The search for extrasolar planets is fundamental for expanding our understanding of the Universe and investigating the likelihood that other worlds might harbour life. Among the several approaches employed for this purpose, the astrometric method offers significant advantages, as it provides an accurate estimate of the mass of the planet under consideration, which is not required to be necessarily aligned with the line of sight of the observer as for the transit or radial velocity techniques. This work aims at analysing the pointing manoeuvres required by a future spacecraft carrying an optical instrument such as RAFTER (Ring Astrometric Field Telescope for Exoplanets and Relativity) to properly fulfil the objectives of an exoplanet astrometric search mission. RAFTER is an annular field telescope conceived and proposed with the goal of achieving consistent optical response over a wide field of view, which exhibits a compact and scalable design and enforces circular symmetry for each optical element. A mathematical model describing the dynamics of the system and the evaluation of an appropriate optimal control strategy will be presented. At the end, the selection of proper actuators will also be discussed.
The CEntral (field) Three-mirror Anastigmat (CETA) telescope is designed on the specifications of the proposed Theia mission, aiming at high precision differential astrometry over a large field, for exo-planetary system characterization and dark matter /dark energy search through the dynamics of star clusters. Usually, Three Mirror Anastigmat designs are either off-axis in terms of field, or decentered in terms of pupil. We propose a family of solutions using fully centred optics and a large on-axis field, at the expense of a non negligible central obscuration. We analyse in particular a 1 m class compact telescope, with 15 m effective focal length, i.e. suited to small pixel (4-6 $micro$m) CMOS detectors operating in the visible and near IR. Due to the underlying symmetry, the resulting optical response is quite good over a 14 arcmin radius field, and it is of special interest to astrometry applications. Also, manufacturing, alignment and calibration can be expected to benefit significantly; some basic aspects are preliminarily considered.
RAFTER (Ring Astrometric Field Telescope for Exo-planets and Relativity) is a TMA telescope concept aimed at astrometric missions, and providing a wide FOV and high optical response uniformity over an annular region around the optical axis. This paper describes and analyzes the process of miniaturization and implementation of this idea into a Cubesat for technology demonstration purposes, and to evaluate its feasibility by analysing the performance and challenging aspects of different designs, calculating their mechanical tolerances and thermal sensitivity. We outline the critical aspects of the payload that can be tested and optimized in the framework of a dedicated CubeSat mission, in order to demonstrate the enabling technological contributors crucial to the development of a future larger scale mission.
With sub-microarcsecond angular accuracy, the Theia telescope will be capable of revealing the architectures of nearby exoplanetary systems down to the mass of Earth. This research addresses the challenges inherent in space astrometry missions, focusing on focal plane calibration and telescope optical distortion. We propose to assess the future feasibility of large-format detectors (50 to 200 megapixels) in a controlled laboratory environment. The aim is to improve the architecture of the focal plane while ensuring that specifications are met. The use of field stars as metrological sources for calibrating the optical distortion of the field may help to constrain telescope stability. The paper concludes with an attempt to confirm in the laboratory the performance predicted by simulations. We will also address the possibility of using such techniques with a dedicated instrument for the Habitable World Observatory.
The Italian National Institute for Astrophysics (INAF) groups together 16 Observatories and Institutes. Each hosts one or more laboratories and workshops, to support technological research, operations and maintenance. This results in a vast panorama of facilities, instrumentation, equipment and skills. During a recent meeting, the INAF technological community clearly expressed the need to share information in order to more easily find tools, facilities, skills, or whatever could be of interest, to increase the working efficiency and minimize dead times and costs. We addressed this need and started developing an interactive tool called MIRTA (Interactive Map for Technological Research in INAF), aimed to effectively collect and share all this information. Its use cases can be very simple, such as, for example, solving a contingent software or technical problem or finding a specific device, or more complex, such as finding a staff member with the necessary skills to collaborate in a new or existing project.
KEYWORDS: Data modeling, Surveillance, Engineering, Databases, Visualization, Telescopes, Systems modeling, Space weather, Space operations, Instrument modeling
Gaia Legacy idea born to enhance the platform system of Gaia's Big Data science data center in Turin and to be a center for the management, visualization, processing, manipulation and analysis of large amounts of data that require the development and implementation of innovative systems with exascale approach, guaranteeing high performances. The system responds to the scientific needs of the INAF community beyond the core science of the Gaia mission itself under a multimessenger approach such as characterization of cosmological gravitational waves and degenerate binary systems in the Milky Way. The system will extend its capability to engineering data collected by space instrumentation for studies of future missions, observation calibration and qualification of instrumental models. We present the Gaia Legacy repository project which goal is the generation of a deep and complete sky, on 4π sterad, as a reference tool and therefore interoperable for the integration of multiband data (from radio to high energies) and multimessenger data (e.g. sources of gravitational waves, neutrinos,...) for efficient data mining aimed at fast multidimensional scientific data exploitation.
AVU-GSR is a pipeline designed to solve the problem of the Global Astrometric Sphere Reconstruction of the Gaia ESA mission whose goal is to replicate the AGIS baseline process. The pipeline produces an independent solution using a different astrometric model and different algorithms for the solution of this problem, thus providing an effective way to assess the reliability of the solution, as it is called by the absolute character of the satellite measurements. It recently passed its qualification phase with real data, successfully solving the sphere reconstruction problem at the sub-mas level with Cycle 2 data. We review the context, the current status of the pipeline, and the development needed to cope with the goal of contributing to the forthcoming Gaia Data Release four.
Small and compact optics are a key element for future small missions, in particular cubesat. We started the miniaturization concept study in order to adapt the idea to the small cubesat envelope; lab tests on representative units are in progress, as part of a INAF Mini Grant awarded in 2022. In particular, we aimed at simplification of the initial design, in order to cope with costs and available space. Preliminary results are shown in this paper. We study standard reflective coatings and propose an innovative approach for future development of the design. We characterize the telescope and put it into the experimental perspective of a ground based instrument, trying to identify and solve the main issues towards the subsequent spatialization.
The opportunity given with cubesats opens new scenarios in the field of astronomy, due to (among the other advantages) the relatively low budget and the replicability features of such devices. This push the research efforts towards the miniaturization and compactness of the traditional optical devices and layouts. The possibility of having small telescopes in operation without the atmospheric disturbances allows newer possibilities for astronomical targets. In this paper, we will describe the coupling of newer astrometric techniques with specific optical layout in order to reach the maximum precision and reliability. We propose and describe a simple acquisition system with a multiple field of view (i.e. 4), to verify and prove the robustness of the astrometric techniques. In addition we study the use of a disperser element, in order to have fast and multiple spectra of the selected target.
The concept of a 3 lines of sight telescope for space astrometry is evaluated in terms of implementation feasibility and some science applications. The beam combination by pupil splitting exploits the Hipparcos concept, extending it to true large bidimensional angle. The PSF symmetry provides equivalent astrometric performance and immediate field identification on the common detector. Operation aspects are investigated in terms of field identification and observing strategy, in particular pointing constraints and sky density of reference bright stars. The approach, based on flat mirrors mounted on a pyramidal structure, provides a simple geometric framework, with immediate mechanical materialization and clear interface to metrology. The geometric arrangements considered place the lines of sight either along the (x, y, z) Cartesian axes, or in a planar layout for a Gaia-like astrometric mission. The application to a single head, multiple boresight star tracker is also outlined.
High-precision astrometry well beyond the capacities of Gaia will provide a unique way to achieve astrophysical breakthroughs, in particular on the nature of dark matter, and a complete survey of nearby habitable exoplanets. In this contribution, we present the scientific cases that require a flexibly-pointing instrument capable of high astrometric accuracy and we review the best mission profiles that can achieve such observations with the current space technology as well as within the boundary conditions defined by space agencies. We also describe the way the differential astrometric measurement is made using reference stars within the field. We show that the ultimate accuracy can be met without drastic constrains on the telescope stability.
Since the publication of the HIPPARCOS catalog in 1997, and with its successor Gaia in operational phase since 2013 having already published 3 data releases, global astrometry has earned itself a prominent role in the field of astrophysics. Both missions rest on the well-established concepts of one-dimensional (or nearly one-dimensional) observations performed by a telescope that is continuously scanning the sky following a predefined scanning law. Moreover, Gaia heavily relies also on the concept of self-calibrating instrument. In this work we explore the possibility of exploiting two-dimensional observations performed by a pointed mission, discussing the feasibility of this concept, and its possible advantages.
The Astrometric Gravitation Probe mission is a modern version of the 1919 Dyson-Eddington-Davidson experiment, based on a space-borne telescope with a permanent built-in eclipse, provided by a coronagraphic system. The expected improvement on experimental bounds to General Relativity and competing gravitation theories is by at least two orders of magnitude. The measurement principle is reviewed, in particular the principle of Fizeau-like combination of a set of individual inverted coronagraphs simultaneously feeding a common high resolution telescope. Also, the payload has a dual field of view property, in order to support simultaneous observations of stellar fields either very close, or far away, from the Sun, i.e. fields affected by either high or low light bending. We discuss a set of solutions introduced in the optical design to improve on technical feasibility and robustness of the optical performance against perturbations, in particular induced by manufacturing and alignment tolerances, and launch stresses.
High precision astrometry aims at source position determination to a very small fraction of the diffraction image size, in high SNR regime. One of the key limitations to such goal is the optical response variation of the telescope over a sizeable FOV, required to ensure that bright reference objects to any selected target. The issue translates into severe calibration constraints, and/or the need for complex telescope and focal plane metrology. We propose an innovative system approach derived from the established TMA telescope concept, extended to achieve high filling factor of an annular field of view around the optical axis of the telescope. The proposed design is a very compact, 1 m class telescope compatible with modern CCD and CMOS detectors (EFL = 15 m). We describe the concept implementation guidelines and the optical performance of the current optical design. The diffraction limited FOV exceeds 1.25 square degrees, and the detector occupies the best 0.25 square degree with 66 devices.
Astrometric Science and Technology Roadmap for Astrophysics (ASTRA) is a bilateral cooperation between China and Italy with the goal of consolidating astrometric measurement concepts and technologies. In particular, the objectives include critical analysis of the Gaia methodology and performance, as well as principle demonstration experiments aimed at future innovative astrometric applications requiring high precision over large angular separations (one to 180 degrees). Such measurement technologies will be the building blocks for future instrumentation focused on the "great questions" of modern cosmology, like General Relativity validity (including Dark Matter and Dark Energy behavior), formation and evolution of structure like proto-galaxies, and planetary systems formation in bio compatibles environments. We describe three principle demonstration tests designed to address some of the potential showstoppers for high astrometric precision experiments. The three tests are focused on the key concepts of multiple fields telescopes, astrometric metrology and very fine sub-pixel precision (goal: < 1/2000 pixel) in white light.
The exoplanet revolution is well underway. The last decade has seen order-of-magnitude increases in the number of known planets beyond the Solar system. Detailed characterization of exoplanetary atmospheres provide the best means for distinguishing the makeup of their outer layers, and the only hope for understanding the interplay between initial composition chemistry, temperature-pressure atmospheric profiles, dynamics and circulation. While pioneering work on the observational side has produced the first important detections of atmospheric molecules for the class of transiting exoplanets, important limitations are still present due to the lack of systematic, repeated measurements with optimized instrumentation at both visible (VIS) and near-infrared (NIR) wavelengths. It is thus of fundamental importance to explore quantitatively possible avenues for improvements. In this paper we report initial results of a feasibility study for the prototype of a versatile multi-band imaging system for very high-precision differential photometry that exploits the choice of specifically selected narrow-band filters and novel ideas for the execution of simultaneous VIS and NIR measurements. Starting from the fundamental system requirements driven by the science case at hand, we describe a set of three opto-mechanical solutions for the instrument prototype: 1) a radial distribution of the optical flux using dichroic filters for the wavelength separation and narrow-band filters or liquid crystal filters for the observations; 2) a tree distribution of the optical flux (implying 2 separate foci), with the same technique used for the beam separation and filtering; 3) an 'exotic' solution consisting of the study of a complete optical system (i.e. a brand new telescope) that exploits the chromatic errors of a reflecting surface for directing the different wavelengths at different foci. In this paper we present the first results of the study phase for the three solutions, as well as the results of two laboratory prototypes (related to the first two options), that simulate the most critical aspects of the future instrument.
This paper describes the current opto-mechanical design of AGP, a mission designed for astrometric verification of General Relativity (GR) and competing gravitation theories by means of precise determination of light deflection on field stars, and of orbital parameters of selected Solar System objects. The optical concept includes a planar rear-view mirror for simultaneous imaging on the CCD mosaic detector of fields of view also from the direction opposite to the Sun, affected by negligible deflection, for the sake of real time calibration. The precision of astrometric measurements on individual stars will be of order of 1 mas, over two fields separated by few degrees around the Sun and observed simultaneously. We describe the optical design characteristics, with particular reference to manufacturing and tolerancing aspects, evidencing the preservation of very good imaging performance over the range of expected operating conditions.
The Gravitation Astrometric Measurement Experiment (GAME) is a space mission for Fundamental Physics tests in the
Solar system, through coronagraphy and Fizeau interferometry for differential astrometry. The precision goal on the γ and β General Relativity PPN parameters is respectively in the 10-8 and 10-6 range. The design is focused on systematic
error control through multiple field simultaneous observation and calibration. The GAME instrument concept is based on
multiple aperture Fizeau interferometry, observing simultaneously regions close to the Solar limb (requiring the adoption
of coronagraphic techniques), and others away from the Sun. The diluted optics approach is selected to achieve an
efficient rejection of the scattered solar radiation, while retaining an acceptable angular resolution on the science targets.
The Interferometric Stratospheric Astrometry for Solar system (ISAS) project is a GAME technology demonstrator,
providing milli-arcsec level astrometry on the main planets of the Solar System. The ISAS technical goal is the
validation of basic concepts for GAME, in particular integration of Fizeau interferometry and coronagraphic techniques
by means of pierced silicon carbide (SiC) mirrors, intermediate angle dual field astrometry, smart focal plane
management for increased dynamic range and pointing correction. The ISAS instrument concept is a dual field, multiple
aperture Fizeau interferometer, using coronagraphy for observation of Solar System planets also close to the Sun. A
prototype SiC multi-aperture mirror was manufactured by Boostec (F), and has been investigated by thermo-elastic
analysis to define the applicability to both GAME and ISAS designs. We describe the development status of both
stratospheric and space options, as well as the current extrapolation of the SiC prototype characteristics to the GAME
and ISAS optical configurations.
The Gaia payload is a highly sophisticated system and much of its instrumental behaviour is tested to proper accuracy during the Commissioning and Early Operations phase. The Astrometric Instrument Modelling (AIM) belongs to the Core Processing, or CU3, software systems devoted to astrometric data processing, instrumental monitoring and calibration.; it was developed in the context of a special unit of CU3 devoted to Astrometric Verification. While waiting for nominal scientific operations, we present the challenges phased in the Gaia initial data treatment and real-time instrument health monitoring and diagnostic, during the non-standard conditions of the Commissioning phase. We describe the dedicated diagnostic and correction procedures implemented for Commissioning and Early Operations and we show some results obtain during still on-going Commissioning activities.
KEYWORDS: Telescopes, Fringe analysis, Data processing, Space operations, Calibration, Signal processing, Satellites, Interferometry, Metrology, Space telescopes
The goal of the Gaia mission is to achieve micro-arcsecond astrometry, making Gaia the most important astro- metric space mission of the 21st century. To achieve this performance several innovative technological solutions have been realized as part of the satellite's scientific payload. A critical component of the Gaia scientific pay- load is the Basic Angle Monitoring device (BAM), an interferometric metrology instrument with the task of monitoring, to some picometers, the variation of the Basic Angle between Gaia's two telescopes. In this paper we provide an overview of the AVU/BAM software, running at the Italian Data Processing Center (DPCT), to analyze the BAM data and to recover the basic angle variations at the micro-arcosecond level. Outputs based on preliminary data from Gaia's Commissioning phase are shown as an example.
The Gaia payload ensures maximum passive stability using a single material, SiC, for most of its elements. Dedicated metrology instruments are, however, required to carry out two functions: monitoring the basic angle and refocusing the telescope. Two interferometers fed by the same laser are used to measure the basic angle changes at the level of μas (prad, micropixel), which is the highest level ever achieved in space. Two Shack- Hartmann wavefront sensors, combined with an ad-hoc analysis of the scientific data are used to define and reach the overall best-focus. In this contribution, the systems, data analysis, procedures and performance achieved during commissioning are presented .
Detailed knowledge of instrument parameters and observing conditions is crucial for the achievement of micro- arcsecond precision and accuracy. It has come to be a key ingredient for optimal definition of data reduction and calibration procedures, since the variation of instrumental response over the field of view with wavelength and in time is both critical and often unavoidable. With this work we provide an overview of Astrometric Instrument Model (AIM) system within the Astrometric Verification Unit for the reduction of the Gaia data. We recall on the original motivations for its development, the changes occurred during the last two years and the actual AIM structure, pointing out the most critical parts in relation to the modeling of the astrometric instrument and of the scientific treatment of the Gaia data. While waiting for the Gaia operations to start, we present first results of AIM system from the on-going testing campaign of the Gaia data reduction software systems.
The Gaia payload is a highly sophisticated system and many of its instrumental behaviors will be tested at proper accuracy only during the operational phase. However simulation results are critical parts for developing system integration, as well as for understanding unexpected behavior during commissioning and operations. The data analysis procedures are sensitive to several instrument parameters, as their variation over the field and with time. We focused our dissertation on the study and analysis of non-nominal configurations effects on astrometric accuracy, putting also in evidence the level of the effects that the difference between the design data and as-built data can produce if not adequately taken into account. We identify and quantify the effects. We move from this forward analysis to look at the data and perform instrument monitoring and diagnostic procedures, an essential activity for the verification of GAIA measurements. We conducted the study in the context of the Astrometric Verification Unit.
KEYWORDS: Data processing, Data analysis, Databases, Data centers, Visualization, Data archive systems, Diagnostics, Data storage, Astronomy, Standards development
This document is the first, systematic description of the approach adopted to support the operations of the
Gaia Astrometric Verification Unit (AVU) systems. A further subsystem that collects and provides useful tools
for a scientific oriented approach to Data Analysis and Access is designed and integrated in Data Processing
Center of Turin. Specifically, its aim is to provide to the AVU system an operative and versatile set of diagnostic
elements useful for the analysis and the manipulation of the stored data. Examples of the different scenarios
targeted by the operation efforts are: - Visualization of the “Runtime” mission status; - Archive and recovery
data, using graphs and log files contained in the Data Base; - get “On-demand” information for ad hoc analyses
and data mining; - Production of tables and reports retrieving custom data in the database. The different cases
are described in terms of the methods and of the environments in which these take place.
The core task of the Gaia mission is the solution of the Global Astrometric Sphere, which is providing the
materialization of the astrometric reference frame for the catalog that will be the main outcome of the mission. Given the absolute character of the measurements, the Gaia Data Processing and Analysis Consortium (DPAC) has decided to replicate a dedicated version of this task, together with two other ones selected for their mission criticality, in an Astrometric Verification Unit (AVU). This task, named Global Sphere Reconstruction (GSR), focusses on the importance of having an implementation of the astrometric sphere solution from a well-defined subset of objects, based on an independent astrometric model as well as on a different solution algorithm. We analyze here these two aspects in the context of the GSR implementation at the Data Processing Center of Torino (DPCT) and the solution to implement the most computationally intensive part of the pipeline as a High-Performance Computing module.
Medium to large angle observations, e.g. for global astrometry, can be implemented in space by means of either a
common telescope, fed by a Beam Combiner (as in Hipparcos), or by individual telescopes set in a rigid geometry
(as in Gaia). We investigate the applicability of auto-collimation and cophasing techniques for implementation of
a monitoring system alternative to more conventional point-to-point metrology. Apart different implementation
constraints, the most relevant difference consists in the auto-collimation approach characteristics of monitoring
simultaneously comparably large sections of the optical system, thus evaluating collective properties closer to
those experienced by the stellar beams.
GAME is a recent concept for a small/medium class mission aimed at Fundamental Physics tests in the Solar
system, by means of an optimised instrument in the visible, based on smart combination of coronagraphy and
Fizeau interferometry. The targeted precision on the γ and β parameters of the Parametrised Post-Newtonian
formulation of General Relativity are respectively in the 10-7-10-8 and 10-5-10-6 range, improving by one or two orders of magnitude with respect to the expectations on current or near future experiments. Such precision
is suitable to detect possible deviations from the unity value, associated to generalised Einstein models for
gravitation, with potentially huge impacts on the cosmological distribution of dark matter and dark energy from
a Solar system scale experiment. The measurement principle is based on the differential astrometric signature on
the stellar positions, i.e. based on the spatial component of the effect rather than the temporal component as in
the most recent experiments using radio link delay timing variation (Cassini). The instrument concept is based
on multiple field, multiple aperture Fizeau interferometry, observing simultaneously regions close to the Solar
limb (requiring the adoption of coronagraphic techniques), and others in opposition to the Sun. The diluted
optics approach is selected for achieving an efficient rejection of the scattered solar radiation, while retaining
an acceptable angular resolution on the science targets. The multiple field observation is aimed at cost-effective
control of systematic effects through simultaneous calibration. We describe the science motivation, the proposed
mission profile, the instrument concept and the expected performance.
Micro-arcsecond precision must rely on the detailed knowledge of instrument parameters and observing conditions for
optimal definition of data reduction and calibration procedures. The variation of instrumental response over the field of
view with wavelength and in time is potentially critical and often unavoidable. This work addresses selected topics in
modeling of the astrometric instrument of the Gaia mission, evidencing their role in the data reduction strategy.
Discussion is extended to how the modeling will impact on the data quality and to how the science data can be used to
trace directly the instrument response. Finally mention is provided of the actual implementation of our recipe into the
Astrometric Instrument Model, a software tool which will be used during the processing of Gaia data.
The Astrometric Instrument Model system comprises several monitoring and diagnostic tasks for the astrometric
instrument aboard Gaia. It is a hierarchy of dedicated software modules aimed at decreasing the parameter degeneration
of the relation linking the observations to the instrumental behavior, and optimize the estimation process at the CCD and
field-of-view crossing level. Critical for the system is the definition and maintenance of a physical instrument model
fitting the science data, and able to accommodate non nominal configurations. Precise modeling of the astrometric
response is required for optimal definition of the data reduction and calibration algorithms, and to ensure high sensitivity
to both instrumental and astrophysical source parameters.
KEYWORDS: Mirrors, Telescopes, Space telescopes, Photons, Signal to noise ratio, Nanoimprint lithography, Sensors, Space operations, Calibration, Astronomy
Improvement of our understanding of Fundamental Physics is more and more based on high precision measurements
over significant fractions of our Universe. Among the crucial tests of General Relativity and competing theories is the
detection of gravitational waves, which is the subject of advanced modern experiments (LISA, VIRGO, LIGO). Our
investigation is focused on a novel concept for pointed observations of selected astronomical objects in our Galaxy, like
compact binary systems, neutron stars and compact white dwarf binaries, which are expected to be sources of
gravitational waves in the Very Low Frequency range, i.e 10-4 Hz < fg < 10-1 Hz. The detection mechanism is based on
indirect astrometric observations by a spaceborne dedicated instrument, monitoring the astrometric light deflection of the
photons crossing the buffer zone of the gravitational source at the microarcsecond level accuracy. We discuss the class of
potential candidates, the mission concept and its high level specifications; furthermore, we present an implementation
concept including basic instrument characteristics (system configuration, telescope size and constraints, operating
wavelength, detector, operation).
The design and performance of a Fizeau interferometer with long focal length and large field of view are discussed. The optical scheme presented is well suited for very accurate astrometric measurements from space, being optimised, in terms of geometry and aberrations, to observe astronomical targets down to the visual magnitude mV=20, with a measurement accuracy of 10 microarcseconds at mV=15.
This study is in the context of the next generation astrometric space missions, in particular for a mission profile similar to that of the Gaia mission of the European Space Agency.
Beyond the accuracy goal, the great effort in optical aberrations reduction, particularly distortion, aims at the optimal exploitation of data acquisition done with CCD arrays working in Time Delay Integration mode. The design solution we present reaches the astrometric goals with a field of view of 0.5 square degrees.
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