Search for Nanosecond Near-infrared Transients around 1280 Celestial Objects

Stars and planetary system

Architectures and synchronization techniques for distributed satellite systems: a survey

Cohesive Distributed Satellite Systems (CDSSs) is a key enabling technology for the future of remote sensing and communication missions. However, they have to meet strict synchronization requirements before their use is generalized. When clock or local oscillator signals are generated locally at each of the distributed nodes, achieving exact synchronization in absolute phase, frequency, and time is a complex problem. In addition, satellite systems have significant resource constraints, especially for small satellites, which are envisioned to be part of the future CDSSs. Thus, the development of precise, robust, and resource-efficient synchronization techniques is essential for the advancement of future CDSSs. In this context, this survey aims to summarize and categorize the most relevant results on synchronization techniques for Distributed Satellite Systems (DSSs). First, some important architecture and system concepts are defined. Then, the synchronization methods reported in the literature are reviewed and categorized. This article also provides an extensive list of applications and examples of synchronization techniques for DSSs in addition to the most significant advances in other operations closely related to synchronization, such as inter-satellite ranging and relative position. The survey also provides a discussion on emerging data-driven synchronization techniques based on Machine Learning (ML). Finally, a compilation of current research activities and potential research topics is proposed, identifying problems and open challenges that can be useful for researchers in the field.This work was supported by the Luxembourg National Research Fund (FNR), through the CORE Project COHEsive SATellite (COHESAT): Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications, under Grant FNR11689919.Award-winningPostprint (published version

Panoramic optical and near-infrared SETI instrument: overall specifications and science program

We present overall specifications and science goals for a new optical and near-infrared (350 - 1650 nm) instrument designed to greatly enlarge the current Search for Extraterrestrial Intelligence (SETI) phase space. The Pulsed All-sky Near-infrared Optical SETI (PANOSETI) observatory will be a dedicated SETI facility that aims to increase sky area searched, wavelengths covered, number of stellar systems observed, and duration of time monitored. This observatory will offer an "all-observable-sky" optical and wide-field near-infrared pulsed technosignature and astrophysical transient search that is capable of surveying the entire northern hemisphere. The final implemented experiment will search for transient pulsed signals occurring between nanosecond to second time scales. The optical component will cover a solid angle 2.5 million times larger than current SETI targeted searches, while also increasing dwell time per source by a factor of 10,000. The PANOSETI instrument will be the first near-infrared wide-field SETI program ever conducted. The rapid technological advance of fast-response optical and near-infrared detector arrays (i.e., Multi-Pixel Photon Counting; MPPC) make this program now feasible. The PANOSETI instrument design uses innovative domes that house 100 Fresnel lenses, which will search concurrently over 8,000 square degrees for transient signals (see Maire et al. and Cosens et al., this conference). In this paper, we describe the overall instrumental specifications and science objectives for PANOSETI.Comment: 15 pages, 7 figures, 1 tabl

Adaptive optics for laser processing

The overall aim of the work presented in this thesis is to develop an adaptive optics (AO) technique for application to laser-based manufacturing processes. The Gaussian beam shape typically coming from a laser is not always ideal for laser machining. Wavefront modulators, such as deformable mirrors (DM) and liquid crystal spatial light modulators (SLM), enable the generation of a variety of beam shapes and furthermore offer the ability to alter the beam shape during the actual process. The benefits of modifying the Gaussian beam shape by means of a deformable mirror towards a square flat top profile for nanosecond laser marking and towards a ring shape intensity distribution for millisecond laser drilling are presented. Limitations of the beam shaping capabilities of DM are discussed. The application of a spatial light modulator to nanosecond laser micromachining is demonstrated for the first time. Heat sinking is introduced to increase the power handling capabilities. Controllable complex beam shapes can be generated with sufficient intensity for direct laser marking. Conventional SLM devices suffer from flickering and hence a process synchronisation is introduced to compensate for its impact on the laser machining result. For alternative SLM devices this novel technique can be beneficial when fast changes of the beam shape during the laser machining are required. The dynamic nature of SLMs is utilised to improve the marking quality by reducing the inherent speckle distribution of the generated beam shape. In addition, adaptive feedback on the intensity distribution can further improve the quality of the laser machining. In general, beam shaping by means of AO devices enables an increased flexibility and an improved process control, and thus has a significant potential to be used in laser materials processing

Single Photon Interferometry and Quantum Astrophysics

abstract: This thesis contains an overview, as well as the history of optical interferometers. A new approach to interferometric measurements of stars is proposed and explored. Modern updates to the classic techniques are described along with some theoretical derivations showing why the method of single photon counting shows significant promise relative to the currently used amplitude interferometry. Description of a modular intensity interferometer system using commercially available single-photon detectors is given. Calculations on the sensitivity and \emph{uv}-plane coverage using these modules mounted on existing telescopes on Kitt Peak, Arizona is presented. Determining fundamental stellar properties is essential for testing models of stellar evolution as well as for deriving physical properties of transiting exoplanets. The proposed method shows great promise in measuring the angular size of stars. Simulations indicate that it is possible to measure stellar diameters of bright stars with AB magnitude 5% in a single night of observation. Additionally, a description is given of a custom time-to-digital converter designed to time tag individual photons from multiple single-photon detectors with high count rate, continuous data logging, and low systematics. The instrument utilizes a tapped-delay line approach on an FPGA chip which allows for sub-clock resolution of <100 ps. The TDC is implemented on a Re-configurable Open Architecture Computing Hardware Revision 2 (ROACH2) board which allows for continuous data streaming and time tagging of up to 20 million events per second. The functioning prototype is currently set-up to work with up to ten independent channels. Laboratory characterization of the system, including RF, pick up and mitigation, as well as measurement of in-lab photon correlations from an incoherent light source (artificial star), are presented. Additional improvements to the TDC will also be discussed, such as improving the data transfer rate by a factor of 10 via an SDP+ Mezzanine card and PCIe 2SFP+ 10 Gb card, as well as scaling to 64 independent channels. Furthermore, a modified nulling interferometer with image inversion is proposed, for direct imaging of exoplanets below the canonical Rayleigh resolution limit. Image inversion interferometry relies on splitting incoming radiation from a source, either spatially rotating or reflecting the electric field from one arm of the interferometer before recombining the signals and detecting the resulting images in the two output ports with an array of high-speed single-photon detectors. Sources of incoming radiation that have cylindrical symmetry and are centered on the rotation axis will cancel in one of the output ports and add in the other output port. The ability to suppress light from a host star, as well as the ability to resolve past the Rayleigh limit, enables sensitive detection of exoplanets from a stable environment without the need for a coronagraph. The expected number of photons and the corresponding variance in the measurement for different initial contrast ratios are shown, with some first-order theoretical instrumental errors. Lastly, preliminary results from a sizeable photometric survey are presented. This survey is used to derive bolometric flux alongside from angular size measurements and the effective stellar temperatures.Dissertation/ThesisDoctoral Dissertation Astrophysics and Astronomy 201

Towards the Intensity Interferometry Stellar Imaging System

The imminent availability of large arrays of large light collectors deployed to exploit atmospheric Cherenkov radiation for gamma-ray astronomy at more than 100GeV, motivates the growing interest in application of intensity interferometry in astronomy. Indeed, planned arrays numbering up to one hundred telescopes will offer close to 5,000 baselines, ranging from less than 50m to more than 1000m. Recent and continuing signal processing technology developments reinforce this interest. Revisiting Stellar Intensity Interferometry for imaging is well motivated scientifically. It will fill the short wavelength (B/V bands) and high angular resolution (< 0.1mas) gap left open by amplitude interferometers. It would also constitute a first and important step toward exploiting quantum optics for astronomical observations, thus leading the way for future observatories. In this paper we outline science cases, technical approaches and schedule for an intensity interferometer to be constructed and operated in the visible using gamma-ray astronomy Air Cherenkov Telescopes as receivers.Comment: Submitted as RFI to 2010 Decadal Survey Panel on behalf of the Stellar Intensity Interferometry working group with IAU commission 5

Ultra-Relativistic Magnetic Monopole Search with the ANITA-II Balloon-borne Radio Interferometer

We have conducted a search for extended energy deposition trails left by ultra-relativistic magnetic monopoles interacting in Antarctic ice. The non-observation of any satisfactory candidates in the 31 days of accumulated ANITA-II flight data results in an upper limit on the diffuse flux of relativistic monopoles. We obtain a 90% C.L. limit of order 10^{-19}/(cm^2-s-sr) for values of Lorentz boost factor 10^{10}<gamma at the anticipated energy E=10^{16} GeV. This bound is stronger than all previously published experimental limits for this kinematic range.Comment: updated to version accepted by Phys. Rev.

A practical guide to photoacoustic tomography in the life sciences

The life sciences can benefit greatly from imaging technologies that connect microscopic discoveries with macroscopic observations. One technology uniquely positioned to provide such benefits is photoacoustic tomography (PAT), a sensitive modality for imaging optical absorption contrast over a range of spatial scales at high speed. In PAT, endogenous contrast reveals a tissue's anatomical, functional, metabolic, and histologic properties, and exogenous contrast provides molecular and cellular specificity. The spatial scale of PAT covers organelles, cells, tissues, organs, and small animals. Consequently, PAT is complementary to other imaging modalities in contrast mechanism, penetration, spatial resolution, and temporal resolution. We review the fundamentals of PAT and provide practical guidelines for matching PAT systems with research needs. We also summarize the most promising biomedical applications of PAT, discuss related challenges, and envision PAT's potential to lead to further breakthroughs