X-shooter is the first second-generation instrument newly commissioned a the VLT. It is a high efficiency single
target intermediate resolution spectrograph covering the range 300 - 2500 nm in a single shot. We summarize
the main characteristics of the instrument and present its performances as measured during commissioning and
the first months of science operations.
X-Shooter is the first 2nd generation instrument to be installed at Paranal early 2008. It is a single target spectrograph covering in a single exposure a wide spectral range from the UV to the K' band with maximum sensitivity. Another key feature of the instrument is its fast response, obtained by making it simple and easy to operate. Compared to other big VLT instruments X-Shooter has a relatively small number of moving functions, but nevertheless the requirements on the whole instrument software are quite demanding. In order to cover the wide spectral range with high efficiency, the instrument is split into three different arms, one being cryogenically cooled. The high level coordinating software architecture provides all the facilities for parallel operation with the maximum achievable level of synchronicity. Low level X-Shooter requirements are also quite stringent, since to compensate for slit misalignments among the three arms, an active piezoelectric actuator system is envisaged. The low-level architecture, besides the typical control of single devices (like motors, sensors and lamps), handles the required real-time operations. The software integration and test is also an issue, being X-Shooter a collaborative effort among several institutes spread around Europe. The whole instrument software architecture is presented here, entering in details into its main modules such as the instrument control software, the observation software and the observing templates structure and their integration in the VLT software environment.
A light photon-counting scientific payload, named AURORA, has been developed and launched on a commercial microsatellite in order to study the near-UV night-sky background emission (channel Notte) and the Aurora (Alba). AURORA is mapping, with the Notte channel, the night-side photon background in the 300-400 nm spectral range, together with a particular 2+ nitrogen line ((lambda) = 337nm). These measurements are required in the framework of the Extreme Universe Space Observatory (EUSO) experiment, approved by the European Space Agency (ESA) for the phase A and to be flown on the International Space Station (ISS) in 2009. The Alba channel studies the Aurora emissions in four different spectral bands centered on: 367nm, 391nm, 535nm, 560nm (OI). The instrument has been integrated on the MEGSAT-1 satellite and launched, on the September, 26th 2000, from the Baikonur cosmodrome. The nearly circular Low Earth Orbit (LEO), with inclination of 64.56 degrees, fully includes the ISS ground track envelope. The satellite overall mass is about 60 kg. An overview of the techniques adopted, including detectors, front-end electronics, Central Processor Unit (CPU), is given in this paper, together with a brief report on the mission status and plans.
SD2000 is a new photon counting MCP based detector. It consists of a single MCP, coated with a suitable photocathode, closely coupled to a Silicon Drift Detector (SDD). The electron clouds generated by the MCP channels are accelerated by a strong electric field applied and proximity focussed on the SDD, that works as a position sensitive read-out detector. The SDD, developed by the INFN laboratories in Trieste, is a butterfly Silicon Drift Detector with no metal deposition on its cathodes. The absence of metallization in the sensitive zone of the chamber allows the electron clouds to penetrate uniformly into the active region of the detector and to be revealed. A suitable front-end amplifier, that works as a charge preamplifier and a bipolar shaper, has been developed starting from SPICE simulations and tested. A proto-type of the detector has been realized and tested and the first results have been achieved and compared with the expected best performances of the detector.
A new photon counting detector for UV Astronomy is presented. The SD2000 detector consists of a single MCP, coated with a suitable photocathode, closely coupled to a Silicon Drift Detector (SDD). A good spatial resolution, of the order of 20 micrometer in both directions, can be achieved with a relatively small number of readout channels (10 divided by 100). The maximum allowable rate, proportional to the drift length, is about 105 Hz for a 20 mm length focal plane. A new type of SDD, without metal deposition on the cathodes, has been developed and tested for this particular application. A single MCP has been coupled also to a metal anode and a silicon diode in order to characterize it and study the interaction between the incoming (low-energy) electron cloud and a silicon p-n junction similar to those present in the drift chamber.