A new clutter rejection method using a robust polarimetricCFAR-detector

Two methods for constructing robust polarimetric constant-false-alarm-rate (CFAR) detectors that use elements of the scattering matrix are discussed. Both methods use robust estimators to recognize outliers and exclude them from further calculations. The first method weighs each sample of the surrounding vectors, and vectors that appear to be outliers are weighted with lower values than the others. The second method uses cluster algorithms to arrange the data in different clusters; some clusters contain the outliers, and others contain observations assumed to come from the main body of the data. The detectors are intended to be used in multitarget and nonhomogeneous-clutter environments     

On-board statistical detection and compensation of anomalous pilot-aircraft interactions

A statistical method for the on-board detection and compensation of adverse oscillations in pilot-aircraft systems is presented. A recursively updated linear model representing the pilot-aircraft system is used to continuously check for stability loss. The instability-related oscillations are detected early, using a statistical hypothesis test. Furthermore, a specially designed stability augmentation system assists the pilot during the instability periods. The method's effectiveness is demonstrated via data obtained from a flight simulator and a detailed simulation model.     

MEMS Electronically Steerable Antennas for Fire Control Radars

Large apertures are of great benefit to applications that are prime powered limited as is found on aerostat and other airborne platforms. Electronically scanned array antennas are often proposed for these applications. However, increasing the aperture area with conventional array technology is met with prohibitive cost, weight, and prime power increases because of the dense spacing of phase shifters and/or active T/R modules. This discusses the recent development of RF MEMS (Microelectromechanical System) switch technology and the use of these switches in a Radanttrade lens configuration for arrays of approximately 10 m² at X-band. A proof-of-concept 0.4 m² MEMS Electronically Steerable Antenna (ESA) containing 25,000 MEMS switches has been successfully designed, fabricated, and tested. The 0.4 m² MEMS ESA was then integrated with an AN/APG-67 radar system to form the MEMS Demonstration Radar System. The MEMS Demonstration Radar System successfully detected both airborne and ground moving targets during a series of extensive radar demonstrations. This is believed to be the first large scale employment of MEMS switches in a scanning antenna and radar system. The low-cost, lightweight, and low power technology demonstrated can enable weight and power constrained platforms with electronic steering.     

Recent Breakthroughs in RF Photonics for Radar Systems

Radar systems require transmission of very high purity signals. Photonics is now mature enough to achieve analog transmission with very low noise, strong immunity, and wide-bandwidth even in harsh environments. We present our recent developments of optimized optical links dedicated to radar and multifunction systems     

Utilization of white potatoes in CELSS.

Potatoes (Solanum tuberosum) have a strong potential as a useful crop species in a functioning CELSS. The cultivar Denali has produced 37.5 g m-2 d-1 when grown for 132 days with the first 40 days under a 12-h photoperiod and a light:dark temperature cycle of 20 degrees C:16 degrees C, and then 92 days under continuous irradiance and a temperature of 16 degrees C. Irradiance was at 725 micromoles m-2 s-1 PPF and carbon dioxide at 1000 micromoles mol-1. The dried tubers had 82% carbohydrates, 9% protein and 0.6% fat. Other studies have shown that carbon dioxide supplementation (1000 micromoles mol-1) is of significant benefit under 12-h irradiance but less benefit under 24 h irradiance. Irradiance cycles of 60 minutes light and 30 minutes dark caused a reduction of more than 50% in tuber weight compared to cycles of 16 h light and 8 h dark. A diurnal temperature change of 22 degrees C for the 12-h light period to 14 degrees C during the 12-h dark period gave increased yields of 30% and 10% for two separate cultivars, compared with plants grown under a constant 18 degrees C temperature. Cultivar screening under continuous irradiance and elevated temperatures (28 degrees C) for 8 weeks of growth indicated that the cvs Haig, Denali, Atlantic, Desiree and Rutt had the best potential for tolerance to these conditions. Harvesting of tubers from plants at weekly intervals, beginning at 8 weeks after planting, did not increase yield over a single final harvest. Spacing of plants on 0.055 centers produced greater yield per m2 than spacing at 0.11 or 0.22 m2. Plants maintained 0.33 meters apart (0.111 m2 per plant) in beds produced the same yields when separated by dividers in the root matrix as when no separation was made.     

Propagation and interaction of interplanetary transient disturbances. Numerical simulations

We study the heliocentric evolution of ICME-like disturbances and their associated transient forward shocks (TFSs) propagating in the interplanetary (IP) medium comparing the solutions of a hydrodynamic (HD) and magnetohydrodynamic (MHD) models using the ZEUS-3D code [Stone, J.M., Norman, M.L., 1992. Zeus-2d: a radiation magnetohydrodynamics code for astrophysical flows in two space dimensions. i – the hydrodynamic algorithms and tests. Astrophysical Journal Supplement Series 80, 753–790]. The simulations show that when a fast ICME and its associated IP shock propagate in the inner heliosphere they have an initial phase of about quasi-constant propagation speed (small deceleration) followed, after a critical distance (deflection point), by an exponential deceleration. By combining white light coronograph and interplanetary scintillation (IPS) measurements of ICMEs propagating within 1 AU [Manoharan, P.K., 2005. Evolution of coronal mass ejections in the inner heliosphere: a study using white-light and scintillation images. Solar Physics 235 (1–2), 345–368], such a critical distance and deceleration has already been inferred observationally. In addition, we also address the interaction between two ICME-like disturbances: a fast ICME 2 overtaking a previously launched slower ICME 1. After interaction, the leading ICME 1 accelerates and the tracking ICME 2 decelerates and both ICMEs tend to arrive at 1 AU having similar speeds. The 2-D HD and MHD models show similar qualitative results for the evolution and interaction of these disturbances in the IP medium.     

Synthetic Environments for Simulated Missions

Synthetic environments offer Space Flight projects an opportunity to perform rapid, comprehensive, and rigorous modeling of the critical elements of a mission in order to compute quantitative measures of design performance, associated risk, and actual mission utility value. Significantly, these studies can be performed early in the mission cycle. These synthetic terrains are generated on parallel, high-performance computers and served to remote simulations at near-interactive speeds. The terrain creation uses a realistic sequence of physical phenomena such as cratering and dusting with parametric control of features such as surface roughness and rock density. Terrain resolution may be arbitrary but typically ranges from 0.01 to 10 meters. The terrain server has been used for two rover simulations, one using the actual Sojourner autonomy flight code, and the other a more general algorithm. Monte Carlo studies of rover designs interacting with synthetic environments were executed in parallel to quickly compute performance statistics and risk estimates.     

Microgravity particle research on the space station: the Gas-Grain Simulation Facility.

In the gravitational field on Earth, the large settling rate of micron-sized particles and the effects of gravity-induced convection prohibit many interesting studies of phenomena such as coagulation, collisions, and mutual interactions of droplets, dust grains and other particles. Examples of exobiology experiments involving these phenomena are the simulation of organic aerosol formation in Titan's atmosphere, studies of the role of comets in prebiotic chemical evolution, and simulations of carbon grain interactions in various astrophysical environments. The Gas-Grain Simulation Facility (GGSF) is a proposed Earth-orbital laboratory that will allow present ground-based experimental programs which study processes involving small particles and weak interactions to be extended to a new domain. Physics issues that scientists wishing to propose GGSF experiments must consider are reviewed in this paper. Specifically, coagulation, motion in gases and vacua, and wall deposition of particles in a microgravity environment are discussed.     

Instrumentation for investigation of the depth-dose distribution by the Liulin-5 instrument of a human phantom on the Russian segment of ISS for estimation of the radiation risk during long term space flights.

Described is the Liulin-5 experiment and instrumentation, developed for investigation of the space radiation doses depth distribution in a human phantom on the Russian Segment of the International Space Station (ISS). Liulin-5 experiment is a part of the international project MATROSHKA-R on ISS. The experiment MATROSHKA-R is aimed to study the depth dose distribution at the sites of critical organs of the human body, using models of human body-anthropomorphic and spherical tissue-equivalent phantoms. The aim of Liulin-5 experiment is long term (4-5 years) investigation of the radiation environment dynamics inside the spherical tissue-equivalent phantom, mounted in different places of the Russian Segment of ISS. Energy deposition spectra, linear energy transfer spectra, flux and dose rates for protons and the biologically-relevant heavy ion components of the galactic cosmic radiation will be measured simultaneously with near real time resolution at different depths of the phantom by a telescope of silicon detectors. Data obtained together with data from other active and passive dosimeters will be used to estimate the radiation risk to the crewmembers, verify the models of radiation environment in low Earth orbit, validate body transport model and correlate organ level dose to skin dose. Presented are the test results of the prototype unit. The spherical phantom will be flown on the ISS in 2004 year and Liulin-5 experiment is planned for 2005 year.