ELP-OA ('Etoile Laser Polychromatique pour l'Optique Adaptative) aims at demonstrating the tip-tilt is measurable
with a Laser Guide Star (LGS) without any natural guide star. This allows a full sky coverage down to
visible wavelengths. ELP-OA is being setup at Observatoire de
Haute-Provence (OHP). To create a polychromatic
LGS, we use two pulsed dye lasers (at 569nm and 589nm) to produce a two-photons excitation of sodium
atoms in the mesosphere. The chromatism of the refractive index of the air yields a difference of the LGS
direction at different wavelengths. The position differences is proportionnal to the tip-tilt. Since the LGS isn't
sharp enough to give us a small enough error in the differential
tip-tilt, we use an interferometric projector to
improve the high spatial information in the laser spot. It requires an adaptive optics working down to 330nm.
This one is done by post-processing algorithms. Two two aperture projectors are used. Each one creates a
fringe-modulated LGS, and a better RMS error in the LGS position is obtained by measuring the information
in a normal direction with respect to the fringes. By using a two aperture projector, we also strongly decrease
the negative effect of the laser star elongation in the mesosphere, and the Rayleigh contribution near the LGS.
We propose a new optimal algorithm to retrieve the tip-tilt from simultaneous images at different wavelengths.
To enhance the RMS error of the measurements, we extend this algorithm to exploit the temporal correlation
of the turbulence.
TAROT (Telescope Action Rapide pour les Objets Transitoires - Rapid Action Telescope for Transient Objects)
is a network of two robotic ground based telescopes. The telescopes are fully automated, from the scheduling of
the observation requests to the processing of the data. All the applications use a specific automated processing
pipeline which has been continuously improved. CADOR (Coordination et Analyse des Donnees d'Observatoires
Robotises - Coordination and Data Analysis of Robotic Observatories) is a set of data base servers which manage
TAROT telescopes. CADOR is the prime interface to request new observations from TAROT and to access all
images saved with the possibility to make additional processing and analysis. Tarot and Cador are compliant
with Virtual Observatory standard and protocols.
We discuss our Polychromatic Laser Guide Star (PLGS) end-to-end model which relies on the 2-photon
excitation of sodium in the mesosphere. We then describe the status of the setup at Observatoire de Haute-
Provence of ELP-OA, the (PLGS) concept demonstrator. The PLGS aims at measuring the tilt from the LGS
without any NGS. Two dye laser chains locked at 589 and 569nm are required. These chains, are similar to those
of our PASS-2 experiment at Pierrelatte (1999). The two oscillators, preamplifiers and amplifiers are pumped
with NdYAGs. Both beams are phase modulated with a double sine function. If required, a third stage can
be added. It is expected that beams will deliver an output average power of 34W each, so that 22W will be
deposited into the mesosphere. If it is not enough, there is enough power supply to twofold it.
These lasers are being settled in the building of the OHP 1.52m telescope, partly at the first floor, and partly
at the top of the North pillar. Beams will propagate from there to the launch telescope attached to the 1.52m
one through a train of mirrors fixed with respect to the beam, so that incident angles are constant.
The coudé focus of the 1.52m telescope will be equipped with an adaptive optics device, closely derived from
the ONERA's BOA one. The Strehl ratio at 330nm for the differential tilt measurement channel is expected to
be 30-40% for r0 = 8 - 10cm. Telescope vibrations will be measured with pendular seismometers upgraded from Tokovinin's prototype. The full demonstrator is planned to run in 2010.
TAROT (Télescope á Action Rapide pour les Objets Transitoires - Rapid Action Telescope for Transient Objects)
is a network of robotic ground based telescopes. Since 2002, we use them for a survey of artificial objects
(satellites, debris) in the geostationary orbit. The objects are detected, their orbit is computed, and follow-up
observations are planned. We are currently implementing new, more efficient, image processing algorithms in
order to improve the processing speed, the sensitivity, and to decrease the rate of false detections. We present
our new implemented methods, as well as the results obtained.
How structures of various scales formed and evolved from the early Universe up to present time is a fundamental
question of astrophysics. EDGE will trace the cosmic history of the baryons from the early generations of massive
stars by Gamma-Ray Burst (GRB) explosions, through the period of galaxy cluster formation, down to the very low
redshift Universe, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing
gravitational collapse by dark matter (the so-called warm hot intragalactic medium). In addition EDGE, with its
unprecedented capabilities, will provide key results in many important fields. These scientific goals are feasible with a
medium class mission using existing technology combined with innovative instrumental and observational capabilities
by: (a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution (R ~ 500). This enables the study
of their (star-forming) environment and the use of GRBs as back lights of large scale cosmological structures; (b)
observing and surveying extended sources (galaxy clusters, WHIM) with high sensitivity using two wide field of view
X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept
includes four main instruments: a Wide-field Spectrometer with excellent energy resolution (3 eV at 0.6 keV), a Wide-
Field Imager with high angular resolution (HPD 15") constant over the full 1.4 degree field of view, and a Wide Field
Monitor with a FOV of 1/4 of the sky, which will trigger the fast repointing to the GRB. Extension of its energy response
up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part
of the Cosmic Vision call. We will briefly review the science drivers and describe in more detail the payload of this
mission.
The Polychromatic Laser Guide Star aims at providing for the tilt measurement from a LGS without any
natural guide star. Thus it allows adaptive optics to provide us with a full sky coverage. This is critical in
particular to extend adaptive optics to the visible range, where isoplanatism is so small that the probability is
negligible to find a natural star to measure the tilt.
We report new results obtained within the framework of the Polychromatic LGS programme ELP-OA. Natural
stars have been used to mimic the PLGS, in order to check the feasibility of using the difference in the tilt at
two wavelengths to derive the tilt itself. We report results from the ATTILA experiment obtained at the 1.52 m
telescope at Observatoire de Haute-Provence. Tilts derived from the differential tilts are compared with direct
tilt measurements. The accuracy of the measurements is currently ≈ 1.5 Airy disk rms at 550 nm. These results
prove the feasibility of the Polychromatic Laser Guide Star programme ELP-OA. New algorithms based on
inverse problems under development within our programme would lead to smaller error bars by 1 magnitude,
as soon as they will run fast enough.
We describe the ELP-OA demonstrator which we are setting up at the same telescope, with a special emphasis
on the optimization of the excitation process, which definitely has to rely on the two-photon excitation of sodium
atoms in the mesosphere. We will describe the implementation at the telescope, including the projector device,
the focal instrumentation and the NdYAG pumped dye lasers.
We present the Advanced Robotic Agile Observatory (ARAGO), a project for a large variability survey of the sky, in the range 10-8Hz (year) to 1Hz. Among its scientific objectives are the detection of cosmic gamma-ray bursts, both on alert and serendipitously, orphan afterglows, extrasolar planets, AGNs, quasar microlensing, variable and flare stars, trans-neptunian asteroids, Earth-grazers, orbital debris, etc. A large Education and Public Outreach program will be an important part of the project. The telescope itself will be made of Silicon Carbide, allowing, among other advantages, a very light weight and agile capabilities. ARAGO will be fully autonomous, i.e. there will be no human intervention from the request to the data processing and result dissemination, nor to assist night or day operations. ARAGO will start routine observation by mid-2005.
We present the progress we have made in implementing a new kind of automatic classifier for astronomical objects. The developed classifier will work both in the image and time domain and take into account the geometrical and temporal characteristics of the sources. We have first constructed a 2D classifier which is based on a Self Organizing Map. The developed network is able to learn through experience and to discriminate between astronomical objects such as stars, galaxies, saturated objects or blended objects.
In order to recognize and classify variable objects, the method had to be improved. We present the next step of classification through our 3D (geometry - time) classifier. The temporal characteristics of the sources are obtained by different analysis of their light curves: time domain, frequency and time-frequency analysis. We add the geometrical and temporal characteristics to obtain a complete classification of the sources. We plan to use the difference image analysis to obtain block of images and analyze them directly through the classifier. Such a complete classification has not yet been realized in the astronomical domain. In general our method works better than other automatic methods and allows a more complete discrimination through astronomical sources.
We present a versatile scheduler for automated telescope observations and operations. The main objective is to optimize telescope use, while taking alerts (e.g., Gamma-Ray Bursts), weather conditions, and mechanical failures into account. Based on our previous experiment, we propose a two steps approach. First, a daily module develops plan schemes during the day that offer several possible scenarii for a night and provide alternatives to handle problems. Secondly, a nightly module uses a reactive technique --driven by events from different sensors-- to select at any moment the "best" block of observations to launch from the current plan scheme. In addition to a classical scheduling problem under resource constraints, we also want to provide dynamic reconfiguration facilities. The proposed approach is general enough to be applied to any other type of telescope, provided that reactivity is important.
The European photon imaging camera (EPIC) is one of the two main instruments onboard the ESA X-Ray Cornerstone Mission XMM. It is devoted to performing imaging and spectroscopy of the x-ray sky in the domain 0.1 10 keV with a peak sensitivity in 105 seconds of 2 multiplied by 10-15 erg/cm-2. The x-ray instrumentation is complemented by a radiation monitor which will measure the particle background. The spectral resolution is approximately 140 eV at 6.4 keV and 60 eV at 1 keV. The instrumentation consists of three separate focal plane cameras at the focus of the three XMM telescopes, containing CCDs passively cooled to typically minus 100 degrees via radiators pointing toward the anti-Sun direction. The two cameras with the field of view partially occulted by the RGS grating boxes will have MOS technology CCDs while the third camera, with full field of view, will be based on p-n technology. The CCDs in the focal plane of the cameras will cover the entire 30 foot by 30 foot field of view of the telescope while the pixel size (40 by 40 (mu) for the MOS camera and 150 multiplied by 150 (mu) for the p-n) will be adequate to sample the approximately 20' PSF of the mirrors. In order to cope with a wide range of sky background and source luminosity in the visible/UV band, a filter wheel with six positions has been implemented in each camera. The six positions correspond to: open position, closed position, one thin filter (1600 angstrom of plastic support and 400 angstrom of Al), one medium filter (1600 angstrom of plastic support and 800 angstrom of Al) and one thick filter (approximately 3000 angstrom of plastic support, approximately 1000 angstrom of Al and 300 Angstrom of Sn). The final position will be a redundant filter of type still to be decided. A set of radioactive sources in each camera will allow the calibration of the CCDs in any of the operating modes and with any filter wheel position. Vacuum doors and valves operated will allow the operation of other camera heads on the ground, in a vacuum chamber and/or in a controlled atmosphere, and will protect the CCDs from contamination until the spacecraft is safely in orbit. The MOS camera will have 7 CCDs, each of 600 by 600 pixels arranged in a hexagonal pattern with one central and six peripheral. The p-n camera head will have 12 CCDs, each with 200 multiplied by 64 pixels, in a rectangular arrangement, 4 quadrants of 3 CCDs each. The radiation monitor is based on two separate detectors to monitor the low (electrons greater than 30 keV) and the high (electrons greater than 200 keV and protons greater than 10 MeV) energy particles impinging on the telescope along its orbit.
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