What is "themis"

Themis \The"mis\, n. [L., fr. Gr. ?, fr. ? that which is laid down or established by usage, law, prob. fr. ? to set, place.] (Gr. Myth.) The goddess of law and order; the patroness of existing rights.

Greek goddess of law and justice, the name means "custom, right," literally "that which is laid down or established" (by custom); also "laws, ordinances," but closer in sense to Latin jus than lex; related to thema "proposition; that which is placed" (see theme).

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 data can be accessed using the SPEDAS software.

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 slightly less than that of Hyperion. The period was supposedly 20.85 days, with prograde motion.

Pickering estimated the diameter at , but since he also gave as the diameter of Phoebe, he was clearly overestimating the albedo; using the modern figure for Phoebe gives Themis a diameter of .

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).

Pickering was awarded the Lalande Prize of the French Academy of Sciences in 1906 for his "discovery of the ninth and tenth satellites of Saturn".

The actual tenth satellite of Saturn (in order of discovery) was Janus, which was discovered in 1966 and confirmed in 1980. Its orbit is far from the supposed orbit of Themis.

There is also an asteroid named 24 Themis.

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

Themis can also refer to

The THEMIS solar power tower is a research and development centre focused on solar energy. It is located near the village of Targassonne, in the department of Pyrénées-Orientales, south of France, 3 kilometres from the world's largest solar furnace in Odeillo.