THEMIS Operations

Bester, M.; Lewis, Mark; Roberts, Bryce; McDonald, John A.; Pease, Deron O.; Thorsness, Jeremy; Frey, S.; Cosgrove, Daniel; Rummel, D.

doi:10.1007/s11214-008-9456-7

Cited by 18 publications

(12 citation statements)

References 13 publications

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“…The observations presented here were obtained from the THEMIS satellites (Angelopoulos, 2008;Sibeck and Angelopoulos, 2008;Bester et al, 2008) and THEMIS groundbased observatories Mende et al, 2008;Russell et al, 2008). Each THEMIS spacecraft carries an identical set of instruments.…”

Section: Instrumentationmentioning

confidence: 99%

THEMIS ground-space observations during the development of auroral spirals

et al. 2009

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Abstract.A simultaneous observation of an auroral spiral and its generator region in the near-Earth plasma sheet is rather unlikely. Here we present such observations using the THEMIS spacecraft as well as the THEMIS ground network of all-sky imagers and magnetometers. Two consecutive auroral spirals separated by approximately 14 min occurred during a substorm on 19 February 2008. The spirals formed during the expansion phase and a subsequent intensification, and were among the brightest features in the aurora with diameters of 200-300 km. The duration for the formation and decay of each spiral was less than 60 s. Both spirals occurred shortly after the formation of two oppositely rotating plasma flow vortices in space, which were also accompanied by dipolarizations and ion injections, at ∼11 R E geocentric distance. Observations and model calculations also give evidence for a magnetic-field-aligned current generation of approximately 0.1 MA via the flow vortices, connecting the generator region of the spirals with the ionosphere, during the formation of both spirals. In the ionosphere, a pair of equivalent ionospheric current (EIC) vortices with opposite rotations (corresponding to upward and downward currents) was present during both auroral spirals with enhanced EICs and ionospheric flows at the locations of the auroral spirals and along the auroral arcs. The combined ground and space observations suggest that each auroral spiral was powered by two oppositely rotating plasma flow vortices that caused a current enhancement in the substorm current wedge.

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Section: Instrumentationmentioning

confidence: 99%

THEMIS ground-space observations during the development of auroral spirals

et al. 2009

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“…Moreover, evidence is given that the space vortices contributed to the field-aligned current of the SCW by applying equation (2) and by comparison with model results of a reconstructed SCW. Properties of one space vortex are described using multipoint measurement from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft [Angelopoulos, 2008;Sibeck and Angelopoulos, 2008;Bester et al, 2008;Auster et al, 2008;McFadden et al, 2008;D. Larson et al, Solid state telescope for THEMIS, manuscript in preparation, 2009).…”

Section: Introductionmentioning

confidence: 99%

Substorm current wedge driven by plasma flow vortices: THEMIS observations

et al. 2009

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[1] A multipoint analysis of conjugate magnetospheric and ionospheric flow vortices during the formation of the substorm current wedge (SCW) on 19 February 2008 is presented. During the substorm, four Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft were located close to the neutral sheet in the premidnight region between 9 and 12 R E geocentric distance, of which three closely ($1-2 R E ) clustered at $23 MLT and one was farther west at $21 MLT. The closely clustered spacecraft were engulfed by a counterclockwise plasma flow vortex, while the single spacecraft recorded a clockwise plasma flow vortex. Simultaneously, a pair of conjugate flow vortices with clockwise and counterclockwise rotation appeared in the ionosphere, as inferred from equivalent ionospheric currents. The counterclockwise space vortex, which corresponded to a downward field-aligned current, was at least 1-2 R E in diameter and had rotational flow speeds of up to 900 km/s. Current density estimates associated with the formation of the space vortex in the first 30 s yielded 2.8 nA/m 2 (14 mA/m 2 mapped to the ionosphere), or a total current of 1.1 Â 10 5 A. Model calculations based on midlatitude ground magnetometer data show a gradual increase of the field-aligned current, with 1-2 Â 10 5 A within the first minute and a peak value of 7 Â 10 5 A after 10 min, associated with the SCW, and a matching meridian of the downward current of the SCW and the downward current (counterclockwise) space vortex. The combined ground and space observations, together with the model results, present a scenario in which the space vortices generated the field-aligned current of the SCW at the beginning of the substorm expansion phase and coupled to the ionosphere, causing the ionospheric vortices.

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“…[3,5] The THEMIS and ARTEMIS probes were designed and implemented as spin-stabilized instrument platforms with a nominal spin rate of 20 rpm. Two pairs of spin-plane wire booms extending out to ±25 m and ±20 m, respectively, two axial stacer booms, and two magnetometer booms were deployed on orbit.…”

Section: Concept Of Operationsmentioning

confidence: 99%

“…The probes were labeled P1-P5, counting from the longest to the shortest orbit period at the time of completion of the initial constellation deployment in early 2008. [2,3] THEMIS successfully completed its primary mission phase in 2009. For the extended mission, THEMIS was split into two new missions.…”

Section: Introductionmentioning

confidence: 99%

ARTEMIS operations - Experiences and lessons learned

Bester

Cosgrove

Frey

et al. 2014

2014 IEEE Aerospace Conference

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THEMIS, a constellation of five spacecraft, referred to as probes, was launched in 2007 to study the physical processes leading to the aurora. In 2009, THEMIS successfully completed its primary mission phase. As an ambitious mission extension, the constellation was then split into two new missions -THEMIS-Low and ARTEMIS. THEMIS-Low refers to three of the five probes that continued magnetospheric observations in Earth orbits while the remaining two probes started a new lunar mission called ARTEMIS. The two ARTEMIS probes were transferred from Earth to lunar orbits via low-energy trajectories with Earth and lunar gravity assists. The complex mission design and navigation operations took the two probes on trajectories along weak stability boundary manifolds, venturing out as far as 1,500,000 km and 1,200,000 km from Earth, respectively. Upon arrival in the lunar environment, both probes were first inserted into libration point orbits where they spent up to ten months collecting science data. Periodic stationkeeping maneuvers were executed to ensure the two probes would not be ejected from these unstable orbits. In 2011, both probes were successfully inserted into stable, retrograde and prograde lunar orbits, respectively. We report on the challenges with executing the complex navigation plans, discuss experiences and lessons learned from operating two spacecraft in lunar libration point orbits for the first time ever, and finally cover mission planning and science operations in the lunar environment.

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THEMIS Operations

Cited by 18 publications

References 13 publications

THEMIS ground-space observations during the development of auroral spirals

THEMIS ground-space observations during the development of auroral spirals

Substorm current wedge driven by plasma flow vortices: THEMIS observations

ARTEMIS operations - Experiences and lessons learned

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