MODIS - Moderate Resolution Imaging Spectrometer (on Terra Satellite, USA)

The Moderate-resolution Imaging Spectroradiometer (MODIS) is a key instrument aboard the NASA's Terra and Aqua satellites. Terra was successfully launched from Vandenberg Air Force Base, CA, on December 18, 1999, carrying the MODIS Proto-Flight Model (PFM). PFM began collecting data on February 24th, 2000. The Aqua satellite, which will also carry the MODIS instrument, is planned to be launched in late 2001. Terra MODIS is viewing the entire Earth's surface every 1 to 2 days, acquiring data in 36 spectral bands. These data, along with data from a second MODIS (which is being developed for the Aqua satellite), will improve understanding of global dynamics and processes occurring on the land, in the oceans, and in the lower atmosphere. MODIS is playing a vital role in the development of validated, global, interactive Earth system models able to predict global change accurately enough to assist policy makers in making sound decisions concerning the protection of our environment. MODIS Instrument Characteristics Orbit: 705 km, 10:30 a.m. descending node (Terra) or 1:30 p.m. ascending node (Aqua), sun-synchronous, near-polar, circular Scan Rate: 20.3 rpm, cross track Swath Dimensions: 2330 km (cross track) by 10 km (along track at nadir) Telescope: 17.78 cm diam. off-axis, afocal (collimated), with intermediate field stop Size: 1.0 x 1.6 x 1.0 m Weight: 228.7 kg Power: 162.5 W (single orbit average) Data Rate: 10.6 Mbps (peak daytime); 6.1 Mbps (orbital average) Quantization: 12 bits Spatial Resolution: 250 m (bands 1-2) 500 m (bands 3-7) 1000 m (bands 8-36) Design Life: 6 years Primary Use Band Bandwidth1 Spectral Radiance2 Required SNR3 Land/Cloud/Aerosols Boundaries 1 620 - 670 21.8 128 2 841 - 876 24.7 201 Land/Cloud/Aerosols Properties 3 459 - 479 35.3 243 4 545 - 565 29.0 228 5 1230 - 1250 5.4 74 6 1628 - 1652 7.3 275 7 2105 - 2155 1.0 110 Ocean Color/ Phytoplankton/ Biogeochemistry 8 405 - 420 44.9 880 9 438 - 448 41.9 838 10 483 - 493 32.1 802 11 526 - 536 27.9 754 12 546 - 556 21.0 750 13 662 - 672 9.5 910 14 673 - 683 8.7 1087 15 743 - 753 10.2 586 16 862 - 877 6.2 516 Atmospheric Water Vapor 17 890 - 920 10.0 167 18 931 - 941 3.6 57 19 915 - 965 15.0 250 Primary Use Band Bandwidth1 Spectral Radiance2 Required NE[delta]T(K)4 Surface/Cloud Temperature 20 3.660 - 3.840 0.45(300K) 0.05 21 3.929 - 3.989 2.38(335K) 2.00 22 3.929 - 3.989 0.67(300K) 0.07 23 4.020 - 4.080 0.79(300K) 0.07 Atmospheric Temperature 24 4.433 - 4.498 0.17(250K) 0.25 25 4.482 - 4.549 0.59(275K) 0.25 Cirrus Clouds Water Vapor 26 1.360 - 1.390 6.00 150(SNR) 27 6.535 - 6.895 1.16(240K) 0.25 28 7.175 - 7.475 2.18(250K) 0.25 Cloud Properties 29 8.400 - 8.700 9.58(300K) 0.05 Ozone 30 9.580 - 9.880 3.69(250K) 0.25 Surface/Cloud Temperature 31 10.780 - 11.280 9.55(300K) 0.05 32 11.770 - 12.270 8.94(300K) 0.05 Cloud Top Altitude 33 13.185 - 13.485 4.52(260K) 0.25 34 13.485 - 13.785 3.76(250K) 0.25 35 13.785 - 14.085 3.11(240K) 0.25 36 14.085 - 14.385 2.08(220K) 0.35 1 Bands 1 to 19 are in nm; Bands 20 to 36 are in µm 2 Spectral Radiance values are (W/m2 -µm-sr) 3 SNR = Signal-to-noise ratio 4 NE(delta)T = Noise-equivalent temperature difference Note: Performance goal is 30-40% better than required

ENVISAT - MERIS - Medium Resolution Imaging Spectrometer (on ENVISAT Satellite, European Space Agancy)

MERIS is a medium resolution imaging instrument to be carried aboard the ESA's Envisate satellite. The Envisat satellite is scheduled to be launched in November 2001.

The primary mission of MERIS is primarily dedicated to ocean and coastal sea water colour observations. Knowledge of the sea colour can be converted into a measurement of chlorophyll pigment concentration, suspended sediment concentration and of aerosol loads over the marine domain. The instrument can also be used for atmospheric and land surface related studies.

The global mission of MERIS will have a major contribution to scientific projects which seek to understand the role of the oceans and ocean productivity in the climate system through observations of water colour and will further our ability to forecast change through models. Secondary objectives of the MERIS mission will be directed to the understanding of atmospheric parameters associated with clouds, water vapour and aerosols in addition to land surface parameters, in particular vegetation processes.

MERIS will have a high spectral and radiometric resolution and a dual spatial resolution (1200m and 300m), within a global mission covering open ocean and coastal zone waters and a regional mission covering land surfaces.

MERIS is designed to acquire 15 spectral bands in the 390 - 1040 nm range. One of the most outstanding features of MERIS is the programmability of its spectral bands in their width and position, in accordance with the priorities of the mission.

The above table has been derived for oceanographic and interdisciplinary applications. The exact position of the MERIS spectral bands will be determined following a detailed spectral characterization of the instrument. The spectral range is restricted to the visible near-infrared part of the spectrum between 390 and 1040 nm. The spectral bandwidth is variable between 1.25 and 30 nm depending on the width of a spectral feature to be observed and the amount of energy needed in a band to perform an adequate observation. Over open ocean an average bandwidth of 10 nm is required for the bands located in the visible part of the spectrum. Driven by the need to resolve spectral features of the Oxygen absorption band occurring at 760 nm a minimum spectral bandwidth of 2.5 nm is required.

ADEOS - GLI - Global Imager (on ADEOS-2 Satellite, Japan)

GLI is an optical sensor developed by NASDA, to be carried on board the NASDA's ADEOS-2 satellite, scheduled to be launched in 2002. It observes the reflected solar radiation from the Earth's surface, including land, oceans and clouds and/or infrared radiation with a multi-channel system for measuring the biological content, such as chlorophyll, organic substance, and vegetation index as well as temperature, snow and ice, and cloud distribution. These data will be used for understanding the global circulation of carbon and climate changes.

The GLI will be equiped with 36 spectral channels from visible to infrared wavelengths. It has many visible channels, especially for ocean color observations. Its wide dynamic range is suitable for land observation. The resolution for all channels is 1-km for global coverage. However, there are six 250 m resolution channels covering the wavelength bands similar to those present in LANDSAT-TM.