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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
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NASA NTRS1992

The ATLAS-1 Shuttle mission

The Atmospheric Laboratory for Applications and Science (ATLAS-1) encompasses instruments which will be useful in determining long-term solar variability as well as in forging links to the measurements obtained by other spacecraft for the perturbed middle and upper atmosphere. The simultaneous measurements that will be conducted by ATLAS-1 of stratospheric concentrations of ozone, chlorine monoxide and water vapor, at relatively high latitudes during the northern spring, will be especially timely.

Torr, Marsha R.↗
NASA NTRS1994

Irregular, long-period boundary oscillations beyond approximately 100 R(sub e): GEOTAIL plasma observations

Near the tail boundary beyond about 100 Re, GEOTAIL often measures irregular, long-period oscillations in plasma velocity and density. Flow speed and density oscillate between magnetosheath values and values an order of magnitude less. The oscillations can persist for days. A typical oscillation lasts 100 minutes, but the range is large. The oscillations are highly asymmetric in that the increasing phase of the oscillation is an order of magnitude faster than the decreasing phase. This asymmetry shows that they are a distinct class of oscillations, not previously explicitly reported, and that they are not mere consequences of tail flapping in a variable solar wind. The changes in flow direction through an oscillation imply that the oscillation results from a motion of the boundary toward and away from the spacecraft with an amplitude between 5 and 10 R(sub e). A consideration of options suggests that the most plausible cause of these oscillations is the 'breathing' of the magnetotail that attends the substorm cycle.

Siscoe, G. L.↗
NASA NTRS1995

Theoretical overview and modeling of the sodium and potassium atmospheres of mercury

A general theoretical overview for the sources, sinks, gas-surface interactions, and transport dynamics of sodium and potassium in the exospheric atmsophere of Mercury is given. Information for these four factors, which control the spatial distribution of these two alkali-group gases about the planet, is incorporated in numerical models. The spatial nature and relative importance of the initial source atom atmosphere and the ambient (ballistic hopping) atom atmosphere are then examined and are shown to be controlled and coupled to a great extent by the extremely large and variable solar radiation acceleration experienced by sodium and potassium as they resonantly scatter solar photons. The lateral (antisunward) transport rate of thermally accommodated sodium and potassium ambient atoms is shown to be driven by the solar radiation acceleration and, over a significant portion of Mercury's orbit about the Sun, is sufficiently rapid to be competitive with the short photoionization lifetimes for these atoms when they are located on the summit surface near or within about 30 deg of the terminator. The lateral transport rate is characterized by a migration time determined by model calculations for an ensemble of atoms initially starting at a point source on the surface (i.e., a numerical spacetime dependent Green's function). Four animations for the spacetime evolution of the sodium (or potassium) atmosphere produced by a point source on the surface are presented on a videotape format. For extended surface sources for sodium and potassium, the local column density is determined by competition between the photoionization lifetimes and the lateral transport times of atoms originating from different surface source locations. Sodium surface source fluxes (referenced to Mercury at perihelion) that are required on the sunlit hemisphere to reproduce the typically observed several megarayleighs of D2 emission-line brightness and the inferred column densities of 1-2 x 10(exp 11) atoms per sq cm range from approximately 2-5 x 10(exp 7) atoms/sq cm/sec. The sodium model is applied to study observational data that document an anticorrelation in the average sodium column density and solar radiation acceleration. Lateral transport driven by the solar radiation acceleration is shown to produce this behavior for combinations of different sources and surface accomodation coefficients. The best fit model fits to the observational data require a significant degree of thermal accommodation of the ambient sodium atoms to the surface and a source rate that decreases as an inverse power of 1.5 to 2 in heliocentric distance.

Smyth, William H.↗
NASA NTRS1995

First realisation of the Space Absolute Radiometric Reference (SARR) during the ATLAS 2 flight period

A number of different solar constant observations all made from space during the ATLAS 2 mission have been gathered and compared to each other. The Sun did not have a single sunspot during several days. As eight of the radiometric channels were all within 0.1%, the mean of the observations has been used to determine a set of adjustment factors providing de facto the definition of the Space Absolute Radiometric Reference (SARR). The differential absolute radiometers of Solar Constant (SOLCON) experiment and the Solar Variability-1 (SOVA 1) experiment, as well as the SOVA 2 and Active Cavity Radiometer (ACR) radiometers that have been brought back to the Earth may, if used in the same conditions, reproduce and maintain the SARR for the future.

Crommelynck, D.↗
NASA NTRS2001

The Living With a Star Space Environment Testbed Program

NASA has initiated the Living with a Star (LWS) Program to develop the scientific understanding to address the aspects of the Connected Sun-Earth system that affects life and society. The Program Architecture includes science missions, theory and modeling and Space Environment Testbeds (SET). This current paper discusses the Space Environment Testbeds. The goal of the SET program is to improve the engineering approach to accomodate and/or mitigate the effects of solar variability on spacecraft design and operations. The SET Program will infuse new technologies into the space programs through collection of data in space and subsequent design and validation of technologies. Examples of these technologies are cited and discussed.

Barth, Janet↗
NASA NTRS2001

The Objectives of NASA's Living with a Star Space Environment Testbed

NASA is planning to fly a series of Space Environment Testbeds (SET) as part of the Living With A Star (LWS) Program. The goal of the testbeds is to improve and develop capabilities to mitigate and/or accommodate the affects of solar variability in spacecraft and avionics design and operation. This will be accomplished by performing technology validation in space to enable routine operations, characterize technology performance in space, and improve and develop models, guidelines and databases. The anticipated result of the LWS/SET program is improved spacecraft performance, design, and operation for survival of the radiation, spacecraft charging, meteoroid, orbital debris and thermosphere/ionosphere environments. The program calls for a series of NASA Research Announcements (NRAs) to be issued to solicit flight validation experiments, improvement in environment effects models and guidelines, and collateral environment measurements. The selected flight experiments may fly on the SET experiment carriers and flights of opportunity on other commercial and technology missions. This paper presents the status of the project so far, including a description of the types of experiments that are intended to fly on SET-1 and a description of the SET-1 carrier parameters.

Barth, Janet L.↗
NASA NTRS2002

Satellite Observations of Solar Irradiance and Sun-Climate Impacts

Solar activity is now near its maximum, with events such as the 2001 "Bastille Day Event", a Coronal Mass Ejection which merited a full session at AGUs annual meeting - and two major sunspot groupings earlier this year, with associated variations in TSI (Total Solar Irradiance). We discuss recent satellite measurements of TSI by ACRIM 2 and 3 and Virgo, and new precision observations of TSI and SSI (Solar Spectral Irradiance) expected from the SORCE mission, planned to launch in fall 2002. SSI has been added to TSI as a required EOS and NPOESS measurement because different spectral components provide energy inputs to different components of the climate system - UV into upper atmosphere and ozone, IR into lower atmosphere and clouds, and Visible into the biosphere. Succeeding satellite missions being planned for 2006 and 2010 will continue to monitor both TSI and SSI. We summarize current ideas about the potential impact of solar variability on Earth's climate on time scales from days to decades to centuries.

Cahalan, Robert↗
NASA NTRS2002

Satellite Observations of Solar Irradiance and Sun-Climate Impacts

Solar activity is now near its maximum, with events such as the 2001 "Bastille Day Event", a Coronal Mass Ejection which merited a full session at AGO'S annual meeting - and two major sunspot groupings earlier this year, with associated variations in TSI (Total Solar Irradiance). We discuss recent satellite measurements of TSI by ACRIM 2 and 3 And Virgo, and new precision observations of TSI and SSI (Solar Spectral Irradiance) expected from the SORCE mission, planned to launch in fall 2002. SSG has been added to TSI as a required EOS and NPOESS measurement because different spectral components provide energy inputs to different components of the climate system - UV into upper atmosphere and ozone, IR into lower atmosphere and clouds, and Visible into the biosphere. Succeeding satellite missions being planned for 2006 and 2010 will continue to monitor both TSI and SSI. We summarize current ideas about the potential impact of solar variability on Earth's climate on time scales from days to decades to centuries.

Cahalan, R.↗
NASA NTRS2002

LWS/SET End-to-End Data System

This paper describes the concept for the End-to-End Data System that will support NASA's Living With a Star Space Environment Testbed missions. NASA has initiated the Living With a Star (LWS) Program to develop a better scientific understanding to address the aspects of the connected Sun-Earth system that affect life and society. A principal goal of the program is to bridge the gap.between science, engineering, and user application communities. The Space Environment Testbed (SET) Project is one element of LWS. The Project will enable future science, operational, and commercial objectives in space and atmospheric environments by improving engineering approaches to the accommodation and/or mitigation of the effects of solar variability on technological systems. The End-to-end data system allows investigators to access the SET control center, command their experiments, and receive data from their experiments back at their home facility, using the Internet. The logical functioning of major components of the end-to-end data system are described, including the GSFC Payload Operations Control Center (POCC), SET Payloads, the GSFC SET Simulation Lab, SET Experiment PI Facilities, and Host Systems. Host Spacecraft Operations Control Centers (SOCC) and the Host Spacecraft are essential links in the end-to-end data system, but are not directly under the control of the SET Project. Formal interfaces will be established between these entities and elements of the SET Project. The paper describes data flow through the system, from PI facilities connecting to the SET operations center via the Internet, communications to SET carriers and experiments via host systems, to telemetry returns to investigators from their flight experiments. It also outlines the techniques that will be used to meet mission requirements, while holding development and operational costs to a minimum. Additional information is included in the original extended abstract.

Giffin, Geoff↗
NASA NTRS2002

LWS/SET Technology Experiment Carrier

This paper examines the approach taken to building a low-cost, modular spacecraft bus that can be used to support a variety of technology experiments in different space environments. It describes the techniques used and design drivers considered to ensure experiment independence from as yet selected host spacecraft. It describes the technology experiment carriers that will support NASA's Living With a Star Space Environment Testbed space missions. NASA has initiated the Living With a Star (LWS) Program to develop a better scientific understanding to address the aspects of the connected Sun-Earth system that affect life and society. A principal goal of the program is to bridge the gap between science, engineering, and user application communities. The Space Environment Testbed (SET) Project is one element of LWS. The Project will enable future science, operational, and commercial objectives in space and atmospheric environments by improving engineering approaches to the accommodation and/or mitigation of the effects of solar variability on technological systems. The SET Project is highly budget constrained and must seek to take advantage of as yet undetermined partnering opportunities for access to space. SET will conduct technology validation experiments hosted on available flight opportunities. The SET Testbeds will be developed in a manner that minimizes the requirements for accommodation, and will be flown as flight opportunities become available. To access the widest range of flight opportunities, two key development requirements are to maintain flexibility with respect to accommodation constraints and to have the capability to respond quickly to flight opportunities. Experiments, already developed to the technology readiness level of needing flight validation in the variable Sun-Earth environment, will be selected on the basis of the need for the subject technology, readiness for flight, need for flight resources and particular orbit. Experiments will be accumulated by the Project and manifested for specific flight opportunities as they become available. The SET Carrier is designed to present a standard set of interfaces to SET technology experiments and to be modular and flexible enough to interface to a variety of possible host spacecraft. The Carrier will have core components and mission unique components. Once the core carrier elements have been developed, only the mission unique components need to be defined and developed for any particular mission. This approach will minimize the mission specific cost and development schedule for a given flight opportunity. The standard set of interfaces provided by SET to experiments allows them to be developed independent of the particulars of a host spacecraft. The Carrier will provide the power, communication, and the necessary monitoring features to operate experiments. The Carrier will also provide all of the mechanical assemblies and harnesses required to adapt experiments to a particular host. Experiments may be hosted locally with the Carrier or remotely on the host spacecraft. The Carrier design will allow a single Carrier to support a variable number of experiments and will include features that support the ability to incrementally add experiments without disturbing the core architecture.

Sherman, Barry↗
NASA NTRS2003

Atmospheric products from the Upper Atmosphere Research Satellite (UARS)

This paper provides information on the products available at the NASA Goddard Earth Sciences (GES) Distributed Active Archive Center (DAAC) from the Upper Atmosphere Research Satellite (UARS) mission. The GES DAAC provides measurements from the primary UARS mission, which extended from launch in September 1991 through September 2001. The ten instruments aboard UARS provide measurements of atmospheric trace gas species, dynamical variables, solar irradiance input, and particle energy flux. All standard Level 3 UARS products from all ten instruments are offered free to the public and science user community. The Level 3 data are geophysical parameters, which have been transformed into a common format and equally spaced along the measurement trajectory. The UARS data have been reprocessed several times over the years following improvements to the processing algorithms. The UARS data offered from the GES DAAC are the latest versions of each instrument. The UARS data may be accessed through the GES DAAC website at

Ahmad, Suraiya P.↗
NASA NTRS2003

SORCE and Future Satellite Observations of Solar Irradiance

With solar activity just passing the maximum of cycle 23, SORCE is beginning a 5 year mission to measure total solar irradiance (TSI) with unprecedented accuracy using phase-sensitive detection, and to measure spectral solar irradiance (SSI) with unprecedented spectral coverage, from 1 to 2000 nm. The new Total Irradiance Monitor (TIM) has 4 active cavity radiometers, any one of which can be used as a fixed-temperature reference against any other that is exposed to the Sun via a shutter that cycles at a rate designed to minimize noise at the shutter frequency. The new Spectral Irradiance Monitor (SIM) is a dual Fery prism spectrometer that can employ either prism as a monochromatic source on the other prism, thus monitoring its transmission during the mission lifetime. Either prism can measure SSI from 200 to 2000 nm, employing the same phase-sensitive electrical substitution strategy as TIM. SORCE also carries dual SOLSTICE instruments to cover the spectral range 100-320 nm, similar to the instruments onboard UARS, and also an XUV Photometer System (XPS) similar to that on TIMED. SSI has now been added to TSI as a requirement of EOS and NPOESS, because different spectral components drive different components of the climate system - UV into upper atmosphere and stratospheric ozone, IR into tropospheric water vapor and clouds, and Visible into the oceans and biosphere. Succeeding satellite missions being planned for 2006 and 2011 will continue to monitor these critical solar variables.

Cahalan, Robert F.↗
NASA NTRS2004

History and Progress of GCM Simulations on Recent Mars Climate Change

The Mars Global Surveyor and Odyssey spacecraft reveal evidence that Mars may have experienced significant climate change in the recent past (105-106 Myr ago). Examples include gullies [1], cold-based tropical glaciers [2], paleolakes [3], and youthful near-surface ice [4]. Except for the gullies, the evidence for recent climate change requires ice and/or liquid water at low latitudes. An obvious question, therefore, is how is it possible for ice and/or liquid water to exist at low latitudes which is not possible in the present climate system? There are several mechanisms to consider. An episode of intense volcanic activity could alter the mean composition of the atmosphere and, therefore, the climate system. Impacts, depending on the size, composition, and velocity of the impactor are another way to dramatically alter the climate system. Polar wander and solar variability are also possibilities. However, the most promising way to change the climate is through changes in orbital properties. Mars, because of its proximity to Jupiter and lack of a large stabilizing moon, experiences much greater changes in its orbit properties than the Earth.

Haberle, R. M.↗
NASA NTRS2004

History and Progress of GCM Simulations on Recent Mars Climate Change

The Mars Global Surveyor and Odyssey spacecraft reveal evidence that Mars may have experienced significant climate change in the recent past (10(exp 5) - 10(exp 6) Myr ago). Examples include gullies, cold-based tropical glaciers, paleolakes, and youthful near-surface ice. Except for the gullies, the evidence for recent climate change requires ice and/or liquid water at low latitudes. An obvious question, therefore, is how is it possible for ice and/or liquid water to exist at low latitudes which is not possible in the present climate system? There are several mechanisms to consider. An episode of intense volcanic activity could alter the mean composition of the atmosphere and, therefore, the climate system. Impacts, depending on the size, composition, and velocity of the impactor are another way to dramatically alter the climate system. Polar wander and solar variability are also possibilities. However, the most promising way to change the climate is through changes in orbital properties. Mars, because of its proximity to Jupiter and lack of a large stabilizing moon, experiences much greater changes in its orbit properties than the Earth.

Haberle, R. M.↗
NASA NTRS2004

Living with a Star (LWS) Space Environment Testbeds (SET), Mission Carrier Overview and Capabilities

NASA has initiated the Living With a Star (LWS) Program to develop the scientific understanding to address the aspects of the Connected Sun-Earth system that affect life and society. A goal of the program is to bridge the gap between science, engineering, and user application communities. This will enable future science, operational, and commercial objectives in space and atmospheric environments by improving engineering approaches to the accommodation and/or mitigation of the effects of solar variability on technological systems. The three program elements of the LWS Program are Science Missions; Targeted Research and Technology; and Space Environment Testbeds (SETS). SET is an ideal platform for small experiments performing research on space environment effects on technologies and on the mitigation of space weather effects. A short description of the LWS Program will be given, and the SET will be described in detail, giving the mission objectives, available carrier services, and upcoming flight opportunities.

Patschke, Robert↗
NASA NTRS2004

Solar Activity and its Impact on Earth's Climate

The Sun's activity is now approaching an expected 2006 minimum, following the dramatic maximum of Solar Cycle 23, that included events such as the 2001 "Bastille Day" Coronal Mass Ejection, and the record-setting Oct-Nov 2003 solar flares, with their associated sunspots and variations in Total Solar Irradiance, or TSI. On Nov 4,2003 the largest X-ray flare ever detected (X-28) was observed in detail. We discuss recent satellite measurements of TSI by ACRIM 2 and 3 and Virgo, and new precision observations of TSI and SSI (Solar Spectral Irradiance) from the SORCE mission, that launched on January 25,2003. TSI variations recorded during the June 8,2004 transit of Venus show the unprecedented precision of the SORCE Total Irradiance Monitor (TIM) instrument, the first of its kind to employ phase-sensitive detection. The SORCE spectral instruments, XPS, Solstice, and SIM, record the Sun's changes over a wide range of wavelengths, from 1 to more than 2000 nanometers, for the first time covering the peak of the solar spectrum, including spectral components that provide energy inputs to key components of the climate system - ultraviolet (UV) into the upper atmospheric ozone layer, infrared (IR) into the lower atmosphere and clouds, and Visible into the Oceans and biosphere. Succeeding satellite missions are planned to monitor both TSI and SSI through Cycle 24. We summarize current ideas about decadal and longer solar variability, and associated potential impacts on Earth's climate on time scales from decades to centuries, especially highlighting the role of feedbacks in the climate system.

Cahalan, Robert F.↗
NASA NTRS2007

Solar Dynamics Observatory High Gain Antenna Handover Planning

The Solar Dynamics Observatory (SDO) is planned to launch in early 2009 as a mission to study the solar variability and its impact on Earth. To best satisfy its science goal, SDO will fly in a geosynchronous orbit with an inclination of approximately 29 deg. The spacecraft attitude is designed so that the science instruments point directly at the Sun with high accuracy. One of SDO's principal requirements is to obtain long periods of uninterrupted observations. The observations have an extremely high data volume so SDO must be in continuous contact with the ground during the observation periods. To maintain this contact, SDO is equipped with a pair of high gain antennas (HGAs) transmitting to a pair of ground antennas at the SDO ground station (SDOGS) located in White Sands, New Mexico. Either HGA can transmit to either SDOGS antenna. Neither HGA can be powered down. During a portion of each year, each of the HGA beams will intersect with the SDO body for a portion of the orbit. The original SDO antenna contact plan used each HGA for the half of each year during which its beam would not intersect the spacecraft. No data would be lost except, possibly, when switching from one antenna to another. After this plan was adopted, further analysis showed that daily handovers would be necessary for significant periods of the year. This unexpected need for extensive handovers necessitated that a handover design be developed to minimize the impact on the mission. This antenna handover design was developed and successfully tested with simulated data using the slew rate limits from preliminary jitter analysis. Subsequent analysis provided significant revision of allowed rates requiring modification of the handover plans.

Hashmall, Joseph A.↗
NASA NTRS2007

Solar Dynamics Observatory High Gain Antenna Handover Planning

The Solar Dynamics Observatory (SDO) is planned to launch in early 2009 as a mission to study the solar variability and its impact on Earth. To best satisfy its science goal, SDO will fly in a geosynchronous orbit with an inclination of approximately 29 deg. The spacecraft attitude is designed so that the science instruments point directly at the Sun with high accuracy. One of SDO s principal requirements is to obtain long periods of uninterrupted observations. The observations have an extremely high data volume so SDO must be in continuous contact with the ground during the observation periods. To maintain this contact, SDO is equipped with a pair of high gain antennas (HGAs) transmitting to a pair of ground antennas at the SDO ground station (SDOGS) located in White Sands, New Mexico. Either HGA can transmit to either SDOGS antenna. Neither HGA can be powered down. During a portion of each year, each of the HGA beams will intersect with the SDO body for a portion of the orbit. The original SDO antenna contact plan used each HGA for the half of each year during which its beam would not intersect the spacecraft. No data would be lost except, possibly, when switching from one antenna to another. After this plan was adopted, further analysis showed that daily handovers would be necessary for significant periods of the year. This unexpected need for extensive handovers necessitated that a handover design be developed to minimize the impact on the mission. This antenna handover design was developed and successfully tested with simulated data using the slew rate limits from preliminary jitter analysis. Subsequent analysis provided significant revision of allowed rates requiring modification of the handover plans.

Hashmall, Joseph A.↗