A precision DC-potentiometer microwave insertion-loss test set

Precision dc potentiometer microwave insertion loss test set for calibrating low noise microwave receiving systems used in space communication

DSN G/T(sub op) and telecommunications system performance

Provided here is an intersystem comparison of present and evolving Deep Space Network (DSN) microwave receiving systems. Comparisons of the receiving systems are based on the widely used G/T sub op figure of merit, which is defined as antenna gain divided by operating system noise temperature. In 10 years, it is expected that the DSN 32 GHz microwave receiving system will improve the G/T sub op performance over the current 8.4 GHz system by 8.3 dB. To compare future telecommunications system end-to-end performance, both the receiving systems' G/T sub op and spacecraft transmit parameters are used. Improving the 32 GHz spacecraft transmitter system is shown to increase the end-to-end telecommunications system performance an additional 3.2 dB, for a net improvement of 11.5 dB. These values are without a planet in the field of view (FOV). A Saturn mission is used for an example calculation to indicate the degradation in performance with a planet in the field of view

Single- and dual-carrier microwave noise abatement in the deep space network

The NASA/JPL Deep Space Network (DSN) microwave ground antenna systems are presented which simultaneously uplink very high power S-band signals while receiving very low level S- and X-band downlinks. Tertiary mechanisms associated with elements give rise to self-interference in the forms of broadband noise burst and coherent intermodulation products. A long-term program to reduce or eliminate both forms of interference is described in detail. Two DSN antennas were subjected to extensive interference testing and practical cleanup program; the initial performance, modification details, and final performance achieved at several planned stages are discussed. Test equipment and field procedures found useful in locating interference sources are discussed. Practices deemed necessary for interference-free operations in the DSN are described. Much of the specific information given is expected to be easily generalized for application in a variety of similar installations. Recommendations for future investigations and individual element design are given

E-Commerce Taxation Issues: A Balanced Perspective and Options for Resolution

This paper is designed to give the reader a balanced perspective on some of the issues surrounding the current discussions related to state and local taxation of Internet access fees and sales transactions on the Internet. The paper will attempt to describe the issues being discussed and present several viewpoints from interest groups on both sides of the issue. The paper is being written at an interesting time, since the Advisory Commission on Electronic Commerce is scheduled to meet in two weeks in Dallas and shape its final recommendations to Congress, which are due in April 2000. Taxation of Internet access and transactions on the Internet is one of the most complicated public policy issues of our time, affecting over 30,000 state and local taxing jurisdictions and literally thousands of businesses and customers worldwide. The paper will develop a next steps strategy to be considered by policy makers

Ultralow noise performance of an 8.4-GHz maser-feedhorn system

A total system noise temperature of 6.6 K was demonstrated with an 8.4-GHz traveling wave maser and feedhorn operating in a cryogenic environment. Both the maser and feedhorn were inserted in the helium cryostat, with the maser operating in the 1.6-K liquid bath and the feedhorn cooled in the helium gas, with a temperature gradient along the horn ranging from the liquid bath temperature at its lower end to room temperature at its top. The ruby maser exhibited 43 dB of gain with a bandwidth of 76 MHz(-3 dB) centered at 8400 MHz. Discussions of the maser, cooled feedhorn, and cryostat designs are presented along with a discussion of the noise temperature measurements

Selective self-categorization: Meaningful categorization and the in-group persuasion effect

Research stemming from self-categorization theory (Turner et al., 1987) has demonstrated that individuals are typically more persuaded by messages from their in-group than by messages from the out-group. The present research investigated the role of issue relevance in moderating these effects. In particular, it was predicted that in-groups would only be more persuasive when the dimension on which group membership was defined was meaningful or relevant to the attitude issue. In two studies, participants were presented with persuasive arguments from either an in-group source or an out-group source, where the basis of the in-group/out-group distinction was either relevant or irrelevant to the attitude issue. Participants' attitudes toward the issue were then measured. The results supported the predictions: Participants were more persuaded by in-group sources than out-group sources when the basis for defining the group was relevant to the attitude issue. However, when the defining characteristic of the group was irrelevant to the attitude issue, participants were equally persuaded by in-group and out-group sources. These results support the hypothesis that the fit between group membership and domain is an important moderator of self-categorization effects

Optical Spectroscopic Survey of High-latitude WISE-selected Sources

We report on the results of an optical spectroscopic survey at high Galactic latitude (|b| ≥ 30°) of a sample of WISE-selected targets, grouped by WISE W1 (λ_eff = 3.4 μm) flux, which we use to characterize the sources WISE detected. We observed 762 targets in 10 disjoint fields centered on ultraluminous infrared galaxy candidates using DEIMOS on Keck II. We find 0.30 ± 0.02 galaxies arcmin–2 with a median redshift of z = 0.33 ± 0.01 for the sample with W1 ≥ 120 μJy. The foreground stellar densities in our survey range from 0.23 ± 0.07 arcmin–2 to 1.1 ± 0.1 arcmin–2 for the same sample. We obtained spectra that produced science grade redshifts for ≥90% of our targets for sources with W1 flux ≥120 μJy that also had an i-band flux gsim 18 μJy. We used this for targeting very preliminary data reductions available to the team in 2010 August. Our results therefore present a conservative estimate of what is possible to achieve using WISE's Preliminary Data Release for the study of field galaxies