A theoretical and experimental study is performed to eliminate the effect of retroreflection of a camera by using masks. Theoretically, different types of masks are studied in terms of their capability to reduce the strength of the retroreflected signal while maintaining good camera image quality. Experimentally, the strength of retroreflected signals and image quality have been measured for different alignments of different masks. The results of these experiments in combination with the presented theory can be used to design masks that can reduce or even completely eliminate the strength of retroreflected signals, while simultaneously maintaining good image quality.
Retro-reflection can be used for the detection and classification of optical systems. The probability of detecting sights
over large ranges depends on parameters of the laser, the sight, the detector and the atmosphere. We have developed a
software tool that simulates a sight detection system. With the use of this tool we can 'test' different sight detection
system designs and make estimations on detection ranges of optical systems. In this paper we give a short overview of
the physical aspects that have been implemented in the model and discuss the experimental validation of our model.
Laser countermeasures against infrared focal plane array cameras aim to saturate the full camera image. In this paper we
will discuss the results of dazzling experiments performed with MWIR lasers. In the "low energy" pulse regime we
observe an increasing saturated area with increasing power. The size of the saturated area can be explained by an
expression derived from the point spread function of the optics.
The experimental results for short "high energy" pulses show a strong non-linear response of the detector arrays.
Physical processes potentially responsible for these effects are described. Possible consequences of this non-linear
detector behaviour for the effectiveness of laser countermeasures applying short high energy pulses are discussed. A
better understanding of the response of infrared detectors to short high energy laser pulses, will allow changing the laser
design in order to mitigate these effects.
Laser countermeasures against infrared focal plane array cameras aim to saturate the full camera image. In this paper we
will discuss the results of three different dazzling experiments performed with MWIR lasers and show that the obtained
results are independent of the read-out mechanism of the camera and can be explained by an expression derived from the
point spread function of the optics. This expression also allows us to estimate the required laser power to saturate a
complete focal plane array in a camera system. Simulated Images with simulated dazzling effects based on this
expression will be shown.
The primary goal of DARWIN is to detect earth-like extrasolar planets and to search for biomarkers. This is achieved by means of nulling interferometry, using three free-flying telescopes and a Beam-Combiner (BC) hub. DARWIN will be able to perform astrophysical imaging with high spectral and spatial resolution. Should one of Darwin's telescope flyers fail, then Darwin's capability of detecting earth-sized exo-planets is dramatically reduced. However, with only two telescopes the imaging mode can continue operating with minimal performance degradation, thus ensuring mission success. This work describes a trade-off study between four conceptual three-beam BC's, that are capable of performing both as a nuller and as an imager. A proposed breadboard design will demonstrate end-to-end Fringe-Tracking (FT) and Optical Path-Length (OPL) control. The BC concept is based on a pupil-plane (Michelson) beam combination scheme. Pupil-plane imaging BC's offer a large overlap in terms of optical layout with the nulling BC concept, making it possible to develop a combined nulling- and imaging BC. This means that a reduced number of optical components can be used compared to a scheme with separate BC's. The BC concept inherently compensates for unequal OPL's, which in ground-based interferometers is compensated for by long stroke Optical Delay Lines (ODL's).
X-ray optics based on pore geometries have opened applications for X-ray telescopes in the planetary and astrophysics areas where very restricted resources are allowed. In this paper the mission design for a limited size X-ray telescope is presented, which is based on a stowed structure to be deployed in a L2 orbit. With the application of silicon based pore optics in the conical approximation of the Wolter geometry [1, 2, 3] an appreciable effective area can be achieved at 1keV. The energy response function can be extended and optimised towards higher energies by the application of more complex reflective coatings including multiplayer designs [4, 5]. The angular resolution is kept compatible with this collecting area, avoiding source confusion. One of the workhorse launchers for the ESA science missions, the Soyuz Fregat, is assumed as vehicle.
The main trade-offs of the mission design will be addressed and the performance of such a telescope is discussed.
XEUS, the 'X-ray Early Universe Spectroscopy Mission', is a potential candidate for inclusion into the Cosmic Visions 1525 Science Programme of the European Space Agency ESA [1,2]. It is being studied jointly with the Japanese Aerospace Exploration Agency JAXA.
The newly developed Silicon-based High resolution Pore Optics (HPO) combines low mass density with good angular resolution, and enables the development of novel mission design concepts for the implementation of a new generation of space based X-ray telescope [3, 4, 5]. This optics technology allows also for the application of complex reflective coatings [6], improving the effective area of the telescope and permitting an enhancement in the engineering of the desired response function.
This paper gives an overview of the telescope optical design and optical bench architecture, including the deployment scheme. Further, the performance predictions based on ray tracing are discussed and the overall telescope design of XEUS is presented.
Future planetary missions will require advanced, smart, low resource payloads and satellites to enable the exploration of our solar system in a more frequent, timely and multi-mission manner. A viable route towards low resource science instrumentation is the concept of Highly Integrated Payload Suites (HIPS), which was introduced during the re-assessment of the payload of the BepiColombo (BC) Mercury Planetary Orbiter (MPO). Considerable mass and power savings were demonstrated throughout the instrumentation by improved definition of the instrument design, a higher level of integration, and identification of resource drivers. The higher integration and associated synergy effects permitted optimisation of the payload performance at minimum investment while still meeting the demanding science requirements. For the specific example of the BepiColombo MPO, the mass reduction by designing the instruments towards a Highly Integrated Payload Suite was found to be about 60%. This has endorsed the acceptance of a number of additional instruments as core payload of the BC MPO thereby enhancing the scientific return. This promising strategic approach and concept is now applied to a set of planetary mission studies for future exploration of the solar system. Innovative technologies, miniaturised electronics and advanced remote sensing technologies are the baseline for a generic approach to payload integration, which is here investigated also in the context of largely differing mission requirements. A review of the approach and the implications to the generic concept as found from the applications to the mission studies are presented.
Producing the next generation of X-ray optics, both for large astrophysics missions and smaller missions such as planetary exploration, requires much lower mass and therefore much thinner mirrors. The use of pore structures allows very thin mirrors in a stiff structure. Over the last few years we have been developing ultra-low mass pore optics based on microchannel plate technology in glass, resulting in square, open-core glass fibres in a concentric geometry. The surface roughness inside the pores can be as low as 0.5 nm due to the extreme stretching of the surface during production. We show how improvements in the production process have led to an improved quality of the fibers and the quality of stacking the fibers in the required geometry. To achieve een higher imaging quality as required for XEUS we have developed in parallel a novel pore optics technology based on silicon wafers. The production process of silicon wafers is extremely optimised by the semiconductor industry, leading to optical qualities that are sufficient for high-resolution X-ray focussing. We have developed the technology to stack these wafers into accurate X-ray optics, set up automated assembly facilities for the production of these stacks and present very promising X-ray test results of 5.3 arcsec HEW from single reflection off such a stack, showing the great potential of this technology for XEUS and other high-resolution low mass X-ray optics.
We present results of experiments obtained using a new nulling
technique that enables deep nulling without the use of achromatic
phase shifters. The experimental set-up consists of a three-beam
interferometer that should provide a nulling depth of several
thousands over a wavelength range of 500 to 650 nm. The intended
depth of null was not achieved and further experiments on
determining the spectrum of each beam revealed why. We describe a
method of obtaining accurate beam spectra in a multi-beam
interferometer. The insights on the need of spectral shape
control were tested with our nulling theory and proved the
sensitivity of this nulling approach with respect to spectral
mismatches.
The next generation astronomical X-ray telescopes (e.g. XEUS) require extremely large collecting area (10 m2) in combination with good angular resolution (5 arcsec). The existing technologies such as polished glass, nickel electroforming and foil optics would lead to excessively heavy and expensive optics, and/or are not able to produce the required large area or resolution. We have developed an entirely novel technology for producing X-ray optics which results in very light, stiff and modular optics which can be assembled into almost arbitrarily large apertures, and which are perfectly suited for XEUS.
The technology makes use of commercially available silicon wafers from the semiconductor industry. The latest generation silicon wafers have a surface roughness that is sufficiently low for X-ray reflection, are planparallel to better than a micrometer, have almost perfect mechanical properties and are considerably cheaper than other high-quality optical materials. The wafers are bent into an accurate cone and assembled to form a light and stiff pore structure with pores of the order of a millimeter. The resulting modules form a small segment of a Wolter-I optic, and are easily assembled into an optic with large collecting area.
We present the production principle of these silicon pore optics, the facilities that have been set up to produce these modules and experimental results showing the excellent performance of the first modules that have been produced. With further improvement we expect to be able to match the XEUS requirements for imaging resolution and mass.
We describe a theoretical concept of achromatic phase shifting using dispersive elements. This concept is able to provide any desirable phase shift. Its achromatic behavior in terms of spectral bandwidth and/or residual phase shift error can be improved by increasing the number of elements. Furthermore, the ability to adjust the optical path through each element enables to overcome manufacturing inaccuracy. We show some theoretical curves of residual phase shift errors obtained with this method over a wavelength region from 400 nm to 1000 nm.
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