KEYWORDS: Observatories, Spectroscopy, Data archive systems, Advanced distributed simulations, X-rays, Data centers, Analytical research, Current controlled current source, Data analysis, Databases
Observing on the Stratospheric Observatory for Infrared Astronomy (SOFIA) requires a strategy that takes the specific circumstances of an airborne platform into account. Observations of a source cannot be extended or shortened on the spot due to flight path constraints. Still, no exact prediction of the time on source is available since there are always wind and weather conditions, and sometimes technical issues. Observations have to be planned to maximize the observing efficiency while maintaining full flexibility for changes during the observation. The complex nature of observations with FIFI-LS - such as the interlocking cycles of the mechanical gratings, telescope nodding and dithering - is considered in the observing strategy as well. Since SOFIA Cycle 3 FIFI-LS is available to general investigators. Therefore general investigators must be able to define the necessary parameters simply, without being familiar with the instrument, still resulting in efficient and flexible observations. We describe the observing process with FIFI-LS including the integration time estimate, the mapping and dithering setup and aspects of the scripting for the actual observations performed in flight. We also give an overview of the observing scenarios, which have proven to be useful for FIFI-LS.
KEYWORDS: Telescopes, Sensors, Human-machine interfaces, Astronomy, Computing systems, Observatories, Signal to noise ratio, Electronics, Signal processing, Signal detection
We describe observational operations and data reduction for the science instrument FIFI-LS (Field Imaging Far Infrared
Line Spectrometer) onboard SOFIA (Stratospheric Observatory for Infrared Astronomy). First, the observation strategy
is explained, which plans all the various observing modes and parameters based on the targets and the limitations of the
observatory and instrument. Next, the observations must be created in a format readable by instrument control software,
via a system of algorithms. Once the observations have been planned and prepared, they must be scheduled, executed
and analysed, and this process is outlined. The data reduction system which processes the results from these
observations, beginning from retrieving raw data, to obtaining a FITS file data cube readable by analysis programs, is
described in detail.
Optical and opto-mechanical components in astronomical instruments are amongst the most expensive and
delicate single parts. Lenses made of special glasses or crystals are sometimes difficult to obtain (if at all),
especially with larger diameters and are figured and polished involving time-consuming and even risky procedures.
At infrared wavelengths (< 5μm), when the instrument is cooled to temperatures even below that of liquid
nitrogen, mechanical stress is induced between e.g. a glass lens and its metal mounting due to different heat
expansion coefficients of the materials involved. This can considerably degrade the performance of the whole
instrument. At infrared wavelengths the optical specifications considering surface roughness and form error
are less tight than in the optical due to the longer wavelengths involved. Hence metal mirrors with a surface
roughness and a form error of around 50 nm (RMS) may generally be favoured due to lower production costs then
lenses. Goal of the project described here is to manufacture plane, spherical or aspherical aluminum mirrors,
which are not hampered in the ways described above, in a cost effective procedure with optical specifications
(surface roughness and form error) of less than 100 nm (RMS) by means of direct diamond milling.
The super-massive 4 million solar mass black hole (SMBH) SgrA* shows variable emission from the millimeter to the X-ray domain. A detailed analysis of the infrared light curves allows us to address the accretion phenomenon in a statistical way. The analysis shows that the near-infrared flux density excursions are dominated by a single state power law, with the low states of SgrA* are limited by confusion through the unresolved stellar background. We show that for 8-10m class telescopes blending effects along the line of sight will result in artificial compact star-like objects of 0.5-1 mJy that last for about 3-4 years. We discuss how the imaging capabilities of GRAVITY at the VLTI, LINC-NIRVANA at the LBT and METIS at the E-ELT will contribute to the investigation of the low variability states of SgrA*.
We present two design concepts and the science drivers of a proposed near-infrared interferometric integral field
spectrograph for the LBT. This instrument will expand the capabilities of the currently-under-construction
interferometric camera LINC-NIRVANA with spectroscopy by means of an integral field unit (IFU) located inside the
LINC cryostat. Two instrument concepts have been studied in detail: a microlens array IFU with a spectrograph built
entirely inside LINC (the LIINUS approach), and a lenslet+fibers IFU feeding an external spectrograph (the SERPIL
approach). In both cases, the instrument incorporates imaging interferometry with integral field spectroscopy, an ideal
combination for detailed studies of astronomical objects down to below 10mas angular resolution in the near-infrared.
The scientific applications range from solar system studies and spectroscopy of exoplanets to the dynamics of stars and
gas in the central regions of the Milky Way and other nearby galaxies.
We present a feasible design concept and the science drivers for the proposed near-infrared interferometric integral field
spectrograph at the LBT. Combining interferometric resolution with an integral field spectrograph is a very promising
instrument concept for detailed studies down to below 10 mas angular resolution in the NIR. If approved, the instrument
will become an extension to the LINC-NIRVANA instrument, which is under construction.
In this contribution an opto-mechanical design concept has been studied in detail: that places the integral field unit into
an existing empty compartment within the LINC hardware. Several optical and mechanical challenges have been
successfully mastered, among them:
- the limitation of the achievable angular resolution due to the parallactic angle rotation versus the LBT baseline,
- the anamorphic magnification required by the LBT optics design to optimize the detector information content, and
- integrating the IFU into the existing LINC cryostat without interfering with the existing optics and mechanics.
The science program spans from solar system studies and spectroscopy of exoplanets to the black hole dynamics in the
center of our and other galaxies.
OSIRIS is an integral field infrared spectrograph designed for the Keck Adaptive Optics System. It utilizes an array of lenses and the latest infrared detector to simultaneously obtain more than 3000 spectra over a rectangular field of view (up to 48x64 spatial elements). In its broad band mode (16x64 spectra), each spectrum contains more than 1700 wavelength channels and covers an entire infrared band at a resolution of 3800. Due to the extremely low backgrounds between night sky lines and at AO spatial samplings, the instrument is also extremely sensitive. Here we present first results obtained during commissioning of the instrument following First Light in February 22, 2005. We demonstrate the performance of the instrument, in particular together with the Keck Observatory's adaptive optics system and provide a flavor of the science addressed with OSIRIS.
LIINUS/SERPIL is a design study to augment LBTs interferometric beam combiner camera LINC-NIRVANA with imaging spectroscopy. The FWHM of the interferometric main beam at 1.5 micron will be about 10 mas, offering unique imaging and spectroscopic capabilities well beyond the angular resolution of current 8-10m telescopes. At 10 mas angular scale, e.g., one resolution element at the distance of the Galactic Center corresponds to the average diameter of the Pluto orbit (79 AU), hence the size of the solar system. Taking advantage of the LBT interferometric beam with an equivalent maximum diameter of 23 m, LIINUS/SERPIL is an ideal precursor instrument for (imaging) spectrographs at extremely large full aperture telescopes. LIINUS/SERPIL will be built upon the LINC-NIRVANA hardware and LIINUS/SERPIL could potentially be developed on a rather short timescale. The study investigates several concepts for the optical as well as for the mechanical design. We present the scientific promises of such an instrument together with the current status of the design study.
We present an overview of the OSIRIS integral field spectrograph which was recently commissioned on the Keck II Telescope. OSIRIS works with the Keck Adaptive Optics system and utilizes an infrared transmissive lenslet array to sample a rectangular field of view at close to the Keck diffraction limit. By packing the spectra close together (2 pixel rows per spectrum) and using the Rockwell Hawaii-2 detector (wavelengths between 1 and 2.5 microns), we achieve a relatively large field of view (up to 6."4) while maintaining full broad-band spectral coverage at a resolution of 3800. Among the challenges of the instrument are: a fully cryogenic design (approximately 250 kg are brought down to 55K); four spatial scales from 0."02 to 0."10; extremely low wavefront error (approximately 25 nm of non-common path error); large all aluminum optics for the spectrograph; extremely repeatable spectral formats; and a sophisticated data reduction pipeline. OSIRIS also serves as a starting point for our design of IRIS which is a planned integral field spectrograph for the Thirty Meter Telescope.
We present first results of an exploratory study to use integral field spectroscopy to observe extrasolar planets. We focus on transiting 'Hot Jupiters' and emphasize the importance of observing strategy and exact timing. We demonstrate how integral field spectroscopy compares with other spectroscopic techniques currently applied. We have tested our concept with a time series observation of HD209458b obtained with SINFONI at the VLT during a superior conjunction.
SPIFFI (SPectrometer for Infrared Faint Field Imaging) is a fully cryogenic, near-infrared imaging spectrograph built at the Max-Planck-Institute for Extraterrestrial Physics (MPE) and upgraded with a new detector and spectrograph camera by ASTRON/NOVA, ESO and MPE. The upgraded instrument will become a facility instrument for the ESO VLT in summer 2004 as part of the SINFONI (SINgle Faint Object Near-IR Investigation) project, which is the combination of SPIFFI and ESOs adaptive optics module MACAO (Multiple Application Curvature Adaptive Optics), at the Cassegrain focus of Yepun (UT4). In spring 2003 we had the opportunity to observe with SPIFFI as a guest instrument without the AO-module at the Cassegrain focus of UT2 of the VLT. In this paper we discuss the performance of SPIFFI during the guest-instrument phase. First we summarize the technical performance of SPIFFI like the spatial and spectral resolution, the detector performance and the instruments throughput. Afterwards we illustrate the power of integral field spectroscopy by presenting data and results of the Galactic Center.
OSIRIS is a near infrared diffraction limited imaging field spectrograph under development for the Keck observatory adaptive optics system and scheduled for commissioning in fall 2004. Based upon lenslet pupil imaging, diffraction grating, and a 2Kx2K Hawaii2 HgCdTe array, OSIRIS is a highly efficient instrument at the forefront of today's technology. OSIRIS will deliver per readout up to 4096 diffraction limited spectra in a complex interleaved format, requiring new challenges to be met regarding user interaction and data reduction. A data reduction software package is under development, aiming to provide the observer with a facility instrument allowing him to concentrate on science rather than dealing with instrumental as well as telescope and atmosphere related effects. Together with OSIRIS, a pipeline for basic data reduction will be provided for a new Keck instrument for the first time. A status report is presented here together with some aspects of the data reduction pipeline.
SINFONI is an adaptive optics assisted near-infrared integral field spectrometer for the ESO VLT. The Adaptive OPtics Module (built by the ESO Adaptive Optics Group) is a 60-elements curvature-sensor based system, designed for operations with natural or sodium laser guide stars. The near-infrared integral field spectrometer SPIFFI (built by the Infrared Group of MPE) provides simultaneous spectroscopy of 32 x 32 spatial pixels, and a spectral resolving power of up to 3300. The adaptive optics module is in the phase of integration; the spectrometer is presented tested in the laboratory. We provide an overview of the project, with particular emphasis on the problems encountered in designing and building an adaptive optics assisted spectrometer.
SPIFFI is the near-infrared integral field spectrograph of the SINFONI VLT instrument. SPIFFI uses an image slicer with plane mirrors as its integral field unit. The integral field unit consists of two stacks of mirrors, each with 32 mirrors, rearranging a two-dimensional field-of-view of 32 x 32 pixels into a one-dimensional pseudo slit, which is fed into a long-slit spectrograph. The image slicer is constructed solely from Zerodur and is operated at a cryogenic temperature of 77 Kelvin. Only optical contacting is used for the assembly of the individual slicer mirrors and the image slicer on its base-plate. The special slicer mount holds the image slicer stress-free and compensates for the different thermal coefficients of expansion of the Zerodur image slicer and the Aluminium mount. Tests at room and cryogenic temperatures show the performance of the image slicer, the durability of the optical contacting technique, and the accuracy of the slicer mount.
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