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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

High Data Rate Instrument Study

The High Data Rate Instrument Study was a joint effort between the Jet Propulsion Laboratory (JPL) and the Goddard Space Flight Center (GSFC). The objectives were to assess the characteristics of future high data rate Earth observing science instruments and then to assess the feasibility of developing data processing systems and communications systems required to meet those data rates. Instruments and technology were assessed for technology readiness dates of 2000, 2003, and 2006. The highest data rate instruments are hyperspectral and synthetic aperture radar instruments which are capable of generating 3.2 Gigabits per second (Gbps) and 1.3 Gbps, respectively, with a technology readiness date of 2003. These instruments would require storage of 16.2 Terebits (Tb) of information (RF communications case of two orbits of data) or 40.5 Tb of information (optical communications case of five orbits of data) with a technology readiness date of 2003. Onboard storage capability in 2003 is estimated at 4 Tb; therefore, all the data created cannot be stored without processing or compression. Of the 4 Tb of stored data, RF communications can only send about one third of the data to the ground, while optical communications is estimated at 6.4 Tb across all three technology readiness dates of 2000, 2003, and 2006 which were used in the study. The study includes analysis of the onboard processing and communications technologies at these three dates and potential systems to meet the high data rate requirements. In the 2003 case, 7.8% of the data can be stored and downlinked by RF communications while 10% of the data can be stored and downlinked with optical communications. The study conclusion is that only 1 to 10% of the data generated by high data rate instruments will be sent to the ground from now through 2006 unless revolutionary changes in spacecraft design and operations such as intelligent data extraction are developed.

Schober, Wayne↗
NASA NTRS2005

Three-System Isotopic of Lunar Norite 78238: Rb-Sr Results

The duration of lunar magma ocean (LMO) crystallization is poorly constrained (Fig. 1). Three techniques employed to determine the age of LMO solidification are 1) dating ferroan anorthosites (FANs), thought to be primary cumulates from the LMO, 2) calculating model ages for KREEP, the most incompatible element enriched material that remained after approx.99.5% of the LMO crystallized [1], and 3) constraining the age of the oldest KREEP-rich magnesium suite (Mg-suite) or alkali suite rock. Dating FANs is difficult because the samples are essentially monomineralic and contain low abundances of many elements used in isotopic dating. In addition, the young ages determined for some FANs may be related to impact metamorphism, potentially making FANs non-ideal for dating the age of LMO crystallization (e.g., [2]). Model ages for KREEP formation are dependent on the assumptions of the initial isotopic composition and parent/daughter ratio of the source. However, lunar rocks are susceptible to isotopic resetting and volatile element loss during shock, and are therefore unlikely to yield consistent model LMO crystallization ages (e.g., [3]). Rocks from the Mg-suite contain KREEP, indicating that they formed after LMO crystallization, and have old ages that indicate they formed almost immediately after the LMO crystallized (Fig. 1). Therefore, precisely dating the oldest Mg-suite rock is a promising way to constrain the age of LMO solidification.

Edmundson, J.↗
NASA NTRS2015

Assessing Wetland Hydroperiod and Soil Moisture With Remote Sensing: A Demonstration for the NASA Plum Brook Station Year 2

Primary Goal: Assist with the evaluation and measuring of wetlands hydroperiod at the PlumBrook Station using multi-source remote sensing data as part of a larger effort on projecting climate change-related impacts on the station's wetland ecosystems. MTRI expanded on the multi-source remote sensing capabilities to help estimate and measure hydroperiod and the relative soil moisture of wetlands at NASA's Plum Brook Station. Multi-source remote sensing capabilities are useful in estimating and measuring hydroperiod and relative soil moisture of wetlands. This is important as a changing regional climate has several potential risks for wetland ecosystem function. The year two analysis built on the first year of the project by acquiring and analyzing remote sensing data for additional dates and types of imagery, combined with focused field work. Five deliverables were planned and completed: 1) Show the relative length of hydroperiod using available remote sensing datasets 2) Date linked table of wetlands extent over time for all feasible non-forested wetlands 3) Utilize LIDAR data to measure topographic height above sea level of all wetlands, wetland to catchment area radio, slope of wetlands, and other useful variables 4) A demonstration of how analyzed results from multiple remote sensing data sources can help with wetlands vulnerability assessment 5) A MTRI style report summarizing year 2 results. This report serves as a descriptive summary of our completion of these our deliverables. Additionally, two formal meetings were held with Larry Liou and Amanda Sprinzl to provide project updates and receive direction on outputs. These were held on 2/26/15 and 9/17/15 at the Plum Brook Station. Principal Component Analysis (PCA) is a multivariate statistical technique used to identify dominant spatial and temporal backscatter signatures. PCA reduces the information contained in the temporal dataset to the first few new Principal Component (PC) images. Some advantages of PCA include the ability to filter out temporal autocorrelation and reduce speckle to the higher order PC images. A PCA was performed using ERDAS Imagine on a time series of PALSAR dates. Hydroperiod maps were created by separating the PALSAR dates into two date ranges, 2006-2008 and 2010, and performing an unsupervised classification on the PCAs.

Brooks, Colin↗
NASA NTRS2017

Comparison of Passive Microwave-Derived Early Melt Onset Records on Arctic Sea Ice

Two long records of melt onset (MO) on Arctic sea ice from passive microwave brightness temperatures (Tbs) obtained by a series of satellite-borne instruments are compared. The Passive Microwave (PMW) method and Advanced Horizontal Range Algorithm (AHRA) detect the increase in emissivity that occurs when liquid water develops around snow grains at the onset of early melting on sea ice. The timing of MO on Arctic sea ice influences the amount of solar radiation absorbed by the ice-ocean system throughout the melt season by reducing surface albedos in the early spring. This work presents a thorough comparison of these two methods for the time series of MO dates from 1979through 2012. The methods are first compared using the published data as a baseline comparison of the publically available data products. A second comparison is performed on adjusted MO dates we produced to remove known differences in inter-sensor calibration of Tbs and masking techniques used to develop the original MO date products. These adjustments result in a more consistent set of input Tbs for the algorithms. Tests of significance indicate that the trends in the time series of annual mean MO dates for the PMW and AHRA are statistically different for the majority of the Arctic Ocean including the Laptev, E. Siberian, Chukchi, Beaufort, and central Arctic regions with mean differences as large as 38.3 days in the Barents Sea. Trend agreement improves for our more consistent MO dates for nearly all regions. Mean differences remain large, primarily due to differing sensitivity of in-algorithm thresholds and larger uncertainties in thin-ice regions.

sea ice↗
NASA NTRSDate not supplied

Variation in Predicted Orbital Lifetime Due to Launch Year

We present trends in predicted orbital lifetimes of CubeSats based not only on orbital parameters, but also launch year and the Area-to-Mass (AtM) ratio of the CubeSat. Determining the orbital lifetime variation of CubeSats in low-Earth orbit (LEO) is an important aspect of mission planning because of two competing factors: (1) the maximum orbital lifetime for orbital debris mitigation requirements, and (2) the minimum orbit duration necessary to accomplish the spacecraft mission requirements. The orbital lifetime is a function of orbital parameters, the AtM ratio of the CubeSat, and date of orbit insertion. Solar flux varies with time, peaking and declining across the 11-year solar cycle and affecting the amount of atmospheric drag on the CubeSat. This results in large variations in orbital lifetime dependent on the mission's launch date. We calculated the variation of orbital lifetime for multiple commonly used 1U to 6U CubeSat mission types across the two upcoming solar cycles. For any given AtM ratio and altitude combination in this analysis, the predicted orbital lifetime varies up to a factor of five due to orbit insertion occurring in a different year. Some examples of orbital lifetime spreads are 5 months to 2 years, and 1.5 to 7.5 years. While orbital lifetimes correlate to the solar cycle, the phasing of the maximum values varies based on a given AtM ratio and altitude combination. Different combinations of these two factors will result in the maximum predicted orbital lifetime occurring at different launch years throughout the solar cycle. Therefore, there is not a specific year within a solar cycle which can be used to calculate the maximum predicted orbital lifetime for all CubeSats. Since CubeSats are typically flown as a rideshare payload on a launch vehicle, mission planners must account for launch date variation in their orbital lifetime predictions. We recommend calculating orbital lifetime for a range of dates to allow for risk planning due to launch date slips, and other mission planning best practices.

CubeSat↗
NASA NTRS2024

Using Commercial Satellite Imagery to Reconstruct 3 m and Daily Spring Snow Water Equivalent

Snow water equivalent (SWE) distribution at fine spatial scales (≤10 m) is difficult to estimate due to modeling and observational constraints. However, the distribution of SWE throughout the spring snowmelt season is often correlated to the timing of snow disappearance. Here, we show that snow cover maps generated from PlanetScope's constellation of Dove Satellites can resolve the 3 m date of snow disappearance across seven alpine domains in California and Colorado. Across a 5-year period (2019–2023), the average uncertainty in the date of snow disappearance, or the period of time between the last date of observed snow cover and the first date of observed snow absence, was 3 days. Using a simple shortwave-based snowmelt model calibrated at nearby snow pillows, the PlanetScope date of snow disappearance could be used to reconstruct spring SWE. Relative to lidar SWE estimates, the SWE reconstruction had a spatial coefficient of correlation of 0.75, and SWE spatial variability that was biased by 9%, on average. SWE reconstruction biases were then improved to within 0.04 m, on average, by calibrating snowmelt rates to track the spring temporal evolution of fractional snow cover observed by PlanetScope, including fractional snow cover over the full modeling domain, and across domain subsections where snowmelt rates may differ. This study demonstrates the utility of fine-scale and high-frequency optical observations of snow cover, and the simple and annually repeatable connections between snow cover and spring snow water resources in regions with seasonal snowpack.

Justin M Pflug↗
NASA NTRSDate not supplied

Aerocapture Solutions for Uranus Flagship-class Orbiter and Probe

Recent planetary mission assessments, such as the 2022 Planetary Science Decadal Survey released by the National Academies of Science, have focused on the need for a flagship-class mission to the Ice Giant planets, particularly Uranus. The Uranus Orbit and Probe mission proposal was used by the National Academies of Science as the baseline while making its recommendation as the top flagship-class mission for NASA in the 2020-2030\'s. This mission which was based on a launch date of 2031 or 2032, used a fully-propulsive orbit insertion maneuver at Uranus (requiring 60-70% of total mass for propellant), and reached the planet after 13 years of interplanetary cruise before the 2049 equinox, a goal of the science community. A pre-2033 launch date is required to conduct a necessary Jupiter fly-by as the giant planet will be not be in the proper alignment for a later launch date. However, as the budget constraints of the NASA budget have pushed back the start date of a Uranus mission, a launch date of a flagship mission before 2033 seems unreasonable. Aerocapture, an orbit insertion maneuver that uses the atmosphere to decelerate, can reduce the propellant load needed for a captured orbit. Additionally, the aerocapture maneuver can decelerate safely while approaching the planet at higher arrival velocities, thus allowing a mission to use a highly energetic trajectory and reduce the cruise time by several years. An aerocapture-enabled solution has launch opportunities in the mid 2030's, including as late as 2038 to reach Uranus by 2049. This paper will discuss the feasibility of an aerocapture option for a Flagship-class mission to Uranus.

Soumyo Dutta↗
NASA NTRSDate not supplied

Aerocapture Solutions for Uranus Flagship-class Orbiter and Probe

Recent planetary mission assessments, such as the 2022 Planetary Science Decadal Survey released by the National Academies of Science, have focused on the need for a flagship-class mission to the Ice Giant planets, particularly Uranus. The Uranus Orbit and Probe mission proposal was used by the National Academies of Science as the baseline while making its recommendation as the top flagship-class mission for NASA in the 2020-2030\'s. This mission which was based on a launch date of 2031 or 2032, used a fully-propulsive orbit insertion maneuver at Uranus (requiring 60-70% of total mass for propellant), and reached the planet after 13 years of interplanetary cruise before the 2049 equinox, a goal of the science community. A pre-2033 launch date is required to conduct a necessary Jupiter fly-by as the giant planet will be not be in the proper alignment for a later launch date. However, as the budget constraints of the NASA budget have pushed back the start date of a Uranus mission, a launch date of a flagship mission before 2033 seems unreasonable. Aerocapture, an orbit insertion maneuver that uses the atmosphere to decelerate, can reduce the propellant load needed for a captured orbit. Additionally, the aerocapture maneuver can decelerate safely while approaching the planet at higher arrival velocities, thus allowing a mission to use a highly energetic trajectory and reduce the cruise time by several years. An aerocapture-enabled solution has launch opportunities in the mid 2030's, including as late as 2038 to reach Uranus by 2049. This paper will discuss the feasibility of an aerocapture option for a Flagship-class mission to Uranus.

Soumyo Dutta↗
NASA NTRS1963

Space Flight Handbooks. Volume 3- Planetary Flight Handbook: Supplementary Trajectory Data: Venus to Earth and Mars to Earth - Part 2

Parts 2 and 3 present tabulations of trajectory data for scheduling flights to and from Venus and Mars during the period 1960-2000. Part 2 contains information for outbound flights to these planets; Part 3 contains information for trajectories returning from the planets to Earth. Each Part contains data for single-plane transfers, as well as for broken-plane transfers which employ a midcourse plane-change to eliminate the high speed "ridges." The mathematical analyses employed for all calculations are described in Part 1 of this handbook. To facilitate the construction of round-trip trajectories, the date at the target planet is held fixed while the trip duration is varied in 10-day increments from zero days to the length of that planet's synodic period with Earth. Dates of arrival at the target planet are presented in the extreme right-hand column of Part 2, and dates of departure from the target planet are presented in the extreme left-hand column of Part 3. Thus, by holding Part 2 directly to the left of Part 3, the analyst may easily and rapidly scan all trip possibilities which involve any desired stopover time at the target planet. Within approximately 200 days of each conjunction or opposition, data are presented in 10-day increments at the target planet. Only those trips are listed for which the hyperbolic excess speeds at either or both ends of the trajectory do not exceed 0.6 EMOS (Earth Mean Orbital Speed). For the remaining mission regions, the requirements are so smoothly varying that a 50-day interval in dates at the target planet may be employed; the 10-day interval in trip times is, however, preserved here. In these regions, only those trips are listed for which either or both speeds do not exceed 0.3 EMOS.

INTERPLANETARY FLIGHT↗
NASA NTRS1971

Navigation analysis for Viking 1979, option B

A parametric study performed for 48 trans-Mars reference missions in support of the Viking program is reported. The launch dates cover several months in the year 1979, and each launch date has multiple arrival dates in 1980. A plot of launch versus arrival dates with case numbers designated for reference purposes is included. The analysis consists of the computation of statistical covariance matrices based on certain assumptions about the ground-based tracking systems. The error model statistics are listed in tables. Tracking systems were assumed at three sites: Goldstone, California; Canberra, Australia; and Madrid, Spain. The tracking data consisted of range and Doppler measurements taken during the tracking intervals starting at E-30(d) and ending at E-10(d) for the control data and ending at E-18(h) for the knowledge data. The control and knowledge covariance matrices were delivered to the Planetary Mission Analysis Branch for inputs into a delta V dispersion analysis.

Mitchell, P. H.↗
NASA NTRS1975

Cosmic ray exposure ages of features and events at the Apollo landing sites

Cosmic-ray exposure ages of lunar samples have been used to date surface features related to impact cratering and downslope movement of material. Only when multiple samples related to a feature have the same rare-gas exposure age or when a single sample has the same Kr-81 -Kr and track-exposure age can a feature be considered as reliably dated. Based on these criteria, there are only five well-dated lunar features: Cone Crater (Apollo 14), 26 m.y,; North Ray Crater (Apollo 16), 50 m.y.; South Ray Crater (Apollo 16), 2 m.y.; the emplacement of the Station 6 boulders (Apollo 17), 22 m.y.; and the emplacement of the Station 7 boulder (Apollo 17), 28 m.y. Other features are tentatively dated or have limits set on their ages: Bench Crater (Apollo 12), upper limit of 99 m.y.; Baby Ray Crater (Apollo 16), upper limit of 2 m.y.; Shorty Crater (Apollo 17), approximately 30 m.y.; Camelot Crater (Apollo 17) upper limit of 140 m.y.; the emplacement of the Station 2 boulder 1 (Apollo 17), 45 to 55 m.y.; and the slide which generated the light mantle (Apollo 17), lower limit of 50 m.y.

Arvidson, R.↗
NASA NTRS1979

Large Area Crop Inventory Experiment (LACIE). Evaluation of the LACIE transition year crop calendar model

The author has identified the following significant results. The estimates of developmental stage dates from the LACIE adjustable crop calendar (ACC) winter wheat model was somewhat more accurate than the historical crop calendar after jointing. The ACC winter wheat model was not so accurate for the Texas Panhandle as it was for the other areas of the USPG-7 because dry soil conditions delayed fall planting in the Panhandle. Since the LACIE ACC winter wheat model does not contain a moisture term and it was started with historical planting dates, lengthy delays in planting mean that the ACC model will probably be started early and will estimate the developmental growth stages to occur too early in the season. The LACIE ACC spring wheat model was also started early in most areas because of late planting due to fields wet from melting snow and rain. The starter model used to estimate spring planting dates was not accurate under these wet soil conditions and tended to predict the developmental stages to occur earlier than the dates observed in the fields.

Cheffin, R. E.↗
NASA NTRS1981

Ar-40-Ar-39 and Rb-Sr age determinations on Quaternary volcanic rocks

Ages of leucite and biotite separates from samples of the potassic volcanics of the Roman Comagmatic region are derived by the stepwise degassing variant of the Ar-39-Ar-40 dating method and compared with those derived from Rb-Sr dating in order to evaluate the abilities of the methods to date Quaternary geological events. Six of the leucite separates are found to contain Ar with very high bulk 40/36 ratios and to have well correlated Ar-40 and Ar-39 contents, yielding ages of approximately 338,000 years. Two leucites observed to contain Ar with lower bulk 40/36 ratios and Ar-40/Ar-36 ratios significantly lower than atmospheric are found to have ages in substantial agreement with those of the other leucites despite the uncertainty in the composition of the trapped component. Ages obtained for the biotites are not as precise as those of the leucites, due to difficulties in obtaining a good separation of in situ radiogenic Ar-40 from trapped Ar-40. Ages determined from Rb-Sr measurements for selected tuff samples are found to be in good agreement with the Ar-40-Ar-39 ages of the leucites. Results demonstrate the possibility of attaining precisions of better than 5% in the dating of rocks 350,000 years old by both the Ar-40-Ar-39 and the Rb-Sr methods.

Radicati Di Brozolo, F.↗
NASA NTRS1984

Meteorological models for estimating phenology of corn

Knowledge of when critical crop stages occur and how the environment affects them should provide useful information for crop management decisions and crop production models. Two sources of data were evaluated for predicting dates of silking and physiological maturity of corn (Zea mays L.). Initial evaluations were conducted using data of an adapted corn hybrid grown on a Typic Agriaquoll at the Purdue University Agronomy Farm. The second phase extended the analyses to large areas using data acquired by the Statistical Reporting Service of USDA for crop reporting districts (CRD) in Indiana and Iowa. Several thermal models were compared to calendar days for predicting dates of silking and physiological maturity. Mixed models which used a combination of thermal units to predict silking and days after silking to predict physiological maturity were also evaluated. At the Agronomy Farm the models were calibrated and tested on the same data. The thermal models were significantly less biased and more accurate than calendar days for predicting dates of silking. Differences among the thermal models were small. Significant improvements in both bias and accuracy were observed when the mixed models were used to predict dates of physiological maturity. The results indicate that statistical data for CRD can be used to evaluate models developed at agricultural experiment stations.

Daughtry, C. S. T.↗
NASA NTRS1985

X-ray satellite

The projected launch date has been delayed approx. 7 weeks from the planned launch date. The Engineering Model (EM) of the automatic measurement and control system (AMCS) is in the critical phase. The contract change no. 1 to the main contract has been signed. A new version of the welding seam location specifications for the wide field camera (WFC) was proposed by the WFC Consortium. The payload integration plan (PIP) has been signed. Production of the EM/QM prototype and ground station equipment has proceeded according to plan with the exception of some delays. Production of the EM equipment has begun. Preparations for the qualification tests of the EM/QM equipment and the integration of EM equipment has begun. The cause of the delay in the launch date include the combined effects of the postponement of the target date for the EM equipment, along with the fact that only a structural model is available.

Source record↗
NASA NTRS1984

Benchmark data on the separability among crops in the southern San Joaquin Valley of California

Landsat MSS data were input to a discriminant analysis of 21 crops on each of eight dates in 1979 using a total of 4,142 fields in southern Fresno County, California. The 21 crops, which together account for over 70 percent of the agricultural acreage in the southern San Joaquin Valley, were analyzed to quantify the spectral separability, defined as omission error, between all pairs of crops. On each date the fields were segregated into six groups based on the mean value of the MSS7/MSS5 ratio, which is correlated with green biomass. Discriminant analysis was run on each group on each date. The resulting contingency tables offer information that can be profitably used in conjunction with crop calendars to pick the best dates for a classification. The tables show expected percent correct classification and error rates for all the crops. The patterns in the contingency tables show that the percent correct classification for crops generally increases with the amount of greenness in the fields being classified. However, there are exceptions to this general rule, notably grain.

Morse, A.↗
NASA NTRS1987

Digital image classification approach for estimating forest clearing and regrowth rates and trends

A technique is presented to monitor vegetation changes for a selected study area in Costa Rica. A normalized difference vegetation index was computed for three dates of Landsat satellite data and a modified parallelipiped classifier was employed to generate a multitemporal greenness image representing all three dates. A second-generation image was created by partitioning the intensity levels at each date into high, medium, and low and thereby reducing the number of classes to 21. A sampling technique was applied to describe forest and other land cover change occurring between time periods based on interpretation of aerial photography that closely matched the dates of satellite acquisition. Comparison of the Landsat-derived classes with the photo-interpreted sample areas can provide a basis for evaluating the satellite monitoring technique and the accuracy of estimating forest clearing and regrowth rates and trends.

Sader, Steven A.↗
NASA NTRS1988

Absolute ages from crater statistics: Using radiometric ages of Martian samples for determining the Martian cratering chronology

In the absence of dates derived from rock samples, impact crater frequencies are commonly used to date Martian surface units. All models for absolute dating rely on the lunar cratering chronology and on the validity of its extrapolation to Martian conditions. Starting from somewhat different lunar chronologies, rather different Martian cratering chronologies are found in the literature. Currently favored models are compared. The differences at old ages are significant, the differences at younger ages are considerable and give absolute ages for the same crater frequencies as different as a factor of 3. The total uncertainty could be much higher, though, since the ratio of lunar to Martian cratering rate which is of basic importance in the models is believed to be known no better than within a factor of 2. Thus, it is of crucial importance for understanding the the evolution of Mars and determining the sequence of events to establish an unambiguous Martian cratering chronology from crater statistics in combination with clean radiometric ages of returned Martian samples. For the dating goal, rocks should be as pristine as possible from a geologically simple area with a one-stage emplacement history of the local formation. A minimum of at least one highland site for old ages, two intermediate-aged sites, and one very young site is needed.

Neukum, G.↗