
  substorms and storms
• Dayside Region 9-12RE is unique to Solar Wind
  Magnetosphere coupling
• Sub-solar Magnetopause streamlines affect energy
  entry along entire magnetopause boundary
• Reconnection topology and rate have not been
  studied before due to lack of multi-point
  observations
• Exciting new possibilities with THEMIS P3,4,5 at
  10-100km separations at those regions
• Prepares the ground for MMS-like studies
• Early dayside period on THEMIS (coast phase)
  provides a glimpse of capabilities
• Early dayside period shows operational complexity
  of achieving small scale separations
• P1 will be unable to contribute to the above
  goals due to extreme shadows
• Inclination changes dont help because apo-apsis
  is at the equator/ecliptic intersection
• Apogee lowering is costly and cumulative
  precession post-prime mission does reduce shadows
• Anticipated since CDR but could not afford
  time/cost to verify or fix by design changes
• P2 may be able to contribute uniquely to inner
  magnetosphere science

3
P1, P2 shadows, nominal orbits
Representative shadow trends for typical P1
orbits (from THEMIS CSR). Note underestimates
3rd year shadows exceed design limit 180min
RAP330deg
4
P1 180/360 Minute Eclipse Power

• Battery Capacity 11.8 Ah
• Battery Depth of Dishcarge (DoD) Requirement lt
  65
• 3hr Eclipse DoD 63
• Margin 2
• Battery Average Voltage 28.8V
• Battery Capacity 340 Wh
• Eclipse Power Reqs 69.5W
• Max Eclipse Sustainable 4.8h
• No recovery for BAU if battery is drained and BAU
  stops operating

5
Thermal Design and Test Limits
Qual Limits
Operational Limits
Predicts
Minimum Predicted
5C
5C
Maximum Predicted
5C
5C
10C
10C
-100C
-120C
-110C

• Bus Thermal Design goal was to be at least 5 C
  inside Operational Limits for passive design
  components. For side panels, Qual limit was
  120C
• FM-1 (TH-A, P5) Qual-tested at 10C beyond
  Operational Limits
• FM 2-5 Acceptance tested at 5C beyond
  Operational Limits

6
P1 180 minute Eclipse Temperatures
A 15deg difference between Localand Bulk Side
Panel temperatures Cold spots on the arrays
wouldresult in break of the vaultedinterconnects
and the cell glass LOSS OF PRIME POWER
7
P1 180/360 Minute Eclipse Transient Temperature
Results
-95oC
Side Panel local temperatures may exceed
operational cold limits (-95o 15o -110oC)
8
P1, P2 can they be saved at Earth orbit?

• P1 consuming all 300m/s (remaining at end of
  mission) in Earth orbit, options
• Apogee reduction to 18RE on Oct 1, 2009 (300m/s)
  Exacerbates P1 shadows Not an option
• Inclination change in June 2009 (change in 2nd
  dayside season) may reduce shadows (TBD)
• 40deg inclination change slows down APER changes,
  may go through minimum shadow in 2010
• In 2011 the long shadow will be inevitable
• Basic reason line of apsides is at the
  equator/ecliptic intersection
• No de-orbit fuel left (128m/s are required) -
  Does not meet de-orbit requirements Not an
  option
• Summary P1 cannot be salvaged with remaining
  fuel in Earth orbit
• Would have to deplete all fuel and placed on a
  re-entry path
• If it survives shadows, Lunar perturbations will
  render orbit polar. Even less useful for P2-5
  then.
• P2 consuming 450m/s (remaining at end of
  mission) in Earth orbit, options
• Additional inclination change and perigee change
  may reduce shadows further
• Requires further investigation
• Depends on fuel margin consumed in prime mission
• At same altitude not so helpful for extended
  science with P3,4,5
• Apogee reduction to 12RE on Oct 1, 2009 (210m/s)
  builds 5deg additional precession
• Can be brought closer to P3,4,5
• Can be used to validate current sheet orientation
  assumption
• Summary P2 can be salvaged with its remaining
  fuel in Earth orbitbut scientific usefulness
  and orbit optimization require further study

9
P3,4,5 tail science P1P2 relationScience of
P1,P2 at current orbits peripheral

• Focus at 10-12RE post prime-THEMIS
• Most important unresolved substorm questions
• Magnetosphere-ionosphere coupling at onset
• How are tail currents diverted to ionosphere?
• How are plasma sheet particles accelerated?
• How do quasi-static electric fields build up?
• Micro-physics of onset mechanism
• If at CD site, extended THEMIS can address
• If at Rx site, MMS will do that in the future
• 1st extended year
• Take P5 to P3,4 altitude (Dec 1, 2009), dV60m/s
• Separate P3-P4 in radial direction (both
  siderial)
• Study 0.1 1RE scale sizes currents, flows, CD
• 2nd , 3rd extended year
• Take P5, P3 closer to P4 (Dec 1, 2010)
• APER180, P5 d(inc) 6deg, dV 110m/s
• Tune period and phase to optimize geometry
• Study 10km-1000km scale sizes
• By the 1st year of THEMIS extension

THEMIS April 15-19, 2010 w/o maneuvers
P1
P2
P4
P5
P3
10
P3,4,5 tail science

• Focus at 10-12RE post prime-THEMIS
• Most important unresolved substorm questions
• Magnetosphere-ionosphere coupling at onset
• How are tail currents diverted to ionosphere?
• How are plasma sheet particles accelerated?
• How do quasi-static electric fields build up?
• Micro-physics of onset mechanism
• If at CD site, extended THEMIS can address
• If at Rx site, MMS will do that in the future

11
P3,4,5 tail science P1P2 relationScience of
P1,P2 at current orbits peripheral

• Consensus
• Use P3,4,5 for Cluster-like science
• Study equatorial magnetosphere
• Cluster did not visit 10-12RE plasma sheet
• Optimize orbits to do cutting edge research
• In different configuration than before
• Send P2 to join P3-5?
• Determine whether or not fuel permits P2 to join
  P3-5 in a tetrahedral formation
• Finalize decision no earlier than 10/2008
• Send P2 to join P1 in ARTEMIS at moon?
• Determine whether ARTEMIS needs one or two THEMIS
  S/C (in view of pending LuSIE and LEO
  selections)
• Finalize decision no later than 03/2009

12
P3,4,5 tail science T3 (2010-04-15)
T3, GSE coords View from tail along
NS dZ(P3-P5) 600-3000km dR(P3-P4)1RE gt
dZ every 8 days
Y
P3
P4
P5
13
P3,4,5 tail science T3 (2010-04-15)
Z
Y
P3
P4
X
P5
T3, GSE coords View from dawn along
NS dZ(P3-P5) 600-3000km dR(P3-P4)1RE gt
dZ every 8 days
14
P3,4,5 dayside science D3 (2010-11-01)
D3, GSE coords View from Sun along
Ecliptic dZ(P3-P5) 1000-3000km dR(P3-P4)1000km
lt dZ every day Apogee12Re
Z
P5
Y
P4
P3
X
15
P3,4,5 dayside science D3 (2010-11-01)
Z
P 5
P4
P3
X
Y
D3, GSE coords View from dawn along
Ecliptic dZ(P3-P5) 1000-3000km dR(P3-P4)1000km
lt dZ every day Apogee12Re
16
P3,4,5 tail science T4 (2011-05-10)
Z
Y
T4, GSE coords View from dawn along
NS dZ(P3-P5) 100-500km dR(P3-P4)1000km gt
dZ every day Apogee 12RE
X
17
P3,4,5 science during last year FY12
P3,4,5 dayside science D4 (2011-12-01) Same
configuration as D3, except smaller
separations dZ (P3-P5) 200-1000km dR
(P4-P3/P5) 200km P3,4,5 dayside science T5
(2012-06-21) Same configuration as T4, except
except smaller separations dZ (P3-P5)
200-1000km dR (P4-P3/P5) 1000km
18
Summary P3,4,5 science at 10-12RE Cluster-class
science at an uncharted region

• Key science questions in the tail at 10-12RE
  region
• How does the cross-tail current get disrupted at
  substorm onset?
• If current disruption is responsible for
  substorm onset, what is the plasma physical
  process?
• If reconnection causes current disruption, how
  does incoming flow disrupt the cross tail
  currents?
• Which are the cross-tail current carriers and
  how does their free energy get reduced?
• How does the cross-tail current get diverted
  into auroral ionosphere at onset?
• By vorticity generation, by pressure gradient
  redistribution, by flow breaking or by Alfven
  waves?
• THEMISs unique Rq configuration provides
  unprecedented measurements in this region of
  space. With Cluster-quality instrumentation and
  orbital separations, in a region never before
  visited in such a formation, THEMIS will measure
  cross-tail and field aligned current
  measurements, particle distributions, and waves
  will be able to answer which mechanism is
  responsible for the current disruption and
  diversion at substorm onset.
• Key science questions in the dayside at 10-12RE
  region
• How solar wind energy couple through the
  subsolar magnetopause?
• Do cold ions in the equatorial magnetosphere
  affect reconnection rate and energy coupling?
• What is the extent, topology and rate of
  reconnection at the subsolar magnetopause?
• THEMISs unique Rq configuration provides
  unprecedented reconnection inflow measurements
  from P4, with simultaneous bracketing of the
  diffusion region by P3 and P5. With
  Cluster-quality instrumentation and orbital
  separations, THEMISs three satellites measure
  (assuming azimuthal invariance) magnetopause and
  field aligned currents for the first time in this
  critical region.

19
How can P2 help P3,4,5? Ans. If it creates good
tetrahedron

• P2 can be brought to siderial orbit
• Daily conjunctions with P3,4,5
• Optimized separations to 1RE
• Provides additional CD timing/context
• Validates 2D planar current sheet
• P2 can be further tuned
• Tetrahedral formation with P3,4,5
• Requires MMS/Cluster know-how
• Study initiated (Concha/Hapgood)
• P2 may require inordinate fuel
• Significant science return
• Cluster was never there
• MMS will not have 0.1-1RE scale
• Summary P2 may be able to dosignificant
  additional science ifplaced at tetrahedral
  formationwith P3,4,5 but it is unclear at this
  point if fuel margin is sufficient for orbit
  maintenance.

Y
2010-04-10 000000
P2
P4
X
P3
P5
20
Optimal use of P1, P2 ARTEMIS

• P1, P2 have sufficient fuel to raise apogee to
  the moon
• Easier to go up than down
• Lunar gravity perturbs orbits sufficiently to
  remove long shadows
• Probes need not stay any longer in Earth orbit
• Mission design and operations can become complex
  and expensive unless new target is found
• Use the moon as anchor to perform new tail and
  new Solar Wind science
• Permits exploration of a unique Lunar-Solar and
  Lunar-Tail environment like never done before
• Optimal use of de-orbit fuel (lunar re-entry)
• Design considerations for Lunar insertion, result
  in a robust mission
• Spin axis at ecliptic normal throughout mission
  optimal communications
• Equatorial Lunar orbit stable for many years
• After Lunar Orbit Insertion operations are
  routine
• A 24hr orbit guarantees
• Less than 3.5hr shadows, acceptable for probe
  design
• Familiar, low risk power, thermal and operations
  environment
• Mission design that satisfies above criteria is
  robust
• Under study by JPL since April 2005
• By same team which validated the THEMIS mission
  design in 2004-2005
• JPL review on 2007-Nov-02 found no technical
  issues

21
ARTEMIS Acceleration, Reconnection, Turbulence
and Electrodynamics of the Moons Interaction
with the Sun
22
What are the important magnetosphericquestions
after THEMIS, before MMS?
Distant magnetotail (after Geotail and WIND
single spacecraft) What is the nature and extent
of the distant tail neutral line? Does the tail
vanish in response to Interplanetary Coronal Mass
Ejections? What are the dimensions and topology
of plasmoids (carry ½ energy of storms) Answers
necessitate multiple THEMIS-type satellites at
0.1-10RE scales Solar Wind and Shocks (after
multiple missions Cluster, ISEE1/2) How do
shocks accelerate particles? (Shock acceleration
or diffusion) What is the nature of solar wind
turbulence in 1-10RE scale lengths (no data)
Answers necessitate multiple THEMIS-type
satellites at 1-20RE scales Lunar Wake (after
Lunar Prospector and WIND) What are the plasma
waves that make up the nature of the Lunar
Wake? How does the wake fill-in from near the
moon to far down What makes up, sustains and
dissipates the electric fields behind the wake
Answers necessitate multiple THEMIS-type
satellites at 1000-50,000km scales
23
ARTEMIS Science Objectives

• Acceleration in shocks, tail and lunar
  environment
• What is the nature of acceleration at shocks?
• Follow evolution of particle distributions at
  two points along the shock.
• How do MeV electrons get accelerated in the
  tail?
• Measure field topology, particle spectra and
  evolution in time and space.
• How do energetic (100s of keV) ions and
  electrons get accelerated in the wake?
• Measure particles and fields in the wake and the
  solar wind simultaneously.
• Reconnection
• What is the distant tail reconnection onset
  mechanism, effects and response to solar wind
  drivers?
• Spontaneous or induced?
• Continuous or impulsive?
• Answers necessitate multiple THEMIS-type
  satellites at 1-20RE scales
• Lunar Wake (after Lunar Prospector and WIND)
• What are the plasma waves that make up the
  nature of the Lunar Wake?
• How does the wake fill-in from near the moon to
  far down
• What makes up, sustains and dissipates the
  electric fields behind the wake
• Measure particles and fiels in the wake and
  outside at 1000-50,000km distance

24
ARTEMIS Mission Profile
25
ARTEMIS Mission Phases
Phase I (Oct 09 Oct 10) - placement
26
ARTEMIS Select Orbits
Phase II (Oct 10 Jan 11) Opposite Sides
Sun-Earth Alignments
27
ARTEMIS Select Orbits
Phase II (Oct 10 Jan 11) Opposite Sides
Dawn-Dusk Alignments
28
ARTEMIS Select Orbits
Phase III (Jan 11 Apr 12) Same Side
Sun-Earth Alignments
29
ARTEMIS Select Orbits
Phase III (Jan 11 Apr 12) Same Side
Dawn-Dusk Alignments
30
ARTEMIS Wake Crossings Phase II,III
31
ARTEMIS Wake Crossings Phase II,III
32
ARTEMIS Distant Wake CrossingsA Perspective
dB
33
Phase IV (Apr 12 May 13) ARTEMIS After
Insertion
34
ARTEMIS Wake Crossings
35
ARTEMIS Ground Operations Concept

• Alternate Downlink OVRO
• RefurbishmentOps 1M
• Can track gt3hrs/day
• A 40m dish better than DSN
• Saves government gt10M

OVRO, 40m TLM Receive Only
DSN, 34m TLM, TRK, CMDTranslunar Orbits
BGS, 11m TRK CMDLunar Orbits

• Flight Dynamics
• Translunar Orbit
• JPL Mission Design, Orbit Determination,
  Ephemeris, Maneuver Planning
• UCB Attitude Determination
• Lunar Orbit
• UCB Mission Design, Orbit/Attitude
  Determination, Ephemeris, Maneuver Planning
• Mission Operations (UCB)
• Pass Scheduling, Mission Planning Command
  Generation
• Data Trending Anomaly Resolution, ITOS CMD
  Control
• Science Operations (UCB)
• Follows Standard THEMIS practices

36
ARTEMIS Science Team
Tail Plasmoids, Scales Slavin, Murphy
Rx/Heating Oieroset, Schriver
Turbulence Weygand, Velli
Acceleration, Scales Slavin, Murphy
Solar Wind Shock acceleration Eastwood, Bale
Turbulence Velli, Weygand
Foreshock Eastwood
Wake Computer sims Travnicek, Schriver, Farrell
Laboratory sims Gekelman
Exosphere Delory
Refilling, Beams Halekas, Farrell, Bale
37
THEMIS Extended Phase Proposal

• Senior Review panel
• Decides how to apportion funds between
  continuing missions (Voyager, Cluster )
• Evaluates and approves plans for FY09/10 hears
  proposals for FY11/12
• THEMIS ends in FY09, would request funding for
  FY10 and present plan for FY11/12
• THEMIS extension funding request for FY10 with
  further extension in FY11/12
• ARTEMIS proposal to slowly ramp up in FY08/09
  and move to operations in FY11/12
• Costs
• Cost Guidance would be sufficient to continue
  THEMIS with minimal operations
• Hinges on scientific publications and
  discoveries made by THEMIS now
• Reviewed on basis of past performance as
  indicator for future output
• Guest Investigator program to accompany THEMIS
  extended mission, also possible
• Hinges on quality and accessibility of THEMIS
  data, and community involvement
• Cost increase due to ARTEMIS team and mission
  operations may necessitate new funds
• Senior review panel chair may have to obtain
  additional funding from Heliophysics director
• Received recommendation to proceed with a
  combined proposal
• Timeline
• Proposal due February 21
• Review of Mission Archive Plan March 2008.
  Presentations April 8-11. Selection Jun 12,
  2008