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1 Introduction

In recent years, destruction of global envi-ronment caused by human activities hasbecome a serious problem. In particular,chemical reactions and the atmosphericdynamics of trace atmospheric elements in theupper troposphere and stratosphere are knownto contribute to depletion of the stratosphericozone layer, global warming, and related cli-matic changes. Many details of these effectsremain to be elucidated. Thus, it is importantto study these reactions and the correlationwith atmospheric dynamic process.

To study ozone depletion, it is necessary tomonitor trace molecules and study reaction

processes in the upper troposphere and strato-sphere. For this purpose, we need to deter-mine a 3-dimensional distribution of such ele-ments by observing the earth on a global scale.These molecules are present in extremelysmall amounts: several million (ppmv) to sev-eral billion (ppbv) parts per volume in thestratospheric atmosphere. Thus, it has beendifficult to date to perform a quantitativemeasurement of these elements.

A submillimeter-wave limb-emission spec-trometer appears promising in the spectro-scopic observation of very weak electromag-netic waves emitted by trace molecules[1].This type of spectrometer may be used,together with a high-sensitivity receiver,

MANABE Takeshi

2 Satelliteborne Measurement Technolo-gies

2-1 Development of Superconducting Submil-limeter-Wave Limb-Emission Sounder(JEM/SMILES) aboard the InternationalSpace Station

MANABE Takeshi

In recent years, stratospheric ozone depletion is one of the most significant global envi-ronmental issues. It is well known that stratospheric trace gases, which include chlorineoxides and bromine oxides, play a crucial role in the process of stratospheric ozonedestruction. Although the abundances of these trace gases are as low as in the order ofparts par billion or less, they are quite efficient to destroy stratospheric ozone by catalyticreactions. In order to establish the techniques to monitor stratospheric Ozone and Ozonedepleting molecules, CRL and NASDA are collaborating to develop Superconducting Sub-millimeter-Limb Emission Sounder (JEM/SMILES) to be aboard the Japanese ExperimentModule (JEM) of the International Space Station. In this paper, the outline of the JEM/SMILSproject and the payload instrument is introduced.

Keywords Submillimeter wave, Ozone depletion, Limb-emission sounding, International SpaceStation, Remote sensing of atmosphere

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aboard a satellite in orbit. To put this equip-ment to practical use for satellite deployment,however, many problems must be solved:technologies must be developed for a high-sensitivity, low-noise submillimeter-wavereceiver with cryogenic and superconductivitytechnologies.

The Communications Research Laboratory(CRL) has cooperated with the National SpaceDevelopment Agency (NASDA) to propose tothe Space Activities Committee Commission aproject of experiments for observing stratos-pheric trace-gas molecules by using Supercon-ducting Submillimeter-wave Limb-EmissionSounder (JEM/SMILES), aboard the ExposedFacility of the Japanese Experiment Module(JEM) of the International Space Station(ISS). One purpose of this project is demon-strating the technology for using submillime-ter waves to observe the middle atmospherefrom a space platform in orbit. In 1997 theproject was approved under the category of“Creation of New Space Applications” as oneof four candidate experimental devices andthemes utilizing an early stage of the JEMExposed Facility. CRL and NASDA thusformed a cooperative team for theJEM/SMILES mission to develop a SMILESsystem for anticipated deployment on theInternational Space Station around 2006. Thisreport outlines the JEM/SMILES mission anddescribes the development of the SMILESsystem.

2 Objective of the JEM/SMILESMission

It is well known that stratospheric tracegases, which include chlorine oxides, nitrogenoxides, and bromine oxides, play a crucial rolein the process of stratospheric ozone destruc-tion through catalytic reactions. Among these,ClOx is formed from chlorofluorocarbons, anindustrial product, while BrOx comes frommethyl bromide (used as a bactericide andfumigating agent) and bromofluorocarbons(used as an extinguisher). This latter sub-stance is said to enhance ozone depletion by

promoting the catalytic reaction of ClOx[2].Currently international protocols are in placefor discontinuing or cutting back on the pro-duction of chlorofluorocarbons and bromoflu-orocarbons. Conversely, the production ofmethyl bromide continues, largely due to therefusal by certain developing countries to dis-continue its production[3]. Since chlorofluoro-carbons and bromofluorocarbons are chemi-cally very stable, once released in the atmos-phere, such elements remain there for anextended period and continue to deplete theozone layer. This would be the case even ifthe production of these substances were dis-continued today. It may therefore take dozensof years to stop ozone depletion and to restorethe ozone layer[2]. NOx and HOx used toexist as natural substances, but commercialproduction is rapidly increasing due to modernhuman activities[2]. Depletion of the ozonelayer is caused by these complex chemicalreactions caused by these substances as wellas by other atmospheric dynamic processes.

Ozone depletion was discovered in thestratosphere above Antarctica in the mid-1980s. Since then, ozone holes have appearednot only above Antarctica, but also in arcticareas. We now know that such holes exist inthe mid-latitudes, indicating a steady trendtoward ozone depletion everywhere on earth.

The JEM/SMILES project intends toestablish observation technologies to clarifythe atmospheric chemical reactions anddynamic processes related to ozone depletionand global warming. For this purpose, it isnecessary to establish technology for quantita-tively observing a 3-dimensional profile oftrace molecules in global regions from theupper troposphere to the mesosphere withhigh resolution and accuracy. It is also impor-tant to demonstrate that the technology canwork successfully in orbit. Thus, SMILESmust incorporate the use of a high-sensitivityspectrometer to detect very weak submillime-ter waves (emitted by trace gas components)from a space-borne platform in orbit. To thisend, we must develop the technology to applysuperconducting electronics to a highly sensi-

Journal of the Communications Research Laboratory Vol.49 No.2 2002

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tive submillimeter-wave receiver. Currently, acryogenic cooler to support this technology isslated for development. A second goal ofJEM/SMILES is to confirm that this technolo-gy works satisfactorily in space.

3 Outline of JEM/SMILES

Many trace-gas molecules have spectra inthe submillimeter-wave bands. JEM/SMILESemploys a sharply directed antenna to receiveweak emissions from these molecules in thetangential direction relative to the earth. Itfeatures a limb-emission sounder to measurespectroscopic emissions to determine the alti-tude profile of the components in question.Fig.1 is a schematic diagram illustrating limb-emission sounding from JEM/SMILES.

3.1 Molecules and Frequency Bandson JEM/SMILES Observation

For the purpose of simultaneously observ-ing as many molecules as possible,JEM/SMILES features two frequency bands inthe submillimeter-wave region of the 640-GHz band: 624.32 GHz to 626.32 GHz and649.12 GHz to 650.32 GHz. The former band(lower sideband, LSB) is further divided intotwo overlapping bands: 624.32 GHz to 625.52GHz (Band A) and 625.12 GHz to 626.32GHz (Band B) for reasons described later.The latter bandwidth (upper sideband, USB) iscalled Band C. Two of these three 1.2-GHz-wide bands are used for simultaneous observa-

tion. Table 1 lists the molecules to beobserved by JEM/SMILES and the center fre-quencies of observed spectra.

Ozone (O3) existing at altitudes between20 km and 50 km in the stratosphere absorbultraviolet light, thus protecting life on earth.In removing and protecting against this harm-ful energy, the ozone layer is compared to aspacesuit. Since it absorbs infrared rays emit-ted from the ground and atmosphere, the layeris known to have a significant effect on globalwarming. Although the stratosphere containsa very small amount of ClO, BrO, and HO2 onthe order of a few ppbv (volume mixing ratio)or less, these substances act as catalysts andhave critical effects on ozone depletion. Mo-lecular species such as HCl, HOCl, H2O2, andHNO3 act as reservoir molecules, playing animportant role in both producing and reducingquantities of the molecules above. Sulfurdioxide (SO2) is a gas that is released during avolcanic eruption. It reacts with water to forman aerosol, and heterogeneous reactions on itssurface are said to have a significant effect onozone depletion in the stratosphere[4].

There are isotopes of ozone in addition tonormal ozone 16O3: 16O18O16O, 18O16O16O,17O16O16O, and 16O17O16O. The transition fre-quencies of these isotopes are within the fre-quencies to be observed by JEM/SMILES. Aphenomenon called ozone isotope enrichmentin the troposphere and stratosphere has puz-zled scientists for almost two decades. Manyobservations indicated that there is a slightenrichment in heavy isotopes of ozone in thetroposphere and stratosphere than in the natu-ral abundance. This phenomenon of ozoneisotope enrichment is not yet well understood[5]. Conventional mass spectrometry of adirectly sampled atmosphere does not allowfor the discrimination of isotopes having thesame mass number and different symmetry,but SMILES may allow such discriminationby its spectroscopic observation[6]. Under-standing such ozone isotope enrichment indetail makes quantitative evaluation of theozone transfer between the lower stratosphereand upper troposphere possible.

MANABE Takeshi

Schematic diagram of limb-emissionsounding from JEM/SMILES on theInternational Space Station orbit

Fig.1

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3.2 Limb-Emission SoundingIn scientific study of the atmosphere, it is

necessary to measure the altitude profile(including variations over time) of the mole-cules above on a global scale. An effectiveway to do this would entail observation, froma platform orbiting the earth, of the submil-limeter electromagnetic waves thermally emit-ted by these molecules. This type of observa-tion is not affected by the position of the orbitor by the sun, unlike absorption observationusing the sun as background. Therefore, it ispossible to continue observation everywhere,both day and night, thus allowing diurnal vari-ations to be observed for any area.

All molecules listed in Table 1 (exceptozone) are trace elements of 10 ppbv or less.Thus, thermal emission of such elements is ofvery low intensity. Since the platform is con-tinually moving along the orbit, a long obser-vation period cannot be used to enhance sensi-tivity. As shown in Fig.2, JEM/SMILESapplies the method of limb-emission soundingto observe the limb of the earth in the tangen-tial direction by which we can gain the signalintensity[1]. A highly directive antenna beamabout 0.08 degrees in width is directed towardthe stratospheric atmosphere in the tangentialdirection. This beam collects emissions frommolecules along the line of sight in the tan-gential direction, resulting in increased signalintensity. The beam is scanned between tan-gent altitudes of 10 km and 60 km during a

cyclic period of 53 seconds, resulting in a highaltitudinal resolution of between 4 km and 3.5km.

As seen in Fig.2, the atmospheric layer isnot flat but spherically stratified, so that mole-cules lying above the tangent altitude of theline of sight contribute to the measured inten-sity. The scanning of a beam between tangentaltitudes of 10 km and 60 km provides infor-mation on changes in the pressure broadeningof spectra. This information is combined withthe retrieval method[7] to calculate an altitudi-nal profile for each type of molecule. Fig.3shows the results of a computer simulation ofthis method of obtaining limb-emission spec-tra during observations with JEM/SMILES.

3.3 Superconducting Submillimeter-Wave Receiver[8] [9]

As seen in Fig.3, for JEM/SMILES toeffectively observe trace molecules, it is nec-essary to enhance the detection sensitivity ofthe superconducting submillimeter-wavereceiver to around 0.5 K. For a detectionequivalent noise bandwidth of 2.5 MHz andan observation integration time of 0.5 second,the system noise temperature of the receivershould be around 600 K or less. To achievesuch a low system noise temperature, a super-conductor-insulator-superconductor (SIS)mixer which operates in cryogenic tempera-tures (approximately 4 K) has been widelyused in radio observatories on the ground, butnot in orbit.

Journal of the Communications Research Laboratory Vol.49 No.2 2002

Observation frequency bands on JEM/SMILES and center frequencies of observed spec-tra

Table 1

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The JEM/SMILES mission in orbit willinclude an SIS mixer, thus representing thefirst such use of this superconductor technolo-gy. The SIS mixer is designed for high-sensi-tivity heterodyne spectroscopic observation oftrace-gas molecules in the stratosphere, and isof the PCTJ type, developed in cooperationwith Nobeyama Radio Observatory of theNational Astronomical Observatory ofJapan[9]. This SIS mixer will be used with amechanical cooler and compact cryostat forspace use, which are currently under develop-ment for JEM/SMILES and is designed tooperate at a cryogenic temperature of 4.5 K.This type of cooler can be made smaller andlighter than a liquid helium cooler, and is suit-able for extended operation in space. The

cryogenic temperature of 4.5 K is expected tobe achieved with JEM/SMILES by using aspace-borne cooler comprised of two-stageSterling cooler combined with a Joule-Thom-son circuit. An engineering model of theabove cryostat and cooler pair was tested forvibration and long-term continuous operation.The test showed that the prototype endured thelaunch environment and was capable of opera-tion for periods longer than one year[10]. This4.5-K mechanical cooler represents the firstcooler of its kind to be used in space. Successin this operation will have a major impact onfuture space-observation projects using sub-millimeter and infrared waves.

MANABE Takeshi

Schematic diagram of scanning the stratospheric atmosphere by limb-emission soundingfrom JEM/SMILES

Fig.2

Computer-simulated limb-emission spectra of stratospheric atmosphere at altitudes between20 km, 30 km, 40 km, and 50 km in lower and upper sidebands of SMILES assuming anatmospheric model at latitude of 45 degrees north.

Fig.3

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3.4 Latitudinal Coverage of Observa-tion on SMILES

The International Space Station follows acircular orbit at an average altitude of 420 km.The orbital inclination is 51.6 degrees. Thus,if the antenna is directed in the traveling direc-tion, the latitudinal range of observation islimited to be less than 51.6 degrees to thenorth and south. This latitudinal range is toolow for observing the ozone in polar regions.We intend to deflect the antenna by 45 degreesfrom the direction of travel to the north so thata range from 65°N to 38°S may be covered.This range covers the peripheral region of apolar vortex where ozone depletion is said tobe significant. A deflection angle of over 45degrees would slightly increase the high-lati-tude area of observation. In this case, howev-er, the gigantic solar paddles rotating aroundthe axis of the ISS main truss will interferewith the line of sight of SMILES, thus pre-venting effective observation. Even with 45degrees of deflection, the time during whichobservation will be impossible amounts up to10% of the time, and 5% on average. This isacceptable from the viewpoint of the scienceteam. In addition to the case when the solarpaddles interfere, observation must be avoidedto protect the receiver when the sun is in the

line of sight. The time percentage of theoccurrence of this interference by the solarradiation is estimated to be less than 2%.Fig.4 shows the trajectory of a one-day orbitof the ISS starting from the ascending nodecorresponding to the prime meridian (blueline) and the corresponding trajectory of thetangent points projected to the ground (redline) observed by SMILES. Each red line seg-ment corresponds to a scan of the antennabeam at altitudes between 10 km and 60 km.

Another problem posed by the Internation-al Space Station is its variations in attitude.Since an important mission of ISS consists ofmicrogravity experiments, its altitude and atti-tude are not controled for most of period.Rotation of the gigantic solar paddles maychange the attitude by ±15 to 20 degrees andthe altitude by ±40 km. Therefore,JEM/SMILES must have its own star trackerto determine the antenna direction with anaccuracy of 0.02 degrees or better.

4 Basic Specifications and Con-figuration of JEM/SMILES

Fig.5 outlines the payload of SMILES.The payload is contained in a mainframestructure 1 m in height, 0.8 m in width, and

Journal of the Communications Research Laboratory Vol.49 No.2 2002

Trajectory of International Space Station (blue line) and corresponding trajectory (red line) ofobservation point on SMILES. Each red line segment corresponds to each single scan.

Fig.4

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1.85 m in length. This structure is attached tothe Exposed Facility of JEM. The payloadconsists of Antenna System (ANT), AmbientTemperature Optics (AOPT), Cryo-electronicsUnit (CRE), Helium Gas Compressor and Stir-ling/JT Drive Electronics (HECP and SJTD),

IF Amplification Section (IFA), Radio Spec-trometer (AOS), Data Processing and ControlSection (DPC), Electric Power System (EPS),JEM Interface Mechanism (JIF), ThermalControl System (TCS), and Star Tracker(STT). Fig.6 is a block diagram of the entire

MANABE Takeshi

Outline of JEM/SMILES payloadFig.5

Block diagram of overall JEM/SMILES systemFig.6

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system and shows the flow of signals.The Antenna System (ANT) consists of an

elliptical offset-parabolic main reflector with a40-cm semi-major axis (in the elevation direc-tion) and 20-cm semi-minor axis (in theazimuth direction), a sub-reflector, a tertiaryreflector, a drive unit for scanning the antennabeam, a beam transfer section, and a switchingmechanism for switching the antenna beam toa noise source used for a hot-load calibration.This system produces an elliptical beam of0.08 degrees in elevation half-power beamwidth and scans it during a cyclic period of 53seconds for limb sounding in a tangent-alti-tude range between 10 km and 60 km.

The Ambient Temperature Optics uses aquasi-optical beam transmission system toguide a signal received by the antenna to thecryo-electronics unit placed in a cryostat. Toprepare for heterodyne reception, a submil-limeter-wave local signal is injected into theabove signal and separated into an upper-side-band signal and lower-sideband signal byusing a Martin-Puplett type interferometernewly developed for SMILES[8] as an SSB fil-ter. The two sideband signals are detectedthrough a SSB filter at two SIS mixers placedon a 4.5-K cooled stage in the cryostat forsimultaneous observation by the Cryo-elec-tronics Unit. Each of these signals is first con-verted into an IF frequency band between 11GHz and 13 GHz, then amplified through aseries of two low-noise HEMT amplifiersplaced at the 20-K stage and 100-K stage.

The Cryo-electronics Unit is very sensitiveto external electromagnetic interference, as itis composed of very high-sensitivity SIS mix-ers for detecting weak signals of 1K or lesscoming from the stratospheric atmosphere andcooled HEMT amplifiers. The InternationalSpace Station uses many frequencies for pur-poses of communication in the vicinity of theIF frequency band used by SMILES. Thus,the cryostat (containing the Cryo-electronicsUnit) and Ambient Temperature Optics aredesigned to form a unified shielded structureto protect the Cryo-electronics Unit from theadverse electromagnetic environment of the

station. This shield structure secures electro-magnetic shields of 54 dB or larger against theexternal electromagnetic environment byusing a back-to-back horn, i.e. a circular cor-rugated wave-guide, at submillimeter-wavebeam input ports to interrupt waves of 40 GHzor less. Fig.7 shows a schematic diagram ofthe cryostat containing the Cryo-electronicsUnit, Helium Gas Compressor and Stirling/JTDrive Electronics, and the Ambient Tempera-ture Optics comprising the Submillimeter-wave Receiver System.

Since the Acousto-Optical Spectrometer(AOS) placed in the latter stage has a limitedbandwidth, the IF Amplification Section (IFA)uses frequency down-converters to convert thethree observation bands [i.e., Band A, Bands Band C], into second IF frequency bandbetween 1.55 GHz and 2.75 GHz. The IFAthus uses a switching circuit to select twobands from the above three bands to yield thesignal to two acousto-optical spectrometers[11]for spectrum analysis. The two acousto-opti-cal spectrometers each having a 1.2-GHzspectroscopic bandwidth analyze the spectrumof the second IF frequency band signal with afrequency resolution of 1.8 MHz, with a fre-quency channel interval of 0.8 MHz andequivalent noise bandwidth of 2.5 MHz tooutput digital data as noise spectra correspon-ding to limb-emission spectra[11].

5 Observation of Altitude Profile ofEach Molecular Species bySMILES

Fig.8 shows a preliminary result of a simu-lation study demonstrating the altitude rangeover which the volume-mixing ratio of eachmolecular species can be retrieved with speci-fied estimation errors for a standard atmos-phere under an assumption that the systemnoise temperature of SMILES is 500 K[12].

It is found in Fig.8 that altitude profiles ofozone and HCl can be obtained with an errorof less than 5 percent in a 53-second singlescan, while that of ClO can be obtained withan error of less than 50 percent. For such

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trace molecules as BrO and HO2, the bright-ness temperature of spectra is lower than thatof ClO. Hence, it is very difficult to measure

BrO and HO2 with satisfactory accuracy in asingle 53-second scan cycle, even given thesensitivity of the SMILES system. For suchmolecules, data should be integrated for a lati-tudinal range of 5 degrees and averaged togive a half-day zonal mean in that latitudinalzone. This procedure sacrifices spatial resolu-tion but increases detection sensitivity due tothe longer integration time. As indicated inFig.8, by taking a half-day zonal mean, theretrieval errors of these less abundant mole-cules might be reduced to less than 50% oversignificant altitude ranges.

6 Data Processing and Utilization

Digitized data of atmospheric limb-emis-sion spectra measured by AOS, are sentthrough the Data-Relay Test Satellites (DRTS)to the Ground Operation System located atTsukuba Space Center. At the same time,housekeeping data for monitoring the condi-

MANABE Takeshi

Outline of submillimeter-wave receiver (left), ambient temperature optics (AOPT, top right),and engineering model assembly of a cryo-electronics unit in a cryostat (bottom right)

Fig.7

Coverage of observation altitudes forobservable molecules by JEM/SMILES(results of computer simulations forstandard profiles at 80°N for HOCl,HNO3, and BrO, and those at 0°N forother molecules.)“1-scan” and “30-scan” indicateranges of altitude covered with speci-fied observation errors achievablefrom each single-scan data availablein every 53 seconds and from dataaveraged over 30 scans, respectively.The 30-scan averaged data corre-sponds to a half-day zonal mean for a5°-zone in latitude.

Fig.8

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tions of equipment are also sent to the GroundOperation System. This SMILES data is thenseparated, extracted, and transferred to theSMILES Ground Data Processing System.After applying the processes of depacketing,overlap-removing, and level-0 treatment (suchas time-line editing) to the raw data, the Pro-cessing System converts the processed datainto engineering values, then into brightnesstemperature spectra (as level-1 data) with thehelp of calibration data. In the level-2process, level-1 data is inverted through aretrieval algorithm to form an altitudinal pro-file of every molecule. We plan to cooperatewith a science team composed of researchersfrom external research institutions and univer-sities to develop such an algorithm, and toanalyze and test the processed data. CRL andEarth Observation Research Center ofNASDA will produce level-3 data—(i.e., grid-ded data obtained by averaging processed datawith respect to latitude and longitude for everyterm). We expect that level-1 and later datawill be sent to the University of Bremen inGermany, one of the overseas cooperativeresearch institutions, for comparative analysisusing an algorithm of its own design. Level-2and level-3 data are scheduled to be accessiblethrough the Internet to registered users. Fig.9shows the flow of data processing.

7 Conclusion

This report outlined the JEM/SMILES

mission and systems. Please refer to Refer-ence[12] for details of the mission plan.

According to the present schedule,JEM/SMILES will be launched by an H- Arocket from the Tanegashima Space Centerand attached to the Exposed Facility of JEMsome time around 2006. One year of observa-tion on SMILES is scheduled. If no succeed-ing mission is expected after the year in ques-tion and SMILES remains operational, anotherterm of observation will be available. Aftercompleting the mission, SMILES will bethrown away into the space by an H- trans-fer vehicle.

According to an agreement between CRLand NASDA, CRL is responsible for develop-ing the submillimeter-wave receiver subsys-tem which includes Ambient TemperatureOptics and Cryo-electronics Unit, and the IFAmplification Section, and NASDA is respon-sible for developing SIS mixers, as well assuch parts as cooled HEMT amplifiers, theantenna system, 4K coolers, and the acoust-optical spectrometers. These units and partswill then be integrated into a system for com-prehensive testing by NASDA. For develop-ment of the SIS mixers and the Ambient Tem-perature Optics, we are working in coopera-tion with the Nobeyama Radio Observatory ofthe National Astronomical Observatory ofJapan and the University of Bern, respectively.

In addition to the sensor-system develop-ment team, a science team of atmospheric sci-ence researchers from various universities andresearch institutions has been formed. Thescience team will submit requirements for sys-tem development, help us conduct observa-tions, develop algorithms, and plan and con-duct validation experiments. In addition, thisteam will hold international workshops andconduct other international cooperative activi-ties.

The Institute of Environmental Physics, atthe University of Bremen, is an internationalcooperative research institute that will developits own algorithm, use its own facilities toprocess ground-data elements, and distributedata to European institutions.

Journal of the Communications Research Laboratory Vol.49 No.2 2002

Flow of data processing in JEM/SMILESFig.9

19MANABE Takeshi

References1 J. W. Waters, "Microwave Limb Sounding", in Atmospheric Remote Sensing by Microwave Radiom-

etry, ed. by M. A. Janssen, Chap. 8, John Wiley and Sons, Inc., 1993.

2 World Meteorological Organization, Scientific Assessment of Ozone Depletion: 1998, World Meteo-

rological Organization Global Ozone Research and Monitoring Project - Report No. 44, Geneva,

1999.

3 United Nations Environmental Programme, The 1987 Montreal Protocol on Substances That Deplete

the Ozone Layer, as adjusted by the seventh Meeting of the Parties (Vienna, 5-7, Dec. 1995), avail-

able at http://www.unep.org/unep/secretar/

4 S. Solomon, S. Borrowmann, R. R. Garcia, R. Portmann, L. Thompson, L. R. Poole, D. Winker, and

M. P. McCormick, "Heterogeneous chlorine chemistry in tropopause region", J. Geophys. Res., Vol.

102, pp. 21411-21429, 1997.

5 D. G. Johnson, K. W. Jucks, W. A. Traub, and K. V. Chance, "Isotope composition of stratospheric

ozone", J. Geophys. Res. Vol. 105, pp. 9025-9031, 2000.

6 K. Takahashi, T. Shirai, H. Ozeki, Y. Kasai, M. Shiotani, and SMILES Mission Team, "Observation of

the stratospheric O3 isotopes by SMILES", First International Symposium on Isotopomers (ISI2001),

Yokohama, Japan, pp. 23-26, Jul. 2001.

7 C. D. Rodgers, "Retrieval of atmospheric temperature and composition from remote measurements

of thermal radiation", Rev. Geophys. Space Sci., Vol. 14, No. 4, pp. 609-624, Nov. 1976.

8 M. Seta, H. Masuko, T. Manabe, S. Ochiai, Y. Irimajiri, J. Inatani, H. Harada, T. Noguchi, S.-C. Shi,

K. Narasaki, and Y. Abe, "Submillimeter-wave SIS receiver for JEM/SMILES", Adv. Space Res., Vol.

26, No. 6, pp. 1021-1024, 2000.

9 Y. Fujii, K. Kikuchi, J. Inatani, Y. Irimajiri, M. Seta, S. Ochiai, T. Manabe, H. Masuko, T. Noguchi, K.

Narasaki, S. Tsunematsu, and T. Shirota, "Space-borne 640-GHz receiver based on 4-K mechanical

cooler", Astronomical Telescopes and Instrumentation, Proc. SPIE, Vol. 4013, pp. 90-99, 2000.

10 J. Inatani, K. Narasaki, S. Tsunematsu, M. Kyoya, T. Manabe, M. Seta, T. Iida, and R. Satoh,

"Mechanical cooler and cryostat for submillimeter SIS mixer receiver in space", Proc. SPIE, Vol.

4540, pp. 197-208, 2001.

11 H. Ozeki, Y. Kasai, S. Ochiai, S. Tsujimaru, J. Inatani, H. Masuko, C. Takahashi, L. Mazuray, and C.

Rosolen, "Submillimeter wave spectroscopy performance of JEM/SMILES", SPIE's Second Interna-

tional Asia-Pacific Symposium on Remote Sensing of the Atmosphere, Environment and Space,

Sendai, Japan, Oct. 9-12, 2000, Proc. SPIE, Vol. 4152, pp. 255-262, 2000.

12 SMILES Mission Team, JEM/SMILES Mission Plan, Committee for Earth Observation Systems, Earth

Science and Technology Forum, Feb. 2001. Available at http://www.crl.go.jp/dk/c214/smiles/Mis-

sion_Plan/

As described above, for the developmentof JEM/SMILES we must develop numeroustechnologies that remain unexplored for spaceuse to date. Another difficulty that we willencounter lies in the short period of time allo-cated to such development. We hope that

these difficulties and problems will be solvedso that the mission succeeds as planned and sothat the technologies for global observationusing submillimeter waves may be establishedand put to practical use.

MANABE Takeshi, Dr. Eng.

Leader, SMILES Group, AppliedResearch and Standards Division

Microwave and Millimeter-Wave Prop-agation and Remote Sensing

20 Journal of the Communications Research Laboratory Vol.49 No.2 2002