An Analytical Investigation of Acquisition Techniques and System Integration Studies for a Radar Aircraft Guidance Research Facility

Boresight camera records for angular tracking accuracy of aircraf

Infrared Colors at the Stellar/Substellar Boundary

We present new infrared photometry for 61 halo and disk stars around the stellar/substellar boundary. These data are combined with available optical photometry and astrometric data to produce color--color and absolute magnitude--color diagrams. The disk and halo sequences are compared to the predictions of the latest model atmospheres and structural models. We find good agreement between observation and theory except for known problems in the V and H passbands probably due to incomplete molecular data for TiO, metal hydrides and H$_2$O. The metal--poor M subdwarfs are well matched by the models as oxide opacity sources are less important in this case. The known extreme M subdwarfs have metallicities about one--hundredth solar, and the coolest subdwarfs have T$_{eff}\sim 3000$ K with masses $\sim$0.09M/M$_{\odot}$. The grainless models are not able to reproduce the flux distributions of disk objects with T$_{eff} <$ 2500 K, however a preliminary version of the NextGen--Dusty models which includes homogeneous formation and extinction by dust grains {\it is} able to match the colors of these very cool objects. The least luminous objects in this sample are GD165B, three DENIS objects --- DBD0205, DBD1058 and DBD1228 --- and Kelu-1. These have T$_{eff}\sim$ 2000 K and are at or below the stellar limit with masses $\leq$0.075M/M$_{\odot}$. Photometry alone cannot constrain these parameters further as the age is unknown, but published lithium detections for two of these objects (Kelu-1 and DBD1228) imply that they are young (aged about 1 Gyr) and substellar (mass $\leq$0.06M/M$_{\odot}$).Comment: ApJ, in press. 18 pages. Also available at ftp://ftp.jach.hawaii.edu/pub/ukirt/skl/dM_preprint

Refinement of the Spitzer Space Telescope Pointing History Based on Image Registration Corrections from Multiple Data Channels

Position reconstruction for images acquired by the Infrared Array Camera (IRAC), one of the science instruments onboard the Spitzer Space Telescope, is a multistep procedure that is part of the routine processing done at the Spitzer Science Center (SSC). The IRAC instrument simultaneously images two different sky footprints, each with two independent infrared passbands (channels). The accuracy of the initial Spitzer pointing reconstruction is typically slightly better than 1". The well‐known technique of position matching imaged point sources to even more accurate star catalogs to refine the pointing further is implemented for SSC processing of IRAC data as well. Beyond that, the optimal processing of redundant pointing information from multiple instrument channels to yield an even better solution is also performed at the SSC. Our multichannel data processing approach is particularly beneficial when the star‐catalog matches are sparse in one channel but copious in others. A thorough review of the algorithm as implemented for the Spitzer mission reveals that the mathematical formalism can be fairly easily generalized for application to other astronomy missions. The computation of pointing uncertainties, the interpolation of pointing corrections and their uncertainties between measurements, and the estimation of random‐walk deviations from linearity are special areas of importance when implementing the method. After performing the operations described in this paper on the initial Spitzer pointing, the uncertainty in the observatory pointing history file is reduced 10–15 fold

Drum Groove Corpora

Patterned microtiming deviations from metronomic regularity are ubiquitous in the performance of metered music. The relevance of microtiming to the perception of music has been studied since the 1980s. Most recently, microtiming has been investigated as a cause of groove (i.e., the pleasant urge to move in response to music). The study of microtiming relies on the availability of microtiming data. This report presents three large corpora of onset timings derived from drum kit performances in popular Anglo-American popular music styles. These data are made freely available (CC 4.0 license) to provide a resource for use by analysts and experimenters alike. They offer a common point of reference for future studies into the temporal facets of music performance. The datasets adhere to FAIR principles; they thus facilitate replication of analyses and experimental stimuli

Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3

We present comprehensive orbital analyses and dynamical masses for the substellar companions Gl~229~B, Gl~758~B, HD~13724~B, HD~19467~B, HD~33632~Ab, and HD~72946~B. Our dynamical fits incorporate radial velocities, relative astrometry, and most importantly calibrated Hipparcos-Gaia EDR3 accelerations. For HD~33632~A and HD~72946 we perform three-body fits that account for their outer stellar companions. We present new relative astrometry of Gl~229~B with Keck/NIRC2, extending its observed baseline to 25 years. We obtain a $<$1\% mass measurement of $71.4 \pm 0.6\,M_{\rm Jup}$ for the first T dwarf Gl~229~B and a 1.2\% mass measurement of its host star ($0.579 \pm 0.007\,M_{\odot}$) that agrees with the high-mass-end of the M dwarf mass-luminosity relation. We perform a homogeneous analysis of the host stars' ages and use them, along with the companions' measured masses and luminosities, to test substellar evolutionary models. Gl~229~B is the most discrepant, as models predict that an object this massive cannot cool to such a low luminosity within a Hubble time, implying that it may be an unresolved binary. The other companions are generally consistent with models, except for HD~13724~B that has a host-star activity age 3.8$\sigma$ older than its substellar cooling age. Examining our results in context with other mass-age-luminosity benchmarks, we find no trend with spectral type but instead note that younger or lower-mass brown dwarfs are over-luminous compared to models, while older or higher-mass brown dwarfs are under-luminous. The presented mass measurements for some companions are so precise that the stellar host ages, not the masses, limit the analysis.Comment: Accepted for publication in AJ. References updated in version 2. See the journal version for the full quality figures. Figure sets and the MCMC chains (reduced to just 1000 samples however) are included with the journal version of the article, and pre-publication at https://drive.google.com/drive/folders/1_A8QYn9NyPgmGqJaY5sMHyT_wAS3uRRK?usp=sharin

Ultradeep Near-Infrared ISAAC Observations of the HDF-S: Observations, Reduction, Multicolor Catalog, and Photometric Redshifts

We present deep near-infrared (NIR) Js, H, and Ks-band ISAAC imaging of the WFPC2 field of the HDF-S. The 2.5'x 2.5' high Galactic latitude field was observed with the VLT under the best seeing conditions with integration times amounting to 33.6 hours in Js, 32.3 hours in H, and 35.6 hours in Ks. We reach total AB magnitudes for point sources of 26.8, 26.2, and 26.2 respectively (3 sigma), which make it the deepest ground-based NIR observations to date, and the deepest Ks-band data in any field. The effective seeing of the coadded images is ~0.45" in Js, ~0.48" in H, and ~0.46" in Ks. Using published WFPC2 optical data, we constructed a Ks-limited multicolor catalog containing 833 sources down to Ks,tot ~< 26 (AB), of which 624 have seven-band optical-to-NIR photometry. These data allow us to select normal galaxies from their rest-frame optical properties to high redshift (z ~< 4). The observations, data reduction and properties of the final images are discussed, and we address the detection and photometry procedures that were used in making the catalog. In addition, we present deep number counts, color distributions and photometric redshifts of the HDF-S galaxies. We find that our faint Ks-band number counts are flatter than published counts in other deep fields, which might reflect cosmic variations or different analysis techniques. Compared to the HDF-N, we find many galaxies with very red V-H colors at photometric redshifts 1.95 < z < 3.5. These galaxies are bright in Ks with infrared colors redder than Js-Ks > 2.3 (in Johnson magnitudes). Because they are extremely faint in the observed optical, they would be missed by ultraviolet-optical selection techniques, such as the U-dropout method.Comment: LaTeX, 24 pages, 15 figures, 3 tables. Accepted for publication in the Astronomical Journal. The paper with full resolution images and figures is available at http://www.strw.leidenuniv.nl/~fires/papers/2002Labbe.ps.gz . The reduced data and catalogs can be found at http://www.strw.leidenuniv.nl/~fires/data/hdfs

Impact of measurement dating inaccuracies in the monitoring of bulk material flows

This paper discusses the negative impact of errors in the dating of information gathered across a distributed network of sensors to be treated by a centralized monitoring algorithm. In this contribution, an example of flow monitoring serves as basis for the analysis. We consider an estimator setup for loss detection. Using a simple probability model, we determine the variance of this estimator and show how it is impacted by the dating uncertainty. A mitigating solution is proposed. Further extensions are discussed

Detection efficiency and bandwidth optimized electro-optic sampling of mid-infrared waves

Electro-optic sampling (EOS) is a powerful method for the characterization of electric fields with frequencies in the range of ~ 1-300 THz. For mid-infrared (MIR) radiation (2-20 µm), it can be understood as a two-step process: first, a sub-MIR-cycle visible/infrared gate pulse generates sum and/or difference frequency radiation with the light field under investigation in a nonlinear medium. Second, the newly generated frequencies are detected in a heterodyne scheme with the transmitted gate pulse serving as the local oscillator. Scanning the delay of the gate pulse with respect to the MIR waveform results in a signal proportional to the incident MIR field, with the spectral response depending on the gate pulse duration and phasematching in the detection crystal. The nonlinear frequency conversion on the one hand transfers the detection to the near-infrared spectral range, affording the use of low-noise photodetectors. On the other hand, it limits the detection efficiency and subjects it to a trade-off against bandwidth. Our research group develops high-power ultrashort-pulsed laser sources for field-resolved infrared spectroscopy. Explicitly, nonlinearly post-compressed femtosecond lasers are used both to drive the generation of waveform-stable MIR light for molecular-sample excitation, as well as for obtaining gate pulses for EOS of the full macroscopic sample response. To maximize the sensitivity of our field-resolved spectrometers, this thesis studied the photon detection efficiency of EOS for MIR radiation with wavelengths in the 6-18-μm range in experiment and theory. Three different types of gate pulses were investigated experimentally: first, the EOS detection efficiency was characterized for gate pulses with 1030-nm central wavelength, generated by an Yb-thin-disk oscillator. Limited by multi-photon-absorption-caused damage of the GaSe crystal, with an average gate-pulse power of 450mW, a conversion efficiency of 2% from the MIR into sum-frequency photons was achieved in a 500-μm-thick detection crystal. Accounting for Fresnel reflections at the crystal and losses in the heterodyne detection, up to 0.76% of the incident MIR photons arrived at the balanced diodes. Together with mW-level MIR average powers, this resulted in 13 orders of magnitude frequency-domain intensity dynamic range at 9-μm wavelength for a measurement time of 16 s and a scan range of 3.3 ps. However, phase-mismatch limited the −20 dB spectral width to 1.2 µm. Using a 85-μm-thick GaSe crystal, the full MIR spectrum of the source, spanning from 6.6 to 10.7 µm at −20 dB, was detected, while trading in two orders of magnitude in peak dynamic range. In our research group, the prototype field-sensitive spectrometer with this record detection efficiency and dynamic range is currently being used for fingerprinting real-world biomedical samples, with up to 40 times higher molecular detection sensitivity than commercial Fourier-transform infrared spectrometers. Due to the dispersion of GaSe, the trade-off between detection efficiency and spectral coverage is mitigated for longer-wavelength gate pulses. Using gate pulses centered at 1550 nm wavelength from an Er-fiber laser and a 300-μm-thick crystal, a comparable detection dynamic range and bandwidth as with the 85-μm-thick crystal at 1030 nm was achieved, despite the lower gate pulse power of 120mW. This performance enables high sensitivity spectroscopic measurements, when employing the Er-laser in a dual-oscillator fast-scanning mode (~ 1 kHz scan rate), avoiding low-frequency noise sources. In addition to the broader phasematching bandwidth, choosing a longer gate-pulse wavelength also increases the detection-crystal damage threshold due to reduced multi-photon absorption, allowing for the use of higher gate pulse powers and, consequently, enhancing the nonlinear interaction. This benefit was harnessed in the investigation of limitations to the detection efficiency with 1.9-W gate pulses from a Tm-fiber laser at 1965 nm central wavelength, comparing several EOS crystal thicknesses with respect to detection efficiency and spectral coverage. Traces measured with 100 to 300-μm-thin crystals closely resemble the incident field, spanning from 8.1 µm to 14.2 µm at −10 dB, with a conversion efficiency from the MIR into sum-frequency photons of up to ~ 10%. Using a 500-μm-thick GaSe crystal, more than 20% of the MIR photons from a 3-μm spectral band around 9.3 µm were upconverted. Further increasing the crystal thickness resulted in saturation of the depletion, explained by temporal walk-off and reduced peak powers due to dispersion. The overall number of detectable MIR photons of ~ 6.4% from within the detection crystal an interaction time window, together with mW-level MIR powers, lead to a peak intensity dynamic range > 10^14, with twice the detection bandwidth as for the 1030-nm gate pulses in the efficiency-optimized configuration, thus spanning ~ 5 μm at −20 dB. Despite the MIR depletion upon detection, the EOS signal scaled linearly with the field strength for average photon numbers between 10^3 and 10^17 per second within our measurement accuracy, because enough MIR photons stay available for nonlinear interaction. The multi-percent-level conversion efficiency allows for characterization of waveforms with an average of 22 photons inside the detection crystal in a 2.2-ms-long integration time window per temporal element. The combination of sensitivity, dynamic range and spectral coverage finds application e.g., in broadband vibrational spectroscopy, where the minimum detectable concentration is only a factor of ~ 4 higher than what would be possible when detecting all incident MIR photons. Furthermore, the detection bandwidth allows for the simultaneous measurement of multiple molecular species with spectrally wide-spread absorption lines. Employing the high detection dynamic range, a further study in the frame of this thesis concerned the use of EOS as a highly sensitive characterization technique for the stability and reproducibility of the MIR waveform and, therefore, for the control over optical fields. These capabilities were demonstrated by measuring the temporal fluctuations of the EOS trace, resulting in a record-low timing jitter of < 10 as over billions of pulses. A theoretical model simulating the chain of nonlinear processes from the laser frontend to EOS detection confirmed the measured values, identifying intensity noise of the modelocked oscillator front-end as the main source of the remaining MIR waveform instabilities. These jitter values were 3 orders of magnitude above the field fluctuations expected from a shot noise- limited driving pulse train