Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

Context. We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. Aims: A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods: The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Results: Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the GBP (330-680 nm) and GRP (630-1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Conclusions: Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy.

/pdf/gaia-data-release-2-summary-of-the-contents-and-survey-539viwt72y.pdf

Gaia Data Release 2. Summary of the contents and survey properties

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim$1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg$^2$ at a luminosity distance of $40^{+8}_{-8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Msun. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim$40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over $\sim$10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position $\sim$9 and $\sim$16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. (Abridged)

Multi-messenger Observations of a Binary Neutron Star Merger

This paper describes the ATLAS experiment as installed in i ts experimental cavern at point 1 at CERN. It also presents a brief overview of the expec ted performance of the detector.

http://absimage.aps.org/image/SES08/MWS_SES08-2008-020010.pdf

The ATLAS Experiment at the CERN Large Hadron Collider

基礎講座 電気泳動(Electrophoresis)

Drone orientation detection at a distance of 50 m using a SPAD array camera

This letter presents a 2-bin single-photon avalanche diode (SPAD)-based indirect time-of-flight (ITOF) pixel circuit with low-power low-voltage differential clock distribution and a partially in-pixel single-slope analog-to-digital converter (ADC). An in-pixel dynamic comparator performs dual functions as a SPAD event-driven low-swing clock sampler and a comparator for self-referenced ADC conversion with digital delta reset sampling (DRS). The pixel achieves a full well capacity of 128–512 photons (6.83–8.82 effective bit depth), a low dynamic power consumption of 13.9–24.5-nW/MHz SPAD rate at a pitch of 7.2 $\mu \text{m}$ in STMicroelectronics’ 40-nm CMOS and is 3-D stacking ready.

An Indirect Time-of-Flight SPAD Pixel With Dynamic Comparator Reuse for a Single-Slope ADC

Time-correlated single-photon counting (TCSPC) has been established as the preferred choice of detection for high resolution depth profiling due to its excellent surface to surface resolution and high optical sensitivity. This presentation will describe an underwater transceiver system based on a planar CMOS silicon single photon avalanche diode (Si-SPAD) detector array, and interfaced with a graphics processing unit (GPU) for real time processing capabilities with video rates up to 25 Hz. Depth and intensity profiles of stationary and moving targets were acquired with the transceiver fully submerged in scattering water, equivalent up to 7.5 attenuation lengths. 

Real-time underwater single-photon three-dimensional imaging

The recent development of single-photon avalanche diode (SPADs) arrays as imaging sensors with both picosecond binning capabilities and single photon sensitivity has led to the rapid development of time-of-flight imaging systems. When used in conjunction with a synchronised light source these sensors produce a 3D image. Here, we apply this 3D imaging ability to the problem of drone identification, orientation, and, segmentation. The proliferation of semi-autonomous aerial multi-copters i.e. drones, has raised concerns over the ability of existing aerial detection systems to accurately characterise such vehicles. Here, we fuse the 3D imaging of SPAD sensors with the classification capabilities of a bespoke convolutional neural network (CNN) into a system capable of determining drone pose in flight. To overcome the lack of publicly available training data we generate a photorealistic dataset to enable the training of our network. After training, we are able to predict the roll, pitch, and yaw of the several different drone types with an accuracy greater than 90%.

Drone segmentation and orientation detection using a SPAD array camera

Time-resolved Raman and fluorescence lifetime spectroscopy imaging yields new research insights with great potential in applications including biomedical diagnostics, carbon materials, and battery development. Single Photon Avalanche Diode (SPAD) arrays are ideal for such applications and we present to our knowledge the first time-resolved Raman images obtained with such sensors. Utilizing motorized and confocal scanning configurations we obtain near shot-noise limited performance, room temperature operation, millisecond spectral acquisition times, and simultaneous acquisition and discrimination of Raman and fluorescence with high spectral resolution and range. Detailed images and spectra from samples including calcite, diamond, and single-wall carbon nanotubes demonstrate the possibility of high-resolution time-resolved Raman and fluorescence imaging.

Robert Henderson

Papers

Drone orientation detection at a distance of 50 m using a SPAD array camera

An Indirect Time-of-Flight SPAD Pixel With Dynamic Comparator Reuse for a Single-Slope ADC

Real-time underwater single-photon three-dimensional imaging

Drone segmentation and orientation detection using a SPAD array camera

Time-correlated Raman imaging with a SPAD line sensor