Design Related Investigations for Media Access Control Protocol Service Schemes in Wavelength Division Multiplexed All Optical Networks

All-optical networks (AON) are emerging through the technological advancement of various optical components, and promise to provide almost unlimited bandwidth. To realise true network utilisation, software solutions are required. An active area of research is media access control (MAC) protocol. This protocol should address the multiple channels by wavelength division mutiplexing (WDM) and bandwidth management. Token-passing (TP) is one such protocol, and is adopted due to its simplicity and collisionless nature. Previously, this protocol has been analysed for a single traffic type. However, such a study may not substantiate the protocol's acceptance in the AON design. As multiple traffic types hog the network through the introduction multimedia services and Internet, the MAC protocol should support this traffic. Four different priority schemes are proposed for TP protocol extension, and classified as static and dynamic schemes. Priority assignments are a priori in static scheme, whereas in the other scheme, priority reassignments are carried out dynamically. Three different versions of dynamic schemes are proposed. The schemes are investigated for performance through analytical modelling and simulations. The semi-Markov process (SMP) modelling approach is extended for the analyses of these cases. In this technique, the behaviour of a typical access node needs to be considered. The analytical results are compared with the simulation results. The deviations of the results are within the acceptable limits, indicating the applicability ofthe model in all-optical environment. It is seen that the static scheme offers higher priority traffic better delay and packet loss performance. Thus, this scheme can be used beneficially in hard real-time systems, where knowledge of priority is a priori. The dynamic priority scheme-l is more suitable for the environments where the lower priority traffic is near real-time traffic and loss sensitive too. For such a scheme, a larger buffer with smaller threshold limits resulted in improved performance. The dynamic scheme-2 and 3 can be employed to offer equal treatment for the different traffic types, and more beneficial in future AONs. These schemes are also compared in their performance to offer constant QoS level. New parameters to facilitate the comparison are proposed. It is observed that the dynamic scheme-l outperforms the other schemes, and these QoS parameters can be used for such QoS analysis. It is concluded that the research can benefit the design of the protocol and its service schemes needed in AON system and its applications

High Resolution Measurements of the Sunyaev-Zel\u27dovich Effect in Galaxy Clusters at 90 GHz

The MUltiplexed SQUID/TES Array at Ninety GHz (MUSTANG) is a 64-pixel array of transition-edge sensor (TES) bolometers built at the University of Pennsylvania (UPenn) for the Green Bank Telescope (GBT) in collaboration with a number of universities and government agencies such as NASA-GSFC, NRAO, and NIST. MUSTANG carried out observations between 2008 and 2013 and will soon be replaced by a new receiver (MUSTANG-1.5). MUSTANG-1.5 is a 223-pixel array of feedhorn-coupled polarimeters, which are read out with a novel microwave SQUID multiplexer. MUSTANG-1.5 offers many advantages over MUSTANG including more stable cryogenics, a larger field of view (5.5\u27 compared to 42 for MUSTANG), and a significant improvement in sensitivity. These capabilities enable a far more comprehensive observing program. MUSTANG is aimed at measuring the distortion in the Cosmic Microwave Background (CMB) spectrum that arises due to the Sunyaev-Zel\u27dovich Effect (SZE). The SZE is the inverse Compton-scattering of CMB photons as they pass through the dense plasma in clusters of galaxies. The SZE is a nearly redshift-independent, complementary probe of the ICM to X-ray emission and combined analyses of both data sets provide a better understanding of astrophysical phenomena such as shocks, cold fronts, and Active Galactic Nucleus (AGN) outbursts. Understanding how substructure, especially in merging clusters, affects the scaling between SZE flux and total cluster mass is essential to placing tight constraints on cosmological parameters with SZE surveys. In this thesis, I present some of the last ever observations carried out by MUSTANG, which are centered on two massive galaxy clusters, MACS J0647.7+7015 and MACS J1206.2-0847. I discuss a model-fitting technique that has been used to quantitatively compare MUSTANG and lower resolution SZE data from Bolocam to study ICM pressure profiles. I report on the design, commissioning, and current status of MUSTANG-1.5 including the detectors, cryogenics, optics, and the microwave multiplexing readout electronics. Finally, I present early characterization of the cryogenics and readout electronics as the instrument nears deployment-readiness and discuss plans for the early science program

Research and technology, fiscal year 1986, Marshall Space Flight Center

The Marshall Space Flight Center is continuing its vigorous efforts in space-related research and technology. Extensive activities in advanced studies have led to the approval of the Orbital Maneuvering Vehicle as a new start. Significant progress was made in definition studies of liquid rocket engine systems for future space transportation needs and the conceptualization of advanced laucnch vehicles. The space systems definition studies have brought the Advanced X-ray Astrophysics Facility and Gravity Probe-B to a high degree of maturity. Both are ready for project implementation. Also discussed include significant advances in low gravity sciences, solar terrestrial physics, high energy astrophysics, atmospheric sciences, propulsion systems, and on the critical element of the Space Shuttle Main Engine in particular. The goals of improving the productivity of high-cost repetitive operations on reusable transportation systems, and extending the useful life of such systems are examined. The research and technology highlighted provides a foundation for progress on the Hubble Space Telescope, the Space Station, all elements of the Space Transportation System, and the many other projects assigned to this Center

Imaging X-ray spectroscopy with micro-X and Chandra

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 245-258).High spectral resolution observations of X-ray phenomena have the potential to uncover new physics. Currently, only point sources can be probed with high resolution spectra, using gratings. Extended objects like supernova remnants cannot be dispersed, leaving the dense forest of emission lines blended by the moderate resolution of modern instruments. In the first half of this thesis, I undertake two investigations of the supernova remnant Cassiopeia A using the flagship X-ray observatory, Chandra. The first study combines the spatial resolution of the ACIS instrument with the spectral resolution of the dispersive HETG to investigate the evolution of ejecta knots. The second improves on statistical limits of radioactive ejecta, and simulates what higher resolution instruments may observe. Micro-X, a new high resolution X-ray telescope, is the focus of the second half. I detail the commissioning of this novel sounding rocket payload, which uses a focal plane of micro-calorimeters to achieve high spectral resolution in each pixel. The flight hardware is in a final state of testing and integration before the launch, which is anticipated in 2014.by John Rutherford.Ph.D

SPICA:revealing the hearts of galaxies and forming planetary systems : approach and US contributions

How did the diversity of galaxies we see in the modern Universe come to be? When and where did stars within them forge the heavy elements that give rise to the complex chemistry of life? How do planetary systems, the Universe's home for life, emerge from interstellar material? Answering these questions requires techniques that penetrate dust to reveal the detailed contents and processes in obscured regions. The ESA-JAXA Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is designed for this, with a focus on sensitive spectroscopy in the 12 to 230 micron range. SPICA offers massive sensitivity improvements with its 2.5-meter primary mirror actively cooled to below 8 K. SPICA one of 3 candidates for the ESA's Cosmic Visions M5 mission, and JAXA has is committed to their portion of the collaboration. ESA will provide the silicon-carbide telescope, science instrument assembly, satellite integration and testing, and the spacecraft bus. JAXA will provide the passive and active cooling system (supporting the

The Apertif Surveys:The First Six Months

Apertif is a new phased-array feed for the Westerbork Synthesis Radio Telescope (WSRT), greatly increasing its field of view and turning it into a natural survey instrument. In July 2019, the Apertif legacy surveys commenced; these are a time-domain survey and a two-tiered imaging survey, with a shallow and medium-deep component. The time-domain survey searches for new (millisecond) pulsars and fast radio bursts (FRBs). The imaging surveys provide neutral hydrogen (HI), radio continuum and polarization data products. With a bandwidth of 300 MHz, Apertif can detect HI out to a redshift of 0.26. The key science goals to be accomplished by Apertif include localization of FRBs (including real-time public alerts), the role of environment and interaction on galaxy properties and gas removal, finding the smallest galaxies, connecting cold gas to AGN, understanding the faint radio population, and studying magnetic fields in galaxies. After a proprietary period, survey data products will be publicly available through the Apertif Long Term Archive (ALTA, https://alta.astron.nl). I will review the progress of the surveys and present the first results from the Apertif surveys, including highlighting the currently available public data