5 research outputs found
Microwave Observations of Venus with CLASS
We report on the disk-averaged absolute brightness temperatures of Venus
measured at four microwave frequency bands with the Cosmology Large Angular
Scale Surveyor (CLASS). We measure temperatures of 432.3 2.8 K, 355.6
1.3 K, 317.9 1.7 K, and 294.7 1.9 K for frequency bands
centered at 38.8, 93.7, 147.9, and 217.5 GHz, respectively. We do not observe
any dependence of the measured brightness temperatures on solar illumination
for all four frequency bands. A joint analysis of our measurements with lower
frequency Very Large Array (VLA) observations suggests relatively warmer
( 7 K higher) mean atmospheric temperatures and lower abundances of
microwave continuum absorbers than those inferred from prior radio occultation
measurements.Comment: 10 pages, 3 figures, published in PS
Venus Observations at 40 and 90 GHz with CLASS
Using the Cosmology Large Angular Scale Surveyor, we measure the
disk-averaged absolute Venus brightness temperature to be 432.3 2.8 K and
355.6 1.3 K in the Q and W frequency bands centered at 38.8 and 93.7 GHz,
respectively. At both frequency bands, these are the most precise measurements
to date. Furthermore, we observe no phase dependence of the measured
temperature in either band. Our measurements are consistent with a
CO-dominant atmospheric model that includes trace amounts of additional
absorbers like SO and HSO.Comment: 7 pages, 3 figures, published in PS
Exploring the universality of the alternating conductivity of disordered materials using the Gaussian distribution of activation energies.
This paper presents a newapproach for the analysis of ACconductivity, s*(w)= s?(w)?+?is?(w), in
disordered solids which brings together the quasi-universal frequency-dependent conductivity and
the idea of a Gaussian distributions of probable activation energy barriers for hopping carriers. An
explicit expression forAC conductivity was obtained using a complex dielectric response function and
a continuous time random walk treatment applied to a lattice obeying the Kubo?s fluctuationdissipation
theorem. This expression provides an insight into the universality of the form
s?(w) ? ws (0 ? s ? 1) and s?(w) ? kw (k is the dielectric constant), aswell into the effect of the
Gaussian disorder on exponent s.We discuss the similarities and differences with the Random Free
Energy Barrier model equivalent to the long-used box model, and it brings support to an extending
expression proposed by JCDyre and one of the authors. The applicability of the model to
experimental observations on poly[(2-methoxy-5-hexyloxy)-p-phenylenevinylene] reveals the dielectric
constant, mean energy and variance of the Gaussian distribution for hopping carriers in this
disordered conjugated polymer
Calibration of TES bolometer arrays with application to CLASS
Current and future cosmic microwave background (CMB) experiments fielding
kilo-pixel arrays of transition-edge sensor (TES) bolometers require accurate
and robust gain calibration methods. We simplify and refactor the standard TES
model to directly relate the detector responsivity calibration and optical time
constant to the measured TES current and the applied bias current
. The calibration method developed for the Cosmology Large
Angular Scale Surveyor (CLASS) TES bolometer arrays relies on current versus
voltage (-) measurements acquired daily prior to CMB observations. By
binning Q-band (40GHz) - measurements by optical loading, we find that
the gain calibration median standard error within a bin is 0.3%. We test the
accuracy of this "- bin" detector calibration method by using the Moon as
a photometric standard. The ratio of measured Moon amplitudes between detector
pairs sharing the same feedhorn indicates a TES calibration error of 0.5%. We
also find that for the CLASS Q-band TES array, calibrating the response of
individual detectors based solely on the applied TES bias current accurately
corrects TES gain variations across time but introduces a bias in the TES
calibration from data counts to power units. Since the TES current bias value
is set and recorded before every observation, this calibration method can
always be applied to raw TES data and is not subject to - data quality or
processing errors.Comment: 18 pages, 7 figures, 5 tables. Submitted to ApJS May 202
Four-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: On-sky Receiver Performance at 40, 90, 150, and 220 GHz Frequency Bands
The Cosmology Large Angular Scale Surveyor (CLASS) observes the polarized
cosmic microwave background (CMB) over the angular scales of 1 90 with the aim of characterizing primordial gravitational
waves and cosmic reionization. We report on the on-sky performance of the CLASS
Q-band (40 GHz), W-band (90 GHz), and dichroic G-band (150/220 GHz) receivers
that have been operational at the CLASS site in the Atacama desert since June
2016, May 2018, and September 2019, respectively. We show that the
noise-equivalent power measured by the detectors matches the expected noise
model based on on-sky optical loading and lab-measured detector parameters.
Using Moon, Venus, and Jupiter observations, we obtain
power-to-antenna-temperature calibrations and optical efficiencies for the
telescopes. From the CMB survey data, we compute instantaneous array
noise-equivalent-temperature sensitivities of 22, 19, 23, and 71 for the 40, 90, 150, and 220 GHz frequency
bands, respectively. These noise temperatures refer to white noise amplitudes,
which contribute to sky maps at all angular scales. Future papers will assess
additional noise sources impacting larger angular scales.Comment: 13 pages, 3 figures, published in Ap