The Cherenkov Telescope Array Observatory (CTAO) will include telescopes of three different sizes, the smallest of which are the Small-Sized Telescopes (SSTs). In particular, the SSTs will be installed at the southern site of CTAO, on the Chilean Andes, and will cover the highest energy range of CTAO (up to ~300 TeV). The SSTs are developed by an international consortium of institutes that will provide them as an in-kind contribution to CTAO. The optical design of the SSTs is based on a Schwarzschild-Couder-like dual-mirror polynomial configuration, with a primary aperture of 4.3m diameter. They are equipped with a focal plane camera based on SiPM detectors covering a field of view of ~9°. The preliminary design of the SST telescopes was evaluated and approved during the Product Review (PR) organised with CTAO in February 2023. The SST project is now going through a consolidation phase leading to the finalisation and submission of the final design to the Critical Design Review (CDR), expected to occur late 2024, after which the production and construction of the telescopes will begin leading to a delivery of the telescopes to CTAO southern site starting at the end of 2025-early 2026 onward. In this contribution we will present the progress of the SST programme, including the results of the PDR, the consolidation phase of the project and the plan up to the on-site integration of the telescopes.
P. Schipani, L. Marty, M. Mannetta, F. Esposito, C. Molfese, A. Aboudan, V. Apestigue-Palacio, I. Arruego-Rodríguez, C. Bettanini, G. Colombatti, S. Debei, M. Genzer, A.-M. Harri, E. Marchetti, F. Montmessin, R. Mugnuolo, S. Pirrotta, C. Wilson
KEYWORDS: Mars, Data archive systems, Planetary science, Sensors, Calibration, Data conversion, Data processing, Data acquisition, Atmospheric sensing, Planets
DREAMS (Dust Characterisation, Risk Assessment, and Environment Analyser on the Martian Surface) is a payload
accommodated on the Schiaparelli Entry and Descent Module (EDM) of ExoMars 2016, the ESA – Roscosmos mission
to Mars successfully launched on 14 March 2016. The DREAMS data will be archived and distributed to the scientific
community through the ESA’s Planetary Science Archive (PSA). All data shall be compliant with NASA’s Planetary
Data System (PDS4) standards for formatting and labelling files. This paper summarizes the format and content of the
DREAMS data products and associated metadata. The pipeline to convert the raw telemetries to the final products for the
archive is sketched as well.
C. Molfese, P. Schipani, L. Marty, F. Esposito, S. D'Orsi, M. Mannetta, S. Debei, C. Bettanini, A. Aboudan, G. Colombatti, R. Mugnuolo, E. Marchetti, S. Pirrotta
KEYWORDS: Space operations, Environmental sensing, Sensors, Power supplies, Aerospace engineering, Temperature metrology, Humidity, Data acquisition, Mars, Near infrared
This paper describes the Electrical Ground Support Equipment (EGSE) of the Dust characterization, Risk assessment, and Environment Analyser on the Martian Surface (DREAMS) scientific instrument, an autonomous surface payload package to be accommodated on the Entry, Descendent and landing Module (EDM) of the ExoMars 2016 European Space Agency (ESA) mission. DREAMS will perform several kinds of measurements, such as the solar irradiance with different optical detectors in the UVA band (315-400nm), NIR band (700-1100nm) and in "total luminosity" (200 –1100 nm). It will also measure environmental parameters such as the intensity of the electric field, temperature, pressure, humidity, speed and direction of the wind. The EGSE is built to control the instrument and manage the data acquisition before the integration of DREAMS within the Entry, Descendent and landing Module (EDM) and then to retrieve data from the EDM Central Checkout System (CCS), after the integration. Finally it will support also the data management during mission operations. The EGSE is based on commercial off-the-shelf components and runs custom software. It provides power supply and simulates the spacecraft, allowing the exchange of commands and telemetry according to the protocol defined by the spacecraft prime contractor. This paper describes the architecture of the system, as well as its functionalities to test the DREAMS instrument during all development activities before the ExoMars 2016 launch.
The present paper focuses on the development of an optimized version of the Proximity Electronics (PE) for dust
analysers based on static light scattering. This kind of instruments, aimed to the systematic measurement of the size of
dust grains in Martian atmosphere, was developed by the Cosmic Physics and Planetology Group at the INAF
Astronomical Observatory of Capodimonte (OAC) and University Parthenope (LFC group), in Naples, Italy. One of
these instruments, the MEDUSA Experiment, was selected for the Humboldt Payload of the ExoMars mission, the first
mission to Mars of the ESA Aurora Programme. Thereafter, this mission was revised because of increasing costs and
lack of funds and the MEDUSA experiment has been completely re-engineered to meet more demanding constraints of
mass and power consumption. The dust analyser under development is named MicroMED, as it is a lighter and more
compact version of MEDUSA. MicroMED is provided with an Optical System (OS) based on the same concept of the
one present in MEDUSA, but with a low power PE and low power laser source. This paper reports the features and the
tests results of three versions of low power PE developed for MicroMED, and also compares two basic approaches, one
based on a linear amplifier, derived from the solution implemented in two different MEDUSA breadboards (B/Bs), and
the other one based on a logarithmic amplifier, with better performance in terms of compactness and low power
consumption.
The VST primary mirror is a 2.6-m meniscus made of Astro-Sitall. An active optics system is implemented to correct
surface errors due to manufacturing or induced by gravity and temperature changes. The primary mirror is axially
supported by 84 supports disposed in four concentric rings. Three of the supports, symmetrically placed and much stiffer
than the other ones, define the axial plane of the primary mirror acting as fixed points. The remaining 81 supports are
force controlled actuators, used to change the shape of the mirror according to wavefront measurements in closed loop
operation, or to a look-up table in open loop. This paper describes the solutions adopted for the axial actuator, as well as
the test campaign to assess their performance and degree of reliability.
The 2.6-m primary mirror of the VST telescope is equipped with an active optics system in order to correct low-order
aberrations, constantly monitoring the optical quality of the image and controlling the relative position and the shape of
the optical elements. Periodically an image analyser calculates the deviation of the image from the best quality. VST is
equipped with both a Shack-Hartmann in the probe system and a curvature sensor embedded in the OmegaCAM
instrument. The telescope control software decomposes the deviation into single optical contributions and calculates the
force correction that each active element has to perform to achieve the optimal quality. The set of correction forces, one
for each axial actuator, is computed by the telescope central computer and transmitted to the local control unit of the
primary mirror system for execution. The most important element of the VST active optics is the primary mirror, with its
active support system located within the primary mirror cell structure. The primary mirror support system is composed
by an axial and a lateral independent systems and includes an earthquake safety system. The system is described and the
results of the qualification test campaign are discussed.
One of the key issues concerning the measurement of size and density of dust grains based on light scattering system is
the compensation of the stray light due to the optical components misalignment and to the possible contamination of
these components by the dust particles during the measurement runs. This paper focuses on the case study of MEDUSA
(Martian Environmental DUst Systematic Analyzer), one of the experiments initially selected for the ExoMars mission,
planned by the European Space Agency (ESA), with the scientific objective to study water and dust in Mars atmosphere.
The MEDUSA experiment foresees an Optical System (OS) aimed at measuring atmospheric dust content and size
distribution. One pump assures that the proper gas and dust flow circulates inside the instrument. This paper reports the
description and trade off analysis of several techniques for the stray-light compensation implemented on the MEDUSA
OS Proximity Electronics (PE) Test Board (2006), designed and manufactured by INAF-Osservatorio Astronomico di
Capodimonte, in the frame of the MEDUSA Bread Board (B/B) activities. The PE Test Board can implement more than
one compensation mode, such as: AC coupling, DC coupling with offset compensation via external loop and DC
coupling with offset compensation via on board HW loop. The choice among the mentioned compensation modes shall
be done also according to the configuration of the overall acquisition system, implemented by the Main Electronics
(ME), as explained in the reported trade-off analysis. For the architecture configuration of the industrial breadboard
(2008) the preferred solution was the one based on the DC coupling with on board HW loop, for which some test results
are reported.
The VST telescope is equipped with an active optics system based on a wavefront sensor, a set of axial actuators to
change the primary mirror shape and a secondary mirror positioner stage. The secondary mirror positioning capability
allows the correction of defocus and coma optical aberrations, mainly caused by incorrect relative positions of the optics.
The secondary mirror positioner is a 6-6 Stewart platform (also called "hexapod"). It is a parallel robot with a mobile
platform moved by 6 linear actuators acting simultaneously. This paper describes the secondary mirror support system
and the current status of the work.
The VLT Survey Telescope (VST), a telescope with a 2.6 m. primary mirror designed and implemented by I.N.A.F. in
cooperation with the European Southern Observatory (ESO), is provided with an active optics system to correct the
optical aberrations due to polishing imperfections, misalignments, thermal and gravity reasons. For the primary mirror, a
distributed control system is required to impose the desired force values in a sufficient number of points to maintain the
optimal shape in different positions of the altitude axis. The forces are applied by means of 84 electro-mechanical
actuators, provided with an electronic Primary Mirror Actuator Control Boards (M1ACB). This paper focuses mainly on
the hardware electronics and is referred to the control system new version, designed in 2007, whose implementation is in
progress. The new design has taken into account all the experience done on the system previous version, solving all the
encountered problems of functionality and reliability.
The VST (VLT Survey Telescope) is a 2.6 m class Alt-Az telescope in installation phase at Cerro Paranal in Northern
Chile, at the European Southern Observatory (ESO) site. The VST is a wide-field imaging telescope dedicated to supply
databases for the ESO Very Large Telescope (VLT) science and to carry out stand-alone observations in the Ultraviolet
to Infrared spectral range. The VST is provided with an active optics control system to actively compensate the optical
aberrations; it is based on 84 actuators controlling the shape of the primary mirror and a hexapode for secondary mirror
positioning. The present paper focuses on the implementation of the microcontroller programming firmware for the
Primary Mirror Actuators Electronic Control Board. The most relevant problems encountered during the implementation
of this real time multitasking distributed control application are described; optimization problems due to low performing
hardware platform, not provided with operating system, are also reported. Several described topics are applicable to
other distributed control systems, requiring closed loop control system and communication capability with a higher level
computer.
MEDUSA (Martian Environmental DUst Systematic Analyzer) is one of the experiments selected for the ExoMars
mission, planned by the European Space Agency (ESA), with the scientific objective to study water and dust on Mars, in
relation to the search of signs of life forms. To achieve this goal, the MEDUSA experiment is based on an optical system
and two micro-balances, integrated together with a dust deposition and electrification sensor. This paper focuses on the
Proximity Electronics (PE) envisaged for the Optical System and reports the results obtained during the development
activities carried out in the breadboard implementation of the instrument. A photodiode amplifier with very high gain
(107) and large output dynamics was developed. The compensation of the offset due to stray light and electronic bias has
been implemented via an adaptive control. The environmental constraints imposed by the space mission to Mars have
been taken into account during the design, not only for the qualified components selection, but also for the minimization
of the overall mass and power consumption.
In a modern telescope the Azimuth (AZ) and Altitude (ALT) Axes have to perform a very accurate pointing and
tracking. The tracking of celestial objects is a critical operation, during which the telescope axes have to compensate the
earth rotation, allowing a stable image integration on the scientific instrument CCD. To accomplish this goal, the two
axes control system is provided with state of the art encoders and tachometers, for position and speed feedback, together
with motors controlled in torque preload, to avoid backlash effect. The closed loop control system is based on an axes
Local Control Unit (LCU), based on VME Computer. In this paper the AZ and ALT Axes Control System of the VST
(VLT Survey Telescope) is described. The VST is a 2.6 m class
Alt-Azimuthal Survey Telescope in installation phase at
Cerro Paranal in Northern Chile, at the European Southern Observatory (ESO) observation site. The VST Telescope was
designed and implemented by I.N.A.F., Osservatorio Astronomico di Capodimonte. Nowadays the AZ and ALT axes
mechanics and the related control system have already been accepted by ESO, shipped to Chile and integrated in Paranal.
The VST (VLT Survey Telescope), a 2.6 m class Alt-Az telescope in installation phase on Cerro Paranal in Northern
Chile, at the European Southern Observatory (ESO) site, is provided with a distributed control system based on electro-mechanical
actuators, aimed at implementing the main mirror active optics. Due to the requirement of dissipated power
reduction under the mirror, a regulated power bus has been chosen, avoiding the use of voltage regulators mounted on
the actuators control board. Because the parallel connection of the all control boards power lines makes this solution
critical from the point of view of cabling drop voltage and fault propagation, a Power Distribution System (PDS)
provided with remote monitoring and control capabilities has been designed. The PDS configuration is based on several
Power Distribution Boxes (PDBs), connected in two separate benches. The harness accommodation was estimated by
means of 3D CAD, to evaluate the length of the single power connections. The cabling drop voltage was verified by
means of PSpice simulation. The single PDS bench has been provided with drop voltage remote sensing function for all
the power supply voltages, while the single PDB has been provided with control and monitoring electronics to
disconnect via tele-command the faulty control boards and to monitor in real time voltages and current consumption.
KEYWORDS: Control systems, Sensors, Telescopes, Transducers, Temperature sensors, Switches, Power supplies, Fluctuations and noise, Observatories, Electronics
The Hydrostatic Bearing System (HBS) control hardware of the VST (VLT Survey Telescope), a 2.6 m. class Alt-Az
telescope in installation phase at Cerro Paranal in Northern Chile, at the European Southern Observatory (ESO) site, is
aimed at controlling all the devices present in the HBS pumping station and at monitoring the pressure values in the
different points of the plant. The HBS control system is based mainly on a Local Control Unit (LCU) mounted in the
HBS control cabinet and connected to the plant by means of proper I/Fs. A distributed pressure and temperature
acquisition system, based on General Purpose (GP) acquisition boards, is also present. A local interlock chain and related
enabling signal for the Azimuth Axis interlock chain have been implemented to avoid fault propagation in case of lack of
delivery pressure. In the present paper all technical details concerning the control and monitoring of the HBS subsystem
are given.
The VLT Survey Telescope (VST) is a co-operative program between the European Southern Observatory (ESO) and the INAF Capodimonte Astronomical Observatory (OAC), Naples, for the study, design, and realization of a 2.6-m wide-field optical imaging telescope to be operated at the Paranal Observatory, Chile. The telescope design, manufacturing and integration are responsibility of OAC. The VST has been specifically designed to carry out stand-alone observations in the UV to I spectral range and to supply target databases for the ESO Very Large Telescope (VLT). The control hardware is based on a large utilization of distributed embedded specialized controllers specifically designed, prototyped and manufactured by the Technology Working Group for VST project. The use of a field bus improves the whole system reliability in terms of high level flexibility, control speed and allow to reduce drastically the plant distribution in the instrument. The paper describes the philosophy and the architecture of the VST control HW with particular reference to the advantages of this distributed solution for the VST project.
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