IUS/payload communication system simulator configuration definition study

The requirements and specifications for a general purpose payload communications system simulator to be used to emulate those communications system portions of NASA and DOD payloads/spacecraft that will in the future be carried into earth orbit by the shuttle are discussed. For the purpose of on-orbit checkout, the shuttle is required to communicate with the payloads while they are physically located within the shuttle bay (attached) and within a range of 20 miles from the shuttle after they have been deployed (detached). Many of the payloads are also under development (and many have yet to be defined), actual payload communication hardware will not be available within the time frame during which the avionic hardware tests will be conducted. Thus, a flexible payload communication system simulator is required

Configurable/adaptive digital FIR filter

En este trabajo de obtención de grado se describe el proceso de diseño y posterior implementación en silicio de un filtro digital de respuesta finita adaptativo que, a la vez, puede ser un filtro configurable.ITESO, A. C

Stellar intensity interferometry over kilometer baselines: Laboratory simulation of observations with the Cherenkov Telescope Array

A long-held astronomical vision is to realize diffraction-limited optical aperture synthesis over kilometer baselines. This will enable imaging of stellar surfaces and their environments, show their evolution over time, and reveal interactions of stellar winds and gas flows in binary star systems. An opportunity is now opening up with the large telescope arrays primarily erected for measuring Cherenkov light in air induced by gamma rays. With suitable software, such telescopes could be electronically connected and used also for intensity interferometry. With no optical connection between the telescopes, the error budget is set by the electronic time resolution of a few nanoseconds. Corresponding light-travel distances are on the order of one meter, making the method practically insensitive to atmospheric turbulence or optical imperfections, permitting both very long baselines and observing at short optical wavelengths. Theoretical modeling has shown how stellar surface images can be retrieved from such observations and here we report on experimental simulations. In an optical laboratory, artificial stars (single and double, round and elliptic) are observed by an array of telescopes. Using high-speed photon-counting solid-state detectors and real-time electronics, intensity fluctuations are cross correlated between up to a hundred baselines between pairs of telescopes, producing maps of the second-order spatial coherence across the interferometric Fourier-transform plane. These experiments serve to verify the concepts and to optimize the instrumentation and observing procedures for future observations with (in particular) CTA, the Cherenkov Telescope Array, aiming at order-of-magnitude improvements of the angular resolution in optical astronomy.Comment: 18 pages, 11 figures; Presented at SPIE conference on Astronomical Telescopes + Instrumentation in Montreal, Quebec, Canada, June 2014. To appear in SPIE Proc.9146, Optical and Infrared Interferometry IV (J.K.Rajagopal, M.J.Creech-Eakman, F.Malbet, eds.), 201

Stellar Intensity Interferometry: Prospects for sub-milliarcsecond optical imaging

Using kilometric arrays of air Cherenkov telescopes, intensity interferometry may increase the spatial resolution in optical astronomy by an order of magnitude, enabling images of rapidly rotating stars with structures in their circumstellar disks and winds, or mapping out patterns of nonradial pulsations across stellar surfaces. Intensity interferometry (pioneered by Hanbury Brown and Twiss) connects telescopes only electronically, and is practically insensitive to atmospheric turbulence and optical imperfections, permitting observations over long baselines and through large airmasses, also at short optical wavelengths. The required large telescopes with very fast detectors are becoming available as arrays of air Cherenkov telescopes, distributed over a few square km. Digital signal handling enables very many baselines to be synthesized, while stars are tracked with electronic time delays, thus synthesizing an optical interferometer in software. Simulated observations indicate limiting magnitudes around m(v)=8, reaching resolutions ~30 microarcsec in the violet. The signal-to-noise ratio favors high-temperature sources and emission-line structures, and is independent of the optical passband, be it a single spectral line or the broad spectral continuum. Intensity interferometry provides the modulus (but not phase) of any spatial frequency component of the source image; for this reason image reconstruction requires phase retrieval techniques, feasible if sufficient coverage of the interferometric (u,v)-plane is available. Experiments are in progress; test telescopes have been erected, and trials in connecting large Cherenkov telescopes have been carried out. This paper reviews this interferometric method in view of the new possibilities offered by arrays of air Cherenkov telescopes, and outlines observational programs that should become realistic already in the rather near future.Comment: New Astronomy Reviews, in press; 101 pages, 11 figures, 185 reference

Definition of a near real time microbiological monitor for space vehicles

Efforts to identify the ideal candidate to serve as the biological monitor on the space station Freedom are discussed. The literature review, the evaluation scheme, descriptions of candidate monitors, experimental studies, test beds, and culture techniques are discussed. Particular attention is given to descriptions of five candidate monitors or monitoring techniques: laser light scattering, primary fluorescence, secondary fluorescence, the volatile product detector, and the surface acoustic wave detector

On the design and implementation of a control system processor

In general digital control algorithms are multi-input multi-output (MIMO) recursive digital filters, but there are particular numerical requirements in control system processing for which standard processor devices are not well suited, in particular arising in systems with high sample rates. There is therefore a clear need to understand the numerical requirements properly, to identity optimised forms for implementing control laws, and to translate these into efficient processor architectures. By taking a considered view of the numerical and calculation requirements of control algorithms, it is possible to consider special purpose processors that provide well-targeted support of control laws. This thesis describes a compact, high-speed, special-purpose processor which offers a low-cost solution to implementing linear time invariant controllers. [Continues.

Study of an attitude reference system utilizing an electrically suspended gyro final report, 1 aug. 1964 - 31 mar. 1965

Miniature electrically suspended gyroscope for spacecraft attitude reference syste

Dissertation review on a new control perspective on phase locked loops

The technique of phase-locked loop (PLL), an essential means for online frequency detection of incoming signal, which is widely used in our modern day communication system. PLL is traditionally viewed as a non-linear feedback control loop that will automatically locks the adjustable frequency of a local oscillator in reference to the incoming signal. However, the classic PLL technique has reviewed its first sign of weakness, limited convergence performance and complex in structure implementation. To overcome these weaknesses and to improve its current performance, the final outcome of the project is to bring about a better developed idea in frequency estimation compared with the present PLL technique.A new approach known as adaptive observer method, which allowed direct estimation on frequency of an incoming signal, was recently proposed in the control literature. The underlying principle of this project is to investigate the possible use of adaptive observer method for detecting frequencies directly from any sinusoidal signals, and as well as to improve its ability in terms of better performance. Both classic PLL technique and adaptive observer method are compared through several aspects, for instance theoretical study and software simulation. However, due to adaptive observer method is significantly over-performed the PLL technique at the stage of simulation