59 research outputs found
Operations and Performance of the PACS Instrument 3He Sorption Cooler on board of the Herschel Space Observatory
A 3He sorption cooler produced the operational temperature of 285mK for the
bolometer arrays of the Photodetector Array Camera and Spectrometer (PACS)
instrument of the Herschel Space Observatory. This cooler provided a stable
hold time between 60 and 73h, depending on the operational conditions of the
instrument. The respective hold time could be determined by a simple functional
relation established early on in the mission and reliably applied by the
scientific mission planning for the entire mission. After exhaustion of the
liquid 3He due to the heat input by the detector arrays, the cooler was
recycled for the next operational period following a well established automatic
procedure. We give an overview of the cooler operations and performance over
the entire mission and distinguishing in-between the start conditions for the
cooler recycling and the two main modes of PACS photometer operations. As a
spin-off, the cooler recycling temperature effects on the Herschel cryostat 4He
bath were utilized as an alternative method to dedicated Direct Liquid Helium
Content Measurements in determining the lifetime of the liquid Helium coolant.Comment: 34 pages, 13 figures, accepted in Experimental Astronom
The Infrared Continuum Spectrum of VY CMa
We combine spectra of VY CMa obtained with the short- and long-wavelength
spectrometers, SWS and LWS, on the Infrared Space Observatory to provide a
first detailed continuum spectrum of this highly luminous star. The
circumstellar dust cloud through which the star is observed is partially
self-absorbing, which makes for complex computational modeling. We review
previous work and comment on the range of uncertainties about the physical
traits and mineralogical composition of the modeled disk. We show that these
uncertainties significantly affect the modeling of the outflow and the
estimated mass loss. In particular, we demonstrate that a variety of quite
diverse models can produce good fits to the observed spectrum. If the outflow
is steady, and the radiative repulsion on the dust cloud dominates the star's
gravitational attraction, we show that the total dust mass-loss rate is yr, assuming that the star is at a distance of
1.5 kpc. Several indications, however, suggest that the outflow from the star
may be spasmodic. We discuss this and other problems facing the construction of
a physically coherent model of the dust cloud and a realistic mass-loss
analysis
ERIS: revitalising an adaptive optics instrument for the VLT
ERIS is an instrument that will both extend and enhance the fundamental
diffraction limited imaging and spectroscopy capability for the VLT. It will
replace two instruments that are now being maintained beyond their operational
lifetimes, combine their functionality on a single focus, provide a new
wavefront sensing module that makes use of the facility Adaptive Optics System,
and considerably improve their performance. The instrument will be competitive
with respect to JWST in several regimes, and has outstanding potential for
studies of the Galactic Center, exoplanets, and high redshift galaxies. ERIS
had its final design review in 2017, and is expected to be on sky in 2020. This
contribution describes the instrument concept, outlines its expected
performance, and highlights where it will most excel.Comment: 12 pages, Proc SPIE 10702 "Ground-Based and Airborne Instrumentation
for Astronomy VII
The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI
The GRAVITY instrument has been revolutionary for near-infrared
interferometry by pushing sensitivity and precision to previously unknown
limits. With the upgrade of GRAVITY and the Very Large Telescope Interferometer
(VLTI) in GRAVITY+, these limits will be pushed even further, with vastly
improved sky coverage, as well as faint-science and high-contrast capabilities.
This upgrade includes the implementation of wide-field off-axis
fringe-tracking, new adaptive optics systems on all Unit Telescopes, and laser
guide stars in an upgraded facility. GRAVITY+ will open up the sky to the
measurement of black hole masses across cosmic time in hundreds of active
galactic nuclei, use the faint stars in the Galactic centre to probe General
Relativity, and enable the characterisation of dozens of young exoplanets to
study their formation, bearing the promise of another scientific revolution to
come at the VLTI.Comment: Published in the ESO Messenge
The infrared spectrum of Neptune at 3.5-4.1 microns: Search for H<SUB>3</SUB><SUP>+</SUP> and evidence for recent meteorological variations
International audienc
The infrared spectrum of Neptune at 3.5-4.1 microns: Search for H<SUB>3</SUB><SUP>+</SUP> and evidence for recent meteorological variations
International audienc
The Infrared Spectrum of Neptune at 3.5-4.1 microns: Search for H3+ and evidence for meteorological variations
International audienc
The Infrared Spectrum of Neptune at 3.5-4.1 microns: Search for H3+ and evidence for meteorological variations
International audienc
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