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2 recordsLinked to original sources
USGS2008

TandEM: Titan and Enceladus mission

TandEM was proposed as an L-class (large) mission in response to ESA’s Cosmic Vision 2015–2025 Call, and accepted for further studies, with the goal of exploring Titan and Enceladus. The mission concept is to perform in situ investigations of two worlds tied together by location and properties, whose remarkable natures have been partly revealed by the ongoing Cassini–Huygens mission. These bodies still hold mysteries requiring a complete exploration using a variety of vehicles and instruments. TandEM is an ambitious mission because its targets are two of the most exciting and challenging bodies in the Solar System. It is designed to build on but exceed the scientific and technological accomplishments of the Cassini–Huygens mission, exploring Titan and Enceladus in ways that are not currently possible (full close-up and in situ coverage over long periods of time). In the current mission architecture, TandEM proposes to deliver two medium-sized spacecraft to the Saturnian system. One spacecraft would be an orbiter with a large host of instruments which would perform several Enceladus flybys and deliver penetrators to its surface before going into a dedicated orbit around Titan alone, while the other spacecraft would carry the Titan in situ investigation components, i.e. a hot-air balloon (Montgolfière) and possibly several landing probes to be delivered through the atmosphere.

Experimental Astronomy↗
USGS2011

Neither a year nor an annus can be a derived unit in the SI

The year is not a unit of the SI. The only SI unit of measurement for time is the second. The word “annus” or “annum” does not appear anywhere in the current SI document. The word “year” is not in the table of “Non-SI units accepted for use with the International System of Units,” nor in the table of “Non-SI units whose values in SI units must be obtained experimentally,” nor even in the table of “Other non-SI units.” The year can be found, however, through the list of “Other non-SI units not recommended for use.” This heading directs the reader to a National Institute of Standards and Technology (NIST) list where three kinds of year (365 days, sidereal, and tropical) are given with conversion to seconds, but are set in type to indicate “in general not to be used in NIST publications.” Table 1 summarizes some of the uses of the year in other publications. For example, in the IUPAC chemistry document, the year is not a constant; in the International Astronomy Union Style Guide, the year (Julian) is a constant.

Chemistry International↗