The Rapid International Scientific Experiment Satellite (RISESAT) is a 50-kg-class Earth observation microsatellite that is currently being developed at the Space Robotics Laboratory (SRL) of Tohoku University, with a planned launch data in 2018. Intended to demonstrate a cost-effective and reliable microsatellite bus system, RISESAT features various scientific payload instruments from institutions and organizations around the world. Among the payloads are the Very Small Optical Transponder (VSOTA), a compact, dual-band (980 nm, 1550 nm), lightweight laser signal transmitter developed by the Japanese National Institute for Information and Communications Technology (NICT), and the High Precision Telescope (HPT), a multi-spectral, high-resolution Cassegrain telescope developed by Hokkaido University and intended for Earth and astronomical observations. Using these two payloads, RISESAT can demonstrate satellite-toground one-way laser communication. This experiment is intended to demonstrate optical communication capability within the scope of the available hardware resources on a microsatellite dedicated to numerous other scientific endeavors. Hence, VSOTA is lighter, less power intensive, and more simplified than other optical transmitter terminals. Internal gimbal mechanisms for fine pointing have also been eliminated, thus the tracking of the optical ground stations will be achieved using body pointing of the satellite. Recently, end-to-end electrical configuration and communication tests have been conducted for both the engineering model (EM) and the flight model (FM) of the VSOTA assembly. This paper provides an overview of VSOTA and its space-to-ground optical communication demonstration, and describes the current status of the RISESAT optical communication subsystem assembly and integration.
An oxidizing agent is needed for silicone oil to be photo-oxidized with Xe2 excimer-lamp. However, the lamp light did
not reach the silicone oil on the surface of the substrate satisfactorily, and the photo-oxidation reaction of the silicone oil
layer was hard to take place properly. In order to find the appropriate conditions for supplying the proper amount of an
oxidizing agent to silicone oil, the vacuum ultraviolet light that passed the silicone oil layer was made fluoresce in the
phosphor to monitor the progress of the photo-oxidation reaction. As the vitrification by photo-oxidation reaction of
the silicone oil layer improved, the fluorescence intensity of the phosphor increased. While monitoring the change of the
fluorescence intensity, the supply of the oxidizing agent and the irradiation time of the vacuum ultraviolet light were
controlled; as a result, the new method to efficiently form a transparent, photo-oxidized thin film has been established.
There is the method to form microscopic roughness on the surface of a sample in order that a film or adhesive is hard to
peel off, but it is unsuitable to optical material surfaces. We, thus, demonstrated the undamaged surface of the optical
material on which the coating agent or adhesive was applied by chemically incorporating the functional groups. Many
thin films are deposited, but most of them come off if wiped. Then, hydrophilic groups (-OH) were incorporated on the
sample surface beforehand, and photo-adhesion or coating was carried out. The sample surface was firstly treated by
discharge plasma for promoting efficiency of hydroxyl group substitution, and hydroxyl groups were incorporated on the
modified side in water ambient when the material temporarily maintained high wettability; as a result, the adhesion or
coating and the modified side were united persistently. The contact angle with water of fused silica is 40 degrees; that
of sapphire is 72 degrees; that of BK7 glass is 31 degrees. When those surfaces were irradiated by glow discharge
plasma of DC pole sputtering system for five minutes, all of the surfaces dropped to five degrees. Under this condition,
silicone oil was applied on each pretreated sample surface and irradiated with excimer lamp light (172nm) for 60 minutes.
The adhesive strength of the silica glass plates with plasma pretreatment improved to 25M pascal when compared with
that of the silica glass plates without pretreatment, which was 18M paschal.
The organic silicone oil applied over the surface of a fused silica glass or Kaliumdihydrogenphosphat (KDP) nonlinear
optical crystal was changed to an inorganic glass by the photochemical oxidization using a Xe2 excimer lamp in the air.
As a result, the thin film acquired a characteristic of high power laser tolerance equivalent to quartz. Dimethylsiloxane
silicone oil was spin-coated on the surfaces of a fused silica substrate and KDP to form a film of 100-nm thickness;
which were irradiated with the Xe2
excimer lamp light (wavelength 172 nm, power density 10 mW/cm2) for 60 minutes
in oxygen atmosphere. The films were further irradiated with the Nd: YAG laser of ω (1.06 μm) or 2ω (0.503 μm), and
the laser damage test (J/cm2/10 ns) was conducted. The laser damage threshold of the photo-oxidized 100 nm thick
film formed on the fused silica substrate was 72 J/cm2 in ω and 107 J/cm2 in 2ω. On the KDP substrate, the laser
damage threshold of the thin film was 32.4J/cm2 in ω and 32.6 J/cm2 in 2ω.
The dot patterned hydrophilic and hydrophobic groups were photo-chemically substituted in minute pattern on the polymethylmethacrylate [PMMA] intraocular lens [IOL] by the Xe2 excimer lamp and the ArF excimer laser; consequently, the IOL that is free from fibrin has been developed.
PMMA has been used as an intraocular lens IOL because of its high transmittance in the visible region and superb mechanical modifiability. However, protein and fat are stuck onto the lens surface after a long-term insertion, where cells proliferate; which causes the surface to get opaque, namely after-cataract.
Firstly, the IOL was irradiated with Xe2 excimer lamp in the presence of perfluoropolyether [PFPE] to be hydrophobic. By the photochemical reaction, the CF3 functional groups were substituted on the IOL surface. In order to substitute hydrophilic groups in matrix-form on the surface, the ArF laser light was then irradiated on the hydrophobic surface in the presence of water through the 50mm f dot-patterned negative mask and the lens to project the reduced pattern. With this selective photochemical surface modification, the hydrophilic and hydrophobic groups were arrayed alternately on the sample surface. The modified IOL was soaked in fibrin [FIB] water solution, and the fibrin-sticking rate was measured by infrared spectroscopy [FT-IR]. The lower fibrin-sticking rate of the IOL surface was achieved by the hydrophobic and hydrophilic micro domain structures. Furthermore, it was confirmed that the fibrin-sticking rate decreased as the OH group interval was narrowed. The modified surface with the 20 mm f domains with hydrophilic and hydrophobic was lowest in fibrin sticking.
Having substituted the hydrophilic and hydrophobic groups alternately on the soft acrylic resin intraocular lens (IOL) surface by using an ArF excimer laser and a Xe2 excimer lamp, we have developed the IOL that is free from fibrin. Acrylic resin or PMMA lens has been used as an intraocular lens for 50 years. However, protein and fat are stuck onto the IOL surface after a long implantation, which opacifies the surface (after-cataract). Thus, we designed the micro domain structures of hydrophilic and hydrophobic groups on the IOL surface for fibrin-free. Firstly, the IOL was irradiated with the Xe2 excimer lamp in the presence of perfluoropolyether in order to make it hydrophobic. By this photochemical reaction, the CF3 functional groups were substituted on the IOL surface. Secondly, the ArF laser was projected on the IOL through the mask pattern in reduced size in the presence of water in order to be hydrophilic. With the photochemical reaction, the OH groups were substituted at the part exposed. The fibrin adsorption test of the modified IOL surface was carried out with FT-IR; which revealed that the fibrin-sticking rate of the treated sample has decreased by 23% compared with that of the non-treated sample. As a result, the fibrin-free IOL has been made by modifying the surface of the IOL to have the micro domain structures of the hydrophilic and hydrophobic groups that are arrayed alternately. In conclusion, the ideal intraocular lens has been demonstrated.
The central part of a PMMA or acrylic resin lens was modified into hydrophobic and the peripheral part to be phydrophilic using teh ArF laser and excimer lamp. PMMA or acrylic resin lens have been used as an intraocular lens for 50 years and is the golden standard in ophthalmology. However, protein and fat are stuck onto the IOL surface after long-term implantation and opacify the surface )after-cataract). Therefore, the central part of the IOL was modified to be hydrophobic to prevent fat and protein deposition; the periphery was made hydrophilic to develop affinity for tissue.
Intractable glaucoma results from hindrances in the eyeball aqueous humor pathways that increase the intraocular pressure above normal physiological levels (over 20 mmHg). In this study porous PTFE membranes were made hydrophilic with a photochemical method that use ethyl alcohol and water for the chemical solution.