Orbits
The five THEMIS spacecraft (probes) were placed in highly elliptical orbits where the spacecraft line up at apogee every four days. The apogee rotates slowly around the Earth to cover the dayside, dawnside, nightside, and duskside of the magnetosphere. Initially, right after launch in 2007, the 5 THEMIS spacecraft were lined up in the same orbit. Since 2011, P1 and P2 have become ARTEMIS and orbit the moon, while the 3 remaining Earth-orbiting THEMIS probes are able to synergize observations with other Heliophysics System Observatory (HSO) missions such as Van Allen Probes (VAP), Magnetospheric Multiscale (MMS), CLUSTER (CL), Geotail (GT) and Arase (ARA).
Stage 56: Dusk Science Phase, HSO Optimization
11/15/22 - 02/25/23
In the dusk science phase the apogee of P3, P4, and P5 are approximately 13 Re. THM-MMS-CLUSTER in clustered orbits.
Stage 55: Tail Science Phase, HSO Optimization
07/31/22 - 11/14/22
In the tail science phase the apogee of P3, P4, and P5 are approximately 13 Re. THM-MMS-CLUSTER in clustered orbits, to study nightside reconnection.
Stage 54: Dawn Science Phase, HSO Optimization
04/25/22 - 07/30/22
In the dawn science phase the apogee of P3, P4, and P5 are approximately 13 Re. THM-MMS-CLUSTER in clustered orbits.
Stage 53: Dayside Science Phase, HSO Optimization
01/05/22 - 04/24/22
In the dayside science phase the apogee of P3, P4, and P5 are approximately 13 Re. THM-MMS-CLUSTER in clustered orbits, to study dayside and foreshock phenomena.
Stage 52: Dusk Science Phase, HSO Optimization
09/31/21 - 01/04/22
In the dusk science phase the apogee of P3, P4, and P5 are approximately 13 Re. THM-MMS-CLUSTER in clustered orbits.
Stage 51: Tail Science Phase, HSO Optimization
07/01/21 - 09/30/21
In the tail science phase the apogee of P3, P4, and P5 are approximately 13 Re. THM-MMS-CLUSTER on resonant orbits, to study the drivers and consequences of tail reconnection.
Stage 50: Dawn Science Phase, HSO Optimization
03/15/21 - 06/30/21
In the dawn science phase the apogee of P3, P4, and P5 are approximately 13 Re. THM-MMS-CLUSTER in clustered orbits. THM explores magnetopause reconnection in response to drivers from foreshock transients.
Stage 49: Dayside Science Phase, HSO Optimization
12/01/20 - 03/14/21
In the dayside science phase the apogee of P3, P4, and P5 are approximately 13 Re. MMS is also in the dayside. THM-MMS on resonant orbits, to study the kinetic/regional drivers of reconnection at the magnetopause.