This paper presents the design, manufacture and characterization results of two optical interference filters to be used in the Lightning Imager (LI) optical head on the Meteosat Third Generation (MTG) mission. The first optical filter is a Solar Rejection Window (SRW) to limit the solar thermal radiation absorbed by the optical head while the second optical filter is a Narrow Band Filter (NBF) intended to only pass the lightning discharge emission wavelengths. Each filter has its own distinctive design considerations and manufacturing challenges. The SRW must pass wavelengths from the 760 to 780 nm spectral range and reject (block) wavelengths from the ultraviolet (UV) to the mid-wave infrared (MWIR) and up to 16.3° angle of incidence (AOI) and over a large temperature range (as when exposed to direct sunlight). The NBF is designed to pass only the oxygen emission triplet, centered around the 777.6 nm (vacuum) wavelength and rejecting other wavelengths. Considering the AOI of the light and the temperature excursion, the center wavelength (CWL) uniformity has to be better than 0.04% peak-to-valley (PV) over the 114 mm diameter clear aperture, which is a formidable challenge. We achieved a coating thickness uniformity less than ±0.01% PV, exceeding the prescribed specification. Post-deposition annealing was carried out to tune the bandpass to within pico-meters (pm) of the target CWL value while maintaining the desired CWL uniformity. To ensure that both the SRW and NBF filter meet the desired optical and physical specifications, a comprehensive series of optical and physical characterization tests, along with durability tests, were carried out on each deposition batch.
PLATO (PLAnetary Transits and Oscillation of stars) is the ESA Medium size dedicated to exo-planets discovery, adopted in the framework of the Cosmic Vision program. The PLATO launch is planned in 2026 and the mission will last at least 4 years in the Lagrangian point L2. The primary scientific goal of PLATO is to discover and characterize a large amount of exo-planets hosted by bright nearby stars, constraining with unprecedented precision their radii by mean of transits technique and the age of the stars through by asteroseismology. By coupling the radius information with the mass knowledge, provided by a dedicated ground-based spectroscopy radial velocity measurements campaign, it would be possible to determine the planet density. Ultimately, PLATO will deliver the largest samples ever of well characterized exo-planets, discriminating among their ‘zoology’. The large amount of required bright stars can be achieved by a relatively small aperture telescope (about 1 meter class) with a wide Field of View (about 1000 square degrees). The PLATO strategy is to split the collecting area into 24 identical 120 mm aperture diameter fully refractive cameras with partially overlapped Field of View delivering an overall instantaneous sky covered area of about 2232 square degrees. The opto-mechanical sub-system of each camera, namely Telescope Optical Unit, is basically composed by a 6 lenses fully refractive optical system, presenting one aspheric surface on the front lens, and by a mechanical structure made in AlBeMet.
Several optical instruments are devoted for diagnostic in physico-chemical experiments, performed in microgravity environment. The aim of this paper is to describe a Wollaston interferometer devoted to measure the refraction index gradient of a transparent liquid media, in order to measure the concentration or temperature gradients around a formed drop. The Wollaston interferometer has been chosen because its sensitivity to the wavefront error can be tuned choosing the shearing component. Moreover this interferometer type has been chosen for his compactness and low sensitivity to the vibrations. This interferometer has been developed for the INEX MAM 3-Welcome project (EADS Space, Bremen / ESA contract), in which two different experiments, one devoted to the execution of the Marangoni migration, the other to the Wetting and Coalescence Prevention, have been carried out during the fly of MAXUS 5 Sounding Rocket.
The Lightning Imager for Meteosat Third Generation is an optical payload with on-board data processing for the detection of lightning.
The instrument will provide a global monitoring of lightning events over the full Earth disk from geostationary orbit and will operate in day and night conditions.
The requirements of the large field of view together with the high detection efficiency with small and weak optical pulses superimposed to a much brighter and highly spatial and temporal variable background (full operation during day and night conditions, seasonal variations and different albedos between clouds oceans and lands) are driving the design of the optical instrument.
The main challenge is to distinguish a true lightning from false events generated by random noise (e.g. background shot noise) or sun glints diffusion or signal variations originated by microvibrations. This can be achieved thanks to a ‘multi-dimensional’ filtering, simultaneously working on the spectral, spatial and temporal domains.
The spectral filtering is achieved with a very narrowband filter centred on the bright lightning O2 triplet line (777.4 nm ± 0.17 nm). The spatial filtering is achieved with a ground sampling distance significantly smaller (between 4 and 5 km at sub satellite pointing) than the dimensions of a typical lightning pulse. The temporal filtering is achieved by sampling continuously the Earth disk within a period close to 1 ms.
This paper presents the status of the optical design addressing the trade-off between different configurations and detailing the design and the analyses of the current baseline. Emphasis is given to the discussion of the design drivers and the solutions implemented in particular concerning the spectral filtering and the optimisation of the signal to noise ratio.
The market of the sights for the 5.56 mm assault rifles is dominated by mainly three types of systems: TWS (Thermal
Weapon Sight), the Pocket Scope with Weapon Mount and the Clip-on. The latter are designed primarily for special
forces and snipers use, while the TWS design is triggered mainly by the DRI (Detection, Recognition, Identification)
requirements. The Pocket Scope design is focused on respecting the SWaP (Size, Weight and Power dissipation)
requirements. Compared to the TWS systems, for the last two years there was a significant technological growth of the
Pocket Scope/Weapon Mount solutions, concentrated on the compression of the overall dimensions.
The trend for the assault rifles is the use of small size/light weight (SWaP) IR sights, suitable mainly for close combat
operations but also for extraordinary use as pocket scopes – handheld or helmet mounted. The latest developments made
by Selex ES S.p.A. are responding precisely to the above-mentioned trend, through a miniaturized Day/Night sight
embedding state-of-the art sensors and using standard protocols (USB 2.0, Bluetooth 4.0) for interfacing with PDAs,
Wearable computers, etc., while maintaining the “shoot around the corner” capability.
Indeed, inside the miniaturized Day/Night sight architecture, a wireless link using Bluetooth technology has been
implemented to transmit the video streaming of the rifle sight to an helmet mounted display. The video of the rifle sight
is transmitted only to the eye-piece of the soldier shouldering the rifle.
In the framework of a research program a broad band lens (1.7÷5.3 μm) has been designed to be inserted in an optoelectronic system of the Italian Navy.
The optoelectronic system operates over full spectral band or over one of the seven sub-bands that are selected inserting spectral filters mounted on a wheel. The optoelectronic system FOV is 20°x15°, aperture F/# 2.4 and it is optically athermalized in the range -30°÷+70° C. Color aberrations correction and athermalization was obtained by means an appropriate choice of optical materials (Cleartran, Sapphire, BaF2 and CaF2). The optical athermalization has been achieved for an all aluminum mechanical mounting. The lens mechanical mounting is quite cheap as no moving parts are present while focusing is obtained regardless the objective temperature.
The optical layout is composed by five lenses. The design was driven to have a low sensitive manufacturing and mounting tolerances. A diffractive lens free solution was selected because of the unacceptable radiation losses in the higher diffractive orders due to the wide spectral band.
Dedicated BBAR coatings for Sapphire and Cleartran have been developed.
In the framework of a modernization program, supported by Italian Army, Galileo Avionica (a Finmeccanica company)
has developed a family of small equipments based on suites of electro-optics sensors. These modules, designed and built
by GA, range from uncooled V0x 25 micron thermal imagers, small and very compact laser rangefinders, CMOS
Visible sensors to the last generation of colour OLED microdisplay based visual units. All the EO assemblies are
integrated to form very small and lightweight Integrated Sight, a Multi Function Target Locator, and Dynamic Aiming
System. Even if the equipments have been developed for military applications many other applications such as law
enforcements or surveillance can be envisaged.
This paper deals with the design of two second generation thermal imagers that Alenia Difesa OFFICINE GALILEO has successfully developed for the Navigation FLIR of the NH90 Tactical Transportation Helicopter (NH90 TTH) and for the Electro-Optical Surveillance and Tracking System for the Italian 'Guardia di Finanza' ATR42 Maritime Patrol Aircraft (ATR42 MPA). Small size, lightweight and low power consumption have been the main design goals of the two programs. In particular the NH90 TTH Thermal Imager is a compact camera operating in the 8 divided by 12 micrometers bandwidth with a single wide field of view. The thermal imager developed for the ATR42 MPA features a three remotely switchable fields of view objective equipped with diffractive optics. Performance goals, innovative design aspects and test results of these two thermal imagers are reported.