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The first observation data from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)

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October 19, 2009

The first observation data from SMILES, the Superconducting Submillimeter-Wave Limb-Emission Sounder, which had been attached to the Exposed Facility of Japan Experiment Module “Kibo” on the International Space Station (ISS), has been obtained.

SMILES, which had been developed under the cooperation of Japan Aerospace Exploration Agency (JAXA) and National Institute of Information & Communication Technology (NICT), carries the mechanical cryocooler for the first time as a spaceborne equipment. According to 4-K supercooled superconducting detector, SMILES realises highly precised observation of Earth’s atmospheric constituents than ever before. At the present, the initial checkout of SMILES components results in no problem, so it can be told that all components including cryocooler and superconducting detector is in a normal state.

The following figure shows the global distribution of ozone on the altitude of 28km which is observed by SMILES in October 12th (in JST) [The unit is “ppmv” (parts per million by volume)]

According to this figure, it can be find that ozone exists more around equator region. This shows the characteristics of stratospheric ozone in its global distribution, which is consistent with the result of past observations performed by other satellites.

Please note that the example of SMILES observation shown in this release is still untested. JAXA and NICT will continue efforts for initial checkout of SMILES instrument, as well as for quality check and initial calibration/validation of observation data using ground-based experiment data and existing satellite observation data, for more than half a year.

Comments from Prof. Masato Shiotani of Kyoto University (SMILES Principal Investigator)
SMILES aboard the ISS can finally initiate its atmospheric observation, after the selection as one of the missions on JEM Exposed Facility. I would appriciate the efforts of those who involved in this mission.

For Japan, it becomes possible to restart the spaceborne observation related to upper atmosphere, which has been absent around a decade.

I expect that SMILES observation results in contributing to the ozone-layer issue as well as air quality problems.

Related Links: (SMILES website in JAXA) (ISS page in JAXA) (SMILES website in NICT)


Fig.1: Global Distribution of Atmospheric Ozone (Same figure as the one shown in the body text)
The global distribution of atmospheric ozone on the altitude of 28km, which is observed with SMILES in October 12th. It can be found that ozone exists more around equator region than in the high latitudes.

Fig.2: Latitude ? Altitude distribution of ozone
Vertical distribution of ozone from the latitude from 38 deg. South to 65 deg. North, using the observation data of October 12th. [The unit is “ppmv” (parts per million by volume)] It can be found that the peak of ozone (colored with red and pink) around the altitude of 30km. This also shows that SMILES observation captures the existence of the “ozone layer” in the stratosphere.

Fig.3: Radiation Spectrum in Submillimeter Region
The radiation spectrum from earth’s atmosphere is directly measured with SMILES instrument. The measurement data are utilized to calculate the result shown in Fig. 1 and 2. The graphes drawn in this figure show the amount of various atmospheric constituents related with stratospheric ozone depletion.

The overview of the Superconducting Submillimeter-Wave Limb-Emission Sounder

SMILES is the earth atmospheric observation instrument which measures weak submillimeter-wave radiated from atmospheric minor constituents with the detector which carries superconducting mixer cooled down to 4K (-269 deg. C) by mechanical cryocooler. By supercooling the detector, its measurement noise will be reduced to nearly the theoretical limits, which will result in improvement of measurement performance. It is expected that SMILES will make one-digit more precised observation than other existing satellite-borne sensors. It is also anticipated that atmospheric constituents which has been difficult to detect will be measured with high precisition by SMILES.

After the on-going initial checkout, SMILES will move to the operational observation phase. In this phase, SMILES will observation on about 100 points each track of International Space Station (ISS), that is, about 1600 points per day, except for the restrictions due to ISS operation.

As a result of processing of observation data, distributions of 10 kinds of atmospheric constituents including ozone will be revealed, which will contribute to various issues of earth atmospheric science.

SMILES can contribute to the atmospheric science issues including inorganic chroline chemistry (ClO/HCl ratio, HOCl production and background ClO distribution etc.), bromine budget which will become key point in the chemical reaction during the term of recovery of stratospheric ozone, the “HOx dilemma” (the problem that stratospheric / mesoshperic HOx number density observed by satellites disagree with results of calculation by atmospheric photochemical models). These issues closely related with stratospheric chemistry including “ozone layer” problem.

The trend of “ozone layer”, which is purported to recover gradually, is still the question under discussion. In addition, change of stratospheric ozone and global warming is seemed to interact each other, so it is important to consider integrated problem of earth atmosphere, not only to treat each component such as ozone depletion and global warming individually.

Therefore, in the sense of contribution to major issues of earth atmospheric environment, SMILES observation is very meaningful.

Contact Points

Japan Aerospace Exploration Agency (JAXA)
Tel. +81-50-3362-4374 Fax. +81-3-6266-6911

National Institute of Information Communications Technology (NICT)
Tel. +81-42-327-6923 Fax. +81-42-327-7587