IMMPDAF for radar management and tracking benchmark with ECM

A framework is presented for controlling a phased array radar for tracking highly maneuvering targets in the presence of false alarms (FAs) and electronic countermeasures (ECMs). Algorithms are presented for track formation and maintenance; adaptive selection of target revisit interval, waveform and detection threshold; and neutralizing techniques for ECM, namely, against a standoff jammer (SOJ) and range gate pull off (RGPO). The interacting multiple model (IMM) estimator in combination with the probabilistic data association (PDA) technique is used for tracking. A constant false alarm rate (CFAR) approach is used to adaptively select the detection threshold and radar waveform, countering the effect of jammer-induced false measurements. The revisit interval is selected adaptively, based on the predicted angular innovation standard deviations. This tracker/radar-resource-allocator provides a complete solution to the benchmark problem for target tracking and radar control. Simulation results show an average sampling interval of about 2.5 s while maintaining a track loss less than the maximum allowed 4%     

Telemetry Transmitters Using Solid-State Wideband Microwave Voltage-Controlled Oscillators

A practical approach for meeting the immediate and future needs of communication systems that require very wideband transmitters capable of operating in the S-, C-, and X-band frequency ranges is described. Included are: 1) a review of the basic studies conducted to determine the most practical transmitter approach for wideband applications; 2) a discussion of a prototype 10-watt frequency-modulated transmitter developed to demonstrate the feasibility of a wideband system; and 3) a review of the preliminary computer analyses and empirical results obtained on the development of a unit capable of wide deviation with reasonable linearity at baseband frequencies up to 10 Megahertz.     

Why explore Venus?

This paper develops the rationale for a program of Venus exploration by man.     

Statistical properties of the IMF clock angle in the solar wind with northward and southward interplanetary magnetic field based on ACE observation from 1998 to 2009: Dependence on the temporal scale of the solar wind

Utilizing ACE satellite observations from 1998 to 2009, we performed the elaborate study on the properties of the clock angle θ_CA (arctan(By/Bz) (?90° to 90°) of the interplanetary magnetic field (IMF) in the solar wind at 1?AU. The solar wind with northward IMF (NW-IMF) and southward IMF (SW-IMF) are analyzed, independently. Statistical analysis shows that the solar wind with SW-IMF and NW-IMF has similar properties in general, including their durations, the IMF Bz and By components, and the IMF θ_CA. Then, the solar wind with NW-IMF (SW-IMF) is classified into five different temporal scales according to the duration of the NW-IMF (SW-IMF), i.e., very-short wind of 10–30?min, short-scale wind of 0.5–1?h, moderate-scale wind of 1–3?h, long-scale wind of 3–5?h, and super-long wind >5?h. Our analysis reveals that the IMF θ_CA has a distinct decrease with increase of the temporal scale of the solar wind. Next, the solar wind is classified into two groups, i.e., the high-speed solar wind (>450?km/s) and the low-speed solar wind (<450?km/s). Our analysis indicates that the IMF θ_CA depends highly on the solar wind speed. Statistically, high-speed solar wind tends to have larger IMF θ_CA than low-speed solar wind. The evolutions of the solar wind and IMF with the solar activity are further studied, revealing no clear solar variation of the IMF θ_CA. Finally, we analyze the monthly variation of the IMF θ_CA. Superposed epoch result strongly suggests the seasonal variation of the IMF θ_CA.     

Enhancing the ATIC charge resolution

The Advanced Thin Ionization Calorimeter (ATIC) experiment is designed to investigate the charge composition and energy spectra of primary cosmic rays over the energy range from about 10¹¹ to 10¹⁴ eV during Long Duration Balloon (LDB) flights from McMurdo, Antarctica. Currently, analysis from the ATIC-1 test flight and ATIC-2 science flight is underway and preparation for a second science flight is in progress. Charge identification of the incident cosmic ray is accomplished, primarily, by a pixilated Silicon Matrix detector located at the very top of the instrument. While it has been shown that the Silicon Matrix detector provides good charge identification even in the presence of electromagnetic shower backscatter from the calorimeter, the detector only measures the charge once. In this paper, we examine use of the top scintillator hodoscope detector to provide a second measure of the cosmic ray charge and, thus, improve the ATIC charge identification.     

CREAM: 70 days of flight from 2 launches in Antarctica

The Cosmic-Ray Energetics And Mass balloon-borne experiment has been launched twice in Antarctica, first in December 2004 and again in December 2005. It circumnavigated the South Pole three times during the first flight, which set a flight duration record of 42 days. A cumulative duration of 70 days within 13 months was achieved when the second flight completed 28 days during two circumnavigations of the Pole on 13 January 2006. Both the science instrument and support systems functioned extremely well, and a total 117 GB of data including 67 million science events were collected during these two flights. Preliminary analysis indicates that the data extend well above 100 TeV and follow reasonable power laws. The payload recovered from the first flight has been refurbished for the third flight in 2007, whereas the payload from the second flight is being refurbished to be ready for the fourth flight in 2008. Each flight will extend the reach of precise cosmic-ray composition measurements to energies not previously possible.     

Gamma-ray detector on board lunar mission Chang’E-1

Gamma-ray spectrometer (GRS) is included in the payload of Chinese first lunar mission Chang’E-1 that will be launched in 2007. Specific objectives of the GRS are to map abundance of O, Si, Fe, Ti, U, Th, K, and perhaps, Mg, Al, and Ca to depths of about 20 cm. There are remarkable advantages for GRS application to remote sensing elemental materials over the entire lunar surface: large effective area and good ability for background rejection. We will describe the design of GRS and present its performance in this paper. Moreover, the GRS calibration will also be introduced.     

Magnetospheric electric field variations caused by storm-time shock fronts

On January 20, 2005 there was an X 7.1 solar flare at 0636 UT with an accompanied halo coronal mass ejection (CME). The resultant interplanetary shock impacted earth ∼36 h later. Near earth, the Advanced Composition Explorer (ACE) spacecraft observed two impulses with a staircase structure in density and pressure. The estimated earth-arrival times of these impulses were 1713 UT and 1845 UT on January 21, 2005. Three MINIature Spectrometer (MINIS) balloons were aloft on January 21st; one in the northern polar stratosphere and two in the southern polar stratosphere. MeV relativistic electron precipitation (REP) observed by all three balloons is coincident (<3 min) with the impulse arrivals and magnetospheric compression observed by both GOES 10 and 12. Balloon electric field data from the southern hemisphere show no signs of the impulse electric field directly reaching the ionosphere. Enhancement of the balloon-observed convection electric field by as much as 40 mV/m in less than 20 min during this time period is consistent with typical substorm growth. Precipitation-induced ionospheric conductivity enhancements are suggested to be (a) the result of both shock arrival and substorm activity and (b) the cause of rapid (<6 min) decreases in the observed electric field (by as much as 40 mV/m). There is poor agreement between peak cross polar cap potential in the northern hemisphere calculated from Super Dual Auroral Radar Network (SuperDARN) echoes and horizontal electric field at the MINIS balloon locations in the southern hemisphere. Possible reasons for this poor agreement include (a) a true lack of north–south conjugacy between measurement sites, (b) an invalid comparison between global (SuperDARN radar) and local (MINIS balloon) measurements and/or (c) radar absorption resulting from precipitation-induced D-region ionosphere density enhancements.     

Temperature effects in the ATIC BGO calorimeter

The Advanced Thin Ionization Calorimeter (ATIC) Balloon Experiment had a successful test flight and a science flight in 2000–01 and 2002–03 and an unsuccessful launch in 2005–06 from McMurdo, Antarctica, returning 16 and 19 days of flight data. ATIC is designed to measure the spectra of cosmic rays (protons to iron). The instrument is composed of a Silicon matrix detector followed by a carbon target interleaved with scintillator tracking layers and a segmented BGO calorimeter composed of 320 individual crystals totaling 18 radiation lengths to determine the particle energy. BGO (Bismuth Germanate) is an inorganic scintillation crystal and its light output depends not only on the energy deposited by particles but also on the temperature of the crystal. The temperature of balloon instruments during flight is not constant due to sun angle variations as well as differences in albedo from the ground. The change in output for a given energy deposit in the crystals in response to temperature variations was determined.     

Unusually strong magnetic fields in Titan’s ionosphere: T42 case study

Observations of unusually large magnetic fields in the ionosphere indicate periods of maximum stress on Titan’s ionosphere and potentially of the strongest loss rates of ionospheric plasma. During Titan flyby T42, the observed magnetic field attained a maximum value of 37 nT between an altitude of 1200 and 1600 km, about 20 nT stronger than on any other Titan pass and close to five times greater in magnetic pressure. The strong fields occurred near the corotation-flow terminator rather than at the sub-flow point, suggesting that the flow which magnetized the ionosphere was from a direction far from corotation and possibly towards Saturn. Extrapolation of solar wind plasma conditions from Earth to Saturn using the University of Michigan MHD code predicts an enhanced solar wind dynamic pressure at Saturn close to this time. Cassini’s earlier exits from Saturn’s magnetosphere support this prediction because the Cassini Plasma Spectrometer instrument saw a magnetopause crossing three hours before the strong field observation. Thus it appears that Titan’s ionosphere was magnetized when the enhanced solar wind dynamic pressure compressed the Saturnian magnetosphere, and perhaps the magnetosheath magnetic field, against Titan. The solar wind pressure then decreased, leaving a strong fossil field in the ionosphere. When observed, this strong magnetic flux tube had begun to twist, further enhancing its strength.