We present the latest results obtained with the wide-field submillimeter camera ArTeMiS that is operating on APEX since July 2013. This camera is presently equipped with 1870 pixels at 350 μm and 800 pixels at 450 μm simultaneously. ArTéMiS is a PI-camera open to the ESO and Swedish community. It has already taken a part in the 2016-2017 scientific results of APEX. So far, it offers the best performance in terms of mapping speed at 350 and 450 μm in the southern hemisphere.
Major improvements of the APEX telescope have been achieved at the end of 2017, requiring a complete removal of the instruments in the C-Cabin. In the meantime, the ArTeMiS camera has been kept safe at the ALMA Operations Support Facility (OSF) building. We took advantage of this re-installation to improve a bit more the optical coupling of detectors. We present here the present status of the camera.
Since APEX operation is now guaranteed until the end of 2022, our prospects are to install in time new detectors presently developed at CEA/Léti in the frame of R&D developments made for the future SPICA space mission. Those detectors, which have new polarization capabilities, are also presented.
TALC, Thin Aperture Light Collector is a 20 m space observatory project exploring some unconventional optical solutions (between the single dish and the interferometer) allowing the resolving power of a classical 27 m telescope. With TALC, the principle is to remove the central part of the prime mirror dish, cut the remaining ring into 24 sectors and store them on top of one-another. The aim of this far infrared telescope is to explore the 600 μm to 100 μm region. With this approach we have shown that we can store a ring-telescope of outer diameter 20m and ring thickness of 3m inside the fairing of Ariane 5 or Ariane 6. The general structure is the one of a bicycle wheel, whereas the inner sides of the segments are in compression to each other and play the rule of a rim. The segments are linked to each other using a pantograph scissor system that let the segments extend from a pile of dishes to a parabolic ring keeping high stiffness at all time during the deployment. The inner corners of the segments are linked to a central axis using spokes as in a bicycle wheel. The secondary mirror and the instrument box are built as a solid unit fixed at the extremity of the main axis. The tensegrity analysis of this structure shows a very high stiffness to mass ratio, resulting into 3 Hz Eigen frequency. The segments will consist of two composite skins and honeycomb CFRP structure build by replica process. Solid segments will be compared to deformable segments using the controlled shear of the rear surface. The adjustment of the length of the spikes and the relative position of the side of neighbor segments let control the phasing of the entire primary mirror. The telescope is cooled by natural radiation. It is protected from sun radiation by a large inflatable solar screen, loosely linked to the telescope. The orientation is performed by inertia-wheels. This telescope carries a wide field bolometer camera using cryocooler at 0.3K as one of the main instruments. This telescope may be launched with an Ariane 6 rocket up to 800 km altitude, and use a plasma stage to reach the Lagrange 2 point within 18 month. The plasma propulsion stage is a serial unit also used in commercial telecommunication satellites. When the plasma launch is completed, the solar panels will be used to provide the power for communication, orientation and power the cryo-coolers for the instruments. The guide-line for development of this telescope is to use similar techniques and serial subsystems developed for the satellite industry. This is the only way to design and manufacture a large telescope at a reasonable cost.
ArTeMiS is a submillimeter camera planned to work simultaneously at 450 μm, 350 μm and 200 μm by use of 3 focal planes of, respectively, 8, 8 and 4 bolometric arrays, each one made of 16 x18 pixels. In July 2013, with a preliminary setting reduced to 4 modules and to the 350 μm band, ArTeMiS was installed successfully at the Cassegrain focus of APEX, a 12 m antenna located on the Chajnantor plateau, Chile. After the summary of the scientific requirements, we describe the main lines of the ArTeMiS nominal optical design with its rationale and performances. This optical design is highly constrained by the room allocation available in the Cassegrain cabin. It is an all-reflective design including a retractable pick off mirror, a warm Fore Optics to image the focal plane of the telescope inside the cryostat, and the cold optics. The large size of the field of view at the focal plane of the telescope, 72 mm x 134 mm for the 350 μm and 450 μm beams, leads to the use of biconical toroidal mirrors. In this way, the nominal image quality obtained on the bolometric arrays is only just diffraction limited at some corners of the field of view. To keep a final PSF as much uniform as possible across the field of view, we have used the technic of manufacturing by diamond turning to machine the mirrors. This approach, while providing high accuracy on the shape of the mirrors, made easier the control of the two sub units, the Fore Optics and the cold optics, in the visible domain and at room temperature. Moreover, the use of the similar material (Aluminium alloy 6061) for the optical bench and the mirrors with their mount ensures a homothetic shrinking during the cooling down. The alignment protocol, drew up at the early step of the study, is also presented. It required the implementation of two additional mechanisms inside the cryostat to check the optical axis of the cold optics, in the real conditions of operation of ArTeMiS. In this way, it was possible to pre-align the Fore Optics sub unit with respect to the cold optics. Finally, despite the high constraints of the operating conditions of APEX, this protocol allowed to align ArTeMiS with respect to the telescope in a single adjustment. The first images obtained on the sky, Saturn with its rings, are given.
ArTeMiS is a wide-field submillimeter camera operating at three wavelengths simultaneously (200, 350 and 450 μm). A preliminary version of the instrument equipped with the 350 μm focal plane, has been successfully installed and tested on APEX telescope in Chile during the 2013 and 2014 austral winters. This instrument is developed by CEA (Saclay and Grenoble, France), IAS (France) and University of Manchester (UK) in collaboration with ESO. We introduce the mechanical and optical design, as well as the cryogenics and electronics of the ArTéMiS camera. ArTeMiS detectors consist in Si:P:B bolometers arranged in 16×18 sub-arrays operating at 300 mK. These detectors are similar to the ones developed for the Herschel PACS photometer but they are adapted to the high optical load encountered at APEX site. Ultimately, ArTeMiS will contain 4 sub-arrays at 200 μm and 2×8 sub-arrays at 350 and 450 μm. We show preliminary lab measurements like the responsivity of the instrument to hot and cold loads illumination and NEP calculation. Details on the on-sky commissioning runs made in 2013 and 2014 at APEX are shown. We used planets (Mars, Saturn, Uranus) to determine the flat-field and to get the flux calibration. A pointing model was established in the first days of the runs. The average relative pointing accuracy is 3 arcsec. The beam at 350 μm has been estimated to be 8.5 arcsec, which is in good agreement with the beam of the 12 m APEX dish. Several observing modes have been tested, like “On- The-Fly” for beam-maps or large maps, spirals or raster of spirals for compact sources. With this preliminary version of ArTeMiS, we concluded that the mapping speed is already more than 5 times better than the previous 350 μm instrument at APEX. The median NEFD at 350 μm is 600 mJy.s1/2, with best values at 300 mJy.s1/2. The complete instrument with 5760 pixels and optimized settings will be installed during the first half of 2015.
A new photonic camera has been developed in the framework of the ArTéMis project (Bolometers architecture for large field of view ground based telescopes in the sub-millimeter). This camera scans the sky in the sub-millimeter range at simultaneously three different wavelengths, namely 200 μm, 350 μm, 450 μm, and is installed inside the APEX telescope located at 5100m above sea level in Chile. Bolometric detectors cooled to 300 mK are used in the camera, which is integrated in an original cryostat developed at the low temperature laboratory (SBT) of the INAC institut. This cryostat contains filters, optics, mirrors and detectors which have to be implemented according to mass, size and stiffness requirements. As a result the cryostat exhibits an unusual geometry. The inner structure of the cryostat is a 40 K plate which acts as an optical bench and is bound to the external vessel through two hexapods, one fixed and the other one mobile thanks to a ball bearing. Once the cryostat is cold, this characteristic enabled all the different elements to be aligned with the optical axis. The cryogenic chain is built around a pulse tube cooler (40 K and 4 K) coupled to a double stage helium sorption cooler (300 mK). The cryogenic and vacuum processes are managed by a Siemens PLC and all the data are showed and stored on a CEA SCADA system. This paper describes the mechanical and thermal design of the cryostat, its command control, and the first thermal laboratory tests. This work was carried out in collaboration with the Astrophysics laboratory SAp of the IRFU institut. SAp and SBT have installed the camera in July 2013 inside the Cassegrain cabin of APEX.
The ArTeMiS submillimetric camera will observe simultaneously the sky at 450, 350 and 200 μm using 3 different focal
planes made of 2304, 2304 and 1152 bolometric pixels respectively. This camera will be mounted in the Cassegrain
cabin of APEX, a 12 m antenna located on the Chajnantor plateau, Chile.
To realize the bolometric arrays, we have adapted the Silicon processing technology used for the Herschel-PACS
photometer to account for higher incident fluxes and longer wavelengths from the ground. In addition, an autonomous
cryogenic system has been designed to cool the 3 focal planes down to 300 mK. Preliminary performances obtained in
laboratory with the first of 3 focal planes are presented.
Latest results obtained in 2009 with the P-ArTeMiS prototype camera are also discussed, including massive protostellar
cores and several star forming regions that have been clearly identified and mapped.
ArTeMiS is a camera designed to operate on large ground based submillimetric telescopes in the 3 atmospheric windows
200, 350 and 450 µm. The focal plane of this camera will be equipped with 5760 bolometric pixels cooled down at 300
mK with an autonomous cryogenic system. The pixels have been manufactured, based on the same technology processes
as used for the Herschel-PACS space photometer. We review in this paper the present status and the future plans of this
A prototype camera, named P-ArTeMiS, has been developed and successfully tested on the KOSMA telescope in 2006 at
Gornergrat 3100m, Switzerland. Preliminary results were presented at the previous SPIE conference in Orlando (Talvard
et al, 2006). Since then, the prototype camera has been proposed and successfully installed on APEX, a 12 m antenna
operated by the Max Planck Institute für Radioastronomie, the European Southern Observatory and the Onsala Space
Observatory on the Chajnantor site at 5100 m altitude in Chile. Two runs have been achieved in 2007, first in March and
the latter in November. We present in the second part of this paper the first processed images obtained on star forming
regions and on circumstellar and debris disks. Calculated sensitivities are compared with expectations. These illustrate
the improvements achieved on P-ArTeMiS during the 3 experimental campaigns.
Submillimetre astronomy is the prime technique to unveil the birth and early evolution of stars and galaxies in the local
and distant Universe. Preliminary meteorological studies and atmospheric transmission models tend to demonstrate that
Dome C might offer atmosphere conditions that open the 200-μm atmospheric windows, and could potentially be a site
for a large ground-based telescope facility. However, Antarctic climate conditions might also severely impact and
deform any telescope mirror and hardware. We present prerequisite conditions and their associate experiments for
defining a large telescope facility for submillimetre astronomy at Dome C: (1) Whether the submm/THz atmospheric
windows open from 200 μm during a large and stable fraction of time; (2) The knowledge of thermal gradient and (3)
icing formation and their impact on a telescope mirror and hardware. This paper will present preliminary results on
current experiments that measure icing, thermal gradient and sky opacity at Dome C. We finally discuss a possible
roadmap toward the deployment of a large telescope facility at Dome C.
Astronomical observations at sub-millimetre wavelengths are limited either by the angular resolution of the telescope or
by the sensitivity and field of view of the detector array. New generation of radio telescopes, such as the ALMA-type
antennas on Chajnantor plateau in Chile, can overcome these limitations if they are equipped with large detector arrays
made of thousands of sensitive bolometer pixels.
Instrumentation developments undertaken at CEA and based on the all silicon technology of CEA/Leti are able to
provide such large detector arrays. The ArTeMiS project consists in developing a camera for ground-based telescopes
that operates in two sets of atmospheric windows at 200-450 μm (channel 1) and 800-1200 μm (channel 2).
ArTeMiS-1 consists in grid bolometer arrays similar to those developed by CEA for the Herschel Space Observatory. A
prototype camera operating in this first atmospheric window was installed and successfully tested in March 2006 on the
KOSMA telescope at Gornergrat (Switzerland) in collaboration with the University of Cologne. ArTeMiS-2 will consist
either in antenna-coupled bolometer arrays or specific mesh bolometer arrays.
By the end of 2008, ArTeMiS cameras could be operated on 10m-class telescopes on the Chajnantor ALMA site, e.g.,
APEX, opening new scientific prospects in the study of the early phases of star formation and in cosmology, in the study
of the formation of large structures in the universe. At longer term, installation of such instrumentation at Dome-C in
Antarctica is also under investigation. The present status of the ArTeMiS project is detailed in this paper.