THEMIS

The Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission was originally a constellation of five NASA satellites (THEMIS A through THEMIS E) to study energy releases from Earth's magnetosphere known as substorms, magnetic phenomena that intensify auroras near Earth's poles. The name of the mission is an acronym alluding to the Titan, Themis.

Three of the satellites remain in the magnetosphere, while two have been moved into orbit near the Moon. Those have been renamed ARTEMIS for Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun. THEMIS B became ARTEMIS P1 and THEMIS C became ARTEMIS P2.

The THEMIS satellites were launched February 17, 2007 from Cape Canaveral Air Force Station Space Launch Complex 17 aboard a Delta II rocket. Each satellite carries identical instrumentation, including a fluxgate magnetometer (FGM), an electrostatic analyzer (ESA), a solid state telescope (SST), a search-coil magnetometer (SCM) and an electric field instrument (EFI). Each has a mass of 126 kg, including 49 kg of fuel.

Themis

Themis /ˈθiːmᵻs/ (Greek: Θέμις) is an ancient Greek Titaness. She is described as "of good counsel", and is the personification of divine order, law, natural law and custom. Themis means "divine law" rather than human ordinance, literally "that which is put in place", from the Greek verb títhēmi (τίθημι), meaning "to put".

To the ancient Greeks she was originally the organizer of the "communal affairs of humans, particularly assemblies".Moses Finley remarked of themis, as the word was used by Homer in the 8th century BCE, to evoke the social order of the 10th- and 9th-century Greek Dark Ages:

Finley adds, "There was themis—custom, tradition, folk-ways, mores, whatever we may call it, the enormous power of 'it is (or is not) done'. The world of Odysseus had a highly developed sense of what was fitting and proper."

Mythology

The personification of abstract concepts is characteristic of the Greeks. The ability of the goddess Themis to foresee the future enabled her to become one of the Oracles of Delphi, which in turn led to her establishment as the goddess of divine justice.

Themis (hypothetical moon)

On April 28, 1905, William H. Pickering, who had seven years earlier discovered Phoebe, announced the discovery of a tenth satellite of Saturn, which he promptly named Themis. The photographic plates on which it supposedly appeared, thirteen in all, spanned a period between April 17 and July 8, 1904. However, no other astronomer has ever confirmed Pickering's claim.

Pickering attempted to compute an orbit, which showed a fairly high inclination (39.1° to the ecliptic), fairly large eccentricity (0.23) and a semi-major axis (1,457,000 kilometres (905,000 mi)) slightly less than that of Hyperion. The period was supposedly 20.85 days, with prograde motion.

Pickering estimated the diameter at 61 kilometres (38 mi), but since he also gave 68 kilometres (42 mi) as the diameter of Phoebe, he was clearly overestimating the albedo; using the modern figure for Phoebe gives Themis a diameter of 200 kilometres (120 mi).

Oddly, in April 1861, Hermann Goldschmidt had also believed that he had discovered a new satellite of Saturn between Titan and Hyperion, which he called Chiron. Chiron also does not exist (however, the name was used much later for the comet/asteroid 2060 Chiron).

Themis (disambiguation)

Themis is one of the original Oracle Titans in Greek mythology.

Themis can also refer to

Space

Technical, Educational

Medicine

Fiction

The Royal Navy frigate HMS Themis served as the fictional backdrop for British naval officer Charles Hayden, a heroic figure created by S. Thomas Russell in his Napoleonic era naval novels, including Under Enemy Colors,' (2007)' A Battle Won, (2010) and Take, Burn or Destroy (2012).