arXiv subjects

Jiangpei Dou

Publications and source records attributed to Jiangpei Dou.

17 recordsLinked to original sources

arXiv2026

Optical-NIR Multi-band Photometric Analysis and Characterization of Giant Exoplanets with CPI-C

We present a multi-band photometric approach to characterize giant exoplanets, which represents one of the anticipated core scientific outcomes of Cool Planet Imaging Coronagraph (CPI-C). CPI-C operates with two observational channels covering visible and near-infrared wavelengths, each equipped with four broadband filters. The planet--star flux ratio integrated over each filter bandpass is calculated for photometric analysis. For cool planets observed in the visible bands, the data are primarily used to fit the overall spectral shape and methane-induced modulation, providing sensitivity to metallicity- and cloud-dependent spectral variations while constraining the reflected-light spectral shape and the combined scaling involving planet radius, orbital separation, and orbital phase. In the near-infrared bands, which probe thermal emission, the data help to better constrain fundamental planetary parameters including the effective temperature, radius, surface gravity and mass. For a synthetic giant planet with measurable reflected-light and thermal-emission components, the combined VIS4+NIR4 data provide tighter same-target constraints than either filter set alone, especially for the planet radius and cloud sedimentation parameter. Our simulations incorporate realistic instrument throughput, detector noise, and residual speckle noise. The results demonstrate that the eight-band design spanning visible to near-infrared wavelengths supports reflected-light diagnostics, thermal-emission characterization, and joint optical--NIR analysis of giant exoplanets within CPI-C science observations.

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arXiv2025

The Role of Self-Gravity in Debris Disk Warp Formation: The Case of HD 110058

We investigate the crucial role of self-gravity in the formation of warps in debris disks, focusing on the HD 110058 system as an example. Using advanced, GPU-accelerated $N$-body simulations, we model the gravitational dynamics of a massive planetesimal disk perturbed by an inclined, inner planet. Our simulations reveal that self-gravity fundamentally alters the disk's evolution compared to massless models. It enforces a coherent, semi-rigid precession of the disk and enables the rapid formation of a global warp structure within 0.5 Myr. The warp angle undergoes a damped oscillation, eventually settling into a quasi-equilibrium state. By generating synthetic scattered-light images, we demonstrate that our model successfully reproduces the observed S-shaped warp morphology of the debris disk in HD 110058, supporting the existence of an unseen planet. Furthermore, we derive an empirical relationship that connects the equilibrium warp angle to the physical parameters of the disk and the planet. Applying this relation to HD 110058, we constrain its disk mass to be likely less than 1,000 $M_\oplus$, offering a new dynamical perspective on the debris disk mass problem.

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arXiv2025

CPI-C: Cool Planet Imaging Coronagraph on Chinese Space Station Survey Telescope

Cool Planet Imaging Coronagraph (CPI-C) on Chinese Space Station Survey Telescope (CSST) is proposed to direct image the cool planets around nearby solar-type stars (within 40 pc). The core scientific objective of CPI-C is to conduct high-contrast directly imaging surveys of exoplanets ranging in size from Neptune-like to Jupiter-like, located at separations of 0.5 to 5 AU from their host stars, and to perform systematic spectroscopic analysis of the detected planets through high-precision multi-band photometry. CPI-C employs a step-transmission apodization technique to suppress the diffraction noises from the telescope pupil and a precise phase correction technique to eliminate the speckle noises due to imperfections of the optical surfaces. The contrast requirement is better than $10^{-8}$ at an inner working angle (IWA) of $3-4\lambda/D$, in the visible wavelength from 600 nm to 900 nm. CPI-C will be the first space-based instrument capable of directly imaging the reflection light from the cool exoplanets in the visible wavelength enabling the measurement of key physical parameters such as the effective temperature, surface gravity, radius, mass, and other key parameters. The potential observation results will significantly contribute to further understand the formation and evolution mechanisms of planets, which will also lay a solid foundation for future confirmation of the Earth-twins in the next generation space flagship missions.

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arXiv2025

Design and dynamics experiment of filter wheel mechanism of space coronagraph

In order to realize multi-spectral imaging of space coronagraph, a compact filter wheel mechanism is designed. The filters with different spectral transmittance can be cut into the optical path at different times by this mechanism. Because the image contrast of space coronagraph is very high, the high stability requirement for the optical unit of coronagraph is put forward. Small modulus worm gear and worm are taken by the mechanism, in order to realize compact structure, high stiffness, the unidirectional 360 degrees rotation and reverse self-locking function. The precision, stiffness, mechanical properties and reliability of the mechanism are analyzed in the paper. The results show that the position accuracy of the filter wheel can meet the requirement of 0.5mm. The first order modal of the mechanism is 313Hz. The results of vibration test indicate that stiffness, dynamic performance and reliability of the mechanism can be meet. Therefore, the design of filter wheel in this paper can ensure the multi-spectral imaging requirements under complex spatial conditions.

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arXiv2025

Lightweight design and analysis of optical cover plate for exoplanet imaging coronagraph

In order to reduce the load mass and solve the problem that the aluminum alloy optical cover plate of exoplanet imaging coronagraph was easy to deform, based on the equal generation design method, this paper designed and determined the configuration of the carbon fiber optical cover plate. Through the simulation of layup by finite element analysis, this paper researched the influence of different layering angles and sequences on the stiffness of optical cover plate. Finally, the carbon fiber layup method was determined as [15/-75/-15/75]s. The dynamic response analysis show that all the indexes satisfy the system requirements, and verify the feasibility of carbon fiber optical cover plate.

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arXiv2025

Performance Calibration of the Wavefront Sensor's EMCCD Detector for the Cool Planets Imaging Coronagraph Aboard CSST

The wavefront sensor (WFS), equipped with an electron-multiplying charge-coupled device (EMCCD) detector, is a critical component of the Cool Planets Imaging Coronagraph (CPI-C) on the Chinese Space Station Telescope (CSST). Precise calibration of the WFS's EMCCD detector is essential to meet the stringent requirements for high-contrast exoplanet imaging. This study comprehensively characterizes key performance parameters of the detector to ensure its suitability for astronomical observations. Through a multi-stage screening protocol, we identified an EMCCD chip exhibiting high resolution and low noise. The electron-multiplying gain (EM Gain) of the EMCCD was analyzed to determine its impact on signal amplification and noise characteristics, identifying the optimal operational range. Additionally, noise properties such as readout noise were investigated. Experimental results demonstrate that the optimized detector meets CPI-C's initial application requirements, achieving high resolution and low noise. This study provides theoretical and experimental foundations for the use of EMCCD-based WFS in adaptive optics and astronomical observations, ensuring their reliability for advanced space-based imaging applications

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arXiv2025

Optimization design and analysis for the mechanical test platform of scientific probe module of the Cool Planet Imaging Coronagraph

This paper optimizes the design and analysis of the mechanical test platform for the scientific probe module of the Cool Planet Imaging Coronagraph, which is the fifth part of the China Space Station survey Telescope. First, according to the module layout and economic requirements, the preliminary structural design of the module mechanical test platform is carried out, and the stiffness sensitive parameters of the assembly are identified to determine the optimization parameters. The Central Composite Design method is used to design the test platform, and a third-order regression model is constructed for response surface analysis. The third-order response surface model of the fundamental frequency and amplitude of the test platform is obtained by fitting the test data with the least squares method, and the structure of the module mechanical test platform is determined. The modal analysis is carried out to determine the fundamental frequency and vibration modes of the mechanical test platform. The vibration response of the platform is simulated by sine, random and swept frequency vibration simulations. The response surface fitting algorithm is verified by the test platform swept frequency test. The agreement between the response surface fitting algorithm and the experiment is good. The fundamental frequency of the test platform is 436.2Hz (>300Hz), which meets the design index requirements of the test platform and can accurately guide the optimization design work. At the same time, it provides the theoretical basis and design method for the structural design of the Chinese manned space station.

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arXiv2025

Mock Observations for the CSST Mission: CPI-C -- Instrument Simulation

To support the development of the data processing pipeline and the scientific performance assessment for the Cool Planet Imaging Coronagraph (CPI-C) on the Chinese Space Station Survey Telescope (CSST), we have developed the end-to-end instrument simulation program, CPISM. This paper details the core modules of CPISM that simulate the CPI-C instrument, focusing on the simulation of the high-contrast imaging optical system and the visible-band science camera. We modeled key optical components, such as the transmission apodizing filter, the wavefront corrector, and the focal plane mask using the HCIPy package. A $10^{-8}$ contrast dark hole region, consistent with design specifications, was simulated using the Electric Field Conjugation (EFC) optimization method, and broadband observation effects were considered. For the science camera, which is an electron multiplying charge-coupled device (EMCCD), we established a detailed model encompassing photon collection, charge transfer, electron multiplication (EM), and readout processes, based on test data. This model simulates complex instrumental features including dark current, charge transfer efficiency, clock-induced charge, multiplication noise factor, and various readout effects like striping and drift. We also proposed and validated an improved statistical model for the EM process to enhance simulation efficiency. CPISM can generate simulated images containing rich instrumental details, closely similar to the expected real observational data, thus laying the foundation for the development and verification of CPI-C data processing algorithms and preparations for future scientific research.

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arXiv2025

Direct Imaging for the Debris Disk around $\epsilon$ Eridani with the Cool-Planet Imaging Coronagraph

We analyze the inner debris disk around $\epsilon$ Eridani using simulated observations with the Cool-Planet Imaging Coronagraph (CPI-C). Using the radiative transfer code MCFOST, we generate synthetic scattered-light images and spectral energy distributions for three disk models that differ in inclination and radial extent, and compare these results with the anticipated performance of CPI-C. CPI-C can resolve disk structures down to $\sim$3 au, offering substantially finer spatial resolution than existing HST/STIS and Spitzer/IRS observations. Recovered inclinations and radial extents closely match the input models, constraining the disk geometry and informing potential planet-disk interactions in the $\epsilon$ Eri system. Although the cold Jupiter-like planet $\epsilon$ Eri b is not detected in our simulations, polarimetric methods may enable detection of its reflected light. These results highlight the capability of next-generation coronagraphs to probe cold dust in nearby planetary systems.

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arXiv2025

Introduction to the Chinese Space Station Survey Telescope (CSST)

The Chinese Space Station Survey Telescope (CSST) is an upcoming Stage-IV sky survey telescope, distinguished by its large field of view (FoV), high image quality, and multi-band observation capabilities. It can simultaneously conduct precise measurements of the Universe by performing multi-color photometric imaging and slitless spectroscopic surveys. The CSST is equipped with five scientific instruments, i.e. Multi-band Imaging and Slitless Spectroscopy Survey Camera (SC), Multi-Channel Imager (MCI), Integral Field Spectrograph (IFS), Cool Planet Imaging Coronagraph (CPI-C), and THz Spectrometer (TS). Using these instruments, CSST is expected to make significant contributions and discoveries across various astronomical fields, including cosmology, galaxies and active galactic nuclei (AGN), the Milky Way and nearby galaxies, stars, exoplanets, Solar System objects, astrometry, and transients and variable sources. This review aims to provide a comprehensive overview of the CSST instruments, observational capabilities, data products, and scientific potential.

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arXiv2018

Portable Adaptive Optics for Exoplanet Imaging

The Portable Adaptive Optics (PAO) is a low-cost and compact system, designed for 4-meter class telescopes that have no Adaptive Optics (AO), because of the physical space limitation at the Nasmyth or Cassegrain focus and the historically high cost of the conventional AO. The initial scientific observations of the PAO are focused on the direct imaging of exoplanets and sub-stellar companions. This paper discusses the PAO concept and the associated high-contrast imaging performance in our recent observational runs. PAO is delivering a Strehl ratio better than $60\%$ in $H$ band under median seeing conditions of $1 ''$. Combined with our dedicated image rotation and subtraction (IRS) technique and the optimized IRS (O-IRS) algorithm, the averaged contrast ratio for a $5\leq V\rm_{mag} \leq 9$ primary star is $1.3 \times 10^{-5}$ and $3.3 \times 10^{-6}$ at angular distance of $0.36 ''$ under exposure time of 7 minutes and 2 hours, respectively. PAO has successfully revealed the known exoplanet of $\kappa$ And b, in our recent observation at 3.5-meter ARC telescope at Apache Point Observatory. We have performed the associated astrometry and photometry analysis of the recovered $\kappa$ And b planet, which gives a projected separation of $0.984 \pm 0.05 ''$, a position angle of $51.1 \pm 0.5^{\circ}$, and a mass of $10.15_{-1.255}^{+2.19}M_{\rm Jup}$. These results demonstrate that PAO can be used for direct imaging of exoplanets with medium-sized telescopes.

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arXiv2017

Design and experimental test of an optical vortex coronagraph

The optical vortex coronagraph (OVC) is one of the promising ways for direct imaging exoplanets because of its small inner working angle and high throughput. This paper presents the design and laboratory demonstration performance at 633nm and 1520nm of the OVC based on liquid crystal polymers (LCP). Two LCPs has been manufactured in partnership with a commercial vendor. The OVC can deliver a good performance in laboratory test and achieve the contrast of the order 10^-6 at angular distance 3λ/D, which is able to image the giant exoplanets at a young stage in combination with extreme adaptive optics.

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arXiv2016

Phase Quantization Study of Spatial Light Modulator for Extreme High contrast Imaging

Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave-front control is a critical technique to attenuate the speckle noise in order to achieve an extremely high contrast. We present a phase quantization study of a spatial light modulator for wave front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different phase accuracy and actuator numbers, which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable phase step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask. The simulation result has constrained the specification for SLM phase accuracy in the above two optical configurations. Finally, we have demonstrated that a SLM with more actuators can deliver a competitive contrast performance to that by using a deformable mirror.

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arXiv2015

A Transmission-Filter Coronagraph: Design and Test

We propose a transmission-filter coronagraph for direct imaging of Jupiter-like exoplanets with ground-based telescopes. The coronagraph is based on a transmission filter that consists of finite number of transmission steps. A discrete optimization algorithm is proposed for the design of the transmission filter that is optimized for ground-based telescopes with central obstructions and spider structures.We discussed the algorithm that is applied for our coronagraph design. To demonstrate the performance of the coronagraph, a filter was manufactured and laboratory tests were conducted. The test results show that the coronagraph can achieve a high contrast of 10 to -6.5 at an inner working angle of 5λ/D, which indicates that our coronagraph can be immediately used for the direct imaging of Jupiter-like exoplanets with ground-based telescopes.

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arXiv2015

A High-contrast Imaging Algorithm: Optimized Image Rotation and Subtraction

Image Rotation and Subtraction (IRS) is a high-contrast imaging technique which can be used to suppress the speckles noise and facilitate the direct detection of exoplanets. IRS is different from Angular Differential Imaging (ADI), in which it will subtract a copy of the image with 180 degrees rotated around its PSF center, rather than the subtraction of the median of all of the PSF images. Since the planet itself will be rotated to the other side of the PSF, IRS does not suffer from planet self-subtraction. In this paper, we have introduced an optimization algorithm to IRS (OIRS), which can provide an extra contrast gain at small angular separations. The performance of OIRS has been demonstrated with ADI data. We then made a comparison of the signal to noise ratio (S/N) achieved by algorithms of locally optimized combination of images (LOCI) and OIRS. Finally we found that OIRS algorithm can deliver a better S/N for small angular separations.

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arXiv2010

An iterative wave-front sensing algorithm for high-contrast imaging systems

Wave-front sensing from focal plane multiple images is a promising technique for high-contrast imaging systems. However, the wave-front error of an optics system can be properly reconstructed only when it is very small. This paper presents an iterative optimization algorithm for the measurement of large static wave-front errors directly from only one focal plane image. We firstly measure the intensity of the pupil image to get the pupil function of the system and acquire the aberrated image on the focal plane with a phase error that is to be measured. Then we induce a dynamic phase to the tested pupil function and calculate the associated intensity of the reconstructed image on the focal plane. The algorithm is to minimize the intensity difference between the reconstructed image and the tested aberrated image on the focal plane, where the induced phase is as the variable of the optimization algorithm. The simulation shows that the wave-front of an optics system can be theoretically reconstructed with a high precision, which indicates that such an iterative algorithm may be an effective way for the wave-front sensing for high-contrast imaging systems.

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arXiv2009

High-contrast coronagraph for ground-based imaging of Jupiter-like planets

We propose a high-contrast coronagraph for direct imaging of young Jupiter-like planets orbiting nearby bright stars. The coronagraph employs a step-transmission filter in which the intensity is apodized with a finite number of steps of identical transmission in each step. It should be installed on a large ground-based telescope equipped with state-of-the-art adaptive optics systems. In that case, contrast ratios around 10^-6 should be accessible within 0.1 arc seconds of the central star. In recent progress, a coronagraph with circular apodizing filter has been developing, which can be used for a ground-based telescope with central obstruction and spider structure. It is shown that ground-based direct imaging of Jupiter-like planets is promising with current technology.

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