Chihiro Mitsuda

Current status of level 2 product of Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)

New level 2 products v2.0 of JEM/SMILES are scheduled to be released in Sep., 2011. This will be the first publicreleased version. In pre-released product v1.3, positive bias of retrieved temperature in the stratosphere was the largest issue since temperature is basic parameter which characterizes the atmospheric structure. The new product use latest L1B 007 which includes gain nonlinearity effect of receivers, bias of temperature in upper stratosphere is suppressed. In addition, we stopped temperature retrieval above 40km and refer MLS temperature product with applying migrating tidal model. HCl profiles in mesosphere become constant, which supports this temperature processing.

Response characteristics of radio spectrometers of the Superconducting Submillimeter-Wave Limb-Emission Sounder (JEM/SMILES)

The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) observes vertical profiles of atmospheric minor constituents related with stratospheric and mesospheric chemical processes. The retrieved profiles contain some error originated from the response characteristics of radio spectrometers of the SMILES instrument. The on-orbit properties are necessary to be characterized and be modeled, in order to minimize the retrieval errors.

On orbit performance of radio spectrometers of Superconducting Submillimeter-Wave Limb-Emission Sounder (JEM/SMILES)

On-orbit performance of the radio spectrometer of SMILES is discussed. We focused on the telemetry data of photodiode current, laser diode current, and laser diode operating temperature. The data showed degradation trend as the mission went on. This is due to a wear-out phenomenon of commercially available laser diode, which is used as the light source of the radio spectrometer. Since the laser diodes have a certain lifetime, both screening procedure and operating condition for them must be properly defined and implemented for ensuring a good performance of the spectrometer throughout designed mission life. For these purposes, we conducted several kinds of qualification tests including an accelerated life time test during design phase, and expected life time of the laser diode was derived on the basis of these test results. In this paper, the results from the qualification tests at ground and the actual performance on orbit with the telemetry and mission data will be presented.

Gain nonlinearity calibration of the SMILES receiver

The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) was launched in September 2009 and has successfully observed the stratosphere for half a year. Before launch we measured the receiver gain nonlinearity. The gain compression of the SMILES receiver is estimated to be 2.6 to 4.3% from the measurement. The nonlinearity correction is applied to the observed data in space. Data are satisfactory corrected in the stratosphere but not in the higher altitude. The reason of the unsuccessful correction is discussed and attributed to our overestimation of the broadband nonlinearity.

Tangent height accuracy of superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on International Space Station (ISS)

The attitude detection system installed in the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) had insufficient angular precision for limb observation. While the SMILES observation provides extremely low-noise emission spectra, the large error in the tangent height of limb viewing due to the poor knowledge of the attitude often limits the accuracy of the SMILES products, such as volume mixing ratio of atmospheric molecules. The attitude data from a ring laser gyroscope (RLG) installed in a nearby experiment unit, Monitor of All-sky X-ray Image (MAXI), is used to improve the tangent-height error. We create a customized attitude data set from the RLG data initialized with information from the SMILES star sensor. Applying this customized RLG attitude, we can know the tangent height of limb observations with an improved precision of less than 140 m.

Sub-MM limb observation of stratosphere and mesosphere using ISS/JEM/SMILES

Performance of Superconducting Submillimeter-Wave Limb Emission Sounder (SMILES) onboard International Space Station was discussed from the analysis of random errors of Chlorine monoxide (ClO) in the stratosphere and mesosphere. Some lessons learned from the SMILES operation in space are discussed.

Verification of pointing and antenna pattern knowledge of Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)

The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) observes O3 and other minor chemical species in the stratosphere and mesosphere. Limb observation of SMILES is sensitive to the quality of the tangent altitude retrieval. To obtain better retrieval result, knowledge of initial tangent height and antenna pattern should be as precise and accurate as possible. It was concluded that initial tangent height is calculated by using ISS attitude and mirror pointing angle, and ISS position. Antenna pattern assuming 6 points moving average was applied to the retrieval and showed reasonable results.