The Earth 2.0 (ET) space mission has entered its phase B study in China. It seeks to understand how frequently habitable Earth-like planets orbit solar-type stars (Earth 2.0s), the formation and evolution of terrestrial-like planets, and the origin of free-floating planets. The final design of ET includes six 28 cm diameter transit telescope systems, each with a field of view of 550 square degrees, and one 35 cm diameter microlensing telescope with a field of view of 4 square degrees. In transit mode, ET will continuously monitor over 2 million FGKM dwarfs in the original Kepler field and its neighboring fields for four years. Simultaneously, in microlensing mode, it will observe over 30 million I < 20.5 stars in the Galactic bulge direction. Simulations indicate that ET mission could identify approximately 40,000 new planets, including about 4,000 terrestrial-like planets across a wide range of orbital periods and in the interstellar space, ~1000 microlensing planets, ~10 Earth 2.0s and around 25 free-floating Earth mass planets. Coordinated observations with ground-based KMTNet telescopes will enable the measurement of masses for ~300 microlensing planets, helping determine the mass distribution functions of free-floating planets and cold planets. ET will operate from the Earth-Sun L2 halo orbit with a designed lifetime exceeding 4 years. The phase B study involves detailed design and engineering development of the transit and microlensing telescopes. Updates on this mission study are reported.
The successful achievement of the scientific objectives of the Visible Telescope (VT) in the Space Multi-band Variable Object Monitor (SVOM) mission relies heavily on high-precision quantum efficiency calibration. The calibration process for the VT CCD presents a challenge due to the requirement for extremely low radiation levels given the long integration time of the CCD. To address the difficulty in accurately measuring such low radiance, a two-step calibration method is employed. This method involves the use of two photodiodes, one positioned at the CCD location and the other in an integrating sphere. In the first step, the proportional relationship between the measured illuminance values of the two photodiodes is calibrated under high illumination conditions. This step establishes a reliable reference for subsequent calibrations. In the second step, the CCD is calibrated using the integrating sphere photodiode under low illumination conditions. The measured illuminance is then converted to the CCD position. Experimental results have demonstrated the effectiveness of this two-step calibration method, achieving a quantum efficiency calibration uncertainty of 1.7%. This approach provides a reliable and accurate means of calibrating the quantum efficiency of the CCD in the VT instrument.
KEYWORDS: Image processing, Medical imaging, Data backup, Video, Video processing, Image acquisition, Field programmable gate arrays, Statistical analysis, Visualization, Surgery
This paper designs a new platform for medical image transfer and process. The hardware part of the platform is based on FPGA, USB and RS232. The software part is based on Windows platform, basing on MFC dialog application developed with C + + programming tools in Microsoft Visual Studio 2010. The platform collects images from medical devices and uses the hardware platform to transmit them to PC for display, the application program on PC can realize the image data process and analysis.
Infrared images and visible images can obtain different image information in the same scene, especially in low-light scenes, infrared images can obtain image information that cannot be obtained by visible images. In order to obtain more useful information in the environment such as glimmer, infrared and visible images can be fused. In this paper, an image fusion method based on anisotropic diffusion and fast guided filter is proposed. Firstly, the source images are decomposed into base layers and detail layers by anisotropic dispersion. Secondly, the visible images and the infrared images are passed through the side window Gaussian filter to obtain the saliency map, and then the saliency map is passed through fast guided filter to obtain the fusion weight. Thirdly, the fused base layers and the fused detail layers are reconstructed to obtain the final fusion image. The application of the side window Gaussian filter helps to reduce the artifact information of the fused image. The results of the proposed algorithm are compared with similar algorithms. The fusion results reveal that the proposed method are outstanding in subjective evaluation and objective evaluation, and are better than other algorithms in standard deviation(STD) and entropy(EN), and other quality metrics are close to the optimal comparison algorithm.
A space mission called “Earth 2.0 (ET)” is being developed in China to address a few of fundamental questions in the exoplanet field: How frequently habitable Earth-like planets orbit solar type stars (Earth 2.0s)? How do terrestrial planets form and evolve? Where did floating planets come from? ET consists of six 30 cm diameter transit telescope systems with each field of view of 500 square degrees and one 35 cm diameter microlensing telescope with a field of view of 4 square degrees. The ET transit mode will monitor ~1.2M FGKM dwarfs in the original Kepler field and its neighboring fields continuously for four years while the microlensing mode monitors over 30M I< 20.6 stars in the Galactic bulge direction. ET will merge its photometry data with that from Kepler to increase the time baseline to 8 years. This enhances the transit signal-to-noise ratio, reduce false positives, and greatly increases the chance to discover Earth 2.0s. Simulations show that ET transit telescopes will be able to identify ~17 Earth 2.0s, about 4,900 Earth-sized terrestrial planets and about 29,000 new planets. In addition, ET will detect about 2,000 transit-timingvariation (TTV) planets and 700 of them will have mass and eccentricity measurements. The ET microlensing telescope will be able to identify over 1,000 microlensing planets. With simultaneous observations with the ground-based KMTNet telescopes, ET will be able to measure masses of over 300 microlensing planets and determine the mass distribution functions of free-floating planets and cold planets. ET will be operated at the Earth-Sun L2 orbit with a designed lifetime longer than 4 years.
The Earth 2.0 (ET) mission is a space mission in China which will be operated at the Earth-Sun L2 orbit with a designed lifetime longer than 4 years. ET’s scientific payload consist of six 30cm diameter transit telescopes with each field of view of 500 square degrees and one 35 cm diameter microlensing telescope with a field of view of 4 square degrees. Each telescope is equipped with a camera with 2×2 9K×9K CMOS detectors, and Front-end Electronics (FEE). Each transit telescope is an f/1.57 eightlens refractive optical system while the microlensing telescope is an f/17.2 catadioptric optical system with diffraction-limited design. The diameter of 90% Encircled Energy (EE90) for transit telescopes is within 5×5 pixels while the FWHM of PSF for the microlensing telescope is less than 0.78 arcsec. Fine Guidance Sensors are mounted at the four edges of the CMOS camera. All seven telescopes are fixed on a common mounting reference plate, and a large sun shield is used to block the heat flow from the Sun and provide a stable thermal environment for the telescopes. It also blocks straylight form the Sun, Earth, and the Moon. Each telescope has an additional top hood to block straylight incident at a large angle while the top hood is also used as a radiator to cool the detectors to below - 40°C. With PID heating loops, each telescope will work at -30±0.3°C while the detectors work at - 40±0.1°C. Details of the conceptual design for the scientific payload will be presented.
The Earth 2.0 (ET) mission is a Chinese space mission to detect thousands of Earth-sized terrestrial planets, including habitable Earth-like planets orbiting solar type stars (Earth 2.0s), cold low-mass planets, and free-floating planets. The six 30 cm diameter transit telescopes will be equipped with a CMOS camera which consists of 4(2×2)9K×9K CMOS sensors. A prototype camera with a 8900×9120 pixel GSENSE 1081 BSI type CMOS sensor and temperature control is designed and developed for high precision photometry measurements. In this paper, details of this camera design and performance test results are reported.
Compared with CCD detector, CMOS detector has the advantages of high integration, low power consumption, fast readout speed and low production cost. CCD detectors are used in traditional astronomical observations. At present, low-noise CMOS detectors are not used to realize spaceborne astronomical projects in the world. From the index analysis of a project, one 6K * 6K CMOS detector which developed by a company can meet application of one project. Based on this detector, designing low noise driver and bias hardware circuit. This design mainly uses LDO with low noise and high PSRR to produce stable low noise driving power supply, in addition, the driving signal waveform required by the detector is controlled by FPGA to ensure the signal integrity to avoid interference feed. The bias voltage required by the detector is generated by low-noise voltage reference device, high-resolution DAC and low-noise operational amplifier.
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) project is a dedicated satellite developed at the cooperation of China and France, aim to make prompt multi-band observations of Gamma-Ray Bursts (GRBs), the afterglows and other high-energy transient astronomical events. The Visible Telescope (VT) is one of the four payloads onboard the SVOM. VT is designed to observe the afterglows of GRBs both in the visible and near infrared bands simultaneously. The telescope can reach a limiting magnitude of +22.5Mv and provide the redshift indicators for high-Z (z<4) GRBs. VT is also designed to measure the Relative Performance Errors (RPEs) for the satellite attitude and orbit control system (AOCS), aiming to improve the pointing stability of the platform during observation. VT adopts a Ritchey-Chrétien (RC) catadioptric optical configuration with a 440mm aperture and uses the dichroic prism before the focal plane to split the incident light into blue (visible) and red (near infrared) band. Two Fine Guidance Sensor (FGS) CCDs are mounted beside the main CCD on the blue band focal plane of VT and provide sub-arcsecond pixel resolution. Fiber reinforced plastic (CFRP) composites is selected as the material of VT’s main structure to ensure enough stiffness and strength during launch. The electrical video processing circuit is carefully designed to make the readout noise below 6e-/pix (rms) in 100s exposure time. Active and passive thermal control are used together to ensure the optical performance and thermoelectric cooler (TEC) is adopted to control the main CCDs working temperature below -65°C to reduce the noise. This paper provides a comprehensive overview of the scientific requirements and the key instrument design aspects of optics, main structure, electrics, thermal control, performance test and validation results of VT.
Optical design of a small reflecting telescope for use in a 1U CubeSat mission is reported in this study. A Ritchey-Chretien with field correction lens type telescope for earth observation techniques is adopted in this design. The primary mirror and secondary mirror are circular apertures with 70-mm and 21-mm in diameter. The effective focal length is 390-mm operated at 600-km altitude. A commercial 2560 × 2160 CCD image sensor CIS2521 with a pixel size of 6.5 μm is applied, which capture a 25km swath area. The ground resolution is better than 10m for CubeSat application. The MTF is expected to be about 0.3 at Nyquist frequency at 77lp/mm. The tolerance analysis is performed for further understanding on fabrication and assembly errors. In order to reduce the telescope size, the optical system uses a reflective optical system, and the circuit board is arranged behind the system and above. The telescope envelope size(all contained) is less than 96mm × 90mm × 90mm and the weight is approximately 600g. At present, the aspherical primary mirror has completed the processing and assembly.
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