Status of the low beta 0.07 cryomodules for SPIRAL2

International audienceThe status of the low beta cryomodules for SPIRAL2, supplied by the Irfu institute of CEA Saclay, is reported in this paper. We summarise in three parts the RF tests performed on the cavities in vertical cryostat, the RF power tests of the qualifying cryomodule performed in 2010 and the RF power tests performed in 2011 on the first cryomodule of the serie

The Mid-Infrared Instrument for the James Webb Space Telescope, III: MIRIM, The MIRI Imager

In this article, we describe the MIRI Imager module (MIRIM), which provides broad-band imaging in the 5 - 27 microns wavelength range for the James Webb Space Telescope. The imager has a 0"11 pixel scale and a total unobstructed view of 74"x113". The remainder of its nominal 113"x113" field is occupied by the coronagraphs and the low resolution spectrometer. We present the instrument optical and mechanical design. We show that the test data, as measured during the test campaigns undertaken at CEA-Saclay, at the Rutherford Appleton Laboratory, and at the NASA Goddard Space Flight Center, indicate that the instrument complies with its design requirements and goals. We also discuss the operational requirements (multiple dithers and exposures) needed for optimal scientific utilization of the MIRIM.Comment: 29 pages, 9 figure

Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project

In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory

Imaging Saturn's rings with CAMIRAS: thermal inertia of B and C rings

Thermal inertias Γ of Saturn's B and C ring particles have been derived from infrared observations using the CAMIRAS camera mounted on the Canada-France-Hawaii Telescope. They are respectively $\Gamma_{\rm B}=5^{+18}_{-2}$ ${\rm J \,m^{-2}\, K^{-1} \,s^{-1/2}}$  and $\Gamma_{\rm C}=6^{+12}_{-4}$ ${\rm J \,m^{-2}\, K^{-1} \,s^{-1/2}}$. Such low values might be characteristic of a frosty and porous regolith fractured by cracks or of very porous particle aggregates. Particles have to be slowly spinning to explain the observed ring temperatures. A large azimuthal asymmetry with an amplitude about 1 K is detected on the West ansa of the B ring. It cannot be explained by a model that considers the ring as a slab of low thermal inertia rapidly warming up to the sunlight after its eclipse into the planetary shadow

Impact Seismology: A Search for Primary Pressure Waves Following Impacts A and H

International audienceThis paper reports part of the seismic observations performed after the impacts of Shoemaker–Levy 9 fragments A and H with the mid-IR camera TIMMI at the ESO 3.6-m telescope. Hodograms have been computed to search for the seismic signature of the primary waves crossing the planet within 2 hr following each impact. The hodogram analysis has been unable to detect any seismic signal. In order to put a limit on the kinetic energy of the fragments, the synthetic thermal signature of the primary wave has been calculated as a function of the incident energy, according to theoretical simulations, and taking into account observational conditions such as the point spread function. The non-detection implies that the kinetic energy of impacts A and H was less than 2 × 1021J, within the frame of the theoretical simulation of Lognonnéet al.(Lognonné, Ph., B. Mosser, and F. Dahlen 1994.Icarus110, 180–195.). The error bar is as large as one order of magnitude, according to other simulations. The seismic wave should have contributed to a non-negligible part of the heating of the region surrounding the impacts, but it is not yet possible to measure its contribution

Optical design for the 5-28mum NGST infrared imager MIRI

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CERES, the CarboEurope Regional Experiment Strategy in les Landes, South West France, May-June 2005

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Optical design for the 5-28mum NGST infrared imager MIRI

International audienc

CERES, the CarboEurope Regional Experiment Strategy in les Landes, South West France, May-June 2005

International audienc