Cassegrain Focus Research Articles

A suggested 12-m telescope optical system configuration for China

This is an optical/infrared telescope. It is a general purpose telescope. A segmented primary mirror is adopted with diameter 12 m and f-ratio 1.6. This telescope has prime focus, Cassegrain, Nasmyth and coud´e systems. The prime focus system has a 1.◦5 field-of-view corrector with excellent image quality. It will be used for multi-object fibre spectroscopic observation and CCD photography. In this 12-m telescope, all systems except the prime focus system share the same secondary mirror; the Nasmyth and coud´e systems are formed byadding relay mirrors; and the method of moving a secondary mirror is used to enhance image quality. All these features originate from the innovative optical system of the Chinese 2.16-m telescope. At the Cassegrain focus, a dark object spectrograph, for example, can be installed without any corrector; and in case a field of view is needed, a corrector may be added. Both the Nasmyth and coud´e systems have exceptionally excellent image quality and the exchange between them occurs very conveniently. Many instruments in visible and infrared wavebands, some with an adaptive optics system, will be installed at the Nasmyth platform. Coud´e system will be used for interferometry and for those instruments which require high stability. This configuration has a nearly full range of systems but it is not complex, and it can even be adopted by 20–40-m class telescopes.

Design of a Lightweight W-band Cassegrain Reflector Antenna

본 논문에서는 정밀 포탄의 자탄용 센서에 적용 가능한 경량형 W-대역 카세그레인 반사경 안테나를 설계, 제작, 측정하였다. 이중 모드 피드 혼, 부 반사경 및 주반경으로 구성된 카세그레인 반사경 안테나를 최적 설계하였다. 폴리카보네이트 플라스틱 재료를 사용하여 주 반사경, 부 반사경－레이돔 몸체를 사출 성형으로 제작한 후 반사면을 PVD 공법으로 도금함으로써 경량화된 안테나를 구현하였다. 피드 혼은 알루미늄 블록을 정밀 가공하여 제작하였다. 제작품을 측정한 결과 제안한 안테나는 1.2%의 대역폭에서 -16dB 이하의 반사계수, 중심 주파수에서 1.8°의 빔폭과 38.6dBi의 이득을 가짐을 확인하였다.

Optical configuration and optical tests of the HartRAO Lunar Laser Ranger

The telescope to be used for the HartRAO Lunar Laser Ranging system is a 1-m Classical Cassegrain donated by a French observatory called the Observatoire de la Cote d’Azur. Limited technical details of the telescope exist so tests were conducted to determine its optical characteristics and performance. The optical performance of the telescope was determined through its transmission efficiency. The optical efficiency of any telescope highly hinges on the reflectivity and surface accuracy of optics through which the laser signal is delivered. We present possible coude paths and their respective components for beaming the laser signal from its source and through the telescope. Spectroscopic measurements of each of the coude optics were conducted in order to determine the total throughput of the system. The surface accuracy of the primary mirror was validated by performing a structural analysis of the mirror under its support system. Taking into account the honeycomb geometry of the mirror, its material properties and support mechanism, a finite element analysis was done with ANSYS to predict the gravitational deformations the mirror will experience under operational angles. High optical performance telescopes require that deformations be kept to a small fraction of the wavelength of light the telescope is designed to use. A system efficiency of ~ 90% can be expected if obstructions and number of reflective surfaces are limited on the coude path.

Ka-Band User Terminal Antennas for Satellite Communications [Antenna Applications Corner

The growing need for bidirectional mobile satellite communications in the Ka-band necessitates the development of dedicated antenna systems. In this article, we describe two different solutions for mobile user-terminal antennas intended for an operation in emergency scenarios. The first solution, a high-gain antenna, consists of a Cassegrain reflector, fed from a multimode monopulse tracking system for circular polarization at a satellite downlink frequency of 20 GHz. The structure is operational at 30 GHz to cover the uplink frequency range. The antenna system is mounted on a high-performance mechanical positioner to facilitate a fast compensation of the movements of the carrier vehicle. The second solution, a low-profile antenna, consists of leaky-wave antenna (LWA) panels employing two-layer partially reflective surfaces (PRSs). A hybrid tracking technique is used, and a unique feature of this antenna is its dual-band operation, to overcome the challenge of widely separated uplink and downlink ranges in the Ka-band. This article describes the design of the two types of antennas and analyzes the measurement results. Furthermore, tracking issues considered from the view of control engineering are addressed, and an evaluation of tracking accuracy is presented.

Passive focusing techniques for piezoelectric air-coupled ultrasonic transducers

This paper proposes a novel passive focusing system for Air-Coupled Ultrasonic (ACU) piezoelectric transducers which is inspired by the Newtonian–Cassegrain (NC) telescope concept. It consist of a primary spherical mirror with an output hole and a flat secondary mirror, normal to the propagation axis, that is the transducer surface itself. The device is modeled and acoustic field is calculated showing a collimated beam with a symmetrical focus. A prototype according to this design is built and tested with an ACU piezoelectric transducer with center frequency at 400kHz, high-sensitivity, wideband and 25mm diameter flat aperture. The acoustic field is measured and compared with calculations. The presented prototype exhibit a 1.5mm focus width and a collimated beam up to 15mm off the output hole. In addition, the performance of this novel design is compared, both theoretically and experimentally, with two techniques used before for electrostatic transducers: the Fresnel Zone Plate – FZP and the off-axis parabolic or spherical mirror.The proposed NC arrangement has a coaxial design, which eases the transducers positioning and use in many applications, and is less bulky than off-axis mirrors. Unlike in off-axis mirrors, it is now possible to use a spherical primary mirror with minimum aberrations. FZP provides a more compact solution and is easy to build, but presents some background noise due to interference of waves diffracted at out of focus regions. By contrast, off-axis parabolic mirrors provide a well defined focus and are free from background noise, although they are bulky and more difficult to build. Spherical mirrors are more easily built, but this yields a non symmetric beam and a poorly defined focus.

Research and analysis on lidar performance with intrinsic fluorescence biological aerosol measurements

Biological aerosols which could cause diseases of human beings, animals and plants, are living particles suspended in the atmosphere. Ultraviolet laser induced fluorescence has been developed as a standard technique used to discriminate between biological and non-biological particles. As an effective tool of remote sensing, fluorescence lidar is capable of detecting concentration of biological aerosols with high spatial and temporal resolutions. Intrinsic fluorescence, one of the most important characteristics of biological aerosols, has quite a large effect on the performances of fluorescence lidar. To investigate the effects of intrinsic fluorescence on biological aerosols, we design an ultraviolet laser induced fluorescence lidar at an excited wavelength of 266 nm, with a repetition rate of 10 Hz. Fluorescence signals are collected by a Cassegrain telescope with a diameter of 254 mm, in which fluorescence spectra of 300-800 nm are mainly considered. A spectrograph and a multichannel photomultiplier tube (PMT) array detector are employed to achieve the fine separation and highefficiency detection of fluorescence signals. According to the present configuration, we perform a series of simulations to estimate the measurement range and the concentration resolution of biological aerosols, with a certain pulse energy. With a relative error less than 10%, theoretical analysis shows that designed fluorescence lidar is able to detect the biological aerosols within a range of 1.5 km at a concentration of 1000 particles·L-1. When the detection distance enlarges to 2.1 km, detectable wavelength range is limited to 300-310 nm. In addition, the lidar is capable of identifying minimum concentrations of biological aerosols with 2 particles·L-1 and 4 particles·L-1 at fluorescence wavelengths of 350 nm and 600 nm, respectively, where the induced pulse energy is set to be 60 mJ and detected range 0.1 km. With setting energies of 40 mJ and 20 mJ, minimum concentrations of biological aerosols decrease to 3 particles·L-1 and 6 particles·L-1, respectively, at a fluorescence wavelength of 350 nm. The relative error of minimum concentration resolution is about 2 particles·L-1, increasing rapidly with range. For a fluorescence wavelength of 600 nm, both the minimum concentration and the relative error show relatively high values, 5 particles·L-1 at 40 mJ and 10 particles·L-1 at 20 mJ, where the relative errors are found to be 2 particles·L-1 and 4 particles·L-1, respectively. The results prove that a shorter intrinsic fluorescence wavelength has a better effect on biological aerosol measurement. We believe that a proper intrinsic fluorescence wavelength will further improve the detection accuracy of biological aerosols.

Pure rotational Raman lidar for absolute detection of atmospheric temperature

A pure rotational Raman lidar has become one of valid methods of profiling atmospheric temperature. However, its proper operation generally needs a certain collocated device of atmospheric temperature to calibrate three retrieval coefficients. This fact seriously restricts the applications of pure rotational Raman lidar in the meteorology and environment fields. In order to execute the detection technique of atmospheric temperature without calibration, we present and design a pure rotational Raman lidar based on the dependence of atmosphere molecular rotational Raman spectral envelope on temperature. It is configured with a laser having a pulse energy of 300 mJ, a pulse repetition rate of 20 Hz, and a Cassegrain telescope with a clear aperture of 250 mm. A two-stage multi-channel pure rotational Raman spectroscopic filter is proposed to extract efficiently the rotational Raman spectral lines with more than 70 dB suppression to the elastic-scattering optical signals. It is configured with one blazed diffraction grating, one convex lens, one linear fiber array and seven groups of fiber Bragg gratings. The blazed diffraction grating and fiber Bragg grating are separately utilized as the primary and secondary spectroscope. The tailor-made fiber array, which is composd of ten single mode fibers of 460-HP type and one multi-mode fiber, is designed to transfer the spectral signals. One end face of multi-mode fiber lies in the focal point of telescope, and then it transfers the lidar echo signals to the pure rotational Raman spectroscopic filter. The other end face of multi-mode fiber lies in the focal point of convex lens. The ten single mode fibers are used to transfer the optical signals from the primary spectroscope to the secondary, and their end faces lie in the focal plane of convex lens. Six pure rotational Raman spectral lines of nitrogen molecule in the anti-Strokes branch are chosen under the condition of the 0.09-nm forbidden band, with the consideration of the relationship between the pure rotational Raman spectral lines of nitrogen and oxygen molecules. While the excited laser wavelength is 532 nm, their central wavelengths are 530.76 nm, 529.86 nm, 529.41 nm, 528.51 nm, 527.62 nm, and 527.17 nm, respectively. Their corresponding positions of fiber end faces on fiber array are 156 m, 407 m, 532 m, 782 m, 1031 m, and 1156 m. Compared with these pure rotational Raman spectral lines, the elastic scattering signal lies on the other side of the focal point of convex lens, which improves the spectral purity of pure rotational Raman spectral lines. A retrieval algorithm of absolute detection technique is presented based on the least square principle. The performance of this lidar is simulated based on the U. S. standard atmospheric model. Simulation results show that this designed lidar can achieve the extraction of the pure rotational Raman spectral lines of nitrogen molecules, and that the atmospheric temperature profile obtained from absolute retrieval algorithm within a measurement time of 17 min can be up to 2.0 km with less than 0.5-K deviation. This pure rotational Raman lidar without calibration will provide a new detection method and retrieval scheme for atmospheric temperature profile.

Measurements of atmospheric NO3 radicals in Hefei using LED-based long path differential optical absorption spectroscopy**Project supported by the “Strategic Priority Research Program” of the Chinese Academy of Sciences (Grant Nos. XDB05040200 and XDB05010500).

NO3 radicals accumulate during the night, thereby being the most critical night oxidant. Owing to the low concentration and dramatic variation, the detection of atmospheric NO3 radicals is still challenging. In this paper, an LED-based Long Path Differential Optical Absorption Spectroscopy (LPDOAS) instrument is developed for measuring the atmospheric NO3 radicals. This instrument is composed of a Schmidt–Cassegrain telescope, a combined emitting and receiving fiber, and a red LED equipped with a thermostat, and has a center wavelength of 660 nm, covering the NO3 strongest absorption peak (662 nm). The influence of LED temperature fluctuations is discussed. The temperature of the LED lamp with a home-made thermostat is tested, showing a stability of ±0.1 °C. The principle and fitting analyses of LED-LPDOAS are presented. A retrieval example and a time series of NO3 radical concentrations with good continuity for one night are shown. The detection limit of NO3 for 2.6-km optical path is about 10 ppt.

Development of shared aperture dual configuration antenna for S/Ka-band communication

Shared aperture dual configuration antenna has been developed for dual linearly/circularly polarized operation at S/Ka-band. The antenna operates in cassegrain configuration at Ka-band and in prime focus configuration at S-band using the same parabolic reflector. Measured gain of the overall antenna at Ka-band is better than 48 dBi in each port and interport isolation is better than 19 dB. Measured gain at S-band is better than 28 dBi in each port and interport isolation is better than 20 dB. Measured 2:1 VSWR bandwidth is better than 7% at either port at Ka-band and is about 10% at either port at S-band. Measured 3-dB axial-ratio bandwidth is better than 7% at each port at Ka-band. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:139–145, 2016

Alignment and assembly process for primary mirror subsystem of a spaceborne telescope

In this study, a multispectral spaceborne Cassegrain telescope was developed. The telescope was equipped with a primary mirror with a 450-mm clear aperture composed of Zerodur and lightweighted at a ratio of approximately 50% to meet both thermal and mass requirements. Reducing the astigmatism was critical for this mirror. The astigmatism is caused by gravity effects, the bonding process, and deformation from mounting the main structure of the telescope (main plate). This article presents the primary mirror alignment, mechanical ground-supported equipment (MGSE), assembly process, and optical performance test used to assemble the primary mirror. A mechanical compensated shim is used as the interface between the bipod flexure and main plate. The shim was used to compensate for manufacturer errors found in components and differences between local coplanarity errors to prevent stress while the bipod flexure was screwed to the main plate. After primary mirror assembly, an optical performance test method called a bench test with an algorithm was used to analyze the astigmatism caused by the gravity effect and deformation from the mounting or supporter. The tolerance conditions for the primary mirror assembly require the astigmatism caused by gravity and mounting force deformation to be less than P−V0.02 λ at 632.8 nm. The results demonstrated that the designed MGSE used in the alignment and assembly processes met the critical requirements for the primary mirror assembly of the telescope.

Precision attitude control of the Gravity Probe B satellite

The Gravity Probe B satellite used ultra-precise gyroscopes in low Earth orbit to compare the orientation of the local inertial reference frame with that of distant space in order to test predictions of general relativity. The experiment required that the Gravity Probe B spacecraft have milliarcsecond-level attitude knowledge for the science measurement, and milliarcsecond-level control to minimize classical torques acting on the science gyroscopes. The primary sensor was a custom Cassegrainian telescope, which measured the pitch and yaw angles of the experiment package with respect to a guide star. The spacecraft rolled uniformly about the direction to the guide star, and the roll angle was measured by star trackers. Attitude control was performed with sixteen proportional thrusters that used boil-off from the experiment’s liquid Helium cryogen as propellant. This paper summarizes the attitude control system’s design and on-orbit performance.

Design and analysis of optimum baffle for a Cassegrain telescope

Optimum baffle parameters to shield the direct rays of stray light are arrived at for a Cassegrain telescope using the iterative method. Further, we have proposed here a design procedure that improves the performance of an optimum baffle arrived at in view of finite reflective nature of the practical blackened-baffle structure. The modeling and performance evaluation of the designed baffle are demonstrated on a realistic numerical Cassegrain telescope using ZEMAX® optical design software. The effectiveness of this method is more perceivable on a wide field of view, large aperture, long focal length Ritchey–Chretien telescope of high resolution earth observation satellites.

In situ analysis of steel melt by double-pulse laser-induced breakdown spectroscopy with a Cassegrain telescope

A laser-induced breakdown spectroscopy (LIBS) system combining a Cassegrain telescope and a double-pulse laser mode was developed for the in situ analysis of steel melt. Optical- and electrical-related devices were sealed in an enclosed box away from the high-temperature steel melt surface. Connected to the box by a flange, a long hollow steel tube was used for the laser and plasma emission transmission path. At the tip of the steel tube, a refractory lance that can withstand high temperatures was immersed into the molten steel surface to pass through the surface slag layer. The designed optical structure successfully keeps the photoelectric-associated system components away from the high-temperature environment, thus reducing the complexity of system protection and maintenance. The signals obtained from single-pulse and double-pulse LIBS were comprehensively compared; the effect of argon blowing on spectral stability was analyzed; and the quantitative analysis of Si, Mn, Cr, Ni and V in molten steel samples was evaluated using both a univariate model and a partial least squares (PLS) model. The relative root mean square error of prediction (RMSEP) values and average relative standard deviations (RSDs) of the PLS model were approximately 5% and 2%–3%, respectively, both of which are less than those of the univariate calibration model. The sealed LIBS setup was also transferred to a steel plant for application testing, and the obtained accuracy approached the plant's accuracy requirements. Furthermore, quantitative analysis of carbon was also achieved on the basis of the PLS models. These results demonstrate that the developed system is promising for the in situ analysis of melt steel in the steelmaking industry.

GREGOR observations of a small flare above a sunspot

AbstractA small flare ribbon above a sunspot umbra in active region 12205 was observed on November 7, 2014, at 12:00 UT in the blue imaging channel of the 1.5-m GREGOR telescope, using a 0.1 nm Ca II H interference filter. Context observations from SDO/AIA, Hinode/SOT, and IRIS show that the ribbon is a part of a larger one that extends through the neighboring positive polarities and also participates in several other flares within the active region. A 140 second long time series of Ca II H images was reconstructed by means of the Multi-Frame Blind Deconvolution method, giving the respective spatial and temporal resolutions of 0”.1 and 1 s. Light curves and horizontal velocities of small-scale bright knots in the observed flare ribbon were measured. Some knots are stationary but three move along the ribbon with speeds of 7–11 km s−1. Two of them move in the opposite direction and exhibit highly correlated intensity changes, providing evidence for the presence of slipping reconnection at small spatial scales.

Millimetre wavelength variable focusing antenna for power beaming and active denial systems

A design of a millimetre wavelength antenna with adjustable focal length is demonstrated in this study. This antenna is designed to operate in the near field regime, and has the ability to change the focal plane position. The structure of the antenna is based on a Cassegrain configuration in order to deliver maximum power density to a pre-defined focal plane. Possible applications are radioactive power beaming and active denial systems. The analysis and development of this antenna were carried-out using the Gaussian beam model and the ABCD matrix method in order to find the focus position and spot size as a function of the axial distance. The development of the quasi-optical components of the Cassegrain antenna, simulation results and experimental results are described in this work.

CARMENES: M dwarfs and their planets

AbstractCARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a new instrument currently undergoing commissioning at the 3.5 m telescope of the Calar Alto Observatory. It has been constructed by a consortium of eleven Spanish and German institutions. The scientific goal of the project is a 600-night radial-velocity survey targeting 300 M dwarfs with sufficient precision to detect terrestrial planets in their habitable zones. The CARMENES instrument consists of two separate échelle spectrographs covering the wavelength range from 0.55 to 1.7 μm at a spectral resolution of R = 82,000, fed by fibers from the Cassegrain focus of the telescope. Both spectrographs are housed in a temperature-stabilized environment in vacuum tanks, to enable a long-term radial velocity precision of 1 m s−1. The wavelength calibration will be done with Th-Ne and U-Ne emission line lamps, and with Fabry-Pérot etalons.

A NEW AUTO-GUIDING SYSTEM FOR CQUEAN

We develop a new auto-guiding system for the Camera for QUasars in the EArly uNiverse (CQUEAN). CQUEAN is an optical CCD camera system attached to the 2.1-m Otto-Struve Telescope (OST) at McDonald Observatory, USA. The new auto-guiding system differs from the original one in the following: instead of the cassegrain focus of the OST, it is attached to the finder scope; it has its own filter system for observation of bright targets; and it is controlled with the CQUEAN Auto-guiding Package, a newly developed auto-guiding program. Finder scope commands a very wide field of view at the expense of poorer light gathering power than that of the OST. Based on the star count data and the limiting magnitude of the system, we estimate there are more than 5.9 observable stars with a single FOV using the new auto-guiding CCD camera. An adapter is made to attach the system to the finder scope. The new auto-guiding system successfully guided the OST to obtain science data with CQUEAN during the test run in 2014 February. The FWHM and ellipticity distributions of stellar profiles on CQUEAN, images guided with the new auto-guiding system, indicate similar guiding capabilities with the original auto-guiding system but with slightly poorer guiding performance at longer exposures, as indicated by the position angle distribution. We conclude that the new auto-guiding system has overall similar guiding performance to the original system. The new auto-guiding system will be used for the second generation CQUEAN, but it can be used for other cassegrain instruments of the OST.

Compact 405-nm random-modulation continuous wave lidar for standoff biological warfare detection

A compact bioaerosol standoff system was developed and tested for bio warfare agent stimulant aerosol detection. It used a continuous-wave semiconductor laser diode with an output power of 100 mW and a wavelength of 405 nm. It was modulated with a pseudorandom code at 100 MHz to provide the 1.5 m range resolution for both scattering and fluorescence detection. A 200-mm-diameter Cassegrain telescope and four photon-counting detection channels centered at 405 nm (two polarization detection channels), 450 nm, and 530 nm constituted the optical receiver. A field-programmable gate array chip was controlled to generate the laser driver signal and record four synchronized channel signals. Field tests were performed with stimulant aerosols of Bacillus subtilis, Staphylococcus aureus, and yeast. The detected biological warfare stimulant aerosol lidar was released at ranges of several hundred meters. The preliminary result showed that the fluorescence channel detected the stimulants at ranges up to 90 m and the elastic scattering channel up to 200 m.

Rapid instrument exchanging system for the Cassegrain focus of the Lijiang 2.4-m Telescope**Supported by the National Natural Science Foundation of China.

As a facility used for astronomical research, the Lijiang 2.4-m telescope of Yunnan Astronomical Observatories, requires the ability to change one auxiliary instrument with another in as short a time as possible. This arises from the need to quickly respond to scientific programs (e.g. transient observation, time domain studies) and changes in observation conditions (e.g. seeing and weather conditions). In this paper, we describe the design, construction and test of hardware and software in the rapid instrument exchange system (RIES) for the Cassegrain focal station of this telescope, which enables instruments to be quickly changed at night without much loss of observing time. Tests in the laboratory and at the telescope show that the image quality and pointing accuracy of RIES are satisfactory. With RIES, we observed the same Landolt standard stars almost at the same time with the Princeton Instruments VersArray 1300B Camera (PICCD) and the Yunnan Faint Object Spectrograph and Camera (YFOSC), while both were mounted at the Cassegrain focus. A quasi-simultaneous comparison shows that the image quality of the optical system inside the YFOSC is comparable with that provided by the PICCD.

Polarization Aberrations in Astronomical Telescopes: The Point Spread Function

Detailed knowledge of the image of the point spread function (PSF) is necessary to optimize astronomical coronagraph masks and to understand potential sources of errors in astrometric measurements. The PSF for astronomical telescopes and instruments depends not only on geometric aberrations and scalar wave diffraction but also on those wavefront errors introduced by the physical optics and the polarization properties of reflecting and transmitting surfaces within the optical system. These vector wave aberrations, called polarization aberrations, result from two sources: (1) the mirror coatings necessary to make the highly reflecting mirror surfaces, and (2) the optical prescription with its inevitable non-normal incidence of rays on reflecting surfaces. The purpose of this article is to characterize the importance of polarization aberrations, to describe the analytical tools to calculate the PSF image, and to provide the background to understand how astronomical image data may be affected. To show the order of magnitude of the effects of polarization aberrations on astronomical images, a generic astronomical telescope configuration is analyzed here by modeling a fast Cassegrain telescope followed by a single 90° deviation fold mirror. All mirrors in this example use bare aluminum reflective coatings and the illumination wavelength is 800 nm. Our findings for this example telescope are: (1) The image plane irradiance distribution is the linear superposition of four PSF images: one for each of the two orthogonal polarizations and one for each of two cross-coupled polarization terms. (2) The PSF image is brighter by 9% for one polarization component compared to its orthogonal state. (3) The PSF images for two orthogonal linearly polarization components are shifted with respect to each other, causing the PSF image for unpolarized point sources to become slightly elongated (elliptical) with a centroid separation of about 0.6 mas. This is important for both astrometry and coronagraph applications. (4) Part of the aberration is a polarization-dependent astigmatism, with a magnitude of 22 milliwaves, which enlarges the PSF image. (5) The orthogonally polarized components of unpolarized sources contain different wavefront aberrations, which differ by approximately 32 milliwaves. This implies that a wavefront correction system cannot optimally correct the aberrations for all polarizations simultaneously. (6) The polarization aberrations couple small parts of each polarization component of the light (∼10-4) into the orthogonal polarization where these components cause highly distorted secondary, or “ghost” PSF images. (7) The radius of the spatial extent of the 90% encircled energy of these two ghost PSF image is twice as large as the radius of the Airy diffraction pattern. Coronagraphs for terrestrial exoplanet science are expected to image objects 10-10, or 6 orders of magnitude less than the intensity of the instrument-induced “ghost” PSF image, which will interfere with exoplanet measurements. A polarization aberration expansion which approximates the Jones pupil of the example telescope in six polarization terms is presented in the appendix. Individual terms can be associated with particular polarization defects. The dependence of these terms on angles of incidence, numerical aperture, and the Taylor series representation of the Fresnel equations lead to algebraic relations between these parameters and the scaling of the polarization aberrations. These “design rules” applicable to the example telescope are collected in § . Currently, exoplanet coronagraph masks are designed and optimized for scalar diffraction in optical systems. Radiation from the “ghost” PSF image leaks around currently designed image plane masks. Here, we show a vector-wave or polarization optimization is recommended. These effects follow from a natural description of the optical system in terms of the Jones matrices associated with each ray path of interest. The importance of these effects varies by orders of magnitude between different optical systems, depending on the optical design and coatings selected. Some of these effects can be calibrated while others are more problematic. Polarization aberration mitigation methods and technologies to minimize these effects are discussed. These effects have important implications for high-contrast imaging, coronagraphy, and astrometry with their stringent PSF image symmetry and scattered light requirements.