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NASA NTRS2012

Characterizing Orbital Debris and Spacecrafts Through a Multi-Analytical Approach

Defining the risks present to both crewed and robotic spacecrafts is part of NASA s mission, and is critical to keep these resources out of harms way. Characterizing orbital debris is an essential part of this mission. We present a proof-of-concept study that employs multiple techniques to demonstrate the efficacy of each approach. The targets of this study are IDCSPs (Initial Defense Communications Satellite Program). 35 of these satellites were launched by the US in the mid-1960s and were the first US communications satellites in the GEO regime. They were emplaced in slightly sub-synchronous orbits. These targets were chosen for this proof-of-concept study for the simplicity of their observable exterior surfaces. The satellites are 26-sided polygons (86cm in diameter), initially spin-stabilized and covered on all sides in solar panels. Data presented here include: (a) visible broadband photometry (Johnson B and Cousins R bands) taken with the University of Michigan s 0.6-m aperture Curtis-Schmidt telescope MODEST (for Michigan Orbital DEbris Survey Telescope) in Chile in November, 2011, (b) laboratory broadband photometry (Johnson BV Cousins RI) of solar cells, obtained using the Optical Measurements Center (OMC) at NASA/JSC (see Cowardin et al., this meeting for more details), (c) visible-band spectra taken using the Magellan 6.5m Baade Telescope at Las Campanas Observatory in Chile in March, 2012 (see also Seitzer et al., this meeting), and (d) visible-band laboratory spectra of solar cells using a Field Spectrometer. Color-color plots using broadband photometry (e.g. B-R vs. R-I) demonstrate that different material types fall into distinct areas on the plots (Cowardin, AMOS 2010). Spectra will be binned in wavelength to compare with photometry results and plotted on the same graph for comparison. This allows us to compare lab data with telescopic data, and photometric results with spectroscopic results. In addition, the spectral response of solar cells in the visible wavelength regime varies from relatively flat (modern black solar cells with uniform albedo as a function of wavelength) to older solar cells whose reflectivity is sharply peaked in the blue (similar to the IDCSP solar cells). With a target like IDCSPs, the material type is known a priori. Therefore, this study will also be used to determine whether laboratory spectra of pre-launch (pristine) solar cells differ from the telescopic spectra of IDCSPs that have been exposed to the harsh environment of space for ~45 years to investigate whether space weathering effects are evident.

Lederer, S. M.↗
NASA NTRS2012

Space-Based Gravitational-wave Mission Concept Studies

The LISA Mission Concept has been under study for over two decades as a spacebased gravitational-wave detector capable of observing astrophysical sources in the 0.0001 to 1 Hz band. The concept has consistently received strong recommendations from various review panels based on the expected science, most recently from the US Astr02010 Decadal Review. Budget constraints have led both the US and European Space agencies to search for lower cost options. We report results from the US effort to explore the tradeoffs between mission cost and science return, and in particular a family of mission concepts referred to as SGO (Space-based Gravitational-wave Observatory).

Livas, Jeffrey C.↗
NASA NTRS2012

Space-Based Gravitational-Wave Observatory (SGO) Mission Concept Study

The LISA Mission Concept has been under study for over two decades as a space-based gravitational-wave detector capable of observing astrophysical sources in the 0.0001 to 1 Hz band. The concept has consistently received strong recommendations from various review panels based on the expected science, most recently from the US Astr02010 Decadal Review. Budget constraints have led both the US and European Space agencies to search for lower cost options. We report results from the US effort to explore the tradeoffs between mission cost and science return.

Livas, Jeffrey↗
NASA NTRS2012

Observations of CMEs and Models of the Eruptive Corona

It is now realized that coronal mass ejections (CMEs) are the most energetic phenomenon in the heliosphere. Although early observations (in the 1970s and 19805) revealed most of the properties of CMEs, it is the extended and uniform data set from the Solar and Heliospheric Observatory (SOHO) mission that helped us consolidate our knowledge on CMEs. The Solar Terrestrial Relations Observatory (STEREO) mission has provided direct confirmation of the three-dimensional structure of CMEs. The broadside view provided by the STEREO coronagraphs helped us estimate the width of the halo CMEs and hence validate CME cone models. Current theoretical ideas on the internal structure of CMEs suggest that a flux rope is central to the CME structure, which has considerable observational support both from remote-sensing and in-situ observations. The flux-rope nature is also consistent with the post-eruption arcades with high-temperature plasma and the charge states observed within CMEs arriving at Earth. The quadrature observations also helped us understand the relation between the radial and expansion speeds of CMEs, which were only known from empirical relations in the past. This paper highlights some of these results obtained during solar cycle 23 and 24 and discusses implications for CME models.

Gopalswamy, Nat↗
NASA NTRS2012

Baby Solar System

What did our solar system look like in its infancy,...... when the planets were forming? We cannot travel back in time to take an image of the early solar system, but in principle we can have the next best thing: images of infant planetary systems around Sun-like stars with ages of 1 to 5 million years, the time we think it took for the giant planets to form. Infant exoplanetary systems are critically important because they can help us understand how our solar system fits within the context of planet formation in general. More than 80% of stars are born with gas- and dust-rich disks, and thus have the potential to form planets. Through many methods we have identified more than 760 planetary systems around middle-aged stars like the Sun, but many of these have architectures that look nothing like our solar system. Young planetary systems are important missing links between various endpoints and may help us understand how and when these differences emerge. Well-known star-forming regions in Taurus, Scorpius. and Orion contain stars that could have infant planetary systems. But these stars are much more distant than our nearest neighbors such as Alpha Centauri or Sirius, making it extremely challenging to produce clear images of systems that can reveal signs of recent planet formation, let alone reveal the planets themselves. Recently, a star with the unassuming name LkCa 15 may have given us our first detailed "baby picture" of a young planetary system similar to our solar system. Located about 450 light-years away in the Taurus starforming region. LkCa 15 has a mass comparable to the Sun (0.97 solar mass) and an age of l to 5 million years, comparable to the time at which Saturn and perhaps Jupiter formed. The star is surrounded by a gas-rich disk similar in structure to the one in our solar system from which the planets formed. With new technologies and observing strategies, we have confirmed suspicions that LkCa 15's disk harbors a young planetary system.

Currie, Thayne↗
NASA NTRS2012

The Size Frequency Distribution of Small Main-Belt Asteroids

The asteroid size distribution informs us about the formation and composition of the Solar System. We build on our previous work in which we harvest serendipitously observed data of the Taurus region and measure the brightness and size distributions of Main-belt asteroids. This is accomplished with the highly sensitive MIPS 24 micron channel. We expect to catalog 104 asteroids, giving us a statistically significant data set. Results from this investigation will allow us to characterize the total population of small, Main-belt asteroids. Here we will present new results on the completeness of our study; on the presence of size distribution variations with inclination and radial distance in the belt; and early result on other archival fields.

Burt, Brian J.↗
NASA NTRS2012

NASA's Launch Propulsion Systems Technology Roadmap

Safe, reliable, and affordable access to low-Earth (LEO) orbit is necessary for all of the United States (US) space endeavors. In 2010, NASA s Office of the Chief Technologist commissioned 14 teams to develop technology roadmaps that could be used to guide the Agency s and US technology investment decisions for the next few decades. The Launch Propulsion Systems Technology Area (LPSTA) team was tasked to address the propulsion technology challenges for access to LEO. The developed LPSTA roadmap addresses technologies that enhance existing solid or liquid propulsion technologies and their related ancillary systems or significantly advance the technology readiness level (TRL) of less mature systems like airbreathing, unconventional, and other launch technologies. In developing this roadmap, the LPSTA team consulted previous NASA, military, and industry studies as well as subject matter experts to develop their assessment of this field, which has fundamental technological and strategic impacts for US space capabilities.

McConnaughey, Paul K.↗
NASA NTRS2012

How NASA Sees the Earth and Its Climate

NASA Research Addresses Broad Questions: (1) How are global ecosystems changing? (2) What changes are occurring in global land cover and land use and what are their causes? (3) How is the Earth s surface being transformed and how can such information be used to predict future changes? (4) What are the consequences of land cover and land use change for the sustainability of ecosystems and economic productivity? NASA uses the view from above to monitor our changing home. Different satellites help us study the various systems of the Earth. No one system can do it all. NASA tools and science helps us to understand how the planet is changing and what the changes mean for us.

BrowndeColstoun, Eric↗
NASA NTRS2013

Orbital Debris: Past, Present, and Future

In the early days of spaceflight, the gBig Sky h theory was the near universally accepted paradigm for dealing with collisions of orbiting objects. This theory was also used during the early years of the aviation industry. Just as it did in aviation, the gBig Sky h theory breaks down as more and more objects accumulate in the environment. Fortunately, by the late 1970 fs some visionaries in NASA and the US Department of Defense (DoD) realized that trends in the orbital environment would inevitably lead to increased risks to operational spacecraft from collisions with other orbiting objects. The NASA Orbital Debris Program was established at and has been conducted at Johnson Space Center since 1979. At the start of 1979, fewer than 5000 objects were being tracked by the US Space Surveillance Network and very few attempts had been made to sample the environment for smaller sizes. Today, the number of tracked objects has quadrupled. Ground ]based and in situ measurements have statistically sampled the LEO environment over most sizes and mitigation guidelines and requirements are common among most space faring nations. NASA has been a leader, not only in defining the debris environment, but in promoting awareness of the issues in the US and internationally, and in providing leadership in developing policies to address the issue. This paper will discuss in broad terms the evolution of the NASA debris program from its beginnings to its present broad range of debris related research. The paper will discuss in some detail current research topics and will attempt to predict future research trends.

Stansbery, Gene↗
NASA NTRS2010

Electrostatic Evaluation of the ARES I FTS Antenna Materials

Surface resistivity and volume resistivity data show all the tested non-metallic materials of the Ares I FTS antenna assembly to be insulative. The external materials (White foam, phenolic) should be able to develop a large surface charge density upon tribocharging with ice crystal impingement. Dielectric breakdown tests on the FTS antenna housing materials show that each of the insulative materials are very resistive to electrical breakdown. The thicknesses of these materials in a nominal housing should protect the antenna from direct breakdown from external triboelectric charging potentials. Per data from the Air Force study, a maximum external electric potential in the range of 100kV can be developed on surfaces tribocharged by ice crystal impingement. Testing showed that under operational pressure ranges, this level of exterior voltage can result in a potential of about 6 kV induced on the electrically floating interior antenna vanes. Testing the vanes up to this voltage level showed that electrostatic discharges can occur between the electrically floating vanes and the center, grounded screw heads. Repeated tests with multiple invisible and visible discharges caused only superficial physical damage to the vanes. Fourier analysis of the discharge signals showed that the frequency range of credible discharges would not interfere with the nominal operation of the FTS antenna. However, due to the limited scope, short timetable, and limited funding of this study, a direct measurement of the triboelectric charge that could be generated on the Ares I antenna housing when the rocket traverses an ice cloud at supersonic speeds was not performed. Instead, data for the limited Air Force study [3] was used as input for our experiments. The Air Force data used was not collected with a sensor located to provide us with the best approximation at the geometry of the Ares I rocket, namely that of the windshield electrometer, because brush discharges to the metal frame of the windshield periodically depleted any charge accumulated. The configuration of the Ares I antenna assembly does not include any exposed metals in the vicinity and the windshield data could not be used. Since the windshield sensor data was unusable, we decided that the Patch 2 location would provide us with a rough approximation to the Ares I antenna configuration and would give us an indication of the possible charging levels that would develop. This was the data that we used in this study. Whether these charging levels would be of the same order of magnitude as the actual charges developed by the Ares I traversing a cloud with ice particles is at this point unknown. An actual experimental test, requiring the acquisition of additional instrumentation, is strongly advised before a final recommendation can be formulated regarding the safe levels of electrostatic charging on the antenna housing. Thus the results of this study should be considered to be preliminary.

Hogue, Michael D.↗
NASA NTRS2012

Overview of NASA's Microgravity Materials Research Program

The NASA microgravity materials program is dedicated to conducting microgravity experiments and related modeling efforts that will help us understand the processes associated with the formation of materials. This knowledge will help improve ground based industrial production of such materials. The currently funded investigations include research on the distribution of dopants and formation of defects in semiconductors, transitions between columnar and dendritic grain morphology, coarsening of phase boundaries, competition between thermally and kinetically favored phases, and the formation of glassy vs. crystalline material. NASA microgravity materials science investigators are selected for funding either through a proposal in response to a NASA Research Announcement or by participation in a team proposing to a foreign agency research announcement. In the latter case, a US investigator participating in a successful proposal to a foreign agency can then apply to NASA for funding of an unsolicited proposal. The program relies on cooperation with other aerospace partners from around the world. The ISS facilities used for these investigations are provided primarily by partnering with foreign agencies and in most cases the US investigators are working as a part of a larger team studying a specific area of materials science. The following facilities are to be utilized for the initial investigations. The ESA provided Low Gradient Facility and the Solidification and Quench Inserts to the Materials Research Rack/Materials Science Laboratory are to be used primarily for creating bulk samples that are directionally solidified or quenched from a high temperature melt. The CNES provided DECLIC facility is used to observe morphological development in transparent materials. The ESA provided Electro-Magnetic Levitator (EML) is designed to levitate, melt and then cool samples in order to study nucleation behavior. The facility provides conditions in which nucleation of the solid is not triggered from the wall and in which fluid flows in the sample can be controlled and manipulated. These conditions allow scientists ideal conditions for understanding the relative amounts and distribution of different phases that form in the solid. Finally, the Coarsening of Solid Liquid Melts hardware allows quenching of low temperature samples in the Microgravity Science Glovebox.

Downey, James Patton↗
NASA NTRS2012

Overview of NASA's Microgravity Materials Science Program

The microgravity materials program was nearly eliminated in the middle of the aughts due to budget constraints. Hardware developments were eliminated. Some investigators with experiments that could be performed using ISS partner hardware received continued funding. Partnerships were established between US investigators and ESA science teams for several investigations. ESA conducted peer reviews on the proposals of various science teams as part of an ESA AO process. Assuming he or she was part of a science team that was selected by the ESA process, a US investigator would submit a proposal to NASA for grant funding to support their part of the science team effort. In a similar manner, a US materials investigator (Dr. Rohit Trivedi) is working as a part of a CNES selected science team. As funding began to increase another seven materials investigators were selected in 2010 through an NRA mechanism to perform research related to development of Materials Science Research Rack investigations. One of these has since been converted to a Glovebox investigation.

Downey, James Patton↗
NASA NTRS2013

United States Forest Disturbance Trends Observed Using Landsat Time Series

Disturbance events strongly affect the composition, structure, and function of forest ecosystems; however, existing U.S. land management inventories were not designed to monitor disturbance. To begin addressing this gap, the North American Forest Dynamics (NAFD) project has examined a geographic sample of 50 Landsat satellite image time series to assess trends in forest disturbance across the conterminous United States for 1985-2005. The geographic sample design used a probability-based scheme to encompass major forest types and maximize geographic dispersion. For each sample location disturbance was identified in the Landsat series using the Vegetation Change Tracker (VCT) algorithm. The NAFD analysis indicates that, on average, 2.77 Mha/yr of forests were disturbed annually, representing 1.09%/yr of US forestland. These satellite-based national disturbance rates estimates tend to be lower than those derived from land management inventories, reflecting both methodological and definitional differences. In particular the VCT approach used with a biennial time step has limited sensitivity to low-intensity disturbances. Unlike prior satellite studies, our biennial forest disturbance rates vary by nearly a factor of two between high and low years. High western US disturbance rates were associated with active fire years and insect activity, while variability in the east is more strongly related to harvest rates in managed forests. We note that generating a geographic sample based on representing forest type and variability may be problematic since the spatial pattern of disturbance does not necessarily correlate with forest type. We also find that the prevalence of diffuse, non-stand clearing disturbance in US forests makes the application of a biennial geographic sample problematic. Future satellite-based studies of disturbance at regional and national scales should focus on wall-to-wall analyses with annual time step for improved accuracy.

Masek, Jeffrey G.↗
NASA NTRS2012

Influences of the El Nino Southern Oscillation and the Pacific Decadal Oscillation on the Timing of the North American Spring

Detrended, modelled first leaf dates for 856 sites across North America for the period 1900-2008 are used to examine how the El Nino Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) separately and together might influence the timing of spring. Although spring (mean March through April) ENSO and PDO signals are apparent in first leaf dates, the signals are not statistically significant (at a 95% confidence level (p <0.05)) for most sites. The most significant ENSO/PDO signal in first leaf dates occurs for El Nino and positive PDO conditions. An analysis of the spatial distributions of first leaf dates for separate and combined ENSO/PDO conditions features a northwest-southeast dipole that is significantly (at p <0.05) different than the distributions for neutral conditions. The nature of the teleconnection between Pacific SST's and first leaf dates is evident in comparable composites for detrended sea level pressure (SLP) in the spring months. During positive ENSO/PDO, there is an anomalous flow of warm air from the southwestern US into the northwestern US and an anomalous northeasterly flow of cold air from polar regions into the eastern and southeastern US. These flow patterns are reversed during negative ENSO/PDO. Although the magnitudes of first leaf date departures are not necessarily significantly related to ENSO and PDO, the spatial patterns of departures are significantly related to ENSO and PDO. These significant relations and the long-lived persistence of SSTs provide a potential tool for forecasting the tendencies for first leaf dates to be early or late.

McCabe, Gregory J.↗
NASA NTRS2014

Usability/Sentiment for the Enterprise and ENTERPRISE

The purpose of the Sentiment of Search Study for NASA Johnson Space Center (JSC) is to gain insight into the intranet search environment. With an initial usability survey, the authors were able to determine a usability score based on the Systems Usability Scale (SUS). Created in 1986, the freely available, well cited, SUS is commonly used to determine user perceptions of a system (in this case the intranet search environment). As with any improvement initiative, one must first examine and document the current reality of the situation. In this scenario, a method was needed to determine the usability of a search interface in addition to the user's perception on how well the search system was providing results. The use of the SUS provided a mechanism to quickly ascertain information in both areas, by adding one additional open-ended question at the end. The first ten questions allowed us to examine the usability of the system, while the last questions informed us on how the users rated the performance of the search results. The final analysis provides us with a better understanding of the current situation and areas to focus on for improvement. The power of search applications to enhance knowledge transfer is indisputable. The performance impact for any user unable to find needed information undermines project lifecycle, resource and scheduling requirements. Ever-increasing complexity of content and the user interface make usability considerations for the intranet, especially for search, a necessity instead of a 'nice-to-have'. Despite these arguments, intranet usability is largely disregarded due to lack of attention beyond the functionality of the infrastructure (White, 2013). The data collected from users of the JSC search system revealed their overall sentiment by means of the widely-known System Usability Scale. Results of the scores suggest 75%, +/-0.04, of the population rank the search system below average. In terms of a grading scaled, this equated to D or lower. It is obvious JSC users are not satisfied with the current situation, however they are eager to provide information and assistance in improving the search system. A majority of the respondents provided feedback on the issues most troubling them. This information will be used to enrich the next phase, root cause analysis and solution creation.

Meza, David↗
NASA NTRS2014

A New Hybrid Spatio-temporal Model for Estimating Daily Multi-year PM2.5 Concentrations Across Northeastern USA Using High Resolution Aerosol Optical Depth Data

The use of satellite-based aerosol optical depth (AOD) to estimate fine particulate matter PM(sub 2.5) for epidemiology studies has increased substantially over the past few years. These recent studies often report moderate predictive power, which can generate downward bias in effect estimates. In addition, AOD measurements have only moderate spatial resolution, and have substantial missing data. We make use of recent advances in MODIS satellite data processing algorithms (Multi-Angle Implementation of Atmospheric Correction (MAIAC), which allow us to use 1 km (versus currently available 10 km) resolution AOD data.We developed and cross validated models to predict daily PM(sub 2.5) at a 1X 1 km resolution across the northeastern USA (New England, New York and New Jersey) for the years 2003-2011, allowing us to better differentiate daily and long term exposure between urban, suburban, and rural areas. Additionally, we developed an approach that allows us to generate daily high-resolution 200 m localized predictions representing deviations from the area 1 X 1 km grid predictions. We used mixed models regressing PM(sub 2.5) measurements against day-specific random intercepts, and fixed and random AOD and temperature slopes. We then use generalized additive mixed models with spatial smoothing to generate grid cell predictions when AOD was missing. Finally, to get 200 m localized predictions, we regressed the residuals from the final model for each monitor against the local spatial and temporal variables at each monitoring site. Our model performance was excellent (mean out-of-sample R(sup 2) = 0.88). The spatial and temporal components of the out-of-sample results also presented very good fits to the withheld data (R(sup 2) = 0.87, R(sup)2 = 0.87). In addition, our results revealed very little bias in the predicted concentrations (Slope of predictions versus withheld observations = 0.99). Our daily model results show high predictive accuracy at high spatial resolutions and will be useful in reconstructing exposure histories for epidemiological studies across this region.

Air pollution↗
NASA NTRS2014

Anthropogenic Emissions of Highly Reactive Volatile Organic Compounds (HRVOCs) Inferred from Oversampling of OMI HCHO Columns

Satellite observations of formaldehyde (HCHO) columns provide top-down constraints on emissions of highly reactive volatile organic compounds (HRVOCs). This approach has been used previously to constrain emissions of isoprene from vegetation, but application to US anthropogenic emissions has been stymied by lack of a discernable HCHO signal. Here we show that oversampling of HCHO data from the Ozone Monitoring Instrument (OMI) for 2005 - 2008 enables quantitative detection of urban and industrial plumes in eastern Texas including Houston, Port Arthur, and Dallas-Fort Worth. By spatially integrating the individual urban-industrial HCHO plumes observed by OMI we can constrain the corresponding HCHO-weighted HRVOC emissions. Application to the Houston plume indicates a HCHO source of 260 plus or minus 110 kmol h-1 and implies a factor of 5.5 plus or minus 2.4 underestimate of anthropogenic HRVOC emissions in the US Environmental Protection Agency inventory. With this approach we are able to monitor the trend in HRVOC emissions over the US, in particular from the oil-gas industry, over the past decade.

AURA↗
NASA NTRS2015

Multilateral Research Opportunities in Ground Analogs

The global economy forces many nations to consider their national investments and make difficult decisions regarding their investment in future exploration. International collaboration provides an opportunity to leverage other nations' investments to meet common goals. The Humans In Space Community shares a common goal to enable safe, reliable, and productive human space exploration within and beyond Low Earth Orbit. Meeting this goal requires efficient use of limited resources and International capabilities. The International Space Station (ISS) is our primary platform to conduct microgravity research targeted at reducing human health and performance risks for exploration missions. Access to ISS resources, however, is becoming more and more constrained and will only be available through 2020 or 2024. NASA's Human Research Program (HRP) is actively pursuing methods to effectively utilize the ISS and appropriate ground analogs to understand and mitigate human health and performance risks prior to embarking on human exploration of deep space destinations. HRP developed a plan to use ground analogs of increasing fidelity to address questions related to exploration missions and is inviting International participation in these planned campaigns. Using established working groups and multilateral panels, the HRP is working with multiple Space Agencies to invite International participation in a series of 30- day missions that HRP will conduct in the US owned and operated Human Exploration Research Analog (HERA) during 2016. In addition, the HRP is negotiating access to Antarctic stations (both US and non-US), the German :envihab and Russian NEK facilities. These facilities provide unique capabilities to address critical research questions requiring longer duration simulation or isolation. We are negotiating release of international research opportunities to ensure a multilateral approach to future analog research campaigns, hoping to begin multilateral campaigns in the latter facilities by 2017. Collaborative use of analog facilities and shared investment in the development of spaceflight countermeasures through multilateral campaigns or missions that leverage the global scientific community will focus high quality research and provide sufficient power to accelerate the development of countermeasures and drive sound recommendations for exploration missions. This panel will provide an overview of efforts to encourage and facilitate multilateral collaboration in analog missions or campaigns and describe the facilities currently under consideration to reach the common goal of enabling safe, reliable, and productive human space exploration.

Corbin, Barbara J.↗