1,721,194 research outputs found
EFFECTS OF THERMAL DEFORMATION ON OPTICAL INSTRUMENTS FORSPACE APPLICATION
No full textOptical instruments for space missions work in hostile environment, it’s thus necessary to accurately study the
effects of ambient parameters variations on the equipment.
In particular optical instruments are very sensitive to ambient conditions, especially temperature. This variable
can cause dilatations and misalignments of the optical elements, and can also lead to rise of dangerous stresses
in the optics. Their displacements and the deformations degrade the quality of the sampled images.
In this work a method for studying the effects of the temperature variations on the performance of imaging
instrument is presented. The optics and their mountings are modeled and processed by a thermo-mechanical
Finite Element Model (FEM) analysis, then the output data, which describe the deformations of the optical
element surfaces, are elaborated using an ad hoc MATLAB routine: a non-linear least square optimization
algorithm is adopted to determine the surface equations (plane, spherical, nth polynomial) which best fit the data.
The obtained mathematical surface representations are then directly imported into ZEMAX for sequential
raytracing analysis. The results are the variations of the Spot Diagrams, of the MTF curves and of the
Diffraction Ensquared Energy due to simulated thermal loads.
This method has been successfully applied to the Stereo Camera for the BepiColombo mission reproducing
expected operative conditions.
The results help to design and compare different optical housing systems for a feasible solution and show that
it is preferable to use kinematic constraints on prisms and lenses to minimize the variation of the optical
performance of the Stereo Camera
A freeform optical design of a 12U CubeSat for Earth observation
No full textLarge-scale, multi-redundant satellite platforms are well known for their high cost and the extensive time required for their construction and deployment. In recent decades, small satellites like CubeSats have gained significant popularity and transformed the field of space exploration.
This article presents a preliminary optical design for a CubeSat dedicated to Earth observation in the 400-900 nm spectral range. The CubeSat is based on a 12U platform, with the optical part occupying 8U and featuring a two-mirror off-axis Schwarzschild configuration. The satellite will perform hyperspectral imaging of the Earth using the pushbroom acquisition technique, all within a compact and efficient system. To achieve this, a linear variable filter will be placed in front of the detector.
Due to their small size, CubeSats present some limitations compared to larger, traditional satellites, which degrade the optical performance of the imaging systems. To overcome these limitations, an optical design based on freeform optics has been developed. A preliminary analysis of a two-mirror system, both with and without freeform optics, will be presented to demonstrate how the integration of freeform surfaces can substantially improve the system optical performance
Distortion definition and correction in off-Axis systems
Get PDFOff-axis optical configurations are becoming more and more used in a variety of applications, in particular they are the
most preferred solution for cameras devoted to Solar System planets and small bodies (i.e. asteroids and comets) study.
Off-axis designs, being devoid of central obstruction, are able to guarantee better PSF and MTF performance, and thus
higher contrast imaging capabilities with respect to classical on-axis designs. In particular they are suitable for observing
extended targets with intrinsic low contrast features, or scenes where a high dynamical signal range is present.
Classical distortion theory is able to well describe the performance of the on-axis systems, but it has to be adapted for the
off-axis case.
A proper way to deal with off-axis distortion definition is thus needed together with dedicated techniques to accurately
measure and hence remove the distortion effects present in the acquired images.
In this paper, a review of the distortion definition for off-axis systems will be given. In particular the method adopted by
the authors to deal with the distortion related issues (definition, measure, removal) in some off-axis instruments will be
described in detail
No wavefront sensor adaptive optics system for compensation of primary aberrations by software analysis of a point source image. 2. Tests
No full textThe description of an adaptive optics (AO) system with no wavefront sensor to correct primary aberrations
is presented. This system is based on closed loop software that iteratively analyzes a point source target
image on the instrument focal plane and suitably modifies the AO device. The performed tests with a
pull-only deformable mirror (DM) have shown that the system works very well, reaching an optimal focusing
condition in a few seconds using standard components. Such a system can be conveniently applied in all the
fields in which a not very fast optical adaptation is acceptable
No wavefront sensor adaptive optics system for compensation of primary aberrations by software analysis of a point source image. 1. Methods
No full textAdaptive optics (AO) has been recently used for the development of ophthalmic devices. Its main objective
has been to obtain high-resolution images for diagnostic purposes or to estimate high-order eye aberrations.
The core of every AO system is an optical device that is able to modify the wavefront shape of the
light entering the system; if you know the shape of the incoming wavefront, it is possible to correct the
aberrations introduced in the optical path from the source to the image. The aim of this paper is to
demonstrate the feasibility, although in a simulated system, of estimating and correcting an aberrated
wavefront shape by means of an iterative gradient-descent-like software procedure, acting on a point
source image, without expensive wavefront sensors or the burdensome computation of the point-spreadfunction
(PSF) of the optical system. In such a way, it is possible to obtain a speed and repeatability
advantage over classical stochastic algorithms. A hierarchy in the aberrations is introduced, in order to
reduce the dimensionality of the state space to be searched. The proposed algorithm is tested on a simple
optical system that has been simulated with ray-tracing software, with randomly generated aberrations,
and compared with a recently proposed algorithm for wavefront sensorless adaptive optics
Distortion calculation and removal for an off-axis and wide angle camera
No full textFor off-axis and wide angle systems, the calculation, calibration and removal of distortion effects from the images are
often challenging tasks. Specific procedures have been implemented to assess and remove the distortion from the images
acquired by the OSIRIS imaging instrument on-board the Rosetta ESA mission.
OSIRIS consisted in a narrow and a wide angle camera. The Wide Angle Camera (WAC) is an off-axis, unobstructed and
wide FoV (i.e. about 12°x12°) optical system. It has a peculiar optical configuration, and due to the off-axis design the
camera presents a high level of intrinsic distortion, with the major component being anamorphism.
The distortion has been estimated theoretically via raytracing during the design phase, then measured on-ground and inflight
during the calibration campaigns.
To obtain correct undistorted images, a distortion removal procedure has been implemented. The first step of the process
has been to remove from the images the theoretical distortion. Then the distortion correction procedure has been refined
using on-ground and in-flight calibration measurements.
This work describes in detai
The optical head of the EnVisS camera for the Comet Interceptor ESA mission: phase 0 study
No full textSpace Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave; Virtual, Online; United States; 14 December 2020 through 22 December 2020; Code 166572.--Proceedings of SPIE - The International Society for Optical Engineering Volume 11443, 2020, Article number 1144379.--Full list of authors: Da Deppo, Vania; Pernechele, Claudio; Jones, Geraint H.; Brydon, George; Zuppella, Paola; Chioetto, Paolo; Nordera, Simone; Slemer, Alessandra; Crescenzio, Giuseppe; Piersanti, Emanuele; Spanò, Paolo; Bucciol, Gino; Consolaro, Luca; Lara, Luisa; Slavinskis, AndrisEnVisS (Entire Visible Sky) is an all-sky camera specifically designed to fly on the space mission Comet Interceptor. This mission has been selected in June 2019 as the first European Space Agency (ESA) Fast mission, a modest size mission with fast implementation. Comet Interceptor aims to study a dynamically new comet, or interstellar object, and its launch is scheduled in 2029 as a companion to the ARIEL mission. The mission study phase, called Phase 0, has been completed in December 2019, and then the Phase A study had started. Phase A will last for about two years until mission adoption expected in June 2022. The Comet Interceptor mission is conceived to be composed of three spacecraft: spacecraft A devoted to remote sensing science, and the other two, spacecraft B1 and B2, dedicated to a fly-by with the comet. EnVisS will be mounted on spacecraft B2, which is foreseen to be spin-stabilized. The camera is developed with the scientific task to image, in push-frame mode, the full comet coma in different colors. A set of ad-hoc selected broadband filters and polarizers in the visible range will be used to study the full scale distribution of the coma gas and dust species. The camera configuration is a fish-eye lens system with a FoV of about 180°x45°. This paper will describe the preliminary EnVisS optical head design and analysis carried out during the Phase 0 study of the mission. © COPYRIGHT SPIE.This activity has been conducted and funded through an Agenzia Spaziale Italiana (ASI) contract to the Istituto Nazionale di Astrofisica (INAF) n. 2020-4-HH.0
A novel optical design for the stereo channel of the imaging system SIMBIOSYS for the BepiColombo ESA mission
Get PDFIn this paper the design of a novel catadioptric optical
solution for the Stereo Channel (STC) of the imaging
system SIMBIOSYS for the BepiColombo ESA
mission to Mercury is presented.
The main scientific objective is the 3D global mapping
of the entire surface of Mercury with a scale factor of
50 m per pixel at periherm in five different spectral
bands.
The system consists of two sub-channels looking at
±20° from nadir. They share the detector and all the
optical components with the exception of the first
element, a rhomboid prism. The field of view of each
channel is 5.3° ́ 4.5° and the scale factor is 23
arcsec/pixel. The system guarantees an aberration
balancing over all the field of view and wavelength
range with optimal optical performance.
For stray-light suppression, an efficient baffling system
able to well decouple the optical paths of the two subchannels
has been designed
Preliminary optical design of the stereo channel of the imaging system simbiosys for the BepiColombo ESA mission
Get PDFThe paper describes the optical design and
performance budget of a novel catadioptric instrument
chosen as baseline for the Stereo Channel (STC) of the
imaging system SIMBIOSYS for the BepiColombo
ESA mission to Mercury.
The main scientific objective is the 3D global mapping
of the entire surface of Mercury with a scale factor of
50 m per pixel at periherm in four different spectral
bands.
The system consists of two twin cameras looking at
±20° from nadir and sharing some components, such as
the relay element in front of the detector and the
detector itself. The field of view of each channel is 4° x
4° with a scale factor of 23’’/pixel. The system
guarantees good optical performance with Ensquared
Energy of the order of 80% in one pixel.
For the straylight suppression, an intermediate field
stop is foreseen, which gives the possibility to design
an efficient baffling system
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