Probing the solar wind acceleration region using spectroscopic techniques

Measurements of the intensities and profiles of UV and EUV spectral lines can provide a powerful tool for probing the physical conditions in the solar corona out to 8 R and beyond. We discuss here how measurements of spectral line radiation in conjunction with measurements of the white light K-corona can provide information on electron, proton and ion temperatures and velocity distribution functions; densities; chemical abundances and mass flow velocities. Because of the fundamental importance of such information, we provide a comprehensive review of the formation of coronal resonance line radiation, with particular emphasis on the H i L line, and discuss observational considerations such as requirements for rejection of stray light and effects of emission from the geocorona and interplanetary dust. Finally, we summarize some results of coronal H i L and white light observations acquired on sounding rocket flights.Paper presented at the IX-th Lindau Workshop The Source Region of the Solar Wind.     

The Goddard Range and Range Rate Tracking System: Concept,design and performance

This paper is concerned with the concept, evolution and performance analysis of a high-accuracy, near-earth and cislunar cooperative target tracking system, known as the Goddard Range and Range Rate System.This system combines the advantages of harmonic (or sidetone) and pseudo-random coded ranging signals in a highly effective and versatile manner, operable either as an all-harmonic system in near-earth orbital tracking or as a hybrid system for tracking more distant spacecraft. The system also combines the utilization of the two types of signals in a very attractive technique for speeding up the process of acquiring the ambiguity resolving code component in tracking spacecraft at cislunar and translunar distances.The theoretical analysis of system performance and errors is followed by a summary of performance data gathered to date by operating GRARR systems on a number of NASA missions.     

Onwards and upwards? The IAC 2012

The IAC, which in 2012 took place in Naples, has been going for 63 years. This report discusses some of the initiatives that have allowed it to continue successfully for so long, highlights some of the main events at the 2012 meeting and pinpoints a few problems that should be addressed.     

A prospectus for automatic target recognition

Aspects of autorecognition technology are discussed. The following topics are covered: The context and role of automatic target recognition (ATR), sensors and ATR systems, generic shape discrimination, countermeasures, and current capabilities. The authors conclude that the material supports a very favorable assessment of the power and importance of emerging ATR technology     

Sounding rocket experiment of bare electrodynamic tether system

An overview of a sounding rocket, S-520-25th, project on space tether technology experiment is presented. The project is prepared by an international research group consisting of Japanese, European, American, and Australian researchers. The sounding rocket will be assembled by the ISAS/JAXA and will be launched in the summer of 2009. The sounding rocket mission includes two engineering experiments and two scientific experiments. These experiments consist of the deployment of bare electrodynamic tape tether in space, a quick ignition test of hollow cathode system in space, the demonstration of bare electrodynamic tether system in space, and the test of the OML (orbital-motion-limit) current collection theory.     

Analysis of a Multiplicative Feed System for Monopulse Tracking Applications

In angle tracking antenna applications, the angle sensing boresight accuracy capabilities are important. The ability of an antenna to precisely determine the bearing angle to a point source is determined by the slope of the control function pattern at boresight. In the presence of extraneous interference, the magnitudes of the sidelobe and backlobe responses are important. Control pattern slope (angular sensitivity) is primarily a function of aperture illumination. It can be described by a current distribution in intensity and phase at every point. Once distribution is defined, lobe structure is defined by the associated transform. When more than one feed is used, the distribution will be a vector sum of the individual feed distributions. The resulting secondary pattern can be defined in terms of the amplitude distribution and the phase center locations of the contributing feeds. With a four-horn monopulse configuration, the feed phase centers are displaced from the boresight axis. Placing the phase centers on the boresight axis by rotating the feeds through 45 degrees results in a different set of intensity and phase values. A quite different secondary pattern results. The control function obtained by the subtraction of the powers from a paired set of on-axis feeds results in a lower sidelobe level than that obtained with a conventional monopulse combiner for a given feed taper.     

Cometary Dust

This review presents our understanding of cometary dust at the end of 2017. For decades, insight about the dust ejected by nuclei of comets had stemmed from remote observations from Earth or Earth’s orbit, and from flybys, including the samples of dust returned to Earth for laboratory studies by the Stardust return capsule. The long-duration Rosetta mission has recently provided a huge and unique amount of data, obtained using numerous instruments, including innovative dust instruments, over a wide range of distances from the Sun and from the nucleus. The diverse approaches available to study dust in comets, together with the related theoretical and experimental studies, provide evidence of the composition and physical properties of dust particles, e.g., the presence of a large fraction of carbon in macromolecules, and of aggregates on a wide range of scales. The results have opened vivid discussions on the variety of dust-release processes and on the diversity of dust properties in comets, as well as on the formation of cometary dust, and on its presence in the near-Earth interplanetary medium. These discussions stress the significance of future explorations as a way to decipher the formation and evolution of our Solar System.     

Electron density retrieval from occulting GNSS signals using a gradient-aided inversion technique

In the coming years, opportunities for remote sensing of electron density in the Earth’s ionosphere will expand with the advent of Galileo, which will become part of the global navigation satellite system (GNSS). Methods for accurate electron density retrieval from radio occultation data continue to improve. We describe a new method of electron density retrieval using total electron content measurements obtained in low Earth orbit. This method can be applied to data from dual-frequency receivers tracking the GPS or Galileo transmitters. This simulation study demonstrates that the method significantly improves retrieval accuracy compared to the standard Abel inversion approach that assumes a spherically symmetric ionosphere. Our method incorporates horizontal gradient information available from global maps of Total Electron Content (TEC), which are available from the International GNSS Service (IGS) on a routine basis. The combination of ground and space measurements allows us to improve the accuracy of electron density profiles near the occultation tangent point in the E and F regions of the ionosphere.     

Flying the Desk

The terminology ``flying the desk' has had a bad connotation for aviators over the years, inferring that a pilot has been relegated from the aircraft cockpit to an earthbound office. A unique advanced transport flight station design, described in this paper, could change that implication. The Lockheed-Georgia Company, in a joint project with NASA, has designed, developed, and fabricated a high fidelity flight station simulator for researching issues pertaining to transport aircraft of the mid-1990s and beyond. Early in the program the need and operational requirements for an advanced transport were identified, operating environments were forecast, and technologies available for application to future aircraft were projected. The flight station and all crew systems were designed and initially tested in a full scale mockup by operational line pilots. The refined design was then incorporated into three identical full-mission flight station simulators located at NASA's Ames and Langley Research Centers and at Lockheed's plant in Marietta, Georgia. These simulators contain the unique Pilot's Desk Flight Station design, a radical departure from traditional transport cockpits. The desk design resembles an office or laboratory workstation.     

The stretched lens array (SLA) [spacecraft solar power]

At IECEC 2001, this team presented a paper on the new stretched lens array (SLA), including its evolution from the successful SCARLET array on the NASA/JPL Deep Space 1 spacecraft. Since that conference, the SLA team has made significant advances in SLA technology, including component-level improvements, array-level optimization, space environment exposure testing, and prototype hardware fabrication and evaluation. This paper describes the evolved version of the SLA, highlighting recent improvements in the lens, solar cell, photovoltaic receiver, rigid panel structure, and complete solar array wing. In addition to excellent durability in the space environment, the near-term SLA will provide outstanding wing-level performance parameters: 180 W/kg specific power; 300 W/m/sup 2/ power density; 300 V operational voltage; 85% savings in cell area (cm/sup 2//W) and cell-related cost ($/W) compared to planar arrays; 9 kW/m/sup 3/ stowed power at launch.