Notes on SCPC-FM System Design and Performance

In many domestic satellite communication systems single-channel per-carrier FM (SCPC-FM) has become the accepted transmission method for thin route communication. The SCPC-FM modem operates over a wide range of carrier frequencies and is designed to use satellite power and bandwidth efficiently. It incorporates elements which make the signal transfer complex, so the system behavior is not immediately obvious. This article investigates the signal processes and analyzes the performance of a companded and preemphasized SCPC-FM system and it furnishes insight into the choice of crucial system parameters.     

A system for obstacle detection during rotorcraft low altitudeflight

An airborne vehicle such as a rotorcraft must avoid obstacles like antennas, towers, poles, fences, tree branches, and wires strung across the flight path. Automatic detection of the obstacles and generation of appropriate guidance and control actions for the vehicle to avoid these obstacles would facilitate autonomous navigation. The requirements of an obstacle detection system for rotorcraft in low-altitude Nap-of-the-Earth (NOE) flight based on various rotorcraft motion constraints is analyzed here in detail. It is argued that an automated obstacle detection system for the rotorcraft scenario should include both passive and active sensors to be effective. Consequently, it introduces a maximally passive system which involves the use of passive sensors (TV, FLIR) as well as the selective use of an active (laser) sensor. The passive component is concerned with estimating range using optical flow-based motion analysis and binocular stereo. The optical flow-based motion analysis that is combined with on-board inertial navigation system (INS) to compute ranges to visible scene points is described. Experimental results obtained using land vehicle data illustrate the particular approach to motion analysis     

Galileo Probe Measurements of D/H and 3He/4He in Jupiter's Atmosphere

The Galileo Probe Mass Spectrometer measurements in the atmosphere of Jupiter give D/H = (2.6 ± 0.7) × 10-5 3He/4He = (1.66 ± 0.05) × 10-4These ratios supercede earlier results by Niemann et al. (1996) and are based on a reevaluation of the instrument response at high count rates and a more detailed study of the contributions of different species to the mass peak at 3 amu. The D/H ratio is consistent with Voyager and ground based data and recent spectroscopic and solar wind (SW) values obtained from the Infrared Spectroscopic Observatory (ISO) and Ulysses. The 3He/4He ratio is higher than that found in meteoritic gases (1.5 ± 0.3) × 10-4. The Galileo result for D/H when compared with that for hydrogen in the local interstellar medium (1.6 ± 0.12) × 10-5 implies a small decrease in D/H in this part of the universe during the past 4.55 billion years. Thus, it tends to support small values of primordial D/H - in the range of several times 10-5 rather than several times 10-4. These results are also quite consistent with no change in (D+3He)/H during the past 4.55 billion years in this part of our galaxy.     

The Flight 2000 avionics suite: paving the way to free flight

The FAA's Flight 2000 project is an innovative initiative to implement and validate selected operational improvements leading to Free Flight. It integrates new avionics, new ground systems, new procedures, avionics certification, and operational approval. Approximately 2000 aircraft operating in Alaska, Hawaii, and Oceanic airspace will be equipped with new capabilities enabling benefits such as improved situational awareness, increased flexibility, and efficiency gains. By developing and fielding these operational improvements, the actual benefits of new procedures and capabilities will be validated and risks associated with national implementation will be reduced