The Raytheon Company is a major American defense contractor and industrial corporation with core manufacturing concentrations in weapons and military and commercial electronics. It was previously involved in corporate and special-mission aircraft until early 2007. Raytheon is the world's largest producer of guided missiles.Established in 1922, the company reincorporated in 1928 and adopted its present name in 1959. The company has around 63,000 employees worldwide and annual revenues of approximately US$25 billion. More than 90% of Raytheon's revenues were obtained from military contracts and, as of 2012, it was the fifth-largest military contractor in the world, and is the fourth largest defense contractor in the United States by revenue.Raytheon's headquarters moved from Lexington, Massachusetts to Waltham, Massachusetts in 2003. The company was previously headquartered in Cambridge, Massachusetts from 1922 to 1928, Newton, Massachusetts from 1928 to 1941, Waltham from 1941 to 1961, Lexington from 1961 to 2003, and back to Waltham from 2003 onwards. Wikipedia.
Urgaonkar R.,Raytheon Co. |
Neely M.J.,University of Southern California
IEEE Journal on Selected Areas in Communications | Year: 2012
We investigate opportunistic cooperation between secondary (femtocell) users and primary (macrocell) users in cognitive femtocell networks. We consider two models for such cooperation. In the first model, called the Cooperative Relay Model, a secondary user cannot transmit its own data concurrently with a primary user. However, it can employ cooperative relaying of primary user data in order to improve the latter's effective transmission rate. In the second model, called the Interference Model, a secondary user is allowed to transmit its data concurrently with a primary user. However, the secondary user can "cooperate" by deferring its transmissions when the primary user is busy. In both models, the secondary users must make intelligent cooperation decisions as they seek to maximize their own throughput subject to average power constraints. The decision options are different during idle and busy periods of the primary user, and the decisions in turn influence the durations of these periods according to a controllable infinite state Markov chain. Such problems can be formulated as constrained Markov decision problems, and conventional solution techniques require either extensive knowledge of the system dynamics or learning based approaches that suffer from large convergence times. However, using a generalized Lyapunov optimization technique, we design a novel greedy and online control algorithm that overcomes these challenges. Remarkably, this algorithm does not require any knowledge of the network arrival rates and is provably optimal. © 2006 IEEE.
Hough M.E.,Raytheon Co.
Journal of Guidance, Control, and Dynamics | Year: 2011
A nonlinear bias characterization filter with measurement biases, denoted by BCF(6), a filter with six state variables, is formulated and radar measurement and bias models are provided for orbit determination. Nonlinear prediction models for the state, bias, and covariances are also formulated from the radar models. At altitudes above 500 km, where drag is not important, orbital motion is described and the dominant gravitational accelerations are found to arise from the central inverse-square gravity field and from Earth oblateness. The results show that BCF(6) improves covariance fidelity in the presence of sensor measurement biases. the BCF(6) covariance matrix is more consistent with the statistics of the biased errors in the estimates compared with the extended Kalman filter EKF(6). Covariance inflation improves position and velocity covariance fidelity early in the track, but fidelity degrades after extended periods in the track.
Dolphin A.E.,Raytheon Co.
Astrophysical Journal | Year: 2012
In most star formation history (SFH) measurements, the reported uncertainties are those due to effects whose sizes can be readily measured: Poisson noise, adopted distance and extinction, and binning choices in the solution itself. However, the largest source of error, systematics in the adopted isochrones, is usually ignored and very rarely explicitly incorporated into the uncertainties. I propose a process by which estimates of the uncertainties due to evolutionary models can be incorporated into the SFH uncertainties. This process relies on application of shifts in temperature and luminosity, the sizes of which must be calibrated for the data being analyzed. While there are inherent limitations, the ability to estimate the effect of systematic errors and include them in the overall uncertainty is significant. The effects of this are most notable in the case of shallow photometry, with which SFH measurements rely on evolved stars. © 2012. The American Astronomical Society. All rights reserved.
Guha S.,Raytheon Co.
Physical Review Letters | Year: 2011
Attaining the ultimate (Holevo) limit to the classical capacity of a quantum channel requires the receiver to make joint measurements over long code-word blocks. For a pure-state channel, we show that the Holevo limit can be attained by a receiver that uses a multisymbol unitary transformation on the quantum code word followed by separable projective measurements. We show a concatenated coding and joint-detection architecture to approach the Holevo limit. We then construct some of the first concrete examples of codes and structured joint-detection receivers for the lossy bosonic channel, which can achieve fundamentally higher (superadditive) capacity than conventional receivers that detect each modulation symbol individually. We thereby pave the way for research into codes and structured receivers for reliable communication data rates approaching the Holevo limit. © 2011 American Physical Society.
Rhiger D.R.,Raytheon Co.
Journal of Electronic Materials | Year: 2011
The InAs/GaSb family of type II superlattices (T2SL) is the only known infrared (IR) detector material having a theoretically predicted higher performance than HgCdTe. The Auger lifetime has been predicted to be much longer, offering the possibility of much lower dark currents. In this paper the present state of the technology for long-wavelength infrared (LWIR) applications is evaluated by examining the dark current density in LWIR T2SL diodes at 78 K as a function of device cutoff wavelength, and comparing it with the HgCdTe benchmark known as Rule 07. The dark current density remains greater than Rule 07, but it has rapidly decreased in recent years with advancing technology, particularly due to innovative barrier structures. © 2011 TMS.