Interstellar Mapping and Acceleration Probe (IMAP): A New NASA Mission

The Interstellar Mapping and Acceleration Probe (IMAP) is a revolutionary mission that simultaneously investigates two of the most important overarching issues in Heliophysics today: the acceleration of energetic particles and interaction of the solar wind with the local interstellar medium. While seemingly disparate, these are intimately coupled because particles accelerated in the inner heliosphere play critical roles in the outer heliospheric interaction. Selected by NASA in 2018, IMAP is planned to launch in 2024. The IMAP spacecraft is a simple sun-pointed spinner in orbit about the Sun-Earth L1 point. IMAP’s ten instruments provide a complete and synergistic set of observations to simultaneously dissect the particle injection and acceleration processes at 1 AU while remotely probing the global heliospheric interaction and its response to particle populations generated by these processes. In situ at 1 AU, IMAP provides detailed observations of solar wind electrons and ions; suprathermal, pickup, and energetic ions; and the interplanetary magnetic field. For the outer heliosphere interaction, IMAP provides advanced global observations of the remote plasma and energetic ions over a broad energy range via energetic neutral atom imaging, and precise observations of interstellar neutral atoms penetrating the heliosphere. Complementary observations of interstellar dust and the ultraviolet glow of interstellar neutrals further deepen the physical understanding from IMAP. IMAP also continuously broadcasts vital real-time space weather observations. Finally, IMAP engages the broader Heliophysics community through a variety of innovative opportunities. This paper summarizes the IMAP mission at the start of Phase A development.     

Studying the positioning accuracy for dynamic (moving) objects with the use of multifrequency oblique-incidence sounding of ionospheric radio channels by chirp signals

The paper presents the methods and algorithms for positioning the dynamic (moving) objects using the oblique-incidence ionospheric sounding by chirp signals. Full-scale experiments have been performed to determine a distance to an object and its location.     

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.     

Radio observations of total solar eclipse of November 3, 1994 at Chapecó (Brzil)

Radio observations of the eclipse on November 3, 1994, were carried out at Chapecó, Brazil by using a decimetric spectrograph having high spectral and time resolution. The light curve shows that: (1) Time variation of the radio flux before the totality was more compared to that after. (2) During the totality radio emission at 1.5 GHz was observed. Advantage of high spatial resolution ( 3.2 arc sec) possible during solar eclipse enabled us to determine the height of radio emission at 1.5 GHz. (3) Microwave bursts were observed associated with metric Type III-RS bursts. The source size of one of the microwave bursts was 7 arc sec and its physical parameters have been estimated. (4) The time difference between radio and optical contacts suggested for the first time asymmetrical limb brightening at 1.5 GHz.     

电磁辅助激光熔化沉积的残余应力

针对激光熔化沉积内部残余应力较大的问题,对其产生的机理作了分析。基于电磁场的应用原理,提出电磁辅助激光熔化沉积以降低其残余应力的方法。利用ANSYS参数化编程语言APDL模拟了电磁辅助激光熔化沉积的过程,分析了成形件残余应力的变化规律,结果表明同步加载轴向电磁力能较好地消减成形件内部残余应力。采用X射线衍射结合电解腐蚀的方法进行深度方向的残余应力测量试验,试验结果验证了电磁辅助的有效性。     

Optical Processing Techniques for Simultaneous Pulse Compression and Beam Sharpening

A technique is described in which the separate techniques of beam sharpening (by synthetic antenna methods) and pulse compression are converted into a single two-dimensional operation, which is carried out with a coherent optical processor.     

GEOS-1 observations of electrostatic waves,and their relationship with plasma parameters

In this paper we describe and discuss the occurrence of natural wave emissions detected by GEOS-1 at frequencies above the electron gyrofrequency. The bulk of the data presented comes from the first six months of satellite operation and thus concerns mainly dayside phenomena. The paper is arranged as follows:After some general remarks, a classification of the wave phenomena is developed in Section 2, and experimental evidence and morphological information relevant to this classification are contained in Section 3. Section 4 includes some preliminary comments on nightside observations. The results are discussed in Section 5, where it is argued that they can be understood as manifestations of electron cyclotron harmonic (Bernstein) wave emission in a plasma parameter range which has only very recently received any theoretical examinations. This theme is further developed in a comparison paper (Ronnmark et al., 1978).     

Sensitivity Reduction in Aircraft Control Systems

A method for reducing trajectory sensitivity to parameter perturbations for linear feedback systems is described. Application of the method to the design of aircraft control systems, with special reference to a helicopter forward flight control system, is illustrated. The response of the system based on this method is found to be better than that obtained with fixed-feedback gain controllers, although the response may not be as good as that of an adaptive control scheme. The main advantage of the method is the simplicity of its implementation relative to that of the adaptive control scheme which requires an on-board computer.     

Optimum Linear Estimation of Stochastic Signals in the Presence of Multiplicative Noise

This paper considers optimum (MMSE) linear recursive estimation of stochastic signals in the presence of multiplicative noise in addition to measurement noise. Often problems associated with phenomena such as fading or reflection of the transmitted signal at an ionospheric layer, and also situations involving sampling, gating, or amplitude modulation, can be cast into such formulation. The different kinds of estimation problems treated include one-stage prediction, filtering, and smoothing. Algorithms are presented for discrete time as well as for continuous time estimation.     

Spectral Analysis with Sinusoids and Walsh Functions

The Walsh spectrum of a sinusoid of frequency f = p/2q with p odd consists entirely of lines at orders s that are odd multiples of 2/2q, and the Fourier spectrum of a Walsh function of order 2p/2q consists entirely of lines at frequencies that are odd multiples of 1/2q. For all other frequencies or orders, the spectrum contains no lines, but the power spectral density takes all values in the range [0,oo] in every interval, however short, while being almost everywhere zero. For detecting the presence of a sinusoid by means of Walsh analysis, the time scale should therefore be chosen so that the order of the Walsh function is a power of 2 and the Walsh function is a Rademacher function, i.e., a hard-limited sinusoid of the frequency being sought.