PLATO (PLAnetary Transits and Oscillations of stars)1 is the M3 class ESA mission dedicated to the discovery
and study of extrasolar planetary systems by means of planetary transits detection. PLATO Payload Camera
units are integrated and vibrated at CSL before being TVAC tested for thermal acceptance and performance
verification at 3 different test facilities (SRON, IAS and INTA). 15 of the 26 Flight Cameras were integrated,
tested and delivered to ESA for integration by the Prime between June 2023 and June 2024, with the remaining
flight units to be tested by the end of 2024. In this paper, we provide an overview of our serial testing approach,
some of the associated challenges, key performance results and an up-to-date status on the remaining planned
activities.
KU Leuven’s CubeSpec mission is pioneering the use of a CubeSat platform for advanced space-based spectroscopy.1 This innovation is partly due to its payload electronics, which must be space-efficient and powerconscious. To achieve exceptional pointing accuracy, CubeSpec employs a High-Pointing Precision Platform (HPPP) that works in tandem with the onboard Attitude Determination and Control System (ADCS). The HPPP utilizes a Fine Steering Mirror (FSM), controlled by piezo actuators, to direct light precisely onto the spectrograph slit. The design incorporates a DC-DC boost converter and a linear amplifier to meet the highvoltage demands of the piezo actuators. The HPPP setup is controlled in a closed-loop system with a Fine Guidance Sensor (FGS), a CMOS detector, and strain gauges that provide real-time feedback. The spectrograph output is captured by the Science Detector, which is the same detector model as the FGS. Due to stringent time requirements, a Xilinx Zynq 7000 FPGA manages the detector readout. The payload processor can communicate with the OBC over a CAN bus employing the CubeSat Space Protocol. This paper outlines the current progression in the development of CubeSpec’s payload electronics.
CubeSpec is an ESA in-orbit-demonstration mission, based on a 12U CubeSat, targeting high-resolution optical astronomical spectroscopy of bright targets. It is developed and funded in Belgium and scheduled for launch early 2026. The CubeSpec payload consists of an off-axis Cassegrain telescope with a rectangular aperture filling the surface area of two CubeSat units, followed by a prism cross-dispersed echelle spectrograph folded behind the primary mirror of the telescope. The complete optical payload fits in approximately 6 units (∼12 x 20 x 30 cm) of the spacecraft. CubeSpec delivers a spectral resolution of R = 55 000 and covers the wavelength range from 420 to 620 nm. The optical design is sufficiently flexible to allow tuning it with minimum hardware changes to a wide range of spectral resolution and coverage. A fine-guidance system consisting of a piezo-actuated fine steering mirror and a fine-guidance sensor provide arcsec-precise centering of the source image on the slit of the spectrograph, cancelling out pointing errors and spacecraft jitter. In this contribution, we describe the optical and optomechanical design of the CubeSpec payload, and discuss the challenged imposed by the extremely compact size and the large temperature excursions endured during each orbit.
CubeSpec is an in-orbit demonstration CubeSat mission in the ESA GSTP programme, developed and funded by the Belgian federal space policy BELSPO. The goal of the mission is to demonstrate high-spectral-resolution astronomical spectroscopy from a 12-unit CubeSat. The technological challenges are numerous. The optical payload, consisting of an off-axis Cassegrain telescope and a compact Echelle spectrometer have been designed to fit in the bigger half of a 12U CubeSat (12x20x30cm). The telescope is built entirely from a ceramic material to limit defocusing when the spacecraft thermal environment changes. The payload radiator is shielded from the Sun via a deploying Sun shade, allowing pointing to a large part of the sky without illuminating the radiator panel. The high resolution spectrograph requires arcsecond-level pointing stability. This is achieved using a performant 3-axis wheel stabilised attitude control system with two star trackers augmented with a piezo-actuated 3-axis fine beam steering mechanism in the payload. CubeSpec is now starting the implementation phase, with a planned launch in 2026. A qualification and a flight model are being constructed and tested. We give an overview of the mission, its technologies and qualification status.
MARVEL is a novel facility targeting extreme-precision radial velocity observations. Dedicated to confirming and characterizing planet candidates from the TESS and future PLATO missions, MARVEL will provide mass measurements of a multitude of exoplanets. The MARVEL instrument consists of an array of four 80-cm robotic telescopes, linked to one state-of-the-art high-resolution echelle spectrograph, through a set of optical fibers. MARVEL can observe the radial velocities of four different stars simultaneously or, alternatively, combine the flux from four telescopes pointing to a single faint target in one spectrum. It will be installed next to the Mercator Telescope at the Roque De Los Muchachos Observatory on La Palma (SPAIN). MARVEL is designed and built by a KU Leuven (Belgium) led consortium, with contributions from Australia, Austria, Denmark, Germany, Spain, Sweden and the UK.
CubeSpec is an in-orbit demonstration CubeSat mission in the ESA technology programme, developed and funded in Belgium. The goal of the mission is to demonstrate high-spectral-resolution astronomical spectroscopy from a 6-unit CubeSat. The technological challenges are numerous. The telescope and echelle spectrometer have been designed to fit in a 10×10×20cm volume. The fast telescope focus and spectrometer alignment is achieved via an athermal design. Shielding from the Sun and Earth infrared flux is achieved via deploying Earth and Sun shades. Arcsecond-level pointing stability is achieved using a performant 3-axis wheel stabilised attitude control system with star tracker augmented with a fine beam steering mechanism. CubeSpec is now starting the implementation phase, with a planned launch in 2024. A qualification and a flight model will be constructed and tested in the next 2 years. In this contribution we will give an overview of the mission, its technologies and qualification status.
PLATO is an exoplanet hunting mission of the European Space Agency. It is a medium-class mission, with a launch foreseen in 2026. Its prime objective is to uncover Earth-sized planets residing in their habitable zone. The payload consists of 26 cameras with a very wide field of view. These cameras consist of a Telescope Optical Unit (TOU), aligned at ambient and characterized at the operational temperature, and a Focal Plane Array bearing the detectors and delivered after coupling with the Front End Electronics. In this contribution, we report on the methods used at TOU level to characterize Focal Plane using a Hartmann Mask, i.e. we illustrate the analysis pipeline after data collection in the cryo-vacuum chamber at Leonardo (LDO), the implementation of new algorithms, and an extended uncertainties study for the Hartmann analysis.
The PLAnetary Transits and Oscillations of stars mission (PLATO) is the M3 mission in ESA’s Cosmic Vision 2015-2025 Programme, see Rauer et al. (2014).1 The PLATO mission aims at detecting and characterizing extrasolar planetary systems, including terrestrial exoplanets around bright solar-type stars up to the habitable zone. To be able to perform the required high precision photometric monitoring of the large target stars sample, PLATO is based on a multi-telescope configuration consisting of 26 Cameras, so as to provide simultaneously a large field of view and a large collecting aperture. The optical design is identical for all cameras and consists of a 6-lens dioptric design with a 120 mm entrance pupil and an effective field of view of more than 1000 square degrees. As for every optical system, especially dioptric ones, the presence of optical ghosts can dramatically affect the scientific observations. Thanks to the application of an excellent anti-reflection coating, PLATO’s cameras are by design very insensitive to ghosts. However, the residual faint back reflections focused on the detectors have to be simulated and considered during science operation (target selection) and in data correction algorithms. This article describes the different optical analyses performed to estimate the importance of ghosts in PLATO’s cameras, as well as the simulations performed to support the preparation of the test campaign on the first PLATO camera: the engineering model. Finally, the test execution, data analysis and results are presented and compared to the simulated data.
CubeSpec is an ESA in-orbit-demonstration mission, based on a 6U CubeSat, targeting high-resolution astronomical spectroscopy. It is developed and funded in Belgium and scheduled for launch at the end of 2024. The CubeSpec payload consists of an off-axis Cassegrain telescope with a rectangular aperture (186x82mm2 ) and a prism cross-dispersed echelle spectrograph. The telescope aperture almost completely covers the surface area of 2 CubeSat units and the entire optical system fits in 4 units (10x20x20cm) of the spacecraft. CubeSpec delivers a spectral resolution of R=55000 and covers the wavelength range from 420 to 620 nm. Furthermore, it is equipped with a fine-guidance system based on a fast beam-steering mirror and a fine-guidance sensor that provide accurate centering of the source image on the spectrograph slit to compensate for spacecraft pointing jitter. In this contribution, we present the optical design of the CubeSpec payload.
CubeSpec is an in-orbit CubeSat mission aiming to demonstrate high-spectral-resolution astronomical spectroscopy with a 10 × 20cm2 aperture telescope. A robust calibration system is crucial for CubeSpec’s spectrograph to operate reliably and autonomously. Typically, flat-field illumination defines order locations, while a line source ties wavelength values to detector pixels. The main challenge is to fit everything into a 10 × 10 × 20cm3 volume without forfeiting quality and control. This work proposes Calibration Unit for CUbespec (CUCU). CUCU offers a compact, energy-efficient calibration solution for space-borne spectrograph platforms, miniaturizing both calibration stages. A blue and white LED coupled into one fiber produce the continuum light source, spanning the spectrograph’s operational range of 420nm to 620nm. The line standards emerge from injecting collimated LED light into a solid Fabry-P´erot etalon. To satisfy the mission requirements, CUCU should deliver calibration exposures with an SNR of 200. Throughput measurements estimate calibration exposures to take no longer than 0.5s.
PLATO (PLAnetary Transits and Oscillations of stars) is a European Space Agency medium class mission, whose launch is foreseen for 2026. Its primary goal is to discover and characterise terrestrial exoplanets orbiting the habitable zone of their host stars. This goal will be reached with a set of 26 wide field-of-view cameras mounted on a common optical bench. Here we show some results of the first cryogenic vacuum test campaign made on the Engineering Model (EM) of one PLATO camera, performed at the Netherlands Institute for Space Research (SRON). In particular we present the search for the best focus temperature, which was done first by using a Hartmann mask, and then by maximizing the ensquared energy fractions of the point spread functions (PSFs) on the entire field of view taken at different temperature plateaus. Furthermore we present the PSF properties of the EM at the nominal focus temperature over all the field of view, focusing on the ensquared energy fractions. The Engineering Model camera was successfully integrated and validated under cryo-vacuum tests, allowing the mission to pass ESA’s Critical Milestone, and confirming the mission is on track for launch in 2026.
PLATO is an exoplanet hunting mission of the European Space Agency. It is a medium-class mission, with a launch foreseen in 2026. Its prime objective is to uncover Earth-sized planets residing in their habitable zone. The payload consists in 26 cameras with a very wide field of view. These cameras consist in a Telescope Optical Unit, aligned at ambient and characterised at the operational temperature, and a Focal Plane Array bearing the detectors, and delivered after coupling with the Front End Electronics. In this contribution, we report on the alignment of the Engineering Model camera of Plato, i.e., the input metrology, the mechanical alignment of the optical unit with the focal plane array, the test environment and the optical characterisation throughout the process until the integrity check after delivery to the cryo-vacuum testing facility where the camera underwent a thorough performance demonstration. We also give a detailed description of the bolting process and the associated error budget.
The future ESA space mission PLATO aims to detect thousands of exoplanets, including Earth-like planets, and constrain their radius and mean density. To achieve this goal, the space based photometric observations are not enough but need to be complemented by ground-based observations to measure the Radial Velocity (RV) of the exoplanet host stars. MARVEL is such a facility consisting of four 80 cm telescope linked through optical fibers to a single high-resolution ´echelle spectrograph, designed for high-precision RV measurements with a uncertainty of ∼ 1 ms−1 . MARVEL is build by a consortium led by the KU Leuven with contributions from the UK, Austria, Australia, Sweden, Denmark, and Spain, and will be commissioned in 2023. To reach such high RV precision, not only ultra-stable hardware is currently being developed, but also a state-of-the-art data processing pipeline for which we present the first results in this poster.
PLATO is an ESA mission to hunt for Earth-sized exoplanets in the habitable zone of their host star. The heart of the payload consists of 26 wide-field cameras. We develop a Common Electrical Ground Support Equipment (EGSE) framework for the testing and verification of these cameras. The focal planes are aligned to the telescope optics at ambient temperature and the performance verification is done at operational temperature in thermal-vacuum conditions in different facilities. The Common-EGSE system will guarantee that tests are executed via the same procedures and are analyzed identically, by providing a software framework that can be tuned for site-specific hardware and avoids duplicate developments. The Common EGSE provides commanding for the camera and the Ground Support Equipment (GSE), telemetry monitoring, logging, data storage, and data analysis. In addition, the design allows for sharing commanding and analysis scripts. We present the design of the system and the generic commanding scheme for test setup hardware.
CUBESPEC is an ESA in-orbit demonstration 6U CubeSat mission, currently in phase A/B. CUBESPEC will deliver months long series of high-resolution spectroscopy to study the structure of massive stars. The payload consists of a Cassegrain telescope with a rectangular primary mirror of 9 x 19 cm2 and a compact high-resolution echelle spectrograph. We aim at a 2023 launch demonstrating the CUBESPEC concept: providing the astronomical community with a generic solution for affordable space-based spectroscopy. The spectrograph design can be configured with minimal hardware changes for low spectral resolution (R = 50) up to high resolution (R ~ 50000) over a over wavelength ranges between 200–1000nm. CUBESPEC will use the KU Leuven ADCS for coarse pointing of the spacecraft, supplemented with a fine-guidance system using a fast steering mirror to center the source on the spectrograph slit. We present the CUBESPEC design and mission analysis, and give an update of the project status.
PLATO is an exoplanet hunting mission from the European Space Agency. It is a medium-class mission, with a launch foreseen in 2026. Its prime objective is to uncover Earth-sized planets residing in the habitable zone of their host star. The payload consists of 26 cameras with a very wide field-of-view. While the operational temperature of the cameras will be -80°C, the focal plane of each camera will be integrated with its telescope assembly (bearing the optics) at room temperature. The degradation of the optical quality at ambient, combined with the detector dark current and with the very high accuracy required from the alignment process bring a number of interesting challenges. In the present article, we review the alignment concept, present optical simulations of the measurements at ambient along with their analysis, and present an error budget for the optical measurements. The derivation of this error budget is easily applicable to all optical measurements to be performed during the alignment, i.e. the definition of the best image plane at the operational temperature and the optical alignment itself, at room temperature.
The space missions TESS and PLATO plan to double the number of 4000 exoplanets already discovered and will measure the size of thousands of exoplanets around the brightest stars in the sky, allowing ground-based radial velocity spectroscopy follow-up to determine the orbit and mass of the detected planets. The new facility we are developing, MARVEL (Raskin et al. this conference1 ), will enable the ground-based follow-up of large numbers of exoplanet detections expected from TESS and PLATO, which cannot be carried out only by the current facilities that achieve the necessary radial velocity accuracy of 1 ms-1 or less. This paper presents the MARVEL observation strategy and performance analysis based on predicted PLATO transit detection yield simulations. The resulting observation scenario baseline will help in the instrument design choices and demonstrate the effectiveness of MARVEL as a TESS and PLATO science enabling facility.
Since the first discovery of a planet outside of our Solar System in 1995, exoplanet research has shifted from detecting to characterizing worlds around other stars. The TESS (NASA, launched 2019) and PLATO mission (ESA, planned launch 2026) will find and constrain the size of thousands of exoplanets around bright stars all over the sky. Radial velocity measurements are needed to characterize the orbit and mass, and complete the picture of densities and composition of the exoplanet systems found. The Ariel mission (ESA, planned launch 2028) will characterize exoplanet atmospheres with infrared spectroscopy. Characterization of stellar activity using optical spectroscopy from the ground is key to retrieve the spectral footprint of the planetary atmosphere in Ariel’s spectra. To enable the scientific harvest of the TESS, PLATO and Ariel space missions, we plan to install MARVEL as an extension of the existing Mercator Telescope at the Roque De Los Muchachos Observatory on La Palma (SPAIN). MARVEL consists of an array of four 80 cm telescopes linked through optical fibers to a single high-resolution echelle spectrograph, optimized for extreme-precision radial velocity measurements. It can observe the radial velocities of four different stars simultaneously or, alternatively, combine the flux from four telescopes pointing to a single faint target in one spectrum. MARVEL is constructed by a KU Leuven (Belgium) led collaboration, with contributions from the UK, Austria, Australia, Sweden, Denmark and Spain. In this paper, we present the MARVEL instrument with special focus on the optical design and expected performance of the spectrograph, and report on the status of the project.
PLATO (PLAnetary Transits and Oscillation of stars) is a medium-class space mission part of the ESA Cosmic vision program. Its goal is to find and study extrasolar planetary systems, emphasizing on planets located in habitable zone around solar-like stars. PLATO is equipped with 26 cameras, operating between 500 and 1000nm. The alignment of the focal plane assembly (FPA) with the optical assembly is a time consuming process, to be performed for each of the 26 cameras. An automatized method has been developed to fasten this process. The principle of the alignment is to illuminate the camera with a collimated beam and to vary the position of the FPA to search for the position which minimizes the RMS spot diameter. To reduce the total number of measurements which is performed, the alignment method is done by iteratively searching for the best focus, decreasing at each step the error on the estimated best focus by a factor 2. Because the spot size at focus is similar to the pixel, it would not be possible with this process alone to reach an alignment accuracy of less than several tens of microns. Dithering, achieved by in-plane translation of the focal plane and image recombination, is thus used to increase the sampling of the spot and decrease the error on the merit function.
We present the first results of a study aimed at finding new and efficient ways to automatically process spacecraft telemetry for automatic health monitoring. The goal is to reduce the load on the flight control team while extending the "checkability" to the entire telemetry database, and provide efficient, robust and more accurate detection of anomalies in near real time. We present a set of effective methods to (a) detect outliers in the telemetry or in its statistical properties, (b) uncover and visualise special properties of the telemetry and (c) detect new behavior. Our results are structured around two main families of solutions. For parameters visiting a restricted set of signal values, i.e. all status parameters and about one third of all the others, we focus on a transition analysis, exploiting properties of Poincare plots. For parameters with an arbitrarily high number of possible signal values, we describe the statistical properties of the signal via its Kernel Density Estimate. We demonstrate that this allows for a generic and dynamic approach of the soft-limit definition. Thanks to a much more accurate description of the signal and of its time evolution, we are more sensitive and more responsive to outliers than the traditional checks against hard limits. Our methods were validated on two years of Venus Express telemetry. They are generic for assisting in health monitoring of any complex system with large amounts of diagnostic sensor data. Not only spacecraft systems but also present-day astronomical observatories can benefit from them.
The Photodetector Array Camera and Spectrometer (PACS), on board the Herschel Space Observatory, is designed for
imaging and low and medium resolution spectroscopy in the wavelength region between 57 and 210 μm. This paper
reports the design and the testing results of the grating cryogenic mechanism of the PACS spectrometer. The PACS
diffraction grating is made from an aluminium substrate, mechanically ruled with a periodicity of 8.5 grooves per mm
and gold coated for optimum reflectivity at PACS operating wavelengths. The grating mechanism is capable of accurate
positioning (4") of the flat diffraction grating within a large angular throw (44°) in cryogenic environment (4.2 K).
Technologies of actuators, position sensors, bearings, servo-control and cryogenic test set-up are presented. The grating
mechanism was thoroughly tested, alone and when integrated in the PACS Focal Plane Unit (FPU). The tests were
performed in cryogenic conditions, in a set-up fully representative of the flight conditions. Actual mechanical and
optical performance obtained with the Flight Model (FM) is presented in detail. Quality of the angular positioning of the
mechanism, spectral resolution and optical quality of the grating are analysed.
KEYWORDS: Sensors, Picture Archiving and Communication System, Signal detection, Solar processes, Infrared sensors, Crystals, Optical filters, Calibration, Spectroscopy, Aluminum
The ESA Herschel space observatory will be launched in 2008 into the Earth-Sun L2 orbit and the three instruments onboard
will be exposed to cosmic radiation during the 4 years lifetime of the satellite. To study the impact of ionizing
radiation on the Ge:Ga photoconductors of the PACS instrument (Photodetector Array Camera and Spectrometer), we
performed a series of irradiation measurements at the cyclotron of the University of Louvain la Neuve, Belgium
simulating the in-flight predicted proton fluxes including solar flare events. The PACS integral field spectrometer
contains two 25×16 pixel arrays of Ge:Ga crystals: a low stressed configuration is used in the wavelength range from 55
to 105 μm, and a high stressed device covers the range 105 to 210 μm. Calibration of the detector modules under
realistic IR background fluxes is done at MPE Garching and MPIA Heidelberg. 70 MeV protons were generated at the
cyclotron test site. They were attenuated on their way to the detectors by beam conditioning elements and the metal
shields of the cryostat before they reached the Ge:Ga crystals with a mean energy of 17 MeV and a standard deviation
of 1.5 MeV. According to predictions the expected proton fluxes were set to nominally 10 ps-1cm-2 and to 400 ps-1cm-2
simulating solar flares. We observed radiation-induced glitches in the detector signal, changes in responsivity, increase
in noise and transient behavior. The ongoing data evaluation indicates optimal operating parameters, the best curing
method and frequency, calibration procedures and data processing algorithms aiming for a high photometric accuracy.
The Photodetector Array Camera and Spectrometer (PACS) is one of the three science instruments for ESA's far infrared and submillimetre observatory, Herschel. It employs two Ge:Ga photoconductor arrays (stressed and unstressed) with 16 x 25 pixels, each, and two filled Si bolometer arrays with 16 x 32 and 32 x 64 pixels, respectively, to perform imaging line spectroscopy and imaging photometry in the 57-210 micron wavelength band. In photometry mode, it will simultaneously image two bands, 60-85 micron or 85-130 micron and 130-210 micron, over a field of view of ~ 1.75'x3.5', with full beam sampling in each band. In spectroscopy mode, it will image a field of ~ 50"x50", resolved into 5 x 5 pixels, with an instantaneous spectral coverage of ~ 1500 km/s and a spectral resolution of ~ 75 - 300 km/s. In both modes background-noise limited peformance is expected, with sensitivities (5σ in 1h) of ~3 mJy or 3-10x10-18 W/m2, respectively.
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