SeaWiFS Global Biosphere

Ocean Floor Depth

Tl&'jlnl ;Vjfl'-JI auuJxly pkit-al imii Lifer aid laaJ iLpiiaii Ol I a Fain ll:\ ML hi l.-114H1-h.il ia

SflffKmbef 1MB. i i utvU^ Half's riilliie MH1 ¿fck'P'f HSU kIbCNWIMl-¡h'till jSiATik MlHld pilliVI". IB prJTHY fmiklll iSI IIBi. U0 UN1-* II KMn I fc.1 Illh1 <Vfl*l '¿ill Iv lud I1" 111 d HI -J J r ■ I Jl'.i pwüirl Ihc .-.'iri'iiiL id nail««: KEtrdcrs Lt> cr.'i11 li3kxI: J ttai^,-.

Tl&'jlnl ;Vjfl'-JI auuJxly pkit-al imii Lifer aid laaJ iLpiiaii Ol I a Fain ll:\ ML hi l.-114H1-h.il ia

SflffKmbef 1MB. i i utvU^ Half's riilliie MH1 ¿fck'P'f HSU kIbCNWIMl-¡h'till jSiATik MlHld pilliVI". IB prJTHY fmiklll iSI IIBi. U0 UN1-* II KMn I fc.1 Illh1 <Vfl*l '¿ill Iv lud I1" 111 d HI -J J r ■ I Jl'.i pwüirl Ihc .-.'iri'iiiL id nail««: KEtrdcrs Lt> cr.'i11 li3kxI: J ttai^,-.

Fig. 7.11 Average distribution of phytoplankton chlorophyll in the global ocean (and also terrestrial vegetation) over an 11-month period in 1997-98, derived from SeaWiFS data. Provided by the SeaWiFS Project, NASA/ Goddard Space Flight Center and ORBIMAGE.

Half Underwater Pond Ecosystem
Fig. 9.5 Mixed coastal phytoplankton, Tasmania, Australia. (Courtesy Ian Jameson, CSIRO Marine & Atmospheric Research.)
Fig. 7.5 SeaWiFS instrument shown deployed on the Seastar™ spacecraft. By permission, Orbital Sciences Corporation, USA.

(launched in May 2002) passes south to north across the equator in the afternoon. Between them they view the entire Earth's surface every one to two days, measuring radiance in 36 wavebands in the visible, near-infrared and infrared.924 For ocean colour, there are seven —10 nm bands in the visible region, centred on 412, 442, 488, 531, 551, 667 and 678 nm, plus two in the near-infrared centred on 748 and 870 nm, for atmospheric correction. The optical system uses a continuously rotating double-sided mirror to scan through ±55°, achieving a cross-track swath width of 2330 km, with 1 km resolution. Radiance values are 12-bit digitized.

The Indian IRS-P4 (Oceansat) satellite, launched in 1999, carries the Ocean Colour Monitor (OCM) sensor, which operates in six visible wavebands - 414, 442, 489, 512, 557 and 670 nm, with 20 nm bandwidth. It also has two near-infrared bands - 768 and 867 nm, with 40 nm bandwidth, for atmospheric correction. Digitization is 12 bit. The instrument, which is of the pushbroom type, has separate wide-angle optics and a linear array CCD detector for each of the eight spectral channels: it can be tilted in the along-track direction to avoid sunglint. The cross-track swath width is —1420 km, with a 360 x 250 m instantaneous field of view. Oceansat travels in a sun-synchronous polar orbit at 720 km.

China has launched a series of meteorological satellites, all with the name Feng Yun ('Wind and Cloud'). Feng Yun 1C, launched in 1999, carried the Multichannel Visible and Infrared Scan Radiometer (MVISR), with rather broad bands (50 nm) in the visible centred on 455, 505, 555, 630 and 685 nm. The spacecraft was in sun-synchronous polar orbit at an altitude of 858 km. Feng Yun 1C had the dubious distinction of being the first space satellite to be destroyed by an antisatellite weapon, fired from Xichang (China) on 11 January 2007. It was replaced in orbit by Feng Yun 1D, with the same sensor.

In November 2000, NASA launched the Earth Observing 1 (EO-1) satellite, which carries three sensors intended primarily for terrestrial observation, but two of which - Hyperion and Advanced Land Imager -are of some value also for marine and inland aquatic systems. EO-1 is flying in formation with Landsat 7 in a sun-synchronous, near-polar orbit at 705 km. The Hyperion sensor is a hyperspectral imager that provides 220 contiguous 10-nm bands from 400 to 2500 nm. It has a much higher ground-level resolution (30 m) than the ocean colour sensors described above, but a correspondingly narrower swath (7.7 km). The Advanced Land Imager (ALI) is a pushbroom instrument, which has four rather broad bands (433-453, 450-515, 525-605 and 630-690 nm)

in the visible and another five in the near-infrared. The swath width is 37 km with 30 m ground-level resolution.

A number of new ocean colour sensors are scheduled to be launched into space in the next few years. These are listed in Table 7.1, together with their optical, and other, characteristics and the proposed launch dates. An additional instrument currently under development is the Ocean Ecosystem Spectrometer (OES), which will fly as part of the Aerosol, Cloud and Ocean Ecosystem mission (ACE), and will be constructed by NASA with international partners (ACE mission overview report - McClain 2009 (available on Web), and Paula Bontempi, personal communication). It is intended to have 86 hyperspectral bands covering the visible/near-infrared range (350-1000 nm), and three short-wave infrared bands. A resolution of 5 nm is aimed for in the 350 to 755 nm range. Four 10 nm bands (667, 678, 710 and 748 nm) will be assigned to chlorophyll fluorescence measurement, and five bands (at wavelengths from 748 to 1640 nm) will be used for aerosol correction. It will have 58.3° cross-track scanning, a 20° sensor tilt for glint avoidance, and a 1 km spatial resolution at the nadir. The satellite will have a sun-synchronous orbit, permitting two-day global coverage of ocean radiometer measurements. The tentative launch date is 2017/18.

0 0

Post a comment