S. Frey, UCB, THEMIS 1 25th ISSFD, Munich, Germany, Oct.19-23, 2015

ARTEMIS

THEMISTHEMIS

ARTEMIS

The Revised Concept of the THEMIS and MMS CoordinationSabine Frey1, Vassilis Angelopoulos2 , Manfred Bester1

1University of California – Berkeley2University of California – Los Angeles

Time

History of Events and Macroscale

Interactions during Substorms

S. Frey, UCB, THEMIS 2 25th ISSFD, Munich, Germany, Oct.19-23, 2015

ARTEMIS

THEMISTHEMIS

ARTEMIS Overview

• Motivation• Revised THEMIS – MMS Alignment • THEMIS – MMS Coordination• THEMIS Orbit Redesign 2015 – 2020• Synchronizing Apogee Passes in 2015 and 2016• Summary

http://themis.ssl.berkeley.edu http://www.nasa.gov/themis

S. Frey, UCB, THEMIS 3 25th ISSFD, Munich, Germany, Oct.19-23, 2015

ARTEMIS

THEMISTHEMIS

ARTEMIS Motivation

Goals: • Improve understanding of coupling mechanisms across the entire magnetospheric system• Quantify the effect of global processes on local phenomena • Predict space weather Achieved by: • Prolonged simultaneous observations at key regions: Reconnection sites at magnetopause (1), In the tail (2) Inner magnetosphere (3), Polar regions (4)Utilized by:• Synchronized Orbits of THEMIS and MMS• Coordinated space and ground assets of the Heliophysics Observatory

Neutral Sheet 1 24

43

S. Frey, UCB, THEMIS 4 25th ISSFD, Munich, Germany, Oct.19-23, 2015

ARTEMIS

THEMISTHEMIS

ARTEMIS Revised THEMIS – MMS Alignment Originally nested tetrahedron of 7 S/C to study reconnection Revised concept:

•Opposing apogees on day and night sides• Apogee passes synchronized with GBOs and HSO space and ground systems to study coupling of day and night sides across polar regions

Orbits shown sun referenced in ecliptic planelooking from north, sun to the left Dayside Dayside

DaysideDayside

Nightside Nightside

Nightside Nightside

Dec. 2015Jun. 2016

Jul. 2017 Jan., Sep. 2020

MMS

MMS

THM

THM

THEMIS Ground Based Observatories in North America A ground asset of the Heliophysics System Observatory

ARTEMIS@55RE

MMS phase 1

MMS phase 1

MMS phase 2

MMS phase 2

S. Frey, UCB, THEMIS 5 25th ISSFD, Munich, Germany, Oct.19-23, 2015

ARTEMIS

THEMISTHEMIS

ARTEMIS THEMIS – MMS Coordination

Challenges of the multi-mission coordination despite similar science goals:

Resolved by planning process that started long before MMS launch: Long term planning to address alignment of lines of apsides by differential precession Short term planning to address synchronization of apogee pass times in coordination with HSO assets

THEMIS • 8 years in orbit• Nominal mission accomplished• Limited fuel reserves• Apogee pass times constrained by GBO conjunctions• Fuel efficiency relies on long term planning

MMS • Launch uncertainties• Fuel committed to ensure nominal science• No time constraints on apogee pass times• Probe separations are frequently reassessed based on recent observations

S. Frey, UCB, THEMIS 6 25th ISSFD, Munich, Germany, Oct.19-23, 2015

ARTEMIS

THEMISTHEMIS

ARTEMIS THEMIS Orbit Redesign 2015 - 2020

Main Design Driver • Primary science of extended mission phases• Resonant orbits with MMS

and HSO conjunctions• Re-entry commitment• Fuel efficiency • Systems safety

Main Orbit Design Component• Apogee altitudes 11.5 – 16 Re, clustered in

2015, string-of-pearls in 2020• Discrete periods resonant with MMS and

GBOs : TS, 8/7∙TS, 1/2∙TMMS, 4/3∙TS • Minimize de-orbit maneuver • Maneuver strategy• Perigee altitude above 650 km

TS sidereal period, TMMS MMS period

P3P4, P4P5

Remaining Fuel

After de-orbit maneuver

Perigee Altitude

No reduction before 2020

2017 2018 2019 2020

Apogee Altitude

Final 13.2 Re defined by P5

MMS phase 1

MMS phase 2

S. Frey, UCB, THEMIS 7 25th ISSFD, Munich, Germany, Oct.19-23, 2015

ARTEMIS

THEMISTHEMIS

ARTEMISSynchronizing Apogee Passes

in 2015 and 2016

P5 T7P5 D7 drp=50km P3,P4 T7,D7 drp=0kmP5 T8 drp=80kmP4 T8 drp=90kmP3 T8 drp=90km

Perigee Raises May 2015 June 2015 Dec 2015

1st Set period to drift per month 15 deg longitude,-1h UT at apogee

2nd Set sidereal period to stop drift target

Dayside season 7

100

0

-100

100

0

-100

Geographic Longitude of Apogee Passes

[deg

[d

eg]

Days since 2016-Feb-16-50 0 50 100 200 300

Dayside season 8

P3 110 days drift to target

P4 80 days drift to target

GBO

MMS on dayside, phase 1THEMIS on nightside, tail 8Centered in December 2015

THEMIS planning had to start prior to MMS launch and account for launch delay and dispersionTwo sequences of small maneuvers in spring 2015 to:• Cluster all three probes by summer • Synchronize apogee with MMS • Raise perigee altitudes above 650 km

MMS on nightside, phase 1 THEMIS on dayside, day 8 Centered in June 2016

Conjunction with South Pole ground observatories and MMS requires different UT targets for THEMIS probes; Set of small maneuvers includes perigee raises

S. Frey, UCB, THEMIS 8 25th ISSFD, Munich, Germany, Oct.19-23, 2015

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THEMISTHEMIS

ARTEMIS

Predicted alignment for 2015-12-11 at 9.5 UT

Summary

Cluster THEMIS (night) , MMS (day), Van Allen Probes,

ARTEMIS at

lunar distances

• THEMIS is committed to align with current and future HSO missions for a system-wide approach to study the dynamic interaction of the Earth’s magnetosphere with its space environment. • THEMIS is progressively utilizing its fuel reserves towards the coordinated multi-mission constellation• The revised alignment of THEMIS-MMS will provide prolonged simultaneous observations on the day and nightside.• Coordinated observations with HSO space assets will deliver the global context. • Synchronized observations with HSO ground systems will link processes across the magnetosphere.• Challenges due to MMS launch delays and dispersion have been overcome.• The first year of coordinated observations is underway.• Many thanks to all supporters of this multi-mission endeavor, the MMS team, and the THEMIS operations and flight dynamics teams