ALTIUS is the next ESA limb-sounding mission for monitoring of stratospheric ozone at high vertical resolution and of NOx molecules and aerosols. With a platform based on the PROBA-NEXT concept flying in a Sun-Synchronous orbit, the data provided by the ALTIUS Mission will support the scientific community addressing key questions related to atmospheric chemistry composition and climate changes. The ALTIUS Instrument features wavelength-tuning capabilities in the UV (250-355nm), VIS (440-675 nm) and NIR (600-1020) bands using a Fabry-Perot interferometer (FPI) stack in the UV band and an Acousto-Optic Tunable Filter technologies (AOTF) in the VIS and NIR bands. This Instrument topology allows ALTIUS to perform 2D imaging with high resolution in the vertical profile of the Earth limb. The optical layout of 2D imagers, characterized by a more extensive field of view (FOV), makes them more susceptible to stray light issues in comparison to more conventional optical designs such as grating systems. These particular design aspects in combination with the use of novel technologies (FPI’s and AOTF’s) and the irradiance distribution of the observed bright limb scenes makes the stray light prediction very interesting and complex. An accurate modelling of scatter contributors involving optical and mechanical surfaces is, therefore, required. Due to the cost-effective model philosophy applied for the ALTIUS Instrument, no hardware model is available for stray light correlation purposes prior to the Instrument Proto-flight. Hence, a study was performed to benchmark the stray light analyses results obtained with Optic Studio with the ones obtained with FRED. This paper provides a description of the optical modelling features of the ALTIUS Instrument with specific attention to the novel optical devices, AOTF and FPI stack. It also addresses the particularities and differences observed when modelling the Instrument using two different commercial optical design suites. A comparison of scattered stray light computations for the ALTIUS Instrument ran in OpticStudio and FRED is also presented highlighting reflections on modelling approach and used mathematical models, with an outlook on consistency at L1. Finally, lessons learned from this exercise are presented along with the conclusions and plans for future work.
Additional presentation content can be accessed on the supplemental content page.
The paper describes the preliminary design of the MICADO calibration assembly. MICADO, the Multi-AO Imaging CAmera for Deep Observations, is targeted to be one of the first light instruments of the Extremely Large Telescope (ELT) and it will embrace imaging, spectroscopic and astrometric capabilities including their calibration. The astrometric requirements are particularly ambitious aiming for ~ 50 μas differential precision within and between single epochs. The MICADO Calibration Assembly (MCA) shall deliver flat-field, wavelength and astrometric calibration and it will support the instrument alignment to the Single-Conjugate Adaptive Optics wavefront sensor. After a complete overview of the MCA subsystems, their functionalities, design and status, we will concentrate on the ongoing prototype testing of the most challenging components. Particular emphasis is put on the development and test of the Warm Astrometric Mask (WAM) for the calibration of the optical distortions within MICADO and MAORY, the multiconjugate AO module.
The LBT (Large Binocular Telescope), located at about 3200m on Mount Graham (Tucson, Arizona) is an innovative project undertaken by institutions from Europe and USA. LINC-NIRVANA is an instrument which provides MCAO (Multi-Conjugate Adaptive Optics) and interferometry, combining the light from the two 8.4m telescopes coherently. This configuration offers 23m-baseline optical resolution and the sensitivity of a 12m mirror, with a 2 arc-minute diffraction limited field of view. The integration, alignment and testing of such a big instrument requires a well-organized choreography and AIV planning which has been developed in a hierarchical way. The instrument is divided in largely independent systems, and all of them consist of various subsystems. Every subsystem integration ends with a verification test and an acceptance procedure. When a certain number of systems are finished and accepted, the instrument AIV phase starts. This hierarchical approach allows testing at early stages with simple setups. The philosophy is to have internally aligned subsystems to be integrated in the instrument optical path, and extrapolate to finally align the instrument to the Gregorian bent foci of the telescope. The alignment plan was successfully executed in Heidelberg at MPIA facilities, and now the instrument is being re-integrated at the LBT over a series of 11 campaigns along the year 2016. After its commissioning, the instrument will offer MCAO sensing with the LBT telescope. The interferometric mode will be implemented in a future update of the instrument. This paper focuses on the alignment done in the clean room at the LBT facilities for the collimator, camera, and High-layer Wavefront Sensor (HWS) during March and April 2016. It also summarizes the previous work done in preparation for shipping and arrival of the instrument to the telescope. Results are presented for every step, and a final section outlines the future work to be done in next runs until its final commissioning.
GRAVITY is a second generation near-infrared VLTI instrument that will combine the light of the four unit or four auxiliary telescopes of the ESO Paranal observatory in Chile. The major science goals are the observation of objects in close orbit around, or spiraling into the black hole in the Galactic center with unrivaled sensitivity and angular resolution as well as studies of young stellar objects and evolved stars. In order to cancel out the effect of atmospheric turbulence and to be able to see beyond dusty layers, it needs infrared wave-front sensors when operating with the unit telescopes. Therefore GRAVITY consists of the Beam Combiner Instrument (BCI) located in the VLTI laboratory and a wave-front sensor in each unit telescope Coudé room, thus aptly named Coudé Infrared Adaptive Optics (CIAO). This paper describes the CIAO design, assembly, integration and verification at the Paranal observatory.
The LBT (Large Binocular Telescope) located in Mount Graham near Tucson/Arizona at an altitude of about
3200m, is an innovative project being undertaken by institutions from Europe and USA. The structure of the
telescope incorporates two 8.4-meter telescopes on a 14.4 center-to-center common mount. This configuration
provides the equivalent collecting area of a 12m single-dish telescope.
LINC-NIRVANA is an instrument to combine the light from both LBT primary mirrors in an imaging Fizeau
interferometer. Many requirements must be fulfilled in order to get a good interferometric combination of the
beams, being among the most important plane wavefronts, parallel input beams, homotheticity and zero optical path
difference (OPD) required for interferometry. The philosophy is to have an internally aligned instrument first, and
then align the telescope to match the instrument.
The sum of different subsystems leads to a quite ambitious system, which requires a well-defined strategy for
alignment and testing. In this paper I introduce and describe the followed strategy, as well as the different solutions,
procedures and tools used during integration. Results are presented at every step.
LINC-NIRVANA is an instrument combining the two 8.4 m telescopes of the Large Binocular Telescope (LBT)
coherently, in order to achieve the optical resolution of the 23 meter baseline. For this interferometric instrument
concept, the common beam combination requires diffraction limited optical performance. The optics, realized as a
Cassegrain telescope design, consists of aluminum mirrors, designed and manufactured to fulfill the challenging
specifications required for interferometric imaging. Due to the science wavelength range from 1 μm to 2.4 μm, covering
the J, H and K band of the atmosphere, the complete beam combiner including the optics is operated in cryogenic
environment at 60 Kelvin. Here, we demonstrate the verification of the optical performance at this temperature for
classical in-coherent and coherent illumination. We outline the test setup and present the achieved results of wavefront
error for the individual beams and fringe contrast for the interferometric point spread function.
This paper continues the already presented integration of the interferometric camera with the focus on the performance
of the cryogenic optics.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.