Rosetta is one of the cornerstone missions of the European Space Agency for having a rendezvous with the comet 67P/Churyumov-Gerasimenko in 2014. The imaging instrument on board the satellite is OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System), a cooperation among several European institutes, which consists of two cameras: a Narrow (NAC) and a Wide Angle Camera (WAC).
The WAC optical design is an innovative one: it adopts an all reflecting, unvignetted and unobstructed two mirror configuration which allows to cover a 12° × 12° field of view with an F/5.6 aperture and gives a nominal contrast ratio of about 10–4.
The flight model of this camera has been successfully integrated and tested in our laboratories, and finally has been integrated on the satellite which is now waiting to be launched in February 2004.
In this paper we are going to describe the optical characteristics of the camera, and to summarize the results so far obtained with the preliminary calibration data. The analysis of the optical performance of this model shows a good agreement between theoretical performance and experimental results.
This paper describes the flight control software of the wave-front correction system that flew on the 2009 science
flight of the Sunrise balloon telescope. The software discussed here allowed fully automated operations of the
wave-front sensor, communications with the adaptive optics sub-system, the pointing system, the instrument
control unit and the main telescope controller. The software was developed using modern object oriented
analysis and design techniques, and consists of roughly 13.000 lines of C++ code not counting code written for
the on-board communication layer. The software operated error free during the 5.5 day flight.
SUNRISE is an international project for the development, construction, and operation of a balloon-borne solar telescope with an aperture of 1 m, working in the UV/VIS spectral domain. The main scientific goal of SUNRISE is to understand the structure and dynamics of the magnetic field in the atmosphere of the Sun. SUNRISE will provide near diffraction-limited images of the photosphere and chromosphere with an unpredecented resolution down to 35 km on the solar surface at wavelengths around 220 nm. The focal-plane instrumentation consists of a polarization sensitive spectrograph, a Fabry-Perot filter magnetograph, and a phase-diverse filter imager working in the near UV. The first stratospheric long-duration balloon flight of SUNRISE is planned in Summer 2009 from the swedish ESRANGE station. SUNRISE is a joint project of the german Max-Planck-Institut fur Sonnensystemforschung (MPS), Katlenburg-Lindau, with the Kiepenheuer-Institut fur Sonnenphysik (KIS), Freiburg, Germany, the High-Altitude Observatory (HAO), Boulder, USA, the Lockheed-Martin Solar and Astrophysics Lab. (LMSAL), Palo Alto, USA, and the spanish IMaX consortium. In this paper we will present an actual update on the mission and give a brief description of its scientific and technological aspects.
The SUNRISE telescope is part of a balloon-borne instrument for spectro-polarimetric high-resolution observations of the solar atmosphere, to be flown 2007/2008 in the Antarctic summer stratosphere. It is a 1-m UV-VIS Gregory type telescope, operating close to the VIS diffraction limit. The telescope has a steel central frame and a lightweight CFRP trusswork structure with Serrurier properties, providing proper alignment of the optical elements over the varying eleva-tion angle. Mechanisms allow a fine adjustment of the optics. Aberrations caused by residual deformations of the stiff silicon carbide (Cesic) primary mirror are lowered by a dedicated offset in the secondary mirror polish (imprint). The telescope is subjected to the changing heat loads caused by the sun and earth radiation, necessitating measures to provide thermal conditions suitable for high-performance observations. Adequate preliminary solutions for an effective baffling are outlined.
A limb sounding cryogenic IR telescope named CRISTA (cryogenic infrared spectrometers and telescopes for the atmosphere) has been developed to study dynamic disturbances in the middle atmosphere with high spatial (horizontal and vertical) resolution. For this purpose, it measures mid and far IR emissions of several trace constituents at earth's limb using three independent telescopes with high off-axis rejection performance. Height profiles are derived from simultaneous scans of the three telescope LOS. The radiation received is spectrally analyzed by grating spectrometers followed by Si:Ga and Ge:Ga detectors. High sensitivity together with improved spatial resolution leads to a spacing of only 500 km to 600 km between two adjacent measurement points and thus to a far more detailed picture of the atmosphere compared to present day satellite experiments. CRISTA, integrated in the free-flyer ASTROSPAS, is launched in 1994 by the space shuttle for a short duration mission and will be part of ATLAS 3.
The CRISTA experiment (CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere) is a limb sounding instrument designed for high spatial resolution measurements of infrared emissions from the Earth's middle atmosphere. The principal scientific aim is to study small and medium scale structures in the concentrations of minor constituents which serve as tracers for the dynamical processes acting on these species. In order to achieve a high spatial resolution CRISTA is equipped with three telescopes each followed by its own grating spectro-meter. The spectrometers cover a wavelength range of 4 micrometers to 17 micrometers (all three viewing directions) and 55 micrometers to 71 micrometers (one telescope only) with a resolving power of about 300. Up to 15 trace gases will thus be measured simultaneously on a 500 X 650 km2 grid reaching from the lower strato-sphere to the upper mesosphere. For special soundings the measurements will occasionally be extended to an altitude of 150 km. The launch of CRISTA is planned for autumn 1994. CRISTA will be integrated into the free- flying platform CRISTA-SPAS and carried to a 57 degree(s) inclination orbit by the Space Shuttle. In the free-flying phase a measuring time of approximately on week is expected. The launch of CRISTA on CRISTA-SPAS will be together with the ATLAS-3 mission.
An electroless nickel plated over aluminum mirror was tested for BRDF and surface profiles at two stages: First, after a standard polish for optical figure, and second, after a `super finishing process' which is designed to minimize optical scatter. BRDF measurements corresponding to spatial frequency range between .0016 micrometers -1 to 1 micrometers -1 were obtained using 0.633 micrometers , 1.06 micrometers , 3.39 micrometers and 10.6 micrometers lasers. The conversion formula used to derive PSD2D from BRDF data is based on the Rayleigh-Rice vector theory. Measurements of the same spots by an optical profilometer (WYKO TOPO-2D) with several objectives were used to cover similar spatial frequency limits. The surface finish statistics, extracted from the profile data, was processed to produce PSD1D. Then, composite PSD1d were fitted to an analytic function for PSD1D using the K- correlation model approach. The derived PSD2D from profile data was readily determined from the A,B,C coefficients associated with the K-correlation model. The derived PSD2D from BRDF and profile measurements were compared to quantify the difference in surface finish statistics between the standard polished mirror and the same mirror after `super finishing.' Good correlation is found for the standard polished surface. This corroborates the `topographic scatter' behavior for the clean, standard polished nickel surface which promise useful interpolation of BRDF values to wavelengths at which direct BRDF data is unavailable. Correlation for the `super finished' surface is worse, probably due to unplanned surface contamination between tests.
This paper presents details of the optical and mechanical layout of a cryogenically cooled IR-sensor named CRISTA (CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere). The instrument is designed to analyze dynamical processes in the middle atmosphere. For this purpose, it measures IR emissions of several trace gases at the limb using three independent telescopes with high off axis rejection performance. CRISTA, integrated in the free-flyer ASTRO-SPAS, will be launched in 1993 by the Space Shuttle for a 9 day mission.
The CRISTA experiment is designed to detect and analyze short term upper atmospheric waves and turbulence of the middle atmosphere. This paper presents two of the more intriguing stray light characteristics of the CRISTA instrument as revealed through a much more extensive stray light analysis. The two topics are the diffraction propagation from a series of edges, and the thermal loading characteristics of the outer baffles by the earth's radiation. The interesting parameters that play very complex roles relative to each other are: CRISTA's three different telescopes peer through a common aperture; the Center Telescope has an image plane shared by two spectrometers offset above or below the axis by 0.358 deg; the point source angles walk away from one slit but across the other; the wavelength bands vary from 4 microns to 70 microns; all of the imaging mirrors are simple spherical surfaces; the major source of stray light is the earth, which is only .5 deg from the optical axis; and the intermediate field stop is oversized.