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We have developed the PolCube payload, a polarimeter camera for 12U CubeSat mission, in order to demonstrate the performance feasibility technically since 2019. Main objectives of the PolCube camera are the dust detection around Korean peninsula and monitoring super-thin clouds distribution on global oceans. KASI and Korean consortium members maintain a good collaboration with NASA LaRC team in this project. PolCube is a compact payload under 5kg in mass and under 15W in power consumption. This payload has two optical heads, two detectors with 1280 x 1024 CMOS array format, and two filter sets with 4 wavelengths and 0, 60, 90, 120 polarization angles. Each optical head has a field of view of 10 degrees (Swath width ~ 98km) at the altitude of 567km Sun-synchronous orbit. 12U CubeSat spacecraft will be made by a CubeSat company managed by Busan city & KIOST in Korea. In this paper, we will describe the current design of the PolCube payload development.

As described in the previous paper (Park et al. 2013), the detector subsystem of optical wide-field patrol (OWL) provides many observational data points of a single artificial satellite or space debris in the form of small streaks, using a chopper system and a time tagger. The position and the corresponding time data are matched assuming that the length of a streak on the CCD frame is proportional to the time duration of the exposure during which the chopper blades do not obscure the CCD window. In the previous study, however, the length was measured using the diagonal of the rectangle of the image area containing the streak; the results were quite ambiguous and inaccurate, allowing possible matching error of positions and time data. Furthermore, because only one (position, time) data point is created from one streak, the efficiency of the observation decreases. To define the length of a streak correctly, it is important to locate the endpoints of a streak. In this paper, a method using a differential convolution mask pattern is tested. This method can be used to obtain the positions where the pixel values are changed sharply. These endpoints can be regarded as directly detected positional data, and the number of data points is doubled by this result.

The correlation between meteorological data collected at the optical wide-field patrol network (OWL-Net) Station No. 1 and the seeing of satellite optical observation data was analyzed. Meteorological data and satellite optical observation data from June 2014 to November 2015 were analyzed. The analyzed meteorological data were the outdoor air temperature, relative humidity, wind speed, and cloud index data, and the analyzed satellite optical observation data were the seeing full-width at half-maximum (FWHM) data. The annual meteorological pattern for Mongolia was analyzed by collecting meteorological data over four seasons, with data collection beginning after the installation and initial set-up of the OWL-Net Station No. 1 in Mongolia. A comparison of the meteorological data and the seeing of the satellite optical observation data showed that the seeing degrades as the wind strength increases and as the cloud cover decreases. This finding is explained by the bias effect, which is caused by the fact that the number of images taken on the less cloudy days was relatively small. The seeing FWHM showed no clear correlation with either temperature or relative humidity.

Inactive space objects are usually rotating and tumbling as a result of internal or external forces. KOREASAT 1 has been inactive since 2005, and its drift trajectory has been monitored with the optical wide-field patrol network (OWL-Net). However, a quantitative analysis of KOREASAT 1 in regard to the attitude evolution has never been performed. Here, two optical tracking systems were used to acquire raw measurements to analyze the rotation period of two inactive satellites. During the optical campaign in 2013, KOREASAT 1 was observed by a 0.6 m class optical telescope operated by the Korea Astronomy and Space Science Institute (KASI). The rotation period of KOREASAT 1 was analyzed with the light curves from the photometry results. The rotation periods of the low Earth orbit (LEO) satellite ASTRO-H after break-up were detected by OWL-Net on April 7, 2016. We analyzed the magnitude variation of each satellite by differential photometry and made comparisons with the star catalog. The illumination effect caused by the phase angle between the Sun and the target satellite was corrected with the system tool kit (STK) and two line element (TLE) technique. Finally, we determined the rotation period of two inactive satellites on LEO and geostationary Earth orbit (GEO) with light curves from the photometry. The main rotation periods were determined to be 5.2 sec for ASTRO-H and 74 sec for KOREASAT 1.

We prepared a number of reaction-bonded silicon carbides (RBSCs) made from various mixing ratios of raw SiC particles, and investigated their microstructure and etch characteristics by Reactive Ion Etch (RIE). Increasing the amount of 9.5 μm-SiC particles results in a microstructure with relatively coarser Si regions. On the other hand, increasing that of 2.6 μm-SiC particles produces much finer Si regions. The addition of more than 50 wt% of 2.6 μm-SiC particles, however, causes the microstructure to become partially coarse. We also evaluated their etching behaviors in terms of surface roughness (Ra), density and weight changes, and microstructure development by employing Confocal Laser Scanning Microscope (CLSM) and Scanning Electron Microscope (SEM) techniques. During the etching process of the prepared samples, we confirmed that the residual Si region was rapidly removed and formed pits isolating SiC particles as islands. This leads to more intensified ion field on the SiC islands, and causes physical corrosion on them. Increased addition of 2.6 μm-SiC particles produces finer residual Si region, and thus decreases the surface roughness (Ra.) as well as causing weight loss after etching process by following the above etching mechanism.

The NISS (Near-infrared Imaging Spectrometer for Star formation history) have been developed by KASI as one of the scientific payloads onboard the first small satellite of NEXTSat program (NEXTSat-1) in Korea. The both imaging and low spectral resolution spectroscopy in the wide near-infrared range from 0.95 to 2.5µm and wide field of view of 2° x 2° is a unique capability of the NISS for studying the star formation in local and distant Universe. In the design of the NISS, special care was taken by implementing the off-axis system to increase the total throughput with limited resources from the small satellite. We confirmed that the mechanical structure of the NISS could be maintained in space through passive cooling of the telescope. To operate the infrared detector and spectral filters at 80K stage, the compact dewar module was assembled after the relay-lens module. The integrations of relay-lens part, primary-secondary mirror assembly and dewar module were independently performed, which alleviated the complex alignment process. The telescope and infrared sensor were validated for the operation at cryogenic temperatures of around 200K and 80K, respectively. The system performance of the NISS, such as focus, cooling efficiency, wavelength calibration and system noise, was evaluated by utilizing our constructed test facility. After the integration into the NEXTSat-1, the flight model of the NISS was tested under the space environments. The NISS is scheduled to be launched in late 2018 and it will demonstrate core technologies related to the future infrared space telescope in Korea.

NISS (Near-infrared Imaging Spectrometer for Star formation history) is a unique spaceborne imaging spectrometer (R = 20) onboard the Korea’s next micro-satellite NEXTSat-1 to investigate the star formation history of Universe in near infrared wavelength region (0.9 – 2.5 μm). In this paper, we introduce the NISS H2RG detector electronics, the test configuration, and the performance test results. Analyzed data will be presented on; system gain, dark current, readout noise, crosstalk, linearity, and persistence. Also, we present basic test results of a Korean manufactured IR detector, 640 x 512 InAsSb 15 μm pixel pitch, developed for future Korean lunar mission.

The Korea Astronomy and Space Science Institute has developed NISS (Near-infrared Imaging Spectrometer for Star formation history) as a scientific payload for the first next generation of small satellite, NEXTSat-1 in Korea. NISS is a NIR imaging spectrometer exploiting a Linear Variable Filter (LVF) in the spectral passband from 0.95 um to 2.5 um and with low spectral resolution of 20. Optical system consists of 150mm aperture off-axis mirror system and 8-element relay-lenses providing a field of view of 4 square degrees. Primary and secondary aluminum mirrors made of RSA6061 are precisely fabricated and all of the lenses are polished with infrared optics materials. In principle, the optomechanical design has to withstand the vibration conditions of the launcher and maintain optical performance in the space environment. The main structure and optical system of the NISS are cooled down to about 200K by passive cooling for our astronomical mission. We also cool the detector and the LVF down to about 90K by using a small stirling cooler at 200K stage. The cooling test for whole assembled body has shown that the NISS can be cooled down to 200K by passive cooling during about 80 hours. We confirmed that the optomechanical structure is safe and rigid enough to maintain the system performance during the cooling, vibration and thermal vacuum test. After the integration of the NISS into the NEXTSat-1, space environmental tests for the satellite were passed. In this paper, we report the design, fabrication, assembly and test of the optomechanical structure for the NISS flight model.

Korea Astronomy and Space Science Institute (KASI) successfully developed the Near-infrared Imaging Spectrometer for Star formation history (NISS), which is a scientific payload for the next-generation small satellite-1 (NEXTSat-1) in Korea and is expected to be launched in 2018. The major science cases of NISS are to probe the star formation in local and early Universe through the imaging spectroscopic observations in the near-infrared. The off-axis catadioptric optics with 150mm aperture diameter is designed to cover the FoV of 2x2 deg with the passband of 0.95-2.5μm. The linear variable filter (LVF) is adopted as a disperse element with spectral resolution of R~20. Given the error budgets from the optical tolerance analysis, all spherical and non-spherical surfaces were conventionally polished and finished in the ultraprecision method, respectively. Primary and secondary mirrors were aligned by using interferometer, resulting in residual wave-front errors of P-V 2.7μm and RMS 0.61μm, respectively. To avoid and minimize any misalignment, lenses assembled were confirmed with de-centering measurement tool from Tri-Optics. As one of the key optical design concepts, afocal beam from primary and secondary mirrors combined made much less sensitive the alignment process between mirrors and relay lenses. As the optical performance test, the FWHM of PSF was measured about 16μm at the room temperature, and the IR sensor was successfully aligned in the optimized position at the cryogenic temperature. Finally, wavelength calibration was executed by using monochromatic IR sources. To support the complication of optical configuration, the opto-mechanical structure was optimized to endure the launching condition and the space environment. We confirmed that the optical performance can be maintained after the space environmental test. In this paper, we present the development of optical system of NISS from optical design to performance test and calibration.

As a governmentally approved domestic entity for Space Situational Awareness, Korea Astronomy and Space Science Institute (KASI) is developing and operating an optical telescopes system, Optical Wide-field PatroL (OWL) Network. During the test phase of this system, it is necessary to determine the range of brightness of the observable satellites. We have defined standard magnitude for Low Earth Orbit (LEO) satellites to calibrate their luminosity in terms of standard parameters such as distance, phase angle, and angular rate. In this work, we report the optical brightness range of five LEO Satellites using OWL-Net.

By using the Optical Wide-field Patrol (OWL) network developed by the Korea Astronomy and Space Science Institute (KASI) we generated the right ascension and declination angle data from optical observation of Low Earth Orbit (LEO) satellites. We performed an analysis to verify the optimum number of observations needed per arc for successful estimation of orbit. The currently functioning OWL observatories are located in Daejeon (South Korea), Songino (Mongolia), and Oukaïmeden (Morocco). The Daejeon Observatory is functioning as a test bed. In this study, the observed targets were Gravity Probe B, COSMOS 1455, COSMOS 1726, COSMOS 2428, SEASAT 1, ATV-5, and CryoSat-2 (all in LEO). These satellites were observed from the test bed and the Songino Observatory of the OWL network during 21 nights in 2014 and 2015. After we estimated the orbit from systematically selected sets of observation points (20, 50, 100, and 150) for each pass, we compared the difference between the orbit estimates for each case, and the Two Line Element set (TLE) from the Joint Space Operation Center (JSpOC). Then, we determined the average of the difference and selected the optimal observation points by comparing the average values.

Several optical monitoring strategies by a ground-based telescope to protect a Geostationary Earth Orbit (GEO) satellite from collisions with close approaching objects were investigated. Geostationary Transfer Orbit (GTO) objects, Inclined GeoSynchronous Orbit (IGSO) objects, and drifted GEO objects forced by natural perturbations are hazardous to operational GEO satellites regarding issues related to close approaches. The status of these objects was analyzed on the basis of their orbital characteristics in Two-Line Element (TLE) data from the Joint Space Operation Center (JSpOC). We confirmed the conjunction probability with all catalogued objects for the domestic operational GEO satellite, Communication, Ocean and Meteorological Satellite (COMS) using the Conjunction Analysis Tools by Analytical Graphics, Inc (AGI). The longitudinal drift rates of GeoSynchronous Orbit (GSO) objects were calculated, with an analytic method and they were confirmed using the Systems Tool Kit by AGI. The required monitoring area was determined from the expected drift duration and inclination of the simulated target. The optical monitoring strategy for the target area was analyzed through the orbit determination accuracy. For this purpose, the close approach of Russian satellite Raduga 1-7 to Korean COMS in 2011 was selected.

Solar proton events (SPEs) can be categorized into four groups based on their associations with flare or CME inferred from onset timings as well as acceleration patterns using multienergy observations. In this study, we have investigated whether there are any typical characteristics of associated events and acceleration sites in each group using 42 SPEs from 1997 to 2012. We find the following: (i) if the proton acceleration starts from a lower energy, a SPE has a higher chance to be a strong event (> 5000 particle flux per unit (pfu)) even if its associated flare and/or CME are not so strong. The only difference between the SPEs associated with flare and CME is the location of the acceleration site. (ii) For the former (Group A), the sites are very low (∼ 1 Rs) and close to the western limb, while the latter (Group C) have relatively higher (mean = 6.05 Rs) and wider acceleration sites. (iii) When the proton acceleration starts from the higher energy (Group B), a SPE tends to be a relatively weak event (

The NISS (Near-infrared Imaging Spectrometer for Star formation history) is the near-infrared instrument optimized to the first next generation of small satellite (NEXTSat-1) in Korea. The spectro-photometric capability in the near-infrared range is a unique function of the NISS. The major scientific mission is to study the cosmic star formation history in local and distant universe. For those purposes, the NISS will perform the large areal imaging spectroscopic survey for astronomical objects and low background regions. We have paid careful attention to reduce the volume and to increase the total throughput. The newly implemented off-axis optics has a wide field of view (2° x 2°) and a wide wavelength range from 0.9 to 3.8μm. The mechanical structure is designed to consider launching conditions and passive cooling of the telescope. The compact dewar after relay-lens module is to operate the infrared detector and spectral filters at 80K stage. The independent integration of relay-lens part and primary-secondary mirror assembly alleviates the complex alignment process. We confirmed that the telescope and the infrared sensor can be cooled down to around 200K and 80K, respectively. The engineering qualification model of the NISS was tested in the space environment including the launch-induced vibration and shock. The NISS will be expected to demonstrate core technologies related to the development of the future infrared space telescope in Korea.