h channels given in Table 4.
Figure 13: IFOV of TOMS projected onto Earth's surface (image credit: NASA)
Legend to Figure 13: The right portion (samples 1-19) of two consecutive scans are shown, and a portion of a scan from the previous orbit is also shown to illustrate the inter-orbit coverage at the equator. In descending mode (North to South) ADEOS/TOMS scans West to East.
Table 4: ADEOS/TOMS albedo calibration constants and gain range ratios
ADEOS-TOMS operations, data processing and data distribution are conducted by the Science Operation Center (SOC) at Goddard Space Flight Center. The SOC processes all near-real-time data obtained at US receiving stations and JAXA's EOC (Earth Observation Center). The preliminary Level 3' data set is available to science or operational users via Internet.
Figure 14: Photo of the TOMS instrument (image credit: NASA)
Figure 15: Sample ozone image of the TOMS instrument on ADEOS (image credit: NASA) 29)
POLDER (Polarization and Directionality of the Earth's Reflectances):
POLDER is a passive optical imaging radiometer of CNES (as passenger instrument on ADEOS). Objectives: Observation of bidirectionality and polarization of the solar radiation reflected by the atmosphere: tropospheric aerosols (inversion of the physical properties); ocean color (accurate determination of sea surface reflectances); land surfaces (determination of surface BRDF and improvement in the correction of the surface bidirectional and atmospheric effects on vegetation indices); Earth radiation budget (determination of cloud BRDF and classification of clouds according to their bidirectional properties). POLDER is capable to observe an area from various directions along with the spectral characteristics of the reflected solar light. 30) 31) 32) 33) 34) 35) 36)
a) Measurement of polarized reflectance in VIS/NIR
Six of POLDER's eight frequencies are optimized for observing atmospheric aerosols, clouds, ocean color, and land surfaces. The other two frequencies are centered on the H2O and O2 absorption bands for retrieving atmospheric water vapor amount and cloud top height, respectively.
Measurement channels: 15 channels (three channels for each polarized band) Swath width = 1440 km x 2200 (across-track) km, ground spatial resolution of 7 km x 6 km at nadir. Data rate: 0.882 Mbit/s, 12 bit quantization. Operation requirements: global observation of the Earth with more than 15º of solar elevation, simultaneous operation with OCTS.
Figure 16: Observation concept of POLDER (image credit: CNES)
POLDER is a 2-D detector array wide-field-of-view, multi-band imaging radiometer/polarimeter. Multi-angle viewing is achieved by the along-track migration of the S/C of a quasi-square footprint. The optical detection unit of the POLDER consists of a telecentric lens, a rotating wheel supporting filters and polarizers, and a matrix CCD sensor (242 x 548 photoelements, the pixels are binned one by two, resulting in 242 x 274 sensitive areas).
The instrument has a focal length of 3.57 mm, f/4.6, FOV=±43º along-track, FOV=±51º across-track, FOV=±57º diagonal. Instrument mass= 33 kg, power=42 W.
Table 5: Spectral characteristics of POLDER
Figure 17: Optical design of the POLDER instrument (image credit: CNES)
Legend to Figure 18: The image is a blue, green and red color composite of POLDER measurements at 443 nm, 670 nm and 865 nm. Marked differences appear between the clouds (in white) and different types of surfaces: vegetation in red, soil in brown and yellow, sea in dark blue. The bright spot in the Mediterranean sea, West of Sardinia, is the sunglint pattern. More than 15000 such images are taken every day by POLDER on ADEOS providing a daily global coverage of the Earth in eight spectral channels of the visible and near infrared spectrum.
Figure 19: Illustration of POLDER Ocean Color products: from daily (Level 2) to 10-day and monthly syntheses (Level 3) over the Mediterranean basin (image credit: LOA/ LPCM/ LSCE/ CNES/JAXA)
IMG (Interferometric Monitor for Greenhouse Gases):
IMG is a MITI-funded sensor developed by JAROS (Japa