Interim Report of Super Low Altitude Satellite Operation

Kawasaki, Hiromu; Konoue, Kazuya; Hoshino, Hiroo; Kaneko, Yutaka; Sasaki, Masanori

doi:10.1109/igarss.2018.8517529

Cited by 16 publications

(9 citation statements)

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“…Low Earth orbit (LEO), at altitudes of several hundreds of kilometers, includes the optimal altitudes for Earth observations and communications. These days, very low Earth orbit (VLEO), at altitudes of 300 km or lower, is expected to be increasingly used for optical observations with higher resolution and lower cost. − In LEO and VLEO, a spacecraft is exposed to the residual atmosphere, whose dominant component at 200–700 km is electrically neutral atomic oxygen (AO) . AO collides with the polymers used for thermal control at a relative velocity of 8 km/s, which is the orbital velocity of a spacecraft and corresponds to a translational energy of 5 eV, , resulting in oxidation and erosion of polymer surfaces.…”

Section: Introductionmentioning

confidence: 99%

Formation of Nanoscale Protrusions on Polymer Films after Atomic Oxygen Exposure: Observations with Positron Annihilation Lifetime Spectroscopy

Goto,

Michishio,

Oka

et al. 2023

Langmuir

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Atomic oxygen (AO) is one of the dominant components of the residual atmosphere in low Earth orbit. AO collides with spacecraft with a translational energy of 5 eV, forming nanoscale protrusions on polymeric materials. To clarify the influences of a polymer’s chemical structure on the formation of AO-induced microstructures, this study investigated the size of free-volume holes and the layer thickness that interacted with AO for polyethylene (PE), polypropylene (PP), and polystyrene (PS) by positron annihilation lifetime spectroscopy. The injection energies of positrons varied from 1.3 to 10 keV to adjust the injection depth (range) into the polymers (40 nm–1.6 μm). For the pristine films, the lifetime of ortho-positronium (o-Ps, τ3) was longer in the order of PS, PP, and PE regardless of the injection energy of positrons, showing the different sizes of free-volume holes with radii of 0.29, 0.31, and 0.32 nm, respectively. The fraction of the decay component corresponding to o-Ps in all decay components (relative intensity of o-Ps, I 3) was used to investigate the chemical change induced by AO exposure. The I 3 values for the three polymers were decreased by AO exposure of (2–5) × 1018 atoms/cm2 or more at a depth of 40–48 nm, obtained by 1.3 keV positrons. This indicates that AO formed polar groups (i.e., an oxidized layer) on the polymer surfaces. The maximum depths of such chemical change for PE and PP were deeper than that for PS. The different sizes of free-volume holes would affect the diffusion or ballistic penetration of AO, resulting in the difference in the oxidized layers’ thicknesses and surface morphologies.

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Section: Introductionmentioning

confidence: 99%

Formation of Nanoscale Protrusions on Polymer Films after Atomic Oxygen Exposure: Observations with Positron Annihilation Lifetime Spectroscopy

Goto,

Michishio,

Oka

et al. 2023

Langmuir

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“…Attention is focused on a mission called S-LEO or VLEO, which operates below LEO. Lower altitudes will benefit Earth observation, such as higher resolution optical imaging, a higher signal/noise ratio of Synthetic-Aperture Radar (SAR), and more significant cost reduction of compact, lightweight satellite sensors and launch services (Kawasaki et al, 2018). Additional benefits include improved geospatial position accuracy, improved communications-link budgets, and greater insertion capability of launch vehicles.…”

Section: Introductionmentioning

confidence: 99%

“…SLATS (Kawasaki et al, 2018) The SLATS mission aims to evaluate orbit-control techniques and demonstrate the ability of high-resolution optical imaging from super-low altitudes. Supplementary Figure S1 shows an overview of SLATS, and Supplementary Table S1 lists general information about SLATS.…”

Section: Introductionmentioning

confidence: 99%

Analysis of upper atmospheric effects on material per onboard atomic oxygen monitor system of SLATS

Kimoto

Tsuchiya²,

Miyazaki³

et al. 2022

Front. Space Technol.

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JAXA has proposed an innovative idea for satellites in Low Earth Orbit (LEO). The Super-Low Altitude Test Satellite (SLATS), also known as TSUBAME, is the first Earth observation satellite to occupy a Super-Low Orbit (S-LEO) or Very Low Earth Orbit (VLEO), below 300 km. The purposes of SLATS are 1) testing the maintenance of the satellite’s altitude with its ion engine against high atmospheric drag at a super-low altitude, 2) acquiring data on atmospheric density and atomic oxygen (AO), and 3) testing optical Earth observation. SLATS was successfully launched on 23 December 2017. SLATS was then altitude-controlled for 636 days to 271.7 km using chemical thrusters, aerodynamic drag, and ion engine propulsion. SLATS finally maintained its orbit of 167.4 km for 7 days and finished its operation on 1 October 2019. All the SLATS and Atomic oxygen MOnitor (AMO) data was acquired during these operations. The AMO is one of the mission sensors that monitor AO and its effects on spacecraft materials. The data from the AMO contributes to the choice of materials in future S-LEO satellite design. The data obtained by the AMO are valuable in that they provide considerable knowledge on AO fluence and its effects on space materials. A precise atmospheric density model and atmospheric composition model are indispensable for predicting the trajectory or re-entry of debris in orbit. Atmospheric models such as NRLMSISE-00, JB 2008, and DTM2013 have been developed, but few studies compare these models and the actual atmospheric environment in LEO. The average atmospheric density obtained from SLATS is lower than the value predicted by the atmospheric models (NRLMSISE-00, JB 2008, and DTM 2013). Understanding the model’s accuracy will contribute to the orbit control of future S-LEO satellites and the orbit prediction and control of debris in LEO.

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“…These days, we expect satellites at altitudes below 300 km, in very low Earth orbit (VLEO), making observations of the Earth at optical wavelengths with increasingly higher resolution [1,2]. To design VLEO satellites, an understanding of the effects of atomic oxygen (AO) on spacecraft materials is essential as materials that are more resistant to AO are needed.…”

Section: Introductionmentioning

confidence: 99%

Property changes in materials due to atomic oxygen in the low Earth orbit

et al. 2021

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We expect satellites at altitude below 300 km, very low Earth orbit (VLEO), making observations of the Earth at optical wavelength with increasingly higher resolution. The density of atomic oxygen (AO) at VLEO is significantly higher than that at LEO; severe degradation of spacecraft materials (polymers) due to the high-flux AO is a serious concern. To clarify VLEO environmental effects on spacecraft materials, we designed the Material Degradation Monitor (MDM) and MDM2 missions. The MDM is a material exposure experiment onboard the Super Low-Altitude Test Satellite (SLATS). It aims to understand reactions and degradation of polymeric materials depending on AO fluence in VLEO. In the MDM, samples of spacecraft material were exposed at altitude of 160–560 km; their degradation behaviors were observed optically by a CCD camera for 1.8 years. The MDM2 is a material exposure experiment onboard the International Space Station (ISS) and aims to correctly understand surface reactions and degradation of the same samples used in the MDM at a given AO fluence. In the MDM2, the samples were exposed at altitude of 400 km for 1 year and then returned to Earth for analysis. Based on the results from both missions, we will help in the molecular design of more-durable materials, and establish design standards for future VLEO satellites. This study aims to quantitatively understand the surface reactions and degradation of the 11 types of thermal control materials exposed on the ISS in the MDM2. Five types of multilayer insulation (MLI) films (three types of Si-containing AO protective materials (a silsesquioxane-(SQ-) containing coated polyimide film, two types of polysiloxane-block polyimide (BSF-30) films), an ITO-coated polyimide film, and a Beta Cloth), and flexible optical solar reflectors (flexible OSRs) were found to have a high durability against erosion by AO. This was determined by measuring their loss of mass and thermo-optical properties. The Ag/Inconel layer’s discoloration and peeling were observed for three types of FEP/Ag films as determined by the Ag layer’s oxidation by AO. Also, X-ray photoelectron spectroscopy (XPS) showed that reactions of the Si-containing materials, the SQ-coated polyimide film and the BSF-30 film, form a layer of silica that protects against AO. Even though the concentration of Si in the SQ-coating is the same or greater than in the BSF-30 film, the amount of the SQ-coating that reacted was larger than that of the BSF-30 film under the same AO fluence. Moreover, the effective ability of the UV-shielding coating, composed of ITO and CeO2 coated onto one of the BSF-30 films, was demonstrated by UV–Vis spectrometry. Its sufficient AO protection was confirmed by mass measurements, XPS analyses, and FE-SEM observations.

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Interim Report of Super Low Altitude Satellite Operation

Cited by 16 publications

References 0 publications

Formation of Nanoscale Protrusions on Polymer Films after Atomic Oxygen Exposure: Observations with Positron Annihilation Lifetime Spectroscopy

Formation of Nanoscale Protrusions on Polymer Films after Atomic Oxygen Exposure: Observations with Positron Annihilation Lifetime Spectroscopy

Analysis of upper atmospheric effects on material per onboard atomic oxygen monitor system of SLATS

Property changes in materials due to atomic oxygen in the low Earth orbit

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