Ground Compatibility Tests for Gravity Measurement of SELENE: Accuracies of Two- and Four-Way Doppler and Range Measurements

The Japanese lunar mission Selenological and Engineering Explorer (SELENE) was launched in September 2007 and continued its mission until June 2009, when the main orbiter impacted with the surface of the Moon. SELENE consisted of three satellites: Main, Rstar, and Vstar. Rstar’s tasks were to forward up-link signals from the Usuada Deep Space Center (UDSC) to Main, and to down-link returning signals from Main to UDSC. We refer to this tracking sub-system as a four-way Doppler measurement. In contrast, conventional tracking systems between Rstar and UDSC as well as between Main and ground stations are referred to as two-way Doppler and range measurements. Using Main and Rstar, we successfully observed the gravity field over the farside of the Moon. Because four-way Doppler measurements via a relay sub-satellite were a fundamental experiment in space for Japanese space agencies, compatibility of radiometric instruments onboard Main and Rstar to UDSC were carefully examined at the UDSC using components manufactured for flight models. These tests not only proved the feasibility of the four-way Doppler measurements but also provided biases and variations of the four-way Doppler and two-way Doppler and range measurements that were later taken into account during the processing of tracking data and the analysis of the lunar global gravity field.     

Oxygen line mapping of SN 1006 with Suzaku

SN 1006 is one of the supernova remnants (SNRs) with relatively low-temperature electrons, considering the young age of just 1000 years. We carried out SN 1006 mapping observations with the X-ray Imaging Spectrometers (XIS) and the Hard X-ray Detector (HXD) onboard Suzaku, the fifth Japanese X-ray satellite. Thanks to the excellent spectral resolution of XIS in the soft X-ray band, H-like and He-like oxygen emission lines were clearly detected, and we could make a map of the line intensity, and as well as a flux and the photon index of nonthermal component. We found that these parameters have spatial dependences from region to region in the SNR; the north region is bright in nonthermal, while dim in thermal; the east region is bright in both nonthermal and thermal; the inner region shows dim nonthermal and bright thermal emission. The photon index is the smallest in the north region.     

Simulation experiments of the cosmic ray isotope telescope on ETS VI

A computer simulation was carried out to evaluate the basic characteristics of a Δ E×E cosmic ray telescope consisting of 23 solid state detectors including 3 position sensitive detectors with large effective area. Based on the simulation, the geometric factor of the telescope is deduced to be as large as 22.5 cm²sr, almost independent of charge and energy concerned. The energy ranges to be covered by the telescope are, for example, 18–98 MeV/n for Li and 56–339 MeV/n for Fe. By analyzing simulated data, the mass resolution for iron in the overall energy range covered by the telescope is estimated as about 0.22 amu in standard deviation. The expected counting rates and mass-histograms are simulated for Galactic cosmic rays and solar energetic particles.     

Self-perspiration garment for extravehicular activity improves skin cooling effects without raising humidity

Introduction

The current U.S. extravehicular activity (EVA) suit in space includes liquid cooling and ventilation garment (LCVG) to control thermal condition. Tubes knitted in LCVG for flowing water interrupt evaporation of perspiration, and astronauts feel discomfort. In the present study, we hypothesized that a self-perspiration garment would effectively lower the skin temperature without raising humidity in the garment. Thus, we developed and examined the effects of the garment.

Methods

Eight healthy subjects were studied with a cyclic ergometer of 30, 60 90 and 120 W loading for 3 min each. Skin temperature and humidity on the back were measured continuously. Subjects wore and tested three types of garments i.e., a spandex wear without any cooling device (Normal), a simulated LCVG (s-LCVG) or the spandex wear knitted a vinyl tube for flowing water, and the spandex wear with a tube, which flows water and self-perspiration with oozing water for evaporative cooling (SPEC).

Results

All measurements were reached to steady state 2–3 min after the setting. The s-LCVG decreased skin temperature 0.39±0.14 °C during 12 min of cooling. With SPEC, skin temperature did not decrease significantly until 6–9 min after starting the cooling. However, the temperature decreased rapidly and significantly after that, and finally decreased 1.59±0.32 °C. Humidity in the SPEC was significantly lower than that in s-LCVG.

Discussion

SPEC was effective for lowering skin temperature without raising humidity in the garment. The concept is expected to use as a better cooling system during EVA.     

Capability for ozone high-precision retrieval on JEM/SMILES observation

We estimate the capability of ozone (O₃) retrieval with the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) instrument attached to the Exposed Facility of the Japanese Experiment Module (JEM) on the International Space Station (ISS). SMILES carries a 4-K mechanical refrigerator to cool superconducting devices in space. Since SMILES has high sensitivity thanks to the superconducting receiver, it is expected that SMILES has ability to retrieve O₃ profiles more precisely than the previous millimeter–submillimeter limb measurements from satellites.     

Design concept of Quasi Zenith Satellite System

The Quasi Zenith Satellite System, a Japanese satellite navigation system, is under development. The system broadcasts GPS-interoperable and augmentation signals as well as original Japanese signals from an inclined, elliptical geosynchronous orbit. Using this system, users around Japan and Oceania can use seamless positioning, navigation, and timing services, even in urban canyons and mountainous areas. A government policy supports the project to promote the use of geographical spatial information linked to satellite-based navigation for a wealthy and secure life in accordance with the rapid increase of satellite navigation users nationwide. To support that policy, JAXA is in charge of developing the first stage of QZSS in collaboration with related ministries and national institutes. Attention is devoted to making the system reliable and economical using legacy Japanese GEO satellite system technologies, not only satellite technology, but also ground systems and operations technologies.     

The spaceborne lidar experiment

Lidar is one of the key sensors to understand global atmospheric environment, so lidar is one of the candidates to be flown on future earth observation satellites. But spaceborne lidar is our first trial and we have some technical issues to resolve before establishing operational sensor. So we start development of the Spaceborne Lidar Experimental Model as a first step of lidar program of NASDA. The Spaceborne Lidar Experimental Model will be launched in early 2001.

The purpose of the Spaceborne Lidar Experiment is technological demonstration of system design and critical components to apply to future operational sensor. And we demonstrate availability of lidar observation data and scientific value.

There are some critical points to resolve such as (1) thermal design of laser oscillator which remove locally-generated-heat effectively and (2) mirror design with little distortion.     

Identification of power analysis models for ETS-III operation

This paper describes the identification of power analysis models of BOP (the Bus Equipment Operation Analysis Program) for ETS-III operation. The ETS-III (Engineering Test Satellite III) was launched in September 1982. BOP simulations are to provide prior confirmation for safe operation in terms of electrical power and thermal control situations. It is necessary to identify power analysis model first and improve the model for higher accuracy. Studies for model identification have been done by using flight data and simulation results. As a result of these studies, the power analysis model meets well with the actual ETS-III power situation and the aimed accuracy of the model has been achieved.     

Friction and Wear Properties of Amorphous Carbon Nitride Coatings in Water Lubrication

The friction and wear properties of amorphous carbon nitride(a-CN x)coatings in water lubrication were reviewed.The influences of mating materials and tribological variables such as normal load(W)and sliding speed(V)on the friction and wear properties of the a-CN x coatings were analyzed.It was indicated that the specific wear rate of the a-CN x coatings was related to the hydration reaction of mating materials with water.If the mating materials were easily hydrated,the specific wear rate of a-CN x coatings was low.The water-lubricated properties of the a-CN x coatings were better in comparison to the a-C coatings.The a-CN x/Si-based non-oxide ceramics tribo-pairs exhibited the lowest friction coefficient and wear rate.To describe their friction and wear properties at the normal loads of 3—15Nand the sliding speeds of 0.05—0.5m/s,the wear-mechanism maps for the a-CN x/SiC(Si3N4)tribo-pairs in water were developed.