Submicrosecond comparisons of time standards via the Navigation Technology Satellites (NTS)

An interim demonstration was performed of the time transfer capability of the NAVSTAR GPS system using a single NTS satellite. Measurements of time difference (pseudo-range) are made from the NTS tracking network and at the participating observatories. The NTS network measurements are used to compute the NTS orbit trajectory. The central NTS tracking station has a time link to the Naval Observatory UTC (USNO,MC1) master clock. Measurements are used with the NTS receiver at the remote observatory, the time transfer value UTC (USNO,MC1)-UTC (REMOTE, VIA NTS) is calculated. Intercomparisons were computed using predicted values of satellite clock offset and ephemeus

Submicrosecond comparison of international clock synchronization by VLBI and the NTS satellite

The intercontinental clock synchronization capabilities of Very Long Baseline Interferometry (VLBI) and the Navigation Technology Satellite (NTS) were compared using both methods to synchronize the Cesium clocks at the NASA Deep Space Net complexes at Madrid, Spain and Goldstone, California. Verification of the accuracy of both systems was examined. The VLBI experiments used the Wideband VLBI Data Acquisition System developed at the NASA Jet Propulsion Laboratory. The NTS Satellites were designed and built by the Naval Research Laboratory used with NTS Timing Receivers developed by the Goddard Space Flight Center. The two methods agreed at about the one-half microsecond level

Betty Jean Oaks Talking About Farm Life in Primera, Cameron County, Texas During 1920s and 1930s

An interview with Betty Jean (Hamilton) Oaks, an RGV community member, explores her experience in the border region. Conducted by Ruby Aguilar, a local school teacher participating in the Porciones to Colonias project. Betty Jean was born in 1925 in Primera, TX. Mrs. Oaks provides an overview of her genealogy and describes farm life in the Valley, providing details about crops and harvests, transportation, local businesses, and more. Betty J. Oaks was interviewed by Ruby A. Aguilar. Mayra Zepeda (videographer)https://scholarworks.utrgv.edu/chapsoralhistories/1109/thumbnail.jp

The Plants Database: Providing Basic Plant Information

The PLANTS database provides basic plant information to the United States Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS), its clients, cooperators, and the general public via the World Wide Web (Fig. 1). The foundation of PLANTS is a taxonomic backbone (checklist) of the vascular and nonvascular plants of North America (north of Mexico) and United States territories in the Caribbean and Pacific regions. Attribute data are appended to this backbone pertaining to distribution, vegetative specifications, nativity, federal and state status, crop data, growth form, growth parameters, species abstracts, and images

Global Positioning System Time Transfer Receiver (GPS/TTR) prototype design and initial test evaluation

Time transfer equipment and techniques used with the Navigation Technology Satellites were modified and extended for use with the Global Positioning System (GPS) satellites. A prototype receiver was built and field tested. The receiver uses the GPS L1 link at 1575 MHz with C/A code only to resolve a measured range to the satellite. A theoretical range is computed from the satellite ephemeris transmitted in the data message and the user's coordinates. Results of user offset from GPS time are obtained by differencing the measured and theoretical ranges and applying calibration corrections. Results of the first field test evaluation of the receiver are presented

Association between Dietary Magnesium Intake and Glycemic Markers in Ghanaian Women of Reproductive Age: A Pilot Cross-Sectional Study

Low magnesium intake has been shown to be associated with an increased risk of type 2 diabetes mellitus (T2DM) in several studies conducted in high-income countries. However, very few studies have been performed in Africa, where many countries have a growing rate of T2DM. We conducted a pilot cross-sectional study among 63 women in Ghana to investigate the association between magnesium intake and glycemic markers. We assessed dietary magnesium using a food frequency questionnaire and glycemic markers using fasting blood glucose and glycated hemoglobin A1c (HbA1c). Our findings showed that the mean magnesium intake was 200 ± 116 mg/day. The prevalence of T2DM was 5% by measuring fasting blood glucose and 8% by measuring HbA1c. Unadjusted linear regression models revealed that higher magnesium intake significantly predicted higher fasting blood glucose levels (β = 0.31; 95% CI: 0.07, 0.55; p = 0.01) and HbA1c levels (β = 0.26; 95% CI: 0.01, 0.51; p = 0.04). In adjusted analyses, magnesium intake was no longer significantly associated with either fasting blood glucose levels (β = 0.22; 95% CI: −0.03, 0.46; p = 0.08) or HbA1c levels (β = 0.15; 95% CI: −0.08, 0.39; p = 0.20). In conclusion, our study did not show a significant association between magnesium intake and glycemic markers in women of reproductive age in Ghana. The results of this study need to be further substantiated because this was the first study to examine magnesium intake and glycemic markers in this population in Africa

Common View Time Transfer Using Worldwide GPS and DMA Monitor Stations

Analysis of the on-orbit Navstar clocks and the Global Positioning System (GPS) monitor station reference clocks is performed by the Naval Research Laboratory using both broadcast and postprocessed precise ephemerides. The precise ephemerides are produced by the Defense Mapping Agency (DMA) for each of the GPS space vehicles from pseudo-range measurements collected at five GPS and at five DMA monitor stations spaced around the world. Recently, DMA established an additional site co-located with the US Naval Observatory precise time site. The time reference for the new DMA site is the DoD Master Clock. Now, for the first time, it is possible to transfer time every 15 minutes via common view from the DoD Master Clock to the 11 GPS and DMA monitor stations. The estimated precision of a single common-view time transfer measurement taken over a 15-minute interval was between 1.4 and 2.7 nanoseconds. Using the measurements from all Navstar space vehicles in common view during the 15-minute interval, typically 3-7 space vehicles, improved the estimate of the precision to between 0.65 and 1.13 nanoseconds. The mean phase error obtained from closure of the time transfer around the world using the 11 monitor stations and the 25 space vehicle clocks over a period of 4 months had a magnitude of 31 picoseconds. Analysis of the low noise time transfer from the DoD Master Clock to each of the monitor stations yields not only the bias in the time of the reference clock, but also focuses attention on structure in the behaviour of the reference clock not previously seen. Furthermore, the time transfer provides a a uniformly sampled database of 15-minute measurements that make possible, for the first time, the direct and exhaustive computation of the frequency stability of the monitor station reference clocks. To lend perspective to the analysis, a summary is given of the discontinuities in phase and frequency that occurred in the reference clock at the Master Control Station during the period covered by the analysis

GPS Moving Vehicle Experiment

The Naval Research Laboratory (NRL) in the development of timing systems for remote locations, had a technical requirement for a Y code (SA/AS) Global Positioning System (GPS) precise time transfer receiver (TTR) which could be used both in a stationary mode or mobile mode. A contract was awarded to the Stanford Telecommunication Corporation (STEL) to build such a device. The Eastern Range (ER) als had a requirement for such a receiver and entered into the contract with NRL for the procurement of additional receivers. The Moving Vehicle Experiment (MVE) described in this paper is the first in situ test of the STEL Model 5401C Time Transfer System in both stationary and mobile operations. The primary objective of the MVE was to test the timing accuracy of the newly developed GPS TTR aboard a moving vessel. To accomplish this objective, a joint experiment was performed with personnel from NRL and the er at the Atlantic Undersea Test and Evaluation Center (AUTEC) test range at Andros Island. Results and discussion of the test are presented in this paper