The Darwin/TPF mission aims at detecting directly extra solar
planets. It is based on the nulling interferometry, concept proposed
by Bracewell in 1978, and developed since 1995 in several European and
American laboratories. One of the key optical devices for this
technique is the achromatic phase shifter (APS). This optical
component is designed to produce a π phase shift over the whole
Darwin spectral range (i.e. 6-18 μm), and will be experimentally
tested on the NULLTIMATE consortium nulling test bench (Labèque et
al). Three different concepts of APS are being simulated: dispersive plates focus crossing and field reversal. In this paper, we show how thermal, mechanical and optical models are merged into a single robust model, allowing a global numerical simulation of the optical component performances. We show how these simulations help us to optimizing the design and present results of the numerical model.
This paper describes the preliminary design of the so-called Transmit/Receive Optics (TRO) for the ADALIN lidar instrument on the future ADMAeolus weather satellite. The TRO is the central optical unit of the instrument, that feeds the optical signals from the laser source to the emitting/receiving telescope, and vice versa, the received back scattered signals from the telescope to the spectrometers for Doppler shift evaluation. Additionally, the TRO supports a calibration branch, that bypasses the telescope (from the laser to the spectrometers) and aims at levelling out the received signals in terms of wavelength and signal height changes due to wavelength and intensity variations of the laser. Since the spectral range of the ALADIN instrument is narrow (centred at 354.8 nm), the TRO makes use of refractive optics (lenses) to a high extend. A 1 nm narrow band interference filter has been implemented on the reception branch on the TRO to suppress disturbing background signals. Special features of the TRO are two so-called aberration generators on the emitting and calibration branch, with which an artificial astigmatism can be realised for eye safety reasons. An opto-mechanical concept has been realised with four afocal optical groups, which are connected by parallel beams. Different design options for the aberration generator are being discussed with clear preference of a pure lens solution. The performance of the optical subsystem is monitored by extensive simulations, which are shortly summarised. As a specific simulation example, the analysis and trade-offs of the aberration generator are given.
SUNRISE is a balloon-borne instrument for spectro-polarimetric high-resolution observation of the solar atmosphere. It has a lightweight UV-VIS telescope of Gregory type with an aperture of 1 m, designed to be close to the VIS diffraction limit. The paper will first present the basic prescriptions of the optical design and the achievable performance. The re-quirements for the mechanisms in order to maintain the alignment over the range of environmental conditions will be derived. Secondly, the structural and thermal requirements will be discussed. Here, structural deflections due to gravity and residual thermal imbalances have to be taken into account. Preliminary structural and thermal designs will be out-lined.
In our digital age, digital cinematography is gaining importance. Therefore the camera lens division of Carl Zeiss decided to extend its conventional cine lenses with a set of digital prime lenses, the DigiPrimes. These lenses are designed for High Definition Television (HDTV) cameras with three 2/3-inch format CCD-Chips and a beamsplitter HDTV prism. There are six lenses with an effective focal length from 5mm to 40mm. The lenses have a telecentric design on the image side, because of the color separating prism. We will discuss some aspects of the mechanical and optical design and their influence on each other.
In 1991 Carl Zeiss started a program to develop powerful telescopes for airborne and spaceborne earth-observation telescopes. This article summarizes some of the main result of this program. To emphasize the importance of these activities a short historical review was added.
The recent developments within the ESA funded HRIS (high resolution imaging spectrometer) technology program -- aiming at an airborne demonstrator model -- yielded rather successful subsystem developments. HRIS is designed as a true pushbroom hyperspectral imager with comparatively high spatial and spectral resolution, covering the spectral range from 450 to 2350 nm. The main breadboard units, with a space-near design, are essentially: a TMA (three mirro anastigmat, Carl Zeiss) front optics, a dual path spectrometer optics (Officine Galileo) with a novel in-field spectral separation unit, a 2-D SWIR CMT detector array with a dedicated CMOS readout multiplexer (GEC Marconi IR, MATRA MSF for testing), the signal processing electronics (DSS), some calibration elements (DLR + DSS), and the extensive testing of all units. The paper presents the essential results per unit, with possible exception of the front optics (which may not be completed at the conference paper presentation yet), including derived further development efforts. Also, the remaining steps towards an airborne test mission are outlined, together with a brief description of the envisaged high-altitude aircraft. We hope that this paper may also stir some potential users of later airborne HRIS test missions over dedicated target areas. Positive responses would support ESA to pursue the program. The technology units development under the HRIS contract have turned out useful for follow-on instrument developments such as the ESA Explorer mission candidate PRISM (processes research by an imaging space mission). This leads to the conclusion that the achieved development results are a sound basis for future airborne and spaceborne hyperspectral imager developments in Europe. A brief survey of the current PRISM baseline concept is added to the paper.
The recent developments of airborne imaging spectrometers, currently mostly designated hyperspectral imagers, in the spectral regime from 400-2400 nm revealed and proved an enormous application potential for remote sensing of vegetation in particular. Current spaceborne instrument developments and soon mission will expand these applications to regional and global scale surveys and monitoring. Hyperspectral imagers covering the a.m. spectral range promise to represent the ideal future remote sensing tool for vegetation type and status monitoring. The paper starts with a compilation of relevant applications - with emphasis on vegetation and soils - and their particular spectral and radiometric requirements which has been established by the main author recently as part of a Dornier Satellitensysteme (DSS) in-house activity, including a survey of existing and planned instruments of this type. To the possible extent, airborne measurement data from existing instruments will be included to underline the application potential. The second part will provide an insight into current development activities at DSS, mainly as results of ESA contracts, covering instruments such as ROSIS, HRIS demo model and current PRISM studies. The two latter instruments are ideally suited for vegetation monitoring in terms of pixel size, spectral resolution and range from 450-2350 nm, and radiometric performance. An outlook will conclude the paper for future developments and planning for operational hyperspectral missions.
PRISM is a spaceborne hyperspectral imager for a future land surface research mission, whose prime objective is the observation of biophysical processes at a local to regional scale. PRISM is designed for a dedicated medium-size satellite in a polar sun-synchronous 11:00 h orbit, and will provide coregistered spectral images in tow spectral regions: from the visible to short-wave IR range with a spectral resolution of about 10 nm and two bands in the thermal IR from 10.3 micrometers to 12.3 micrometers . The presented instrument concept comprises four modules with separate interfaces to the platform: the optical, calibration, cooler and electronics modules. The optics module design is based on a pushbroom type of imaging spectrometer in which the entire field of view is imaged on four detector arrays. The long-wavelength arrays are cooled by tow pairs of Stirling cycle coolers. The instrument layout and platform accommodation are optimized to meet the high radiometric accuracy requirement. The key element of the instrument is the pointing unit, whose mirror is protruding over the platform edge for a wide across track coverage and or access to the three on-board characterization units and to cold space. The pointing unit will provide global accessibility in 3 days. A platform rotation in pitch will enable BRDF measurements of ground test sites by varying along track pointing angles.