Makoto Taguchi

Telescope of extreme ultraviolet (TEX) onboard SELENE: science from the Moon

The Upper Atmosphere and Plasma Imager (UPI) is to be launched in 2007 and sent to the Moon. From the lunar orbit, two telescopes are to be directed towards the Earth. The Moon has no atmosphere, which results in there being no active emission near the spacecraft; consequently, we will have a high-quality image of the near-Earth environment. As the Moon orbits the Earth once a month, the Earth will also be observed from many different directions. This is called a “science from the Moon”. The two telescopes are mounted on a two-axis gimbal system, the Telescope of Extreme ultraviolet (TEX) and Telescope of Visible light (TVIS). TEX detects the O II (83.4 nm) and He II (30.4 nm) emissions scattered by ionized oxygen and helium, respectively. The targets of extreme-ultraviolet (EUV) imaging are the polar ionosphere, the polar wind, and the plasmasphere and inner magnetosphere. The maximum spatial and time resolutions are 0.09 Re and 1 min, respectively.

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.

Development of airglow temperature photometers with cooled-CCD detectors

We have developed three airglow temperature photometers with cooled-CCD detectors. The photometers measure rotational temperatures using the airglow emissions of OH and O2 near the mesopause region (altitude: 80s-100 km). The photometers also measure six other airglow and auroral lines at wavelengths of 557.7, 630.0, 777.4, 589.3, 427.8, and 486.1 nm. The CCD detectors are used to distinguish the emission lines in these airglow bands, similarly to those used by the Spectral Airglow Temperature Imagers (SATI). In this paper, we describe the configuration of the photometers, their calibration, the data processing to extract rotational temperatures and emission intensities from the measured airglow spectra, as well as the initial deployment at Platteville, Colorado (40.2°N, 255.3°E), when their observations were compared with the concurrent and nearly collocated observations by a sodium lidar. We obtain a good correlation and some systematic difference of temperatures from the photometers and the lidar, and discuss possible causes of the temperature difference.

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.

Lunar albedo at hydrogen Lyman α by the NOZOMI/UVS

The geometric albedo of the Moon at the wavelength of hydrogen Lyman α (HLyα 121.6 nm) was derived from an imaging observation by the ultraviolet imaging spectrometer (UVS) during the lunar encounter of the NOZOMI spacecraft. The solar HLyα irradiance data measured by the UARS/SOLSTICE at the time of UVS observation were adopted. We obtained an average geometric albedo of 5.2 ± 0.9% for the sunlit region where the UVS observed. Our result agrees with the geometric albedos obtained from the observations by Apollo 17 and Astro-2/HUT, though the observation geometry and area are completely different from each other. There exists a significant difference of the albedos from place to place in the observed lunar surface ranging from 2.3 ± 1.1% to 6.0 ± 1.0%. It is noted that the observed contrast at the FUV wavelength is positive to that seen in the visible region.

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.

Lyman alpha imaging of solar activity on the interplanetary hydrogen screen for space weather forecasting

[1] Interplanetary hydrogen atoms that penetrate into the heliosphere are illuminated by enhanced hydrogen Lyman alpha emission from solar active regions. Using the data obtained by the Solar Wind Anisotropies (SWAN) instrument on board the Solar and Heliospheric Observatory (SOHO), Bertaux et al. (2000) proposed a new method for earlier detection and monitoring of solar active regions on the far-side hemisphere. However, a quantitative relationship between the sky map of interplanetary Lyman alpha intensity and the enhanced emission from a solar active region was not discussed. Here, we analyze the interplanetary Lyman alpha intensity data obtained by the Ultraviolet Imaging Spectrometer (UVS) on board the Nozomi spacecraft. We develop a method to map the distribution of interplanetary Lyman alpha intensity into the Carrington coordinate system by assuming an interplanetary hydrogen screen at the location of maximum volume emission rate. Analysis period is from January 2000 to March 2000 near solar maximum. The solar activity during this analysis period is much higher as compared with the case study by Bertaux et al. (2000). The sky map of the Lyman alpha emission obtained by the UVS is shown to exhibit a high correlation with the solar extreme ultraviolet (EUV) intensity map obtained by the EUV Imaging Telescope (EIT) on board the SOHO satellite. The highest value of two-dimensional correlation coefficient is 0.80. An observed change in the periodicity of interplanetary Lyman alpha intensity is in good agreement with the growth of an active region on the Sun. It has been also confirmed that the far-side observations of UVS detected the growth of an active region in advance. This case study demonstrates that the location and intensity variation of activity on the far side of the Sun can be detected by far-side measurements of interplanetary Lyman alpha emission intensity. It is thus concluded that the developed method contributes to space weather forecasting on a scale of 2 weeks.