Vertical Path Guidance Computer

A low-cost airborne computer which provides a multiangular glide path for the landing problem is independent of ILS or GCA methods. A barometric altitude signal is divided by slant-range information from a DME interrogator. The resulting ground-based angle is subtracted from the selected approach angle to provide the displayed departure from the glide path. Angular and lineal outputs are available. DME station position may be electrically offset to serve all airdrome runways. Theoretical and experimental results are presented     

The performance of the FGGE drifting buoy system

During the planning of the FGGE, certain objectives were set for various aspects of the performance of the Drifting Buoy Observing System, such as measurement accuracy, coverage and buoy lifetime. When preliminary results from the actual buoy array are reviewed it can be seen that these objectives were clearly satisfied for buoy reliability and sea temperature, and nearly satisfied for barometric pressure, but that complete coverage of the 20° to 65°S zone was never achieved. Nevertheless the performance of the array exceeded all expectations.     

High-Precision Laboratory Measurements Supporting Retrieval of Water Vapor,Gaseous Ammonia,and Aqueous Ammonia Clouds with the Juno Microwave Radiometer (MWR)

The NASA Juno mission includes a six-channel microwave radiometer system (MWR) operating in the 1.3–50 cm wavelength range in order to retrieve abundances of ammonia and water vapor from the microwave signature of Jupiter (see Janssen et al. 2016). In order to plan observations and accurately interpret data from such observations, over 6000 laboratory measurements of the microwave absorption properties of gaseous ammonia, water vapor, and aqueous ammonia solution have been conducted under simulated Jovian conditions using new laboratory systems capable of high-precision measurement under the extreme conditions of the deep atmosphere of Jupiter (up to 100 bars pressure and 505 K temperature). This is one of the most extensive laboratory measurement campaigns ever conducted in support of a microwave remote sensing instrument. New, more precise models for the microwave absorption from these constituents have and are being developed from these measurements. Application of these absorption properties to radiative transfer models for the six wavelengths involved will provide a valuable planning tool for observations, and will also make possible accurate retrievals of the abundance of these constituents during and after observations are conducted.     

Advances in Low-Frequency Radio Navigation Methods

Advances in the analysis and design of low-frequency radio navigation systems are presented in four sections detailing system design, propagation, receivers and processors, and error analyses. Emphasis is on the short-baseline case where radial accuracies of 114 feet are possible for non-line-of-sight operation to ranges of 50 miles from transmitters. Possibel future applications for LF include an efficient solution for commercial ground transportation management, remotely piloted vehicle navigation, and cruise missile guidance. An error budget and experimental results are included plus a countermeasures analysis.     

Long-term observations of the trapped high-energy proton population (L < 4) by the NOAA Polar Orbiting Environmental Satellites (POES)

The Space Environment Monitor (SEM) onboard the NOAA POES satellites has been measuring the near-Earth charged particle environment since 1978, providing an extensive database that can be used for studying the long-term behavior of this population of trapped particles. POES stands for Polar Orbiting Environmental Satellite. These satellites orbit at ∼840 km altitude and at an inclination of 98°. The SEM-1 instrument was flown on the POES satellites beginning in 1978 with TIROS-N and NOAA-6 in 1979 and continuing to NOAA-14 launched in 1995 with the exception of NOAA-9 and NOAA-11 (NOAA-13 failed shortly after launch). Its replacement, SEM-2, has flown on the POES NOAA-15, -16, and -17 satellites (from 1998). Here we present the results of a study on the statistical variations of the high-energy trapped proton environment. Among the detectors in SEM, the four SEM-2 omni-directional proton detectors for energies >16 MeV, >36 MeV, >70 MeV, and >140 MeV provide the data most relevant to this study.     

Adaptive Maximum Likelihood Receiver for Direct-Ranging Applications

Recent interest in direct-ranging navigation methods has prompted new research into practical receiver structures which provide improved signal processing. Maximum likelihood receivers are compared with conventional phase-locked receivers by theoretical and simulation methods as phase estimators based on signal measurements only. Signal-to-noise ratio (SNR) enhancement is examined and filter recommendations made. An adaptive maximum likelihood receiver is then developed which uses both signal measurements and a priori data to improve phase estimation accuracy. Simulation results indicate a 33.3 dB processing gain yielding a ranging error standard deviation of ±15 feet for zero dB received SNR. Nonadaptive and adaptive receivers are fabricated, flight tested, and experimental results reported.