biology and biotechnology

SUPERCONDUCTING SUBMILLIMETER-WAVE LIMB-EMISSION SOUNDER (SMILES)

Research Area: Earth Remote Sensing

Expedition(s): 19-ongoing

Principal Investigator(s): ● Masato Shiotani, PhD, Kyoto University, Kyoto, Japan

RESEARCH OBJECTIVES

Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) is aimed at global

mappings of stratospheric trace gases by means of a sensitive submillimeter receiver. From the

International Space Station (ISS) altitude, the instrument detects a weak submillimeter

electromagnetic wave that is emitted from atmospheric molecules as a “radiance spectrum.”

The spectra are analyzed with algorithms so that the amounts of several kinds of atmospheric

molecules on various altitudes are calculated.

EARTH BENEFIT

The global distributions of ozone and related atmospheric constituents (eg, HCl, ClO and BrO)

monitored from SMILES observation data with high resolution. The distribution of these species

vary during the 24-hour day/night cycle on Earth, and SMILES can be observed, something

previously not possible in such detail. The highly sensitive observations of SMILES will help to

gain a better understanding of processes controlling the stratospheric ozone chemistry, and

those related to climate change.

SPACE BENEFIT

The technologies of the cryogenic system used in SMILES to

provide cooling for the scientific instruments will be used in

future space science programs.

RESULTS

SMILES performed atmospheric observation of Earth for 6

months from October 12, 2009, to April 21, 2010. Due to a

failure of the local oscillator component, the observation

period was terminated. However, SMILES obtained sub-

millimeter spectrum data with extremely low noise, and

the instrument demonstrated its high potential for minor

atmospheric constituent observations in the middle

atmosphere.

For example, SMILES data revealed anomalous distribution

of stratospheric ozone in tropic regions from autumn of 2009 to spring of 2010. In January of

2010, ozone depletion in the arctic (caused by the same mechanism as the antarctic ozone

hole) was observed based upon SMILES data of ozone and chlorine compounds. Detailed

comparisons with previous ground-based and spaceborne experiment data revealed that

SMILES data quality is comparable or more high-precision than previous methods. This

conclusion is also based upon comparisons with the multiple atmospheric numerical models.

For example, diurnal variations of stratospheric ozone was revealed by SMILES data by

Sample of global distribution of ozone, HCl
and ClO on certain altitude in
stratosphere, which were measured with
SMILES instrument. It measures
electromagnetic wave emitted from
atmospheric molecules on various altitude.
Vertical distributions of such molecules
are retrieved from the submillimeter
spectra. JAXA image.