Takuki Sano

Seasonal variation of tropospheric ozone in Indonesia revealed by 5‐year ground‐based observations

Regular ozonesonde observation and total ozone observation with the Brewer spectrophotometer have been conducted at Watukosek (7.5°S, 112.6°E), Indonesia, since 1993. Three seasons are recognized for the vertical distribution of tropospheric ozone. (1) During the local wet season, between December and March, the ozone mixing ratio is nearly constant at 25 ppbv throughout the troposphere. (2) During the transition season from wet to dry, between April and July, the mixing ratio is often enhanced in the uppermost troposphere. (3) During the local dry season, between August and November, the concentration is enhanced in the planetary boundary layer, and extensive forest fires in Indonesia associated with the strong El Nino events of 1994 and of 1997 have enhanced the ozone mixing ratio in the middle troposphere, the integrated tropospheric ozone, and the total ozone at Watukosek.

Overview and early results of the Global Lightning and Sprite Measurements mission

Global Lightning and Sprite Measurements on Japanese Experiment Module (JEM-GLIMS) is a space mission to conduct the nadir observations of lightning discharges and transient luminous events (TLEs). The main objectives of this mission are to identify the horizontal distribution of TLEs and to solve the occurrence conditions determining the spatial distribution. JEM-GLIMS was successfully launched and started continuous nadir observations in 2012. The global distribution of the detected lightning events shows that most of the events occurred over continental regions in the local summer hemisphere. In some events, strong far-ultraviolet emissions have been simultaneously detected with N2 1P and 2P emissions by the spectrophotometers, which strongly suggest the occurrence of TLEs. Especially, in some of these events, no significant optical emission was measured by the narrowband filter camera, which suggests the occurrence of elves, not sprites. The VLF receiver also succeeded in detecting lightning whistlers, which show clear falling-tone frequency dispersion. Based on the optical data, the time delay from the detected lightning emission to the whistlers was identified as ∼10 ms, which can be reasonably explained by the wave propagation with the group velocity of whistlers. The VHF interferometer conducted the spaceborne interferometric observations and succeeded in detecting VHF pulses. We observed that the VHF pulses are likely to be excited by the lightning discharge possibly related with in-cloud discharges and measured with the JEM-GLIMS optical instruments. Thus, JEM-GLIMS provides the first full set of optical and electromagnetic data of lightning and TLEs obtained by nadir observations from space.

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.

In-Orbit Measurement of the AOS (Acousto-Optical Spectrometer) Response Using Frequency Comb Signals

The in-orbit response characteristic of the AOS (Acousto-Optical Spectrometer) was estimated from spectral profiles taken by using a frequency comb generator, which was originally used for frequency axis calibration. Frequency comb signals taken under various environmental conditions in orbit were consolidated to deduce the response profile of the spectrometer. The fluctuation bandwidth calculated from the deduced spectral response compared well with that derived from the noise characteristic of the spectrometer.

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.

Ozone dynamics ultraviolet spectrometer (ODUS)

The Ozone Dynamics Ultraviolet Spectrometer (ODUS) is a satellite-borne, nadir-looking ultraviolet spectrometer for measuring total ozone amount. It will be launched in 2005 onboard Japanese earth observation satellite GCOM-A1. The ODUS instrument measures continuous spectrum from 306 to 420 nm with 0.5 nm spectral resolution and 20 km spatial resolution, using an Ebert-type polychromator and a one-dimensional silicon CMOS array detector, which will improve the accuracy of the retrieved total ozone amount. We have completed the conceptual design of system, and manufactured and tested the laboratory model of the detector and the optical assembly. We have succeeded in developing a detector with sufficient sensitivity and a polychromator with little stray light. We have also confirmed the optical performance and evaluated the detailed wavelength structure of the instrument function. This paper presents an overview of the ODUS instrument, the summary of the evaluation results of the laboratory models.

Performance verification and calibration of Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)

Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) has been operated on orbit since late September 2009. The on-orbit performance of the SMILES submillimeter receiver satisfied the specifications and demonstrated a high capability of superconducting technology for atmospheric science by providing an invaluable low-noise atmospheric limb-emission spectral data in 640-GHz band. The accuracy of the limb spectral data are going to be improved by radiometric calibration based on the instrumental knowledge measured on the ground and measurements on orbit. The observation by SMILES was unfortunately halted because of a failure of the submillimeter-wave local oscillator on 21 April 2010.

Recent results from the superconducting submillimeter-wave limb-emission sounder (SMILES) onboard ISS/JEM

The Superconducting submillimeter-wave limb-emission sounder (SMILES) employs superconducting detectors mechanically cooled down to ~4K, and it is extremely sensitive (Tsys < 400K), for the weak emission from trace species of stratosphere and mesosphere, such as O3, HCl, HNO3, ClO, HO2, and BrO. SMILES was launched onboard HTV spacecraft by using H-IIB launcher and started atmospheric observation in autumn of 2009. Using 2 bands among 3 bands in the 625 and 650 GHz submillimeter region, SMILES has been observing precise spectra with ~1K noise. Level- 2 (L2) data processing is on going at ISAS/JAXA in semi-real time basis. O3, HCl, HNO3 and ClO have strong emission signal in the SMILES frequency coverage and we already found that SMILES L2 data is comparable or even better than the existing best satellite observation of the atmosphere. HO2 and BrO have been retrieved with single scan data successfully and the results are under verification. Since SMILES observation is much better than any previous observation, validation of SMILES L2 data will be challenging. This paper describes L2 processing at ISAS/JAXA and early results of SMILES.

Ozone mapping and expected products by ODUS

The Ozone Dynamics Ultraviolet Spectrometer (ODUS) will be on board the GCOM (Global Change Observation Mission)-A1 satellite. The main objectives of the ODUS mission are global mapping of total ozone field, monitoring of volcanic sulfur dioxide (SO/sub 2/), surface UV-B, and surface albedo. The total ozone will be derived in high accuracy of about 2% with a spatial resolution of 20 km /spl times/20 km at nadir view. By combining data obtained by ODUS and other instruments (SOFIS and SWIFT) on board GCOM-A1, the dynamical features of stratosphere will be revealed using ozone as a tracer. The tropospheric ozone field will also be derived. Spectroscopic measurement of solar scattered UV from the Earths atmosphere by ODUS also makes it possible to derive SO/sub 2/ and NO/sub 2/ over polluted atmospheric conditions. Other minor constituents such as BrO, OClO, and HCHO will also be measured. Information on aerosol amount and their types over land area are also research targets of the ODUS instrument. As for the system design of ODUS, investigations are extensively made from many aspects to construct a light and low power consumption sensor with high performance for measuring the UV spectra. The algorithm development is also important and started.

Design and preliminary performance evaluation of airborne hyper-spectral imaging spectograph Air-OPUS

Air-OPUS is a hyper spectral imaging spectrograph, with 0.34 nm spectral step, 190-455 nm spectral coverage, and 330 spatial channels covering 15 degrees field of view (FOV). It is designed as an airborne instrument for the demonstration of spaceborne-OPUS. After two-demonstration campaign using the Gulfstream-II aircraft, the performances of AIR-OPUS, such as spectral resolution, signal-to-noise ration (SNR) have been evaluated. It is concluded that the performances have agreed with designed value. This paper describes design, the performance, and the first results of Air-OPUS. Concept of next generation Air-OPUS, with wider FOV and visible/near-IR spectral coverage, will be also briefly presented.