scispace - formally typeset
Search or ask a question
Author

Daniel J. Hoppe

Other affiliations: Jet Propulsion Laboratory
Bio: Daniel J. Hoppe is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Antenna (radio) & NASA Deep Space Network. The author has an hindex of 16, co-authored 77 publications receiving 1046 citations. Previous affiliations of Daniel J. Hoppe include Jet Propulsion Laboratory.


Papers
More filters
Journal ArticleDOI
01 Aug 2015
TL;DR: In this article, the authors developed a precision pulsar timing backend for the NASA Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to time pulses from an ensemble of MSPs.
Abstract: Abstract Millisecond pulsars (MSPs) are a class of radio pulsars with extremely stable rotation. Their excellent timing stability can be used to study a wide variety of astrophysical phenomena. In particular, a large sample of these pulsars can be used to detect low-frequency gravitational waves. We have developed a precision pulsar timing backend for the NASA Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to time pulses from an ensemble of MSPs. The DSN operates clusters of large dish antennas (up to 70-m in diameter), located roughly equidistant around the Earth, for communication and tracking of deep-space spacecraft. The backend system will be capable of removing entirely the dispersive effects of propagation of radio waves through the interstellar medium in real-time. We will describe our development work, initial results, and prospects for future observations over the next few years.
Proceedings ArticleDOI
15 Mar 2023
TL;DR: In this article , the authors describe the development, characterization, and integration of a 16-channel, 400-μm diameter active area, double-ended read-out NbTiN superconducting nanowire single-photon detector (SNSPD) array and the supporting electronics used in an RF/Optical hybrid telescope for deep-space laser communications.
Abstract: In this work we describe the development, characterization, and integration of a 16-channel, 400-μm diameter active area, double-ended read-out NbTiN superconducting nanowire single-photon detector (SNSPD) array and the supporting electronics used in an RF/Optical hybrid telescope for deep-space laser communications. This is the first fielddemonstration of a multi-channel, co-wound, double-ended read-out SNSPD array. With the number and complexity of future space exploration missions expected to increase, NASA is investigating ways to augment the information capacity of the Deep Space Network (DSN) global array of RF receivers used to track and communicate with these spacecrafts. Optical communication offers a path toward increasing the overall bandwidth of the DSN while allowing for higher data throughput for the same size weight and power (SWAP) transmitter on the spacecraft. NASA’s RF/Optical Hybrid (RFO) program proposes using a segmented, 8-10-meter equivalent aperture primary mirror mounted on existing 34- meter diameter beam waveguide (BWG) RF antennas to couple light into photon counting detectors for pulse position modulation (PPM) and on-off keying (OOK) data formats. JPL has deployed a pathfinder hybrid telescope on a DSN BWG antenna in Goldstone, California. The pathfinder couples light from a 1.2-meter effective diameter, 7-hexagonalsegment mirror assembly to a 400-μm core graded-index multimode fiber. This fiber is then routed to a cryostat and coupled to an SNSPD array through free-space optics. Coupling from a large diameter fiber to an SNSPD array while maintaining a small number of readout channels from the cryostat presents some unique challenges for the SNSPD array and receiver design.
01 Oct 2005
TL;DR: For the past 2 years, NASA has invested substantial resources to study the design and performance of the Terrestrial Planet Finder Coronagraph (TPF-C) as mentioned in this paper, which has achieved 1e-9 contrast in a laboratory experiment.
Abstract: For the past 2 years, NASA has invested substantial resources to study the design and performance of the Terrestrial Planet Finder Coronagraph (TPF-C). The work, led by the Jet Propulsion Laboratory with collaboration from Goddard Space Flight Center and several university and commercial entities, encompasses observatory design, performance modeling, materials characterization, primary mirror studies, and a significant technology development effort including a high-contrast imaging testbed that has achieved 1e-9 contrast in a laboratory experiment.
Proceedings ArticleDOI
18 Jun 1995
TL;DR: In this article, the finite element method (FEM) is used in conjunction with the method of moments (MoM) and the mode matching technique (MM) to calculate reflection coefficients and radiation patterns for axisymmetric waveguide fed horns.
Abstract: The finite element method (FEM) is used in conjunction with the method of moments (MoM) and the mode matching technique (MM) to calculate reflection coefficients and radiation patterns for axisymmetric waveguide fed horns. The coupling of FEM to the MoM, on one hand, and the coupling of the FEM to the MM, on the other, are performed by using boundary integrals. One advantage of this approach is that it allows for the presence of inhomogeneous materials to be included in the modelling domain as this poses no special problems for the FEM. In this respect, this method differs from the work of Berthon and Bills [1989] who use only the MoM with a single waveguide mode serving as the excitation. After describing the basic theory, the method is applied to a horn antenna on the Cassini spacecraft. The two dimensional modelling domain for this horn clearly shows where the FEM/MoM and the FEM/MM boundary surfaces are located. Comparisons of measured and calculated far field radiation patterns and reflection coefficients are then shown. It is noted that this method generates a sparse, diagonally dominant, complex-symmetric system matrix which may be solved with standard library routines. Moreover, this FEM formulation has been shown to be free of spurious solutions.
DOI
TL;DR: In this article , the International Celestial Reference Frame (ICRF) with observations of distant (typical redshift) active galactic nuclei (AGN) is used to provide a well-defined system of reference.
Abstract: Accurate measurement of angular positions on the sky requires a well-defined system of reference, something that in practice is realized by the International Celestial Reference Frame (ICRF) with observations of distant (typical redshift $\sim$1) Active Galactic Nuclei (AGN). At such great distances a subset of these objects exhibit as little as 10$-$50 $\mu$as/year observed parallax or proper motion, thus giving the frame excellent spatial and temporal stability. Until fairly recently the majority of AGN centered imaging was accomplished in the S (2.3 GHz) and X (8.4 GHz) radio frequency bands, however S-band observations for reasons such as sensitivity “plateauing”, increased source structure (jets), and radio frequency interference (RFI) have become less productive. Following spacecraft telemetry moves to higher frequencies and a desire to strengthen JPL's leadership in defining the next-generation of celestial reference frames has motivated the development of a “Quad-band” prototype receiver that operates in X, Ku, K, and Ka band in both right hand (RCP) and left hand (LCP) circular polarization. The goal of this receiver is to achieve less than a 20 % increase in noise over the Jansky Very Large Array (JVLA, NRAO) performance specification, which in such a wide bandwidth represents a revolutionary capability. To evaluate the various technical developments of the 8 GHz$-$40 GHz receiver the feedhorn optical beam was designed to interface to the US based Very Long Baseline Array (VLBA). The receiver's intermediate frequency (IF) spans 4 GHz$-$8 GHz, giving rise to up to eight 4 GHz IF channels for a fully populated instrument. This paper outlines the technical development of a 2$^{1}$/$_{2}$ octave wide (8 GHz$-$40 GHz) X-Ka band prototype receiver, fulfilling a need for super broadband technology within the VLBI network. An important additional benefit of the wideband receiver approach is its simplicity and low cost of operation.

Cited by
More filters
Patent
16 Jul 2002
TL;DR: In this paper, the fabrication and growth of sub-microelectronic circuitry is described, and the arrangement of such articles to fabricate electronic, optoelectronic, or spintronic devices and components.
Abstract: The present invention relates generally to sub-microelectronic circuitry, and more particularly to nanometer-scale articles, including nanoscale wires which can be selectively doped at various locations and at various levels. In some cases, the articles may be single crystals. The nanoscale wires can be doped, for example, differentially along their length, or radially, and either in terms of identity of dopant, concentration of dopant, or both. This may be used to provide both n-type and p-type conductivity in a single item, or in different items in close proximity to each other, such as in a crossbar array. The fabrication and growth of such articles is described, and the arrangement of such articles to fabricate electronic, optoelectronic, or spintronic devices and components. For example, semiconductor materials can be doped to form n-type and p-type semiconductor regions for making a variety of devices such as field effect transistors, bipolar transistors, complementary inverters, tunnel diodes, light emitting diodes, sensors, and the like.

598 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the literature related to the vibratory behavior of carbon nanotubes and their composites is presented, along with key conclusions and recommendations from these studies.

502 citations

Patent
04 Oct 2006
TL;DR: A bulk-doped semiconductor is a semiconductor that is at least one of the following: a single crystal, an elongated and bulk-depletioned semiconductor with a largest cross-sectional dimension less than 500 nanometers as discussed by the authors.
Abstract: A bulk-doped semiconductor that is at least one of the following: a single crystal, an elongated and bulk-doped semiconductor that, at any point along its longitudinal axis, has a largest cross-sectional dimension less than 500 nanometers, and a free-standing and bulk-doped semiconductor with at least one portion having a smallest width of less than 500 nanometers. Such a semiconductor may comprise an interior core comprising a first semiconductor; and an exterior shell comprising a different material than the first semiconductor. Such a semiconductor may be elongated and may have, at any point along a longitudinal section of such a semiconductor, a ratio of the length of the section to a longest width is greater than 4:1, or greater than 10:1, or greater than 100:1, or even greater than 1000:1. At least one portion of such a semiconductor may a smallest width of less than 200 nanometers, or less than 150 nanometers, or less than 100 nanometers, or less than 80 nanometers, or less than 70 nanometers, or less than 60 nanometers, or less than 40 nanometers, or less than 20 nanometers, or less than 10 nanometers, or even less than 5 nanometers. Such a semiconductor may be a single crystal and may be free-standing. Such a semiconductor may be either lightly n-doped, heavily n-doped, lightly p-doped or heavily p-doped. Such a semiconductor may be doped during growth. Such a semiconductor may be part of a device, which may include any of a variety of devices and combinations thereof, and a variety of assembling techniques may be used to fabricate devices from such a semiconductor. Two or more of such a semiconductors, including an array of such semiconductors, may be combined to form devices, for example, to form a crossed p-n junction of a device. Such devices at certain sizes may exhibit quantum confinement and other quantum phenomena, and the wavelength of light emitted from one or more of such semiconductors may be controlled by selecting a width of such semiconductors. Such semiconductors and device made therefrom may be used for a variety of applications.

460 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a wideband ultra wideband (UWB) communication protocol with a low EIRP level (−41.3dBm/MHz) for unlicensed operation between 3.1 and 10.6 GHz.
Abstract: Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

452 citations

Book
01 Oct 2002
TL;DR: In this article, a method of moments (MoM) was proposed for electromagnetic modeling of composite metallic and dielectric structures using entire-domain basis functions defined over bilinear surfaces, resulting in a remarkably small number of unknowns.
Abstract: Starting from the equivalence theorem any composite metallic and dielectric structure can be analyzed by using SIE (surface integral equations). Such integral equations are usually solved by MoM (method of moments). Most of the existing MoM methods for solving SIE are developed for BORs (bodies of revolution). There are only few such methods that can handle structures of arbitrary shape. These methods use sub-domain basis functions defined over triangles, requiring a very large number of unknowns even for the simplest problems. This paper presents a new MoM method for electromagnetic modeling of composite metallic and dielectric structures. The method uses entire-domain basis functions defined over bilinear surfaces, resulting in a remarkably small number of unknowns.

439 citations