Shoichi Okano

Observations of thermospheric wind velocities and temperatures by the use of a Fabry–Perot Doppler imaging system at Syowa Station, Antarctica

A new optical instrument, the Fabry-Perot Doppler imaging system (FPDIS), has been developed for observations of two-dimensional distributions of thermospheric wind velocities and temperatures by the measurement of the Doppler shift and width of the aurora or of the airglow emission lines of atomic oxygen OI 557.7 nm and OI 630.0 nm over a wide field of view (165°). A technique for the derivation of Doppler temperatures and wind velocities was developed by use of a truncated Fourier series. Thermospheric wind velocities and temperatures have been obtained with unprecedented high temporal (1 min) and spatial (24 points for an all-sky image) resolutions. Errors in the derived wind velocities and temperatures are estimated to be less than 25 m/s and 100 K, respectively, for inner-fringe positions and 35 m/s and 170 K for outer-fringe positions, respectively. This system was applied to observations of thermospheric wind velocities and temperatures at Syowa Station (69.00° S, 39.58° E), Antarctica for the period of one austral winter in 1990.

Ultraviolet imaging spectrometer (UVS) experiment on board the NOZOMI spacecraft : Instrumentation and initial results

An ultraviolet imaging spectrometer (UVS) on board the PLANET-B (NOZOMI) spacecraft has been developed. The UVS instrument consists of a grating spectrometer (UVS-G), an absorption cell photometer (UVS-P) and an electronics unit (UVS-E). The UVS-G features a flat-field type spectrometer measuring emissions in the FUV and MUV range between 110 nm and 310 nm with a spectral resolution of 2–3 nm. The UVS-P is a photometer separately detecting hydrogen (H) and deuterium (D) Lyman α emissions by the absorption cell technique. They take images using the spin and orbital motion of the spacecraft. The major scientific objectives of the UVS experiment at Mars and the characteristics of the UVS are described. The MUV spectra of geocoronal and interplanetary Lyman α emissions and lunar images taken at wavelength of hydrogen Lyman α and the background at 170 nm are presented as representative examples of the UVS observations during the Earth orbiting phase and the Mars transfer phase.

Japanese research project on Arctic and Antarctic observations of the middle atmosphere

Abstract An all-sky optical imager is in routine observation at the South Pole. Monochromatic images of aurora and air glow at N 2 + 427.8nm, OI 557.7nm, OI 630nm and OH 730nm are supplying significant information on the magnetospheric process in the polar cap and cusp/cleft region along with atmospheric wave signature at this particular point. SuperDARN radars in Antarctica make observations over the South Pole. At Syowa Station, Antarctica, a multi-instrumental observation project is now being implemented for the study of the polar upper atmosphere from the mesosphere to the thermosphere, where complex physical and chemical processes take place making the region very attractive for scientific research. Two HF radars, which are part of SuperDARN radars, have been already installed and started observations. By the end of 1999, all-sky imagers, photo meters, a Na temperature Lidar, an MF radar and a Fabry-Perot interferometer will be introduced and start collecting various physical parameters on a routine basis. In the Arctic region, we are planning to deploy coordinated ground-based observations with optical, radio and radar sensing of the polar middle and upper atmosphere in conjunction with EISCAT radars. Scientific goals are versatile to shed light on the tangled coupling processes in response to magnetospheric disturbances from above and bi-lateral interactions with high-density lower atmospheric layers. These are outlined in this paper.

Coordinated observations of the mesopause region with radar and optical techniques

Abstract This paper reports the development of coordinated observations carried out with the use of the MU radar (middle and upper atmosphere radar) and optical measurement techniques in Shigaraki. Since the start of the MU radar operation, mesosphere wind and turbulence were studied using mesospheric turbulence echo in the daytime. More recently, meteor echoes have been used to observe wind and temperature around the mesopause, during day and night. Comparative observations with the MU radar meteor mode and sodium lidars were used to study gravity waves and variation of sodium layers. Airglow observations were also carried out as a campaign basis, with which small scale and large scale gravity waves have been studied. We have also developed two CCD imagers to observe airglow images at the MU radar site for long term observations with the radar. Now Shigaraki has become an integrated optical/radar site ready to contribute to the PSMOS (Planetary Scale Mesopause Observing System) project being carried out between 1998–2002.

Distribution of sodium cloud near Io and in the inner jovian magnetosphere

Abstract We made observations of sodium atoms to investigate the spatial distribution of Iogenic gas. From the observational results, the shapes of emission distribution are classified into three types. They are (i) brighter (∼kilorayleighs) cloud around Io as far as ∼ 50RIo(Io radii), (ii) cloud which is directed away from Jupiter and concentrated along the equatorial plane of Jupiter outside Ios orbit, and (iii) diffuse and faint cloud spreading outside Ios orbit. We also detected that the D-line emission distribution shows intensity asymmetry between the north and south sides of the equatorial plane. We conclude that this asymmetry results from the temperature anisotropy of the torus plasma which makes charge exchange with neutral atoms around Io. The value of the anisotropy is determined to be A = T ∥ T ∥ = 8 and T∥ = 60[eV]. From a comparison of the observational results with the results obtained from model calculation, we estimate that the sodium atom source for charge exchange is 6.0 × 1025 atoms/sec.

MARS ULTRAVIOLET IMAGING SPECTROMETER EXPERIMENT ON THE PLANET-B MISSION

ABSTRACT An ultraviolet imaging spectrometer (WS) has been developed for the PLANET-B spacecraft. The WS instrument is composed of a grating spectrometer (WS-G) and a D/I-I absorption cell photometer (WS-P) . The UVS-G is a flat-field type spectrometer measuring optical emissions in the FW and MW range between 115 mn and 3 10 mn with a spectral resolution of 2 - 3 nm. The WS-P is a photometer detecting hydrogen ( H) and deuterium (D) Lyman Q emissions separately by an absorption cell technique. Scientific targets of the WS experiment are the investigation of ( 1) hydrogen and oxygen coronas around Mars, (2) the D/H ratio in the upper atmosphere, (3) dayglow, (4) aurora and nightglow, (5) dust, clouds and ozone, and (6) the surface composition of Phobos and Deimos. Q 1999 COSPAR. Published by Elsevier Science Ltd. INTRODUCTION Our knowledge about the Martian atmosphere has been enriched by remote sensing from fly-by or orbiting spacecraft of the USA and the USSR. The structure and composition of the Martian upper atmosphere have been investigated by ultraviolet remote sensing from Mariners’ 6, 7 and 9. Mariners 6 and 7, which had ultraviolet Fastie-Ebert scanning type monochromators, flew by Mars in July and August, 1969, respectively. Mariner 9 placed into a low-inclination orbit in November 1971 had 349 Earth days of operation and achieved all of its objectives.

Glass-type hydrogen and deuterium absorption cells developed for D/H ratio measurements in the Martian atmosphere.

Hydrogen and deuterium absorption cells of a new glass type have been developed for the D/H ratio measurements on the Japanese Mars mission PLANET-B. The H/D cells work as narrow-band rejection filters for the H/D Lyman-alpha line, respectively, when the H or D atoms are produced at a heated filament inside the cells. The absorption profiles of the cells were successfully measured with a high-resolution vacuum ultraviolet spectrometer with a wavelength resolution of 6.6 x 10(-4) nm. The derived optical thickness was found to be ~7 and ~14 for the hydrogen and deuterium cells, respectively. It was also found that the derived temperature of atomic gas ranges between the temperature of the cell wall and that of the heated filament, and it increases with increasing filament temperature. The measured profiles showed that the absorption efficiencies of the developed absorption cells are sufficient to observe the D/H ratios of the Martian atmosphere.

Variability of [SII] emission from the Io plasma torus

Io, the innnermost Galilean satellite of Jupiter, is a main source of heavy ions in the Jovian magnetosphere. Therefore variability of the plasma in the vicinity of Io produces large effects to the magnetospheric environment. We have started optical observations of the Io plasma torus in order to study the plasma environment in the Jovian magnetosphere. Observed emissions are forbidden line emissions of S+ ions (λλ 671.6 and 673.1 nm) in the plasma torus. In 1997, the observations were carried out at Alice Springs, Northern Territory of Australia. We mainly report the results of the observations at [SII] 673.1 nm.

Global scale Earth's upper atmosphere monitoring by SACI-1 micro-satellite

Abstract The first Brazilian scientific micro-satellite, SACI-1, is scheduled to be launched in the 2nd semester of 1999. It will be placed in a sun-synchronous polar orbit at a height of 750 km. Four scientific payloads, airglow photometer, high energy particle telescopes, plasma probes and high sensitive magnetometer, are on board to monitor the Earths upper atmosphere environment. The main scientific goal is focused on upper atmospheric dynamics, ionospheric plasma irregularities, anomalous cosmic ray and field-aligned electric current system in the magnetosphere. International collaboration will be necessary, and this will be a key point in order to maximize the utilization of the data.

Airglow observation by Fabry-Perot Interferometer

An all-sky and a scanning Fabry-Perot interferometers (FPI) have been developed for observations of vertical winds and two-dimensional atmospheric motions in the low-thermosphere and the mesosphere region by the measurement of Doppler shift and broadening of airglow emission lines. The system of FPI is described and the method of data analysis is proposed, an example of observation is also given.