F. Bortoletto

The International Robotic Antarctic Infrared Telescope (IRAIT)

Thanks to exceptional coldness, low sky brightness and low content of water vapour of the above atmosphere Dome C, one of the three highest peaks of the large Antarctic plateau, is likely to be the best site on Earth for thermal infrared observations (2.3-300 μm) as well as for the far infrared range (30 μm-1mm). IRAIT (International Robotic Antarctic Infrared Telescope) will be the first European Infrared telescope operating at Dome C. It will be delivered to Antarctica at the end of 2006, will reach Dome C at the end of 2007 and the first winter-over operation will start in spring 2008. IRAIT will offer a unique opportunity for astronomers to test and verify the astronomical quality of the site and it will be a useful test-instrument for a new generation of Antarctic telescopes and focal plane instrumentations. We give here a general overview of the project and of the logistics and transportation options adopted to facilitate the installation of IRAIT at Dome C. We summarize the results of the electrical, electronics and networking tests and of the sky polarization measurements carried out at Dome C during the 2005-2006 summer-campaign. We also present the 25 cm optical telescope (small-IRAIT project) that will installed at Dome C during the Antarctic summer 2006-2007 and that will start observations during the 2007 Antarctic winter when a member of the IRAIT collaboration will join the Italian-French Dome C winter-over team.

Euclid near-infrared spectrophotometer instrument concept at the end of the phase A study

The Euclid mission objective is to map the geometry of the dark Universe by investigating the distance-redshift relationship and the evolution of cosmic structures. The NISP (Near Infrared Spectro-Photometer) is one of the two Euclid instruments operating in the near-IR spectral region (0.9-2μm). The instrument is composed of: - a cold (140K) optomechanical subsystem constituted by a SiC structure, an optical assembly, a filter wheel mechanism, a grism wheel mechanism, a calibration unit and a thermal control - a detection subsystem based on a mosaic of 16 Teledyne HAWAII2RG 2.4μm. The detection subsystem is mounted on the optomechanical subsystem structure - a warm electronic subsystem (280K) composed of a data processing / detector control unit and of an instrument control unit. This presentation will describe the architecture of the instrument, the expected performance and the technological key challenges. This paper is presented on behalf of the Euclid Consortium.

Neural network algorithm controlling a hexapod platform

An hexapod, or Stewart, platform consists essentially of two platforms and six extensible linear actuators (legs), each one connected to the platforms with a couple of universal joints, one at each end. Several applications have been developed involving such a contrivance and many control systems have been developed. In our case, an astronomical telescope secondary mirror is supported by a hexapod platform and it is complete with its own control system. It is actually functioning on the Telescopio Nazionale Galileo (La Palma Island-Spain). The complete movement-position loop control involves a nonlinear equation system and the basic control algorithm is written using a numerical solution for this non-linear set. In order to permit a better real-time control of the optics, faster algorithms have been explored. Among those, a neural network approach has been studied. Comparison between numerical and neural network performances are reported.

Multiphoton Fluorescence Microscopy with GRIN Objective Aberration Correction by Low Order Adaptive Optics

Graded Index (GRIN) rod microlenses are increasingly employed in the assembly of optical probes for microendoscopy applications. Confocal, two–photon and optical coherence tomography (OCT) based on GRIN optical probes permit in–vivo imaging with penetration depths into tissue up to the centimeter range. However, insertion of the probe can be complicated by the need of several alignment and focusing mechanisms along the optical path. Furthermore, resolution values are generally not limited by diffraction, but rather by optical aberrations within the endoscope probe and feeding optics. Here we describe a multiphoton confocal fluorescence imaging system equipped with a compact objective that incorporates a GRIN probe and requires no adjustment mechanisms. We minimized the effects of aberrations with optical compensation provided by a low–order electrostatic membrane mirror (EMM) inserted in the optical path of the confocal architecture, resulting in greatly enhanced image quality.

An active telescope secondary mirror control system

One of the main constraints for a modern astronomical telescope is the active control of the secondary mirror, mainly for the correction of the decentering coma and defocus induced by thermomechanical distortions. The mirror movements should be smooth, as precise as the optical design requires, and restricted to within predefined limits. It should be possible to perform mirror alignment and focus corrections without pausing the exposure (online control). The Galileo telescope achieves all this by using a support structure driven via six actuator bars (a hexapod system or Stewart platform) and a real-time control system based on a transputer network that allows parallel control of each actuator. Both the hexapod secondary support and the control system have been built and tested at the telescope. The results show that the errors introduced during mirror positioning lead to optical aberrations well below the diffraction figure of the telescope, and the systems work smoothly enough to allow online control.

The on-board electronics for the near infrared spectrograph and photometer (NISP) of the EUCLID Mission

The Near Infrared Spectrograph and Photometer (NISP) is one of the instruments on board the EUCLID mission. The focal plane array (FPA) consists of 16 HAWAII-2RG HgCdTe detectors from Teledyne Imaging Scientific (TIS), for NIR imaging in three bands (Y, J, H) and slitless spectroscopy in the range 0.9−2µm. Low total noise measurements (i.e. total noise < 8 electrons) are achieved by operating the detectors in multiple non-destructive readout mode for the implementation of both the Fowler and Up-The-Ramp (UTR) sampling, which also enables the detection and removal of cosmic ray events. The large area of the NISP FPA and the limited satellite telemetry available impose to perform the required data processing on board, during the observations. This requires a well optimized on-board data processing pipeline, and high-performance control electronics, suited to cope with the time constraints of the NISP acquisition sequences. This paper describes the architecture of the NISP on-board electronics, which take charge of several tasks, including the driving of each individual HAWAII-2RG detectors through their SIDECAR ASICs, the data processing, inclusive of compression and storage, and the instrument control tasks. We describe the implementation of the processing power needed for the demanding on-board data reduction. We also describe the basic operational modes that will be managed by the system during the mission, along with data flow and the Telemetry/TeleCommands flow. This paper reports the NISP on-board electronics architecture status at the end of the Phase B1, and it is presented on behalf of the Euclid Consortium.

The E-NIS instrument on-board the ESA Euclid Dark Energy Mission: a general view after positive conclusion of the assesment phase

The Euclid Near-Infrared Spectrometer (E-NIS) Instrument was conceived as the spectroscopic probe on-board the ESA Dark Energy Mission Euclid. Together with the Euclid Imaging Channel (EIC) in its Visible (VIS) and Near Infrared (NIP) declinations, NIS formed part of the Euclid Mission Concept derived in assessment phase and submitted to the Cosmic Vision Down-selection process from which emerged selected and with extremely high ranking. The Definition phase, started a few months ago, is currently examining a substantial re-arrangement of the payload configuration due to technical and programmatic aspects. This paper presents the general lines of the assessment phase payload concept on which the positive down-selection judgments have been based.

Autonomous operations in extreme environments: the AMICA case

An autonomous observatory is being installed at Dome C in Antarctica. It will be constituted by the International Robotic Antarctic Infrared Telescope (IRAIT) and the Antarctic Multiband Infrared CAmera (AMICA). Because of the extreme environment, the whole system has been developed to operate robotically, paying particular attention to the environmental conditions and the subsystems activity monitoring. A detailed description of the IRAIT/AMICA data acquisition process and management will be shown, focusing on automated procedures and solutions against safety risks.

DMD multi-object spectroscopy in space: the EUCLID study

The benefits Astronomy could gain by performing multi-slit spectroscopy in a space mission is renown. Digital Micromirror Devices (DMD), developed for consumer applications, represent a potentially powerful solution. They are currently studied in the context of the EUCLID project. EUCLID is a mission dedicated to the study of Dark Energy developed under the ESA Cosmic Vision programme. EUCLID is designed with 3 instruments on-board: a Visual Imager, an Infrared Imager and an Infrared Multi-Object Spectrograph (ENIS). ENIS is focused on the study of Baryonic Acoustic Oscillations as the main probe, based on low-resolution spectroscopic observations of a very large number of high-z galaxies, covering a large fraction of the whole sky. To cope with these challenging requirements, a highmultiplexing spectrograph, coupled with a relatively small telescope (1.2m diameter) has been designed. Although the current baseline is to perform slit-less spectroscopy, an important option to increase multiplexing rates is to use DMDs as electronic reconfigurable slit masks. A Texas Instrument 2048x1080 Cinema DMD has been selected, and space validation studies started, as a joint ESA-ENIS Consortium effort. Around DMD, a number of suited optical systems has been developed to project sky sources onto the DMD surface and then, to disperse light onto IR arrays. A detailed study started, both at system and subsystem level, to validate the initial proposal. Here, main results are shown, making clear that the use of DMD devices has great potential in Astronomical Instrumentation.

The data processing unit of the NISP instrument of the Euclid mission

In this paper we describe the status of the development of the Data Processing Unit (DPU) of the Near-Infrared Spectro- Photometer (NISP) of the Euclid mission. The architecture of this unit is described, along with the Detector Control Unit (DCU), which operates the 16 HAWAII-2RG (H2RG), composing the NISP Focal Plane Array (FPA), by an equivalent number of SIDECAR systems. The design is evolved from the previous phases, with the implementation of a different approach in the data processing and consequently with the implementation of a large data buffer. The approach in implementing failure tolerance on this unit is described in detail; effort has been made to realize an architecture in which the impact of a single failure can be limited, in the worst case, to the loss of only one detector (out of 16). The main requirements driving the design are also described, in order to emphasize the most challenging areas and the foreseen solutions. The foreseen implementation of the on-board processing pipeline is also described, along with the basic interactions with the Instrument Control Unit (ICU) and with the Mass Memory Unit (MMU). Finally, we outline the on going activity for DPU/DCU bread-boarding.