Yugo Kimoto

Total dose orbital data by dosimeter onboard Tsubasa (MDS-1) satellite

The total dose data from a Tsubasa (MDS-1) satellite, flying in a highly eccentric orbit, is analyzed. The total dose is measured by the small dosimeter using RADFETs. The RADFETs have been calibrated with the Co60 gamma ray source, and 56 devices (denoted DOS-S) were mounted in several experimental modules in the satellite. The total dose data behind certain Aluminum shield domes have been analyzed initially. The total dose change is affected by electron flux in the thin shield. In thicker shield, electron and proton affect the total dose profile.

Degradation Property of Commercially Available Si-containing Polyimide in Simulated Atomic Oxygen Environments for Low Earth Orbit

Real-time measurement of the erosion rate of a commercially available Si-containing polyimide (BSF30) under hyperthermal atomic oxygen (AO) beam exposure condition, which simulates the AO environment in low Earth orbit (LEO), was performed. It was found that the erosion rate of BSF30 decreased with increasing AO fluence and it reached as low as 4% of the standard PMDA-ODA polyimide. X-ray photoelectron spectroscopy confirmed that the surface of AO-exposed BSF30 was covered by a SiO2 layer which functioned as a protective coating. In contrast, an SiO2 surface layer thick enough to protect bulk BSF30 was not formed by thermal AO, which was generated by vacuum ultraviolet exposure in an O2 atmosphere. Exposure to hyperthermal AO collision in LEO can also form an SiO2 layer which enables the surface to be self-healing and is desirable for a polyimide that would be used in LEO.

Space radiation environment and its effects on satellites: analysis of the first data from TEDA on board ADEOS-II

The Advanced Earth Observing Satellite II (ADEOS-II) was launched into sun-synchronous, sub-recurrent orbit on December 14, 2002, and its operation terminated unexpectedly on October 24, 2003. While in orbit, the Technical Data Acquisition equipment on board ADEOS-II monitored the space radiation environment and its effects, including total-dose and single-event upset, recording them on 16 M and 64 M-DRAM memories. In this paper, we analyze the first data results from these monitors.

Compact, lightweight spectrometer for energetic particles

We have developed an energetic particle spectrometer called a standard dose monitor (SDOM) that can discriminate and analyze the energy of electrons, protons, and alphas. SDOMs unique characteristics include a large G-factor, a wide energy range, and the ability to simultaneously identify and analyze the energy of multiple particle types. We plan to use this instrument to update current space radiation environment models.

Passive Space-Environment-Effect Measurement on the International Space Station

The Micro-Particles Capturer and Space Environment Exposure Device is the Japan Aerospace Exploration Agency’s experiment on particle capture and space exposure of material mounted on an aluminum tray. The trays were placed on the exterior of the Russian service module of the International Space Station. All trays were retrieved and returned toEarth. This paperpresents our analysis of the effects that space exposure imparted on themonitoring samples in the firstand second-retrievedMicro-Particles Capturer and Space Environment Exposure Device trays. The monitoring samples yield space-environment data such as atomic oxygen, ultraviolet, fluence, and space radiation dose data. The exposure and monitoring samples were retrieved after 315 and 865 days of exposure.

Passive Space Environment Effect Measurement on JEM/MPAC&SEED

A space materials exposure experiment was conducted on the exterior of the International Space Station (ISS) using the Micro-Particles Capturer and Space Environment Exposure Device (MPAC&SEED) of the Japan Aerospace Exploration Agency (JAXA). The MPAC&SEED experiments were aboard both the Russian Service Module (SM/MPAC&SEED) and the exposed Facility of the Japanese Experiment Module, KIBO Exposed Facility (JEM/MPAC&SEED). The JEM/MPAC&SEED was attached to the Space Environment Data Acquisition Equipment-Attached Payload (SEDA-AP).

Space Environment Effects on Materials at Different Positions and Operational Periods of ISS

A space materials exposure experiment was condcuted on the exterior of the Russian Service Module (SM) of the International Space Station (ISS) using the Micro‐Particles Capturer and Space Environment Exposure Device (MPAC&SEED) of the Japan Aerospace Exploration Agency (JAXA). Results reveal artificial environment effects such as sample contamination, attitude change effects on AO fluence, and shading effects of UV on ISS. The sample contamination was coming from ISS components. The particles attributed to micrometeoroids and/or debris captured by MPAC might originate from the ISS solar array. Another MPAC&SEED will be aboard the Exposure Facility of the Japanese Experiment Module, KIBO Exposure Facility (EF) on ISS. The JEM/MPAC&SEED is attached to the Space Environment Data Acquisition Equipment‐Attached Payload (SEDA‐AP) and is exposed to space. Actually, SEDA‐AP is a payload on EF to be launched by Space Shuttle flight 2J/A. In fact, SEDA‐AP has space environment monitors such as a high‐energy partic...

Compact Energetic Light Particle Detector and Spectrometer

We have developed a megaelectron-volt class energetic charged-particle spectrometer based on a novel configuration and processing algorithm. The National Space Development Agency of Japan has undertaken a program to develop a particle monitor capable of discriminating and measuring protons in the range from 0.9 to 150 MeV, electrons in the range from 0.5 to >10 MeV and alpha particles >8 MeV, all within a single sensor called the standard dose monitor. The goal is to utilize sensors with nearly identical design and performance on several simultaneous missions to develop a clearer understanding of particle energies and their variability as a function of solar activity, latitude, and altitude. To date, four flight model sensors have been delivered. The sensors are designed to detect accurately the higher-energy particles and high count rates present during active solar periods. In addition, this sensor exhibits extremely efficient discrimination between low-energy electrons and protons. The sensors have been calibrated over nearly their entire particle-energy range. The design is described and calibration data are compared with the results of a Monte Carlo sensor performance model.

First Evaluation of Contamination on the JEM/MPAC&SEED

JEM/MPAC&SEED were exposed to the space environment for 8.5 months and retrieved via EVA in April 2010. We subsequently analyzed the surface of JEM/MPAC&SEED to determine the state of contamination.

Flight Experiment Results of the Polysiloxane-Block-Polyimide “BSF-30” on the JEM/MPAC&SEED Mission on the ISS

Atomic oxygen (AO) in low Earth orbit (LEO) is one of the most dangerous environmental factors leading to erosion of the external materials of a spacecraft. As one of the methods to improve AO tolerance, the use of silicon-containing materials has been proposed. On such materials, an SiO2 layer is formed from the reaction of the silicon contained in the material and the AO existing in orbit, which can therefore be called a “self-organized” layer. In the present study, polysiloxane-block-polyimide “BSF-30”, which is a silicon-containing polyimide, was investigated by ground testing and in a flight experiment. BSF-30 was exposed to the LEO space environment on the Japanese Experimental Module/Micro Particles Capturer & Space Environment Exposure Device (JEM/MPAC&SEED) mission on the ISS for 8.5 months. As a result, a mass loss of 0.011 mg was measured, which is about 1/500 times smaller than that of a common polyimide. From a cross sectional transmission electron microscopy analysis the formation of a layer about ~50 nm thick was observed on the exposed surface, within which high fractions of Si and O were also detected. In conclusion, it is verified that BSF-30 has sufficient AO tolerance in a LEO environment by the JEM/MPAC&SEED.