adeos klorofol

Journal of Oceanography, Vol. 54, pp. 383 to 399. 1998

383Copyright The Oceanographic Society of Japan.

OCTS Mission Overview

HIROSHI KAWAMURA1,2 and THE OCTS TEAM2*

1Center for Atmospheric and Oceanic Studies, Faculty of Science, Tohoku University, Sendai 980, Japan2OCTS team, NASDA Earth Observation Research Center, Roppongi First Building, 1-9-9, Roppongi, Minato-ku, Tokyo 106, Japan

(Received 1 April 1998; in revised form 2 September 1998; accepted 2 September 1998)

The Ocean Color and Temperature Scanner (OCTS) on board the Advanced EarthObserving Satellite (ADEOS) observed the chlorophyll-a concentration in the surfacelayer and sea surface temperature in global oceans from October 1996 to June 1997. TheOCTS team was formed in the National Space Development Agency of Japan (NASDA)Earth Observation Research Center (EORC) to develop algorithm, calibrate and validateOCTS products and promote OCTS data usage. Intensive efforts to improve the qualityof the OCTS products were made after the launch of ADEOS. Much sea-truth data wascollected, and the algorithms to retrieve the ocean parameters have been revised severaltimes. The OCTS data were distributed to the user community through the Internet whileOCTS was functioning. An overview of the OCTS mission is presented in this paper.

1. IntroductionThe Advanced Earth Observing Satellite (ADEOS)

was launched by an H-II launch vehicle on 17 August 1996,carrying eight different sensors for monitoring changes inthe global environment. Its operation was terminated on 30June 1997 following an unexpected accident of the satellite.The Ocean Color and Temperature Scanner (OCTS) onboard ADEOS observed the distribution of chlorophyll-a(Chl-a) in the surface layer of the oceans as well as seasurface temperature (SST). Although the ADEOS lifetimewas relatively short (about 10 months), OCTS left a huge,invaluable data set for oceanographic research.

In recent years, global environmental changes origi-nating from human activities have been reaching detectablelevels, causing much concern in regard to their possibleadverse impacts. The main objective of the ADEOS missionis to contribute to investigating phenomena of the Earthsystem through integrated observation of geophysical pa-rameters using the eight sensors. Of the eight sensors,NASA scatterometer and OCTS were dedicated tooceanographic studies and applications. Chl-a and SSTimages with 700 m spatial resolution were obtained togetherwith the surface wind vectors in the global oceans. Varioustypes of research are now being conducted using theseimages together with the other observation data. Because ofthe unique characteristics of the ADEOS mission, OCTSdata will continue to be of immense value to the oceano-

graphic community.Prior to this mission, the Coastal Zone Color Scanner

(CZCS) on board the Nimbus-7 satellite was the only sourceof global ocean color data. CZCS was launched in 1978 asa “proof-of-concept” instrument to demonstrate the feasi-bility of satellite ocean color remote sensing in monitoringChl-a distributions which are related to phytoplankton ac-tivities in the global oceans. CZCS operated until 1986 andcontributed greatly to the understanding of marine envi-ronment and the biological, biochemical and physical pro-cesses in the ocean (Abbott and Chelton, 1991; McClain,1993; Barale and Schlittenhardt, 1993; Mitchell, 1994). TheCZCS sensor, which had four visible wavebands plus one inthe near infrared and one in the thermal infrared band, wasthe first generation of ocean color sensors. After a decadebreak in ocean color monitoring, the OCTS sensor, a suc-cessor to CZCS, provided the only source of global, high-spatial-resolution ocean color data from November 1996 toJune 1997. OCTS can be considered a second-generationglobal ocean color sensor. It performed highly sensitivemultispectral observations of the ocean with eight visibleand near-infrared channels and four thermal infrared chan-nels.

The OCTS mission is reviewed in this paper. TheADEOS sensor and OCTS instruments are described inSubsections 2.1 and 2.2. The National Space DevelopmentAgency (NASDA) established the Earth Observation Re-search Center in 1995 and formed the OCTS team to developOCTS algorithms, calibrate and validate (Cal/Val) theproducts, and encourage OCTS data usage (Subsection 2.3).

Keywords:⋅Ocean Color andTemperatureScanner (OCTS),

⋅Advanced EarthObserving Satellite(ADEOS),

⋅bio-chemical-physical interac-tion,

⋅multi sensormission.

*The OCTS Team is formed by NASDA personnel andsupporting scientists listed in Appendix 1.

384 H. Kawamura and The OCTS Term

Table 1. Chrohology of ADEOS and OCTS, 1995–1998.

The OCTS team reorganized preexisting OCTS-related ac-tivities for generating OCTS products useful for scientificand application research. The main OCTS targets were 1)Chl-a, 2) SST of the global oceans, and 3) Land vegetationindex, and intensive efforts were made to improve quality ofthe OCTS products (Section 3). During the OCTS lifetime,much sea-truth and air-truth data was collected through theNASDA in situ projects and provided by the cooperatingresearchers (Subsection 3.3). Examples of the OCTS im-ages are presented in Section 4. Section 5 is devoted to

introducing dissemination of the OCTS products. Discus-sions of the ADEOS mission and oceanography are presentedin Section 6.

2. ADEOS Mission and OCTS Instruments

2.1 ADEOS and sensorsThe initial work on ADEOS feasibility began in 1987.

Actual development efforts commenced in 1990, and ADEOSwas launched in August 1996 after nine long years of

Fig. 1. ADEOS in orbit (NASDA, 1997). The acronyms are defined in Appendix 2.

OCTS Mission Overview 385

bility was 4,500 W. It had a sun-synchronous, subrecurrentpolar orbit with an altitude of 796.75 km and an inclinationangle of 98.50 degree. The ADEOS recurrent period was 41days and one cycle period 100.92 minutes. Descending localtime was set at about 10:30AM. Figure 2 shows an exampleof one-day orbits with the OCTS swaths.

ADEOS carried two core sensors (OCTS and AVNIR)and six Announcement of Opportunity (AO) sensors,

preparation (NASDA, 1997). Table 1 shows the history ofADEOS and OCTS for 1995 to 1998.

ADEOS was a large satellite with dimensions of 4 m ×4 m × 5 m as shown in Fig. 1. When the solar array paddle(3 m × 24 m) and the NASA scatterometer (NSCAT) weredeployed in space, ADEOS had a span of 11 m in the flightdirection and 29 m in the perpendicular direction. Its launchmass was 3,500 kg, and its in-orbit power generation capa-

Table 2. Sensors aboard ADEOS.

Fig. 2. ADEOS orbits and OCTS coverage on 25 February 1997. Blue swaths show regions observed by the OCTS ocean-high gain,yellow the ocean-normal gain, and red the land gain.


NSCAT, TOMS, POLDER, IMG, ILAS and RIS. The in-strument providers and the main targets of each sensor interms of the Earth environment studies are listed in Table 2,and the acronyms are defined in Appendix 2. The sensorswere provided by five organizations in Japan, the US andFrance, which made the ADEOS mission international andmultidisciplinary. ADEOS observed the Earth environmentusing a wide range of wavelengths from ultraviolet tomicrowave. The swaths and the utilized wavelengths ofADEOS sensors are illustrated in Figs. 3 and 4.

ADEOS was successfully launched by H-II launchvehicle No. 4 (H-II 4F) from the Tanegashima Space Centerat 10:53 on 17 August 1996 (Table 1). After ADEOS wasconfirmed in orbit, it was named “Midori” in Japanese,which is the satellite nickname and means “green” repre-senting luxuriant trees. The initial operation and initial on-orbit checkout phases from August to November 1996confirmed that all eight sensors functioned well. ADEOSwas supposed to operate for 3 years.

Since the volume of ADEOS observation data was sohuge, the burden of data acquisition was shared by theNASDA Earth Observation Center (EOC) and NASA groundstations (the Alaska SAR Facility and the Wallops FlightFacility). All the data were transferred to EOC, and Level-0 products of each sensor were generated for further pro-cessing at facilities of the sensor providers.

On 30 June 1997, ADEOS ceased to reply to anycommands from the ground due to a power loss, and NASDAstopped further operation on 1 July (Table 1).

Fig. 4. Schematic diagram showing observation bands of the ADEOS sensors.

Fig. 3. Schematic picture showing the swaths of six sensors at theEarth’s surface and direction of the ILAS observation. Therelative sizes of swaths drawn in the figure are not correct; theOCTS swath was about 1400 km, the AVNIR swath 80 km, theTOMS swath 2,800 km and the NSCAT swaths were 450 kmon each side of the orbit. The POLDER swath dimensionswere 2447 km × 1809 km. The IMG observation area was8 km × 8 km on the ground. ILAS looked at the Sun.


2.2 OCTS and its operationThe detailed information of OCTS bands is shown in

Table 3, together with the other characteristics. The con-ceptual drawing of OCTS measurements cited from NASDA(1997) is depicted in Fig. 5. OCTS performed daytimeobservation of the Earth’s surface using the tilt function toprevent the OCTS color images from being disturbed by sunglitter. The sensor swath was about 1400 km (±40 degrees),which covered the whole Earth’s surface within 3 days.Figure 2 shows an example of the OCTS global coverage inone day and the operation gains for the ocean and land. Forseasonal and latitudinal changes of the sun altitude and thealternation of land and ocean in the view, the OCTS gain waschanged several times per orbit. Its spatial resolution was700 m at the surface, which is finer than resolutions ofCZCS, SeaWiFS and AVHRR.

ADEOS had a subsystem called Direct Transmissionfor Local users (DTL), which was developed for real-timebroadcasting of the 4-band data (443 nm, 565 nm, 665 nm,11.0 µm) with 6 km spatial resolution. The transmissionfrequency of DTL was 467.7 MHz, and the data rate 23.4375kbps (Table 3). The coarse image data with the relevanttelemetry data was transmitted to local users for applicationsresearch.

The first visible and near-infrared images of OCTSwere acquired on 3 September, and the first infrared imageson 1 October 1996 (Table 1). OCTS data was collected from14 October 1996 while the initial operation and on-orbit

checkout were conducted. The post-launch evaluation of thesatellite and sensors was terminated on 25 November, andthe on-orbit routine operation phase started on 26 November1996 and continued until 29 June 1997. The initial checkoutproved that the OCTS instrument was performing at orbeyond engineering specifications (Oaku et al., 1997;Shimada et al., 1998).

Using the algorithms developed by the OCTS team inthe Earth Observation Research Center (EORC), EOCprocessed the OCTS data to generate the Level 1, 2 and 3products. For semi-real-time distribution of the OCTSproducts to the Japan Meteorological Agency (JMA) andJapan Fisheries Information Service Center (JAFIC), EOCprocessed the OCTS data around Japan received by theirantenna within 3 hours after reception. These products werealso registered in the I-LAC database (see Section 5) foraccess through the internet.

2.3 The OCTS team and NASDA EORCNASDA established EORC in April 1995 (Table 1).

EORC is responsible for conducting high-level analysesincluding algorithm development, carrying out pilot projects,and promoting the use of Earth observation data; NASDAHeadquarters (Earth Observation Promotion Division) co-ordinates general matters for Earth observation. EOC re-ceives and archives satellite observation data and generatesstandard satellite products (NASDA, 1997).

The OCTS team, which consists of NASDA personnel

Table 3. Characteristics of OCTS.


Fig. 5. Conceptual drawing of OCTS measurement (NASDA, 1997).

and non-NASDA researchers, was formed in July 1995(Table 1). The members are listed in Appendix 1. The OCTSteam develops the OCTS algorithms and evaluates thegenerated products through calibration and validation forscientific and applications research. Integrating all the pre-existing OCTS-related activities, the OCTS team screenedand reorganized these activities for the OCTS Cal/Val andalgorithm development. The supporting scientists joined theteam to perform in situ oceanographic observations andcooperate with the NASDA personnel in the OCTS Cal/Val.At the same time, the suggestions relating to the productgeneration and distribution to promote research using theOCTS data were reviewed by the supporting scientists. Thecooperative relationship between the non-NASDA re-searchers and NASDA personnel was maintained through-out the OCTS team working period.

3. OCTS Algorithms and Product Generation

3.1 Algorithms for the OCTS productsLight intensity observed by satellite over the clear-sky

ocean is significantly influenced by the atmosphere. In orderto retrieve the ocean color information from the OCTSobservations, the obtained signals must be corrected for theatmospherically induced changes. Fukushima et al. (1998)developed an atmospheric correction algorithm to retrievethe upward radiance at the water surface from the OCTSdata. Sharing the some basic structure with the SeaWiFSalgorithm by Gordon and Wang (1994), the OCTS algorithmuses ten candidate aerosol models including the “Asian dust

model” (Fukushima and Toratani, 1997).An in-water algorithm was developed by Kishino et al.

(1998) to retrieve Chl-a concentration, pigment concentra-tion and attenuation coefficient at a wavelength of 490 nmfrom the atmospherically corrected OCTS data. They adoptedempirical formulae including water leaving radiance ofthree OCTS bands and used the 77 bio-optical measurementsmade in the oceans around Japan for the algorithm devel-opment. It has been shown that the Chl-a estimated by the insitu radiance at the water surface agrees well with the in situChl-a in the range below 10 mg/m3.

A multi channel SST (MCSST) algorithm was madeusing data of three infrared bands (Sakaida et al., 1998). Aunique point of the OCTS MCSST algorithm is usage of the8.5 µm band (see Table 3), which was not provided by thepervious sensors, together with the bands of 10.5 and 11.5µm. The formula was tuned by using the sea-truth SSTsobtained from buoys in the global oceans.

An algorithm for the OCTS vegetation index is stillbeing developed (August 1998). Since field experimentswere planned for the summer of 1997, the research scheduleto collect the ground truth-data was completely upset. TheOCTS vegetation products will be generated around the endof 1998 by acquiring vicarious ground truth data and exam-ining it together with other satellite data.

3.2 OCTS calibrationOptical sensors on board satellites degrade while func-

tioning in space. Since the degradation influences the qualityof the sensor products, continuous calibration of the sensor


Table 4. List of sea-truth data providers for OCTS Cal/Val.

outputs is essential. While OCTS was functioning, theobserved radiance of each band was calibrated using internalcalibration sources and OCTS observation data, i.e., internallamps, sunlight, nighttime data, and uniform ground targetdata (Oaku et al., 1997; Shimada et al., 1998). Radiometric

calibration using the Airborne Visible and Infrared ImagingSpectrometer (AVIRIS) was first tried for vicarious cali-bration of the ocean color sensor; AVIRIS on board anaircraft flying at an altitude of 20,000 m observed the clear-sky ocean when OCTS overflew. The OCTS radiance esti-


Fig. 6. (a) Photograph of the deployed Yamato Bank optical moored buoy system (YBOM), and (b) its schematic diagram (Kishinoet al., 1997).

mated by the preflight calibration data agreed with thatobtained by AVIRIS within 3 to 7% differences (Shimada etal., 1998). It can be concluded through the above-mentionedcalibrations that the degradation of OCTS visible bands wasnot significant during the ten-month OCTS lifetime.

The outputs of infrared bands were calibrated by thespace radiance and the on board black body as a warm target.The black body temperature was monitored at five points(Oaku et al., 1997).

3.3 Validation and algorithm tuning3.3.1 Acquisition of sea-truth data for ocean color products

In order to validate the OCTS products and tune thealgorithms to improve the quality of the target geophysicalparameters, the OCTS team collected many in situ obser-vations. Ship-observed Chl-a and optical measurements wereprovided by the various organizations and researchers listedin Table 4. While OCTS was functioning, 1,666 Chl-aobservations and 496 observations of in situ sea surfaceradiance were collected.

The Yamato Bank optical moored buoy system (YBOM)was specially designed to calibrate and validate OCTS andNSCAT (Ishizaka et al., 1997; Kishino et al., 1997). Aphotograph and schematic drawing of YBOM are shown in

Fig. 6. This buoy was deployed at 39°29′06″ N, 135°5′16″E over the Yamato Bank, which is in the central part of theJapan sea, in August 1996. Two underwater radiometerswere installed on the buoy at depths of 1.8 m and 6.8 m tomeasure spectra of the upward radiance and downwardirradiance. Incident irradiance at 860 nm was measured at5.2 m height in the air. In vivo chlorophyll fluorescence wasalso measured by a fluorometer. Marine meteorologicalparameters and sea water temperatures were also measured.The buoy transmitted some observation data in real timethrough the Data Collection System of Geostationary Me-teorological Satellite-5. The observation period was fromAugust 1996 to June 1997. The collected data were used forthe OCTS and NSCAT calibration and validation (e.g.,Shimada et al., 1998; Kawamura and Wu, 1998).

The National Research Institute of Fisheries Agency(NRIFS) and NASDA concluded a special agreement topromote the OCTS Cal/Val and applications of OCTS data.Under this agreement, the Fisheries Agency and NASDAplanned a practical demonstration of the DTL subsystemand ADEOS data applicability for forecasting promisingfishing grounds. The DTL receivers were specially devel-oped and installed on research vessels to examine its fea-sibility for fisheries. To demonstrate the applicability of


OCTS data for fisheries, the Chl-a and SST products weredistributed to the fishery research community through theInternet in the intensive LAC project described in Section 5.

In order to collect reliable Chl-a data for validating theOCTS-estimated Chl-a, a “round robin” workshop was heldto compare Chl-a measurements eight months before theADEOS launch (Furuya, 1996). This was a kind of “blindtest” in which Chl-a solutions were distributed to partici-pants from 14 research institutes and 12 universities, and themeasurements results were returned. The comparison showsthat the measurements agreed well with the true valuesdetermined by HPLC, which demonstrates that Chl-a ob-tained by the fluorometric and spectrophotometric deter-minations can be used as reliable sea-truth data. Based onthe comparison experience, a manual (Kishino et al., 1996)describing methods to conduct bio-optical measurementsfor OCTS Cal/Val was compiled for distribution to Japanesesea-truth data providers.

A field experiment called the “Sanriku Campaign” wasspecially planned for the OCTS Cal/Val and demonstrationof OCTS applicability in scientific and applications re-search. The campaign was conducted in the northwesternPacific Ocean off the Sanriku coast during the spring of1997. Much and various types of in situ observation data wascollected. The data was subsequently used for the OCTSCal/Val and combined with the OCTS products for theoceanographic studies presented in the special issue of theJournal of Oceanography (Saino, 1998).3.3.2 Validation and algorithm tuning

To generate the OCTS products in NASDA EOC, theretrieval algorithm has been modified several times. Thehigher product version numbers correspond to significantimprovements of the OCTS algorithm. A CZCS-type at-mospheric correction algorithm proposed by Fukushima etal. (1997) was applied to generate the Ver. 1.0 OCTS colorproducts from November 1996 to March 1997. The OCTS-type atmospheric correction algorithm was used for Ver. 2.0product generation from April 1997, though the algorithmswere still under development. The Ver. 3.0 products weregenerated from October 1997 after the ADEOS failure.Product generation using the Ver. 4.0 algorithm began inJune 1997 (Table 1). The algorithms used for the Ver. 3.0products were described in detail by Fukushima et al. (1998),Kishino et al. (1998), and Sakaida et al. (1998). The latestalgorithm for the Ver. 4.0 products is briefly introduced byMitomi et al. (1998) and will be fully described elsewhere.

OCTS Ver. 3.0 Chl-a products were validated; theestimated Chl-a correlates well with the in situ Chl-a but isa little overestimated below 2 mg/m3. The estimated Chl-atends to saturate in a sea-truth range above 2 mg/m3 (Shimadaet al., 1998). In order to compare the accuracy of the Ver. 3.0and 4.0 Chl-a, an error factor (EF) is defined as

EF = 10r,

where

r = 1N

log10 OCTS_Chl - a( )i − log10 in situ_Chl - a( )i{ } 2

i

N

∑ ,

and N is the total number of match-up data sets (Mitomi etal., 1998). EFs of the estimated Chl-a for the ranges below2 mg/m3 and above 2 mg/m3 were 1.67 and 3.53. EF for thewhole Chl-a range was 2.20. These tendencies of Ver. 3.0Chl-a were confirmed through validation using the sea-truthChl-a data collected in global oceans.

In March 1998, the OCTS team started tuning the Ver.3.0 algorithm to eliminate the bias and extend the propor-tional range according to the accumulated understanding ofthe OCTS sensor and the algorithms (Shimada et al., 1998;Fukushima et al., 1998). The main modification of the al-gorithm was made for atmospheric correction, especiallythe aerosol selection method (Mitomi et al., 1998). It wasfound (Shimada et al., 1998; Mitomi et al., 1998) that theestimation errors of color products strongly depend on theratios of the OCTS radiances based on the preflight calibrationto those based on the vicarious calibration. In the algorithmdevelopment for the Ver. 4.0 products, the ratios weretreated as the algorithm correction coefficients of inputradiance and tuned to minimize the estimation errors ofproducts against the sea-truth radiance and Chl-a (Mitomi etal., 1998).

Figure 7 compares the Ver. 4.0 Chl-a and the in situChl-a (Mitomi et al., 1998). The bias seen in the Ver. 3.0

Fig. 7. Comparison of in-situ Chl-a and Ver. 4.0 estimated Chl-a.


Fig. 8. Comparison of Ver. 3.0 and Ver. 4.0 Chl-a values estimated in the global oceans from 16 February to 20 March 1997. The colorshows the frequency of appearance.

products below 2 mg/m3 (Shimada et al., 1998) was re-moved, and the estimation for Chl-a above 2 mg/m2 wasimproved. The EF of the Ver. 4.0 Chl-a below 2 mg/m3 is1.83 and that above 2 mg/m3 is 2.61. For the whole Chl-arange, the EF was 2.05. The estimation accuracy of the Ver.4.0 products is improved for the higher Chl-a values and forthe whole range. Note that Chl-a values estimated by the insitu radiances through the in-water algorithm by Kishino etal. (1998) tend to deviate from the sea-truth Chl-a above 10mg/m3.

The comparison between Ver. 3.0 and Ver. 4.0 EFsdemonstrates that the algorithm tuning significantly improvedthe estimate accuracy. The Ver. 4.0 normalized water-leaving radiance also shows better agreements with in situobservations than Ver. 3.0 (Mitomi et al., 1998). The tuningresults can be visualized well by viewing Fig. 8, whichcompares Ver. 3.0 and Ver. 4.0 Chl-a in the global oceansfrom 16 February to 20 March 1997. This confirms that theabove-mentioned tuning was effective for Chl-a products inthe global oceans.

The SST products were also validated, and OCTS Ver.3.0 SSTs were shown to have an rms error of 0.7 K (Sakaidaet al., 1998) with respect to buoy-observed SSTs.

4. OCTS Global and LAC ImagesThe OCTS Ver. 3.0 products released in October 1997

have been used for various types of research, some results ofwhich were published in a special issue of the Journal ofOceanography (Saino, 1998). Figures 9 and 10 show ex-amples of the monthly Chl-a and SST distribution in theglobal oceans for April 1997. The high quality of the OCTSChl-a field is demonstrated, capturing characteristic Chl-apatterns in the global oceans.

Figure 11 shows the OCTS Chl-a distribution in thePacific Ocean off Peru and Chile. The image has the highestspatial resolution of 700 m. Along the coastline, high con-centrations of Chl-a are observed. An eddy-like structure isprominent off the Patagonia coast, and a wavy patternreminiscent of fluid dynamical instability is seen off thecoast of northern Chile. Fine features near the coast and


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Fig. 11. Chl-a distribution in the Pacific Ocean off Peru and Chile on 4 April 1997. The image has the highest spatial resolution of700 m. The lands are shown in gray, and the clouds and the flagged pixels in black.


Fig. 12. SST distribution in the Pacific Ocean off Peru and Chile on 4 April 1997. The image has the highest spatial resolution of700 m. The lands are shown in gray, and the clouds and the flagged pixels in black.


inside the eddies were well represented in the Chl-a image.Figure 12 depicts the SST image with a spatial resolution of700 m obtained at the same time as the Chl-a image of Fig.11. Although the patterns in both images are similar, thedetailed features are not the same. These differences shouldbe investigated in detail to understand the bio-physicalinteractions in the upper ocean. These images demonstratethe characteristics and capability of OCTS as a powerfultool for oceanography, i.e., the combination of the simul-taneously acquired Chl-a and SST images with a fine spatialresolution of 700 m.

5. Dissemination of OCTS ProductsThe OCTS products are distributed to the ADEOS

principal investigators from NASDA EOC. The OCTSLevel-3 products (global maps) showing Chl-a concentra-tions and SSTs in the global oceans can be obtained fromNASDA EORC home page (http://www.eorc.nasda.go.jp/)and EOC home page (http://www.eoc.nasda.go.jp/). Infor-mation of the OCTS/ADEOS is available from the NASDAEORC home page.

In order to distribute the OCTS images in a timelymanner, the Intensive LAC (I-LAC) project was initiated inDecember 1996. In this project, NASDA EORC distributes,through the internet, the daily images of OCTS Chl-a and SSTwith the highest spatial resolution for the oceans aroundJapan. The project name stands for intensive processing ofOCTS images for a local area coverage.

Throughout the OCTS lifetime, the OCTS I-LAC im-ages were generated by using the updated algorithms (Table1), and all the Chl-a and SST images in the oceans aroundJapan are archived in NASDA EORC. Monthly records ofthe I-LAC data distribution are shown in Fig. 13, whichindicates that distribution of the I-LAC images increasedwith time until the very end of the ADEOS operation. Thehighest access rate in a day, about 1 Gbyte, was recorded on18 June 1997. The I-LAC project is carried out in coopera-tion with I-LAC partners (NASA, NOAA, ESA, JRC).

NASDA provides regional OCTS data with the partners topromote research using the OCTS data. The OCTS imagesof the US waters are distributed by NASA through theInternet (http://seawifs.gsfc.nasa.gov/).

6. Discussions—ADEOS Mission and OceanographyDuring the lifetime of ADEOS, ocean color in the

global oceans was observed from space together with sur-face wind vector by NSCAT. Since the TOPX/POSEIDONmission and ERS-1/2 mission were being conducted inparallel, the global oceans were investigated by an almostcomplete set of satellite sensors for oceanography. OCTSobserved the global oceans with 700 m spatial resolution,which was achieved by powerful data recorders on boardADEOS. This means that any small area of the global oceanscan be investigated by the OCTS images with the highestspatial resolution. The data volume obtained by the OCTSobservation is about 4700 GByte which is much larger thanobtained by CZCS for 1978 to 1986. All the observation dataare archived in NASDA EOC, together with the data of otherADEOS sensors. In a historical context of satellite ocean-ography, the ADEOS mission may be characterized by 1)multi sensor observations for the ocean surface layer and 2)global coverage of ocean color and SST with 700 m spatialresolution.

Although there are many social requirements originatingfrom the necessity of monitoring the coastal environments,coastal waters are technically difficult targets in terms of theocean color remote sensing. The large variability in thecoastal waters and the atmosphere over the seas near landproduces various types of errors in the ocean color products.In order to improve the ocean color technology to meet thesocial requirements, we must conduct intensive regionalresearch for each of the coastal waters. The Intensive LACproject, in which the OCTS data were passed to the partnersfor research of their coastal waters, was motivated to con-duct feasibility research of the world coastal ocean moni-toring. Using the OCTS observation data with the samequality and the high spatial resolution for the global coastalseas, we can compare results of the regional research. TheNSCAT 25-km wind product specially designed for re-search of the coastal seas will support the OCTS investiga-tions.

Since ADEOS carried eight sensors, it becomes possibleto investigate the same points on the Earth with differentwavelengths, angles, and polarizations (Figs. 3 and 4).Combined use of the OCTS data with the data from the othersensors may enable us to understand the characteristics ofOCTS signals and to retrieve highly accurate parameters(NASDA, 1997). POLDER had visible and near-infraredchannels similar to those of OCTS. While the OCTS spatialresolution (700 m) was finer than that of POLDER (about 7km), POLDER measured polarization by three visible andnear-infrared channels, and observed the same point from

Fig. 13. Monthly volume of the I-LAC data transfer through theinternet from August 1996 to September, 1997.


nine different angles. Combined use of POLDER and OCTSdata may improve the atmospheric correction and retrievalof ground parameters. The spatial resolution of AVNIRvisible and near infrared bands was quite high, approxi-mately 16 m at the Earth’s surface. AVNIR could image theEarth surface in the OCTS sub-pixel, which contributes tounderstanding effects from the subpixel clouds, white caps,and the fine ground-surface features on the OCTS parameterretrieval. The measurement principle of IMG was theMichelson interferometer. IMG looked downward to mea-sure the radiance of atmospheric radiation in the thermalinfrared band with a high spectral resolution as well as highradiometric accuracy. SST retrieval using the OCTS infra-red channels may be improved by comparing radiance fromboth sensors and by examining the IMG-derived atmospherictemperature and water vapor profiles.

Although the ADEOS lifetime was not so long, OCTSand NSCAT left a huge new data set for oceanography. Itreminds us of Seasat, which was launched in 1978. Thelifetime of Seasat was only 3 months. However, its obser-vation data was carefully analyzed and used to producenumerous scientific and remote sensing papers, contribut-ing to the understanding of physical aspects of global oceans(Katsaros and Brown, 1991). ADEOS was the first to realizesimultaneous acquisition of Chl-a, SST, and surface windsin the global oceans. We believe that the ADEOS missionwill contribute to progress of understanding biological,chemical and physical interaction in the surface layer of theglobal oceans.

AcknowledgementsWe would like to thank Mr. T. Tanaka (the previous

director of EORC), Dr. Y. Toba (the previous Chief Scientistof EORC), and Professor H. Shimoda (the ADEOS projectscientist) for their support and encouragement. We alsothank one anonymous reviewer for valuable comments andsuggestions on this manuscript.

Appendix 1. The OCTS Team

Location:National Space Development Agency of Japan, Earth Ob-servation Research CenterRoppongi First Building, 1-9-9, Roppongi, Minato-ku, Tokyo106, Japan

NASDA Pesonnel:Hiroshi Kawamura (Leader)Masanobu Shimada (Sub leader)Yasuhisa Nakamura (Sub leader)Hiromi Oaku (Calibration-group leader)Yasushi Mitomi (Algorithm-group leader)Akira Mukaida (Validation-group leader)Hiroshi Murakami (Application-group leader)

Supporting ScientistsHajime Fukushima (Tokai University)Ken Furuya (University of Tokyo)Yoshiaki Honda (Chiba University)Joji Ishizaka (Nagasaki University)Kiyoshi Kawasaki (National Research Institute for Fisher-ies Research)Motoaki Kishino (Institute of Physical and Chemical Re-search)Satsuki Matsumura (National Research Institute for FarSeas Fisheries)Masao Moriyama (Nagasaki University)Teruyuki Nakajima (University of Tokyo)Futoki Sakaida (Kobe University of Mercantile Marine)Sei-ichi Saitoh (Hokkaido University)Toshiro Saino (Nagoya University)Yasuhiro Senga (Tokai University)Sumio Tanba (Hirosaki University)

Appendix 2. AcronymsADEOS: Advanced Earth Observation SatelliteAOCS: Attitude and Orbit Control SystemAO: Announcement of OpportunityAVNIR: Advanced Visible and Near Infrared RadiometerAVIRIS: Airborne Visible and Inrared Imaging Spectrom-eterCNES: Centre National d’Etudes SpatialesC&DH: Communication and Data HandlingCal/Val: calibration/validationChl-a: chlorophyll-aDT: Direct Transmission SubsystemDTL: Direct Transmission for Local usersEA: Environment AgencyEOC: Earth Observation CenterEORC: Earth Observation Research CenterEPS: Electrical Power SubsystemESA: European Space AgencyGAC: Global Area CoverageGMS: Geostationary Meteorological SatelliteGSFC: Goddard Space Flight CenterILAS: Improved Limb Atmospheric SpectrometerIMG: Interferometric Monitor for Greenhouse GassesIOCS: Inter Orbit Communication SubsystemJPL: Jet Propulsion LaboratoryJSNFRI: Japan Sea National Fisheries Research InstituteLAC: Local Area CoverageMDP: Mission Data ProcessorMITI: Ministry of International Trade and IndustryNASA: National Aeronautics and Space AdministrationNASDA: National Space Development Agency of JapanNNFRI: Nansei National Fisheries Research InstituteNOAA: National Oceanic and Atmospheric AdministrationNRIFS: National Research Institute of Fisheries AgencyNRIFSF: National Research Institute of Far Seas Fisheries


NSCAT: NASA ScatterometerOCTS: Ocean Color and Temperature ScannerPDL: Paddle SubsystemPOLDER: Polarization and Directionality of the Earth’sReflectanceRIS: Retroreflector In SpaceSeaWiFS: Sea-viewing Wide Field-of-view SensorSNR: Signal-to-Noise RatioSST: Sea Surface TemperatureTOMS: Total Ozone Mapping Spectrometer

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