THEMIS

Swales Aerospace, now part of Orbital ATK which is now part of Northrop Grumman, Beltsville, Maryland, manufactured all five probes for this mission. Each was built-up and tested at the Beltsville facility, before being delivered to University of California, Berkeley for instrument integration. Swales was responsible for integrating the BAU, IRU, Solar arrays, antenna, battery, and other components necessary for functionality. This was the second major satellite built by Swales, the first being the Earth Observing-1 (EO-1) spacecraft, which continues to orbit Earth. Swales was also responsible for designing and building the Electrical Ground Support Equipment (EGSE) used for monitoring the probes during all phases of pre-launch activities, including use at the launch site.

After the installation of instruments at SSL, Berkeley, pre-launch testing including thermal-vacuum, vibration and acoustic tests, was conducted at NASA's Jet Propulsion Laboratory in Pasadena, California.

The launch of THEMIS atop the Delta II 7925-10C launch vehicle, at SLC-17B, Cape Canaveral

THEMIS was originally scheduled to launch on 19 October 2006. Owing to delays caused by workmanship problems with Delta II second stages — an issue that also affected the previous mission, STEREO — the THEMIS launch was delayed to 15 February 2007. Due to weather conditions occurring on 13 February 2007, fueling of the second stage was delayed, and the launch pushed back 24 hours. On 16 February 2007, the launch was scrubbed in a hold at the T-4 minute point in the countdown due to the final weather balloon reporting a red, or no-go condition for upper-level winds. A 24-hour turnaround procedure was initiated, targeting a new launch window between 23:01 and 23:17 UTC on 17 February 2007.

Favorable weather conditions were observed on 17 February 2007, and the countdown proceeded smoothly. THEMIS successfully launched at 23:01:00 UTC. The spacecraft separated from the launch vehicle approximately 73 minutes after liftoff. By 03:07 UTC, on 18 February, mission operators at the Space Sciences Laboratory (SSL) of the University of California, Berkeley, commanded and received signals from all five spacecraft, confirming nominal separation status.

The launch service was provided by the United Launch Alliance through the NASA Launch Services Program (LSP).

The Fast Auroral SnapshoT Explorer (FAST) mission supported THEMIS in 2008 and 2009 before being retired.[8] FAST was a Small Explorer program (SMEX) mission launched in 1996.[8]

From 15 February 2007 until 15 September 2007, the five THEMIS satellites coasted in a string-of-pearls orbital configuration. From 15 September until 4 December 2007, the satellites were moved to more distant orbits in preparation for data collection in the magnetotail. This phase of the mission was called the "Dawn Phase" because the satellites' orbits were in apogee on the dawn side of the magnetosphere. On 4 December 2007, the first tail science phase of the mission began. In this segment of the mission scientists will collect data from the magnetotail of the Earth's magnetosphere. During this phase the satellites' orbits are in apogee inside the magnetotail. The scientists hope to observe substorms and magnetic reconnection events. During these events charged particles stored in the Earth's magnetosphere are discharged to form the aurora borealis. Tail science is performed in the winter of the northern hemisphere because the ground magnetometers that Themis scientists correlate the satellite data with have relatively longer periods of night. During the night, observations are not interrupted by charged particles from the Sun.[9]

In 2007, THEMIS "found evidence of magnetic ropes connecting Earth's upper atmosphere directly to the Sun", reconfirming the theory of solar-terrestrial electrical interaction (via "Birkeland currents" or "field-aligned currents") proposed by Kristian Birkeland circa 1908.[10][11] NASA also likened the interaction to a "30 kiloVolt battery in space", noting the "flux rope pumps 650,000 Ampere current into the Arctic!"[12]

On 26 February 2008, THEMIS probes were able to determine, for the first time, the triggering event for the onset of magnetospheric substorms.[13] Two of the five probes, positioned approximately one third the distance to the Moon, measured events suggesting a magnetic reconnection event 96 seconds prior to Auroral intensification.[14] Vassilis Angelopoulos of the University of California, Los Angeles, who is the principal investigator for the THEMIS mission, claimed, "Our data show clearly and for the first time that magnetic reconnection is the trigger".[15]

ARTEMIS

Not to be confused with Artemis program, a NASA attempt to return humans to the Moon by 2025, or the European Geostationary Navigation Overlay Service satellite ARTEMIS.

ARTEMIS probes in lunar orbit

In early 2010, ARTEMIS-P1 (THEMIS-B) performed two lunar flybys and one Earth flyby, and approached insertion into a Lissajous orbit around a lunar Lagrange point. Lunar orbit insertion was targeted for April 2011. ARTEMIS-P2 (THEMIS-C) completed a lunar flyby and was on the inbound leg of the first of three deep space excursions on its way to a Lissajous orbit and was targeted for lunar orbit in April 2011.[16]

On 22 June 2011, ARTEMIS-P1 began firing its thrusters to move out of its kidney-shaped libration orbit on one side of the Moon, where it had been since January 2011.[17] On 2 July 2011 at 16:30 UTC, ARTEMIS-P1 entered lunar orbit. The second spacecraft, ARTEMIS-P2, moved into lunar orbit on 17 July 2011.[18] Along the way, the two spacecraft were the first to ever achieve orbit around the Moon's Lagrange points.[17][19]

As of October 2019, both lunar probes are in stable orbits, and are expected to remain operational for a long time.[5]

Animation of THEMIS-B

Geocentric orbit phase

Trans-lunar injection phase

Lissajous orbit phase

Selenocentric orbit phase

  THEMIS-B ·   Earth ·   Moon

The THEMIS instruments have been used to track whistler-mode chorus waves during can persist in periods of low geomagnetic activity.[21][22]

• Explorer program

Wikimedia Commons has media related to THEMIS (satellite).

Wikinews has related news:

• Aurora Borealis caused by electrical space tornadoes

• NASA THEMIS page
• THEMIS mission page (UCB)
• THEMIS Mission Profile by NASA's Solar System Exploration
• Space Ref news release Archived 12 February 2021 at the Wayback Machine
• Canadian Ground-based observatory web page
• Berkeleyan Launch Coverage
• See page 8 in this document for antenna reference
• THEMIS email lists Archived 19 August 2019 at the Wayback Machine