As early as 1960, Farquhar (1960, 1968) proposed the Lagrange-1 (L-1) point as an ideal deep space location for Earth and solar observations. Triana will be the first Earth-observing mission to the Earth/Sun L-1 point . From this stable vantage, the satellite will have a continuous view of the entire sunlit face of the rotating Earth 1.5 million km away. Named for the sailor on Columbus‚s voyage who first spotted the New World, Triana is an exploratory mission to investigate the scientific and technological advantages of L-1 for Earth observation. The L-1 perspective provides a global, all-day view from sunrise to sunset, where daily climatological phenomenon will unfold in clear view of Triana's instrumentation. This will allow for continuous measurements over large areas for long periods of time; a viewpoint that is not possible from Low Earth Orbit (LEO) and Geosynchronous Earth Orbit (GEO) satellites. Hourly variations in the atmosphere will be clearly observed simultaneously over widely dispersed geographic areas.
Global climatic studies focus heavily on determining the interaction of incoming solar radiation with clouds and other constituents of the Earth's atmosphere. Triana is flying three scientific instruments that will make a broad set of measurements in this field, some unique to this mission, others collaborative with data from other sources, and some complementary to previous work. Taken together as a whole, this data will make significant advances in completing the "patchwork mosaic" of geographically and time-of-day restricted measurements collected by other observing platforms.
This paper discusses the unique features of the Triana deep space Earth and Solar observatory. The instrumentation is briefly described and some details are presented in the appendices. The planned retrievals are essentially similar to those possible from LEO and GEO, but with the unique added value of combining high time resolution and synoptic view (daytime only).
Triana will provide a global synoptic (i.e. simultaneous over the entire globe) view of water vapor, aerosols, column ozone, upper troposphere winds, stratospheric wave structures and circulation, cloud amount and properties, albedos, and aerosols, plus accurate broadband measurements of the Earth's reflected and emitted radiation from 0.2 to 100 µm. This comprehensive and synoptic view of the Earth will enable us to test and develop new understanding of the climate system. The quantities retrieved from the Triana measurements (data products) will be used to address a variety of scientific problems and generate new applications.
Triana carries a combination of three new instruments: the Scripps-Earth Polychromatic Imaging Camera (EPIC) 10-channel telescope-spectroradiometer, the Scripps-NIST Advanced Radiometer (NISTAR) four-channel radiometer (three absolute cavities plus one photo-diode), and the Goddard Space Flight Center (GSFC) Plasma-Mag solar weather magnetometer, electron spectrometer, and Faraday cup. Triana will obtain entirely new observations of the Earth's atmosphere and surface, its radiation balance, and the Earth's space environment. A small, highly capable spacecraft, the GSFC SMEX-Lite, will support the instruments in orbit and provide the data transmission capabilities.