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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

NASA Delay Tolerant Networks: Operational, Evolving, an Ready for Expansion

The future of humanity’s presence beyond Earth depends on the successful commercialization of space. For commercialization to succeed, companies need cost-efficient architectures to support their business models and minimize risks for human capital, design, development, and operations. An ongoing challenge to any space enterprise is the reality that terrestrial network technologies are insufficient to provide reliable communications between assets in space. Whether you need to ensure your valuable data is safely transmitted to the ground or reliably delivered between platforms in orbit, ensuring data integrity over intermittent communication links is a necessity. Current solutions to space communications rely heavily on manual recording, storing, and retrieval of data from spacecraft. The current standard in space communication protocols, Consultative Committee for Space Data Systems (CCSDS) Space Packet standard, is reliant on inflexible network architectures based around mission-critical infrastructure to ensure data delivery. However, by automating the recording, storing, retrieval, and verification of data with Delay Tolerant Networks (DTN), the operator is freed from the dependence on manual data management and expensive mission critical infrastructure. NASA has been developing delay tolerant systems since the late 1990’s. Multiple DTN implementations have been established during that time, each suited to different use cases. Most notably, the DTN deployment for the International Space Station (ISS) includes demonstration of two DTN technologies: Interplanetary Overlay Network (ION) and Delay Tolerant Network Marshall Enterprise (DTNME). Beyond ISS, there are even more NASA DTN deployments being considered. Now that DTN implementations are maturing, it is appropriate to reflect upon these decades of work, review the integration and performance of the existing ISS deployment, and explore the future possibilities for DTN deployment industry-wide. The ISS DTN deployment is a complex architecture consisting of different DTN implementations for the onboard and ground network environments. The ION DTN implementation is being used in the on-board network. The Huntsville Operations Support Center (HOSC) DTN implementation, DTNME, is used by the ground network supporting ISS and will soon be a second onboard gateway too. The two implementations work cooperatively to provide high fidelity data services to flight operations users and payload developers across the globe. Though the two implementations yield a quality service, limitations are evident. Data rate, data storage, and device management are constrained by the services themselves and the complex nature of the deployment. Evolution of operations concepts will improve system capabilities and stability, but significant improvement will require additional development to the implementations themselves and to the overall deployment architecture. Taking advantage of the ongoing development and operation of the ISS DTN service will be central to the success of the future evolutions of NASA DTN deployments while demonstrating the benefits of DTN’s low-cost reliable data communication protocols for the growing commercial space industry. A broad effort on DTN integration and support is necessary to promote expansion beyond existing applications. NASA is developing several useful DTN implementations across a number of different systems: ION, DTNME, High-Rate DTN (HDTN), Bundle Protocol Library (BPLib), and others. To prevent fragmentation, DTN implementation teams need to communicate, collaborate, and integrate with one another to build a solid operational foundation for new DTN deployments. The establishment of a group that can assist new DTN users with understanding the purpose of each DTN implementation, provide best practices, and serve as a general knowledge base is paramount. Potential use of DTN on Gateway and other future NASA missions further drives the need for streamlined communication between DTN implementation teams. A well-integrated and highly engaged NASA DTN working group should help provide system architects the best DTN solutions for future commercial space efforts. This paper will first review the history of DTN implementations, explore the shortcoming of current space networking solutions given available limits in technology, and therefore establish the need for Delay Tolerant Networking in space communications. Secondly, the authors will explore NASA’s array of DTN implementations and highlight their usefulness to space applications. Thirdly, this paper will establish general DTN implementation distinguishing factors. Fourthly, the authors will discuss attempts to create a generic DTN comparison matrix, and the authors will review potential future topics in DTN innovation and collaboration, highlighting several key future efforts. Finally, this paper will describe how the institution of a NASA DTN Working Group will benefit DTN adoption across the governmental and commercial space sector. The goal of this paper is to encourage enthusiasm for DTN, share strategies for improving DTN on both current and future applications, promote the collaboration of DTN implementation groups within the international space operations community, and open the conversations about DTN, priorities, complexities, and innovation to the wider spaceflight industry.

DTN↗
NASA NTRSDate not supplied

NASA Delay Tolerant Networks: Operational, Evolving, an Ready for Expansion

The future of humanity’s presence beyond Earth depends on the successful commercialization of space. For commercialization to succeed, companies need cost-efficient architectures to support their business models and minimize risks for human capital, design, development, and operations. An ongoing challenge to any space enterprise is the reality that terrestrial network technologies are insufficient to provide reliable communications between assets in space. Whether you need to ensure your valuable data is safely transmitted to the ground or reliably delivered between platforms in orbit, ensuring data integrity over intermittent communication links is a necessity. Current solutions to space communications rely heavily on manual recording, storing, and retrieval of data from spacecraft. The current standard in space communication protocols, Consultative Committee for Space Data Systems (CCSDS) Space Packet standard, is reliant on inflexible network architectures based around mission-critical infrastructure to ensure data delivery. However, by automating the recording, storing, retrieval, and verification of data with Delay Tolerant Networks (DTN), the operator is freed from the dependence on manual data management and expensive mission critical infrastructure. NASA has been developing delay tolerant systems since the late 1990’s. Multiple DTN implementations have been established during that time, each suited to different use cases. Most notably, the DTN deployment for the International Space Station (ISS) includes demonstration of two DTN technologies: Interplanetary Overlay Network (ION) and Delay Tolerant Network Marshall Enterprise (DTNME). Beyond ISS, there are even more NASA DTN deployments being considered. Now that DTN implementations are maturing, it is appropriate to reflect upon these decades of work, review the integration and performance of the existing ISS deployment, and explore the future possibilities for DTN deployment industry-wide. The ISS DTN deployment is a complex architecture consisting of different DTN implementations for the onboard and ground network environments. The ION DTN implementation is being used in the on-board network. The Huntsville Operations Support Center (HOSC) DTN implementation, DTNME, is used by the ground network supporting ISS and will soon be a second onboard gateway too. The two implementations work cooperatively to provide high fidelity data services to flight operations users and payload developers across the globe. Though the two implementations yield a quality service, limitations are evident. Data rate, data storage, and device management are constrained by the services themselves and the complex nature of the deployment. Evolution of operations concepts will improve system capabilities and stability, but significant improvement will require additional development to the implementations themselves and to the overall deployment architecture. Taking advantage of the ongoing development and operation of the ISS DTN service will be central to the success of the future evolutions of NASA DTN deployments while demonstrating the benefits of DTN’s low-cost reliable data communication protocols for the growing commercial space industry. A broad effort on DTN integration and support is necessary to promote expansion beyond existing applications. NASA is developing several useful DTN implementations across a number of different systems: ION, DTNME, High-Rate DTN (HDTN), Bundle Protocol Library (BPLib), and others. To prevent fragmentation, DTN implementation teams need to communicate, collaborate, and integrate with one another to build a solid operational foundation for new DTN deployments. The establishment of a group that can assist new DTN users with understanding the purpose of each DTN implementation, provide best practices, and serve as a general knowledge base is paramount. Potential use of DTN on Gateway and other future NASA missions further drives the need for streamlined communication between DTN implementation teams. A well-integrated and highly engaged NASA DTN working group should help provide system architects the best DTN solutions for future commercial space efforts. This paper will first review the history of DTN implementations, explore the shortcoming of current space networking solutions given available limits in technology, and therefore establish the need for Delay Tolerant Networking in space communications. Secondly, the authors will explore NASA’s array of DTN implementations and highlight their usefulness to space applications. Thirdly, this paper will establish general DTN implementation distinguishing factors. Fourthly, the authors will discuss attempts to create a generic DTN comparison matrix, and the authors will review potential future topics in DTN innovation and collaboration, highlighting several key future efforts. Finally, this paper will describe how the institution of a NASA DTN Working Group will benefit DTN adoption across the governmental and commercial space sector. The goal of this paper is to encourage enthusiasm for DTN, share strategies for improving DTN on both current and future applications, promote the collaboration of DTN implementation groups within the international space operations community, and open the conversations about DTN, priorities, complexities, and innovation to the wider spaceflight industry.

DTN↗
NASA NTRS2000

General Aviation in Nebraska: Nebraska SATS Project Background Paper No. 1

The Nebraska SATS project is a state-level component of NASA's Small Aircraft Transportation System (SATS). During the next several years the project will examine several different factors affecting SATS implementation in Nebraska. These include economic and taxation issues, public policy issues, airport planning processes, information dissemination strategies, and systemic change factors. This background paper profiles the general aviation system in Nebraska. It is written to provide information about the "context" within which SATS will be pursued. The primary focus is thus on describing and providing background information about the current situation. A secondary focus is on drawing general conclusions about the ability of the current system to incorporate the types of changes implied by SATS. First, some brief information on the U.S. aviation system is provided. The next two sections profile the current general aviation aircraft and pilot base. Nebraska's system of general aviation airports is then described. Within this section of the paper, information is provided on the different types of general aviation airports in Nebraska, airport activity levels and current infrastructure. The fourth major section of the background paper looks at Nebraska's local airport authorities. These special purpose local governments oversee the majority of the general aviation airports in the state. Among the items examined are total expenditures, capital expenditures and planning activities. Next, the paper provides background information on the Nebraska Department of Aeronautics (NDA) and recent Federal funding for general aviation in Nebraska. The final section presents summary conclusions.

Smith, Russell↗
NASA NTRS2008

Promoting Robust Design of Diode Lasers for Space: A National Initiative

The National Diode-laser Array Working Group is approaching the end of its fourth year. Group facilitates focused interaction between the LDA user and provider communities. Group is authoring standards documents that address the specification and qualification of LDAs for operation in the space environment. NASA test and evaluation facilities are available to the community.

Tratt, David M.↗
NASA NTRS1963

Telstar I, volume 1

NASA Special Publication SP-32 is being published in accordance with the cooperative agreement executed on July 27, 1961 between the National Aeronautics and Space Administration and the American Telephone and Telegraph Company for the development and experimental testing of active communications satellites. This report consists of four volumes. The first three are composed of papers originally published together as a regular issue of the Bell System Technical Journal. The fourth volume, to be published at a later date, will contain pertinent papers contributed by various authors at the NASA Goddard Space Flight Center; the General Post Office of the United Kingdom; the Centre National d'Etudes des Telecommunications, France; and Telespazio, Italy.

SATELLITE DESIGN↗
NASA NTRS1963

Telstar I, Volume 2

NASA Special Publication SP-32 is being published in accordance with the cooperative agreement executed on July 27, 1961 between the National Aeronautics and Space Administration and the American Telephone and Telegraph Company for the development and experimental testing of active communications satellites. This report consists of four volumes. The first three are composed of papers originally published together as a regular issue of the Bell System Technical Journal. The fourth volume, to be published at a later date, will contain pertinent papers contributed by various authors at the NASA Goddard Space Flight Center; the General Post Office of the United Kingdom; the Centre National d'Etudes des Telecommunications, France; and Telespazio, Italy.

SATELLITE COMMUNICATION↗
NASA NTRS1963

Telstar I, Volume 3

NASA Special Publication SP-32 is being published in accordance with the cooperative agreement executed on July 27, 1961 between the National Aeronautics and Space Administration and the American Telephone and Telegraph Company for the development and experimental testing of active communications satellites. This report consists of four volumes. The first three are composed of papers originally published together as a regular issue of the Bell System Technical Journal. The fourth volume, to be published at a later date, will contain pertinent papers contributed by various authors at the NASA Goddard Space Flight Center; the General Post Office of the United Kingdom; the Centre National d'Etudes des Telecommunications, France; and Telespazio, Italy.

COMMUNICATION SYSTEM↗
NASA NTRS2004

Spatial Information Technology Center at Fulton-Montgomery Community College

The Spatial Information Technology Center (SITC) at Fulton-Montgomery Community College (FMCC) continued to fulfill its mission and charter by successfully completing its fourth year of operations under Congressional funding and NASA sponsorship. Fourth year operations (01 Oct 03 - 30 Sep 04) have been funded and conducted utilizing an authorized Research Grant NAG 13-02053 (via a one-year no-cost extension expiring Sep 04). Drawdown and reporting of fiscal activities for SITC operations passes through the Institute for the Application of Geo-spatial Technology (IAGT) at Cayuga Community College in Auburn, New York. Fiscal activity of the Center is reported quarterly via SF 272 to IAGT, this report contains an overview and expenditures for the remaining funds of NAG 13-02053. NAG 13-02053, slated for operating costs for the fiscal year FY02-03, received a one-year no-cost extension. SITC also received permission to use remaining funds for salaries and benefits through December 31,2004. The IAGT receives no compensation for administrative costs. This report includes addendums for the NAG award as required by federal guidelines. Attached are the signed Report of New Technology/Inventions and a Final Property Report. As an academic, economic, and workforce development program, the Center has made significant strides in bringing the technology, knowledge and applications of the spatial information technology field to the region it serves. Through the mission of the Center, the region's communities have become increasingly aware of the benefits of Geospatial technology, particularly in the region s K-12 arena. SITC continues to positively affect the region's education, employment and economic development, while expanding its services and operations.

Source record↗
NASA NTRS1995

New observations with the HST Goddard High Resolution Spectrograph of the low-redshift Lyman-Alpha clouds in the 3C 273 line of sight

We presenty spectra of 3C 273 between 1216 and 1250 A obtained in the (pre-COSTAR (Corrective Optics Space Telescope Axial Replacement instrument)) configuration of the Goddard High Resolution Spectrograph (GHRS) taken with the G160M grating with a resolution approximately = 20 km/s. The two strong Ly alpha lines at velocities of approximately 1000 and approximately 1600 km/s are well fitted with Voigt profiles and yield column densities, Doppler parameters and redshifts of log N(H I)=14.19 +/- 0.04 V(sub Dop)=40.7 +/- 3.0 km/s, V = 1012.4 +/- 2.0 km/s, and log N(H I)=14.22 +/- 0.07, V(sub Dop)=34.2 +/- 3.3 km/s and V = 1582.0 +/- 2.0 km/s, respectively. Motivated by the initial announcement by Williams and Schommer of detectable H alpha emission associated with the approximately 1600 km/s cloud, we discuss the difficulty of finding models which can account for emission of that magnitude given the observed neutral hydrogen column density, though a recent reobservation by these authors has shown the initial detection to be spurious. The C/H abundance ratio is probably less than about one-fourth of the solar abundance in these clouds, although this result is very uncertain and model dependent.

Weymann, Ray↗
NASA NTRS2002

Transients in Pacific/North American Plate Boundary Deformation: Synthesis and Modeling of GPS and Borehole Strain Observations

This is the Final Technical Report on research conducted between 1 June 1997 and 14 September 2001 entitled "Transients in Pacific/North American plate boundary deformation: Synthesis and modeling of GPS and borehole strain observations." As the project title implies, our effort involved a geodetic study of strain transients, i.e., temporal variations in deformation rates, that occur within plate boundary zones and their relationship to earthquakes and plate motions. Important transients occur during and following large earthquakes, and there are also strain transients not apparently associated with earthquakes. A particularly intriguing class of transients, for which there is a modest but growing list of examples, are preseismic anomalies. Such earthquake precursors, if further documented and understood, would have obvious importance for earthquake hazard mitigation. Because the timescales for these diverse transients range over at least 6 orders of magnitude (minutes to years), no single geodetic technique is optimum. We therefore undertook a systematic synthesis of Global Positioning Satellite (GPS) and borehole strainmeter data in three areas in California where there are adequate numbers of both types of instruments (or their equivalent): the San Francisco Bay region (within the Bay Area Regional Deformation network), southern California (within the Southern California Integrated GPS Network), and Parkfield (where a two-color laser system provides a proxy for continuous GPS measurements). An integral component of our study was the elucidation of the physical mechanisms by which such transients occur and propagate. We therefore initiated the development of multiple forward models, using two independent approaches. In the first, we explored the response to specified earthquake slip in viscoelastic models that incorporated failure criteria and the geometry of major faults in California. In the second approach, we examined the dynamical response of a complex rheological medium to the application of a far-field stress imposed by plate motions. The forward models were used both to gain insight into the range of strain transients to be expected under different assumed mechanical conditions and to develop representations for strain fields that allow GPS, borehole, and other strain data to be combined in a self-consistent, yet well-determined, manner. The models also provided a basis for hypothesis testing, by which data from a strain transient well characterized by GPS and borehole observations were utilized to distinguish among competing candidates for the causative physical mechanism and the governing physical characteristics. During the three years of this project, continued to a fourth year through a no-cost extension of the grant, we published 14 papers and presented or co-authored 37 papers at national scientific meetings.

Solomon, Sean C.↗
NASA NTRS2004

Spatial Information Technology Center at Fulton-Montgomery Community College

The Spatial Information Technology Center (SITC) at Fulton-Montgomery Community College (FMCC) continued to fulfill its mission and charter by successfully completing its third year of operations under Congressional funding and NASA sponsorship. Third year operations (01 Oct 02 - 30 Sep 03) have been funded and conducted utilizing two authorized Research Grants NAG 13-00043 (via a one-year no-cost extension expiring Sep 03) and NAG 13-02053 (one-year no-cost extension expiring Sep 04). Drawdowns and reporting of fiscal activities for SlTC operations continues to pass through the Institute for the Application of Geo-spatial Technology (IAGT) at Cayuga Community College in Auburn, New York. Fiscal activity of the Center is reported quarterly via SF 272 to IAGT, thus this report contains only a budgetary overview and forecast of future expenditures for the remaining funds of NAG 13 - 02053. Funds from NAG 13 - 00043 were exhausted during the fourth quarter of fiscal year FY02 - 03, which necessitated initial draw down of NAG 13 - 02053. The IAGT receives no compensation for administrative costs as authorized and approved by NASA in each award budget. This report also includes the necessary addendums for each NAG award, as required by federal guidelines, though no reportable activities took place within this report period. Attached are the signed Report of New Technology/lnventions and a Final Property Report identifying qualifying equipment purchased by the Center. As an academic, economic and workforce development oriented program, the Center has made significant strides in bringing the technology, knowledge and applications of the spatial information technology field to the region it serves. Through the mission of the Center, the region's educational, economic development and work force communities have become increasingly educated to the benefits of spatial (Geospatial) technology, particularly in the region's K-12 arena. SlTC continues to positively affect the region's education, employment and economic development, while expanding its services and operations designed to be customer driven, growing infrastructure and affecting systemic change.

Flinton, Michael E.↗
NASA NTRS1990

Radio line and continuum observations of quasar-galaxy pairs and the origin of low reshift quasar absorption line systems

There are a number of known quasars for which our line of sight to the high redshift quasar passes within a few Holmberg radii of a low redshift galaxy. In a few of these cases, spectra of the quasar reveal absorption by gas associated with the low redshift galaxy. A number of these pairs imply absorption by gas which lies well outside the optical disk of the associated galaxy, leading to models of galaxies with 'halos' or 'disks' of gas extending to large radii. The authors present observations of 4 such pairs. In three of the four cases, they find that the associated galaxy is highly disturbed, typically due to a gravitational interaction with a companion galaxy, while in the fourth case the absorption can be explained by clouds in the optical disk of the associated galaxy. They are led to an alternative hypothesis concerning the origin of the low redshift absorption line systems: the absorption is by gas clouds which have been gravitationally stripped from the associated galaxy. These galaxies are rapidly evolving, and should not be used as examples of absorption by clouds in halos of field spirals. The authors conclude by considering the role extended gas in interacting systems plays in the origin of higher redshift quasar absorption line systems.

Carilli, C. L.↗
NASA NTRS1999

The Contribution of Ionizing Stars to the Far-Infrared and Radio Emission in the Galaxy

A summary of research activities carried out in this eighth and final progress report. The final report includes: this summary document, copies of three published research papers, plus a draft manuscript of a fourth research paper entitled "The Contribution of Ionizing Stars to the FarInfrared and Radio Emission in the Milky Way; Evidence for a Swept-up Shell and Diffuse Ionized Halo around the W4 Chimney/Supershell." The main activity during the final quarterly reporting period was research on W4, including analysis of the radio and far-infrared images, generation of shell models, a literature search, and preparation of a research manuscript. There will be additional consultation with co-authors prior to submission of the paper to the Astrophysical Journal. The results will be presented at the 4th Tetons Summer Conference on "Galactic Structure, Stars, and the ISM" in May 2000. In this fourth and last paper we show W4 has a swept-up partially ionized shell of gas and dust which is powered by the OCl 352 star cluster. Analysis shows there is dense interstellar material directly below the shell, evidence that that the lower W4 shell "ran into a brick wall" and stalled, whereas the upper W4 shell achieved "breakout" to form a Galactic chimney. An ionized halo is evidence of Lyman continuum leakage which ionizes the WIM (warm ionized medium). It has long been postulated that the strong winds and abundant ionizing photons from massive stars are responsible for much of the large scale structure in the interstellar medium (ISM), including the ISM in other galaxies. However standard HII region theory predicts few photons will escape the local HII region. The significance of W4 and this work is it provides a direct example of how stellar winds power a galactic chimney, which in turn leads to a low density cavity from which ionizing photons can escape to large distances to ionize the WIM.

Terebey, S.↗
NASA NTRS1978

Some observations on four current subjects related to aeroelastic stability

After introductory comments on the literature and the purposes of this paper, a table is presented summarizing the author's views on some currently solved vs partially unsolved problems related to aeroelastic stability. The term 'solved' is used in the practical sense that engineers are able to cope confidently with that problem during the process of structural design. Selected entries in the table are reviewed, partially to motivate the topics in the rest of the paper. The 'four current subjects' are chosen both for timeliness and because they are among the ongoing interests of the Stanford group. The first involves the prediction of linearized unsteady aerodynamic loads due to arbitrary motions of streamlined shapes. Some contributions by Edwards are refined, which were motivated by the requirements of active control system design. The second subject is nonlinear unsteady aerodynamics for the transonic regime. After describing a few useful developments from locally-linear theory and computational fluid dynamics, there is suggested an empirical procedure for interim-analysis purposes. The third and fourth subjects concern recent discoveries regarding the aeroelastic stability of large-aspect-ratio wings and wind turbines. The former work is mainly that of Petre and Boyd. The latter includes some of the author's own preliminary discoveries about the performance and dynamics of vertical-axis machines.

Ashley, H.↗
NASA NTRS1999

Measurements of Acidic Gases and Aerosol Species Aboard the NASA DC-8 Aircraft During the Pacific Exploratory Mission in the Tropics (PEM-Tropics A)

We received funding to provide measurements of nitric acid (HNO3), formic acid (HCOOH), acetic acid (CH3COOH), and the chemical composition of aerosols aboard the NASA Ames DC-8 research aircraft during the PEM-Tropics A mission. These measurements were successfully completed and the final data resides in the electronic archive (ftp-gte.larc.nasa.gov) at NASA Langley Research Center. For the PEM-Tropics A mission the University of New Hampshire group was first author of four different manuscripts. Three of these have now appeared in the Journal of Geophysical Research-Atmospheres, included in the two section sections on PEM-Tropics A. The fourth manuscript has just recently been submitted to this same journal as a stand alone paper. All four of these papers are included in this report. The first paper (Influence of biomass combustion emissions on the distribution of acidic trace gases over the Southern Pacific basin during austral springtime) describes the large-scale distributions of HNO3, HCOOH, and CH3COOH. Arguments were presented to show, particularly in the middle tropospheric region, that biomass burning emissions from South America and Africa were a major source of acidic gases over the South Pacific basin. The second paper (Aerosol chemical composition and distribution during the Pacific Exploratory Mission (PEM) Tropics) covers the aerosol aspects of our measurement package. Compared to acidic gases, O3, and selected hydrocarbons, the aerosol chemistry showed little influence from biomass burning emissions. The data collected in the marine boundary layer showed a possible marine source of NH3 to the troposphere in equatorial areas. This source had been speculated on previously, but our data was the first collected from an airborne platform to show its large-scale features. The third paper (Constraints on the age and dilution of Pacific Exploratory Mission-Tropics biomass burning plumes from the natural radionuclide tracer Pb-210) utilized the unexpectedly high concentrations of Pb-210 in the combustion plumes to estimate their ages and mixing along the transport route to the South Pacific basin. The final paper in the group (Tropospheric reactive-odd nitrogen over the South Pacific in austral springtime). This paper provides a summary of reactive nitrogen during PEM-Tropics A, with HNO3 and PAM showing the most impact from combustion emission.

Talbot, Robert W.↗
NASA NTRS1974

On the origin of the solar system. I

The empirical information on protostars is reviewed. 'Globules' are described, found to have the typical range of stellar masses and with gaseous compositions now well known thanks largely to radio astronomy. They also contain particulate matter identified as silicates, ice, and probably graphite and other carbon compounds. Current knowledge of the degree of stability of the planetary orbits over the past 4.5 b.y. is summarized. The statistics on the frequency and masses of asteroids and information on the Kirkwood gaps, both empirical and theoretical, are cited. An analogous discussion is made for the Rings of Saturn, including its extension observed in 1966 to the fourth Saturn satellite, Dione. The three main classes of meteorites - irons, stones, and carbonaceous chondrites - all appear to be of asteroidal origin and they yield the most direct evidence on the early thermal history of the solar system. The author sees in this evidence definite confirmation of the cold origin of the planetary system, followed by a hot phase due to the evolving sun that caused the dissolution of the solar nebula.

Kuiper, G. P.↗
NASA NTRS1973

Feasibility study for locating archaeological village sites by satellite remote sensing techniques

The author has identified the following significant results. Examination of NASA-provided aerial photography at the Pt. Hope, Alaska area has revealed numerous house pits, or the remains of former subterranean houses which have caved in. Although three major groupings of former house sites have previously been identified, a fourth area, north of the group known as Jabbertown had not previously been identified. It appears that this fourth site is quite extensive and may be of significance to understanding the sequence of habitation of the Pt. Hope location.

Cook, J. P.↗
NASA NTRS2001

Toward a Unified Parameterization of the Boundary Layer and Moist Convection: A New Type of Mass-Flux Model - Part 1

Higher-order closure (HOC) models have been proposed for parameterization of the turbulent planetary boundary layer (PBL). HOC models must include closures for higher-order moments (e.g., fourth moments in third-order closure models), for pressure terms, and for dissipation terms. Mass-flux closure (MFC) models have been proposed for parameterization of cumulus convection and, more recently, the convective PBL. MFC models include closures for lateral mass exchanges and for pressure terms (which are usually ignored). The authors developed a new kind of model that combines HOC and MFC, which they hope will be useful for the parameterization of both the PBL and cumulus convection, in a unified framework. Such a model is particularly well suited to regimes in which the PBL turbulence and the cumulus convection are not well separated, for example, the broken stratocumulus and shallow cumulus regimes. The model makes use of an assumed joint probability distribution for the variables of interest, and the equations typically used in HOC models can be derived by integrating over the distribution. Accordingly, the model is called Assumed-Distribution Higher-Order Closure (ADHOC). The prognostic variables of ADHOC are the mean state, the second and third moments of the vertical velocity, and the vertical fluxes of other quantities of interest. All of the parameters of the distribution can be determined from the predicted moments, thereafter the joint distribution is effectively known, and so any and all moments can be constructed as needed. In this way, the usual closure problem of "higher moments" is avoided. The pressure-term parameterizations previously developed for HOC models are used to predict the convective fluxes and the moments of the vertical velocity. In companion papers, parameterizations of lateral mass exchanges and subplume-scale fluxes are presented, and then ADHOC is applied to several observationally based tropical, subtropical, and dry convective boundary layers.

Lappen, Cara-Lyn↗