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NASA NTRS2016

NASA RPS Program Overview: A Focus on RPS Users

The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to support the exploration of the solar system in environments where the use of conventional solar or chemical power generation is impractical or impossible to meet the needs of the missions. To meet this goal, the RPS Program, working closely with the Department of Energy, performs mission and system studies (such as the recently released Nuclear Power Assessment Study), assesses the readiness of promising technologies to infuse in future generators, assesses the sustainment of key RPS capabilities and knowledge, forecasts and tracks the Programs budgetary needs, and disseminates current information about RPS to the community of potential users. This process has been refined and used to determine the current content of the RPS Programs portfolio. This portfolio currently includes an effort to mature advanced thermoelectric technology for possible integration into an enhanced Multi-Mission Radioisotope Generator (eMMRTG), sustainment and production of the currently deployed MMRTG, and technology investments that could lead to a future Stirling Radioisotope Generator (SRG). This paper describes the program planning processes that have been used, the currently available MMRTG, and one of the potential future systems, the eMMRTG.

Radioisotope↗

NASA NTRS2016

NASA's Radioisotope Power Systems Planning and Potential Future Systems Overview

Radioisotope↗

NASA NTRS2016

NASA's Radioisotope Power Systems Planning and Potential Future Systems Overview

The goal of NASA's Radioisotope Power Systems (RPS) Program is to make RPS ready and available to support the exploration of the solar system in environments where the use of conventional solar or chemical power generation is impractical or impossible to meet the needs of the missions. To meet this goal, the RPS Program, working closely with the Department of Energy, performs mission and system studies (such as the recently released Nuclear Power Assessment Study), assesses the readiness of promising technologies to infuse in future generators, assesses the sustainment of key RPS capabilities and knowledge, forecasts and tracks the Program's budgetary needs, and disseminates current information about RPS to the community of potential users. This process has been refined and used to determine the current content of the RPS Program's portfolio. This portfolio currently includes an effort to mature advanced thermoelectric technology for possible integration into an enhanced Multi-Mission Radioisotope Generator (eMMRTG), sustainment and production of the currently deployed MMRTG, and technology investments that could lead to a future Stirling Radioisotope Generator (SRG). This paper describes the program planning processes that have been used, the currently available MMRTG, and one of the potential future systems, the eMMRTG.

Nuclear↗

NASA NTRS2004

Prototype Test Results for the Single Photon Detection SLR2000 Satellite Laser Ranging System

NASA's aging Satellite Laser Ranging (SLR) network is scheduled to be replaced over the next few years with a fully automated single photon detection system. A prototype of this new system, called SLR2000, is currently undergoing field trials at the Goddard Space Flight Center in Greenbelt, Maryland to evaluate photon counting techniques and determine system hardware, software, and control algorithm performance levels and limitations. Newly developed diode pumped microchip lasers and quadrant microchannel plate-based photomultiplier tubes have enabled the development of this high repetition rate single photon detection SLR system. The SLR2000 receiver threshold is set at the single photoelectron (pe) level but tracks satellites with an average signal level typically much less than 1 pe. The 2 kHz laser fire rate aids in satellite acquisition and tracking and will enable closed loop tracking by accumulating single photon count statistics in a quadrant detector and using this information to correct for pointing errors. Laser transmitter beamwidths of 10 arcseconds (FWHM) or less are currently being used to maintain an adequate signal level for tracking while the receiver field of view (FOV) has been opened to 40 arcseconds to accommodate point ahead/look behind angular offsets. In the near future, the laser transmitter point ahead will be controlled by a pair of Risley prisms. This will allow the telescope to point behind and enable closure of the receiver FOV to roughly match the transmitter beam divergence. Bandpass filters (BPF) are removed for night tracking operations while 0.2 nm or 1 nm filters are used during daylight operation. Both day and night laser tracking of Low Earth Orbit (LEO) satellites has been achieved with a laser transmitter energy of only 65 microjoules per pulse. Satellite tracking is presently limited to LEO satellites until the brassboard laser transmitter can be upgraded or replaced. Simultaneous tracks have also been observed with NASA s SLR standard, MOBLAS 7, for the purposes of data comparison and identification of biases. Work continues to optimize the receive optics; upgrade or replace the laser transmitter; calibrate the quadrant detector, the point ahead Risley prisms, and event timer verniers; and test normal point generation with SLR2000 data. This paper will report on the satellite tracking results to date, issues yet to be resolved, and future plans for the SLR2000 system.

Zagwodzki, Thomas W.↗

NASA NTRS1993

New approaches for tracking earth orbiters using modified GPS ground receivers

A Global Positioning System (GPS) flight receiver provides a means to precisely determine orbits for satellites in low to moderate altitude orbits. Above a 5000-km altitude, however, relatively few GPS satellites are visible. New approaches to orbit determination for satellites at higher altitudes could reduce DSN antenna time needed to provide navigation and orbit determination support to future missions. Modification of GPS ground receivers enables a beacon from the orbiter to be tracked simultaneously with GPS data. The orbit accuracy expected from this GPS-like tracking (GLT) technique is expected to be in the range of a few meters or better for altitudes up to 100,000 km with a global ground network. For geosynchronous satellites, however, there are unique challenges due to geometrical limitations and to the lack of strong dynamical signature in tracking data. We examine two approaches for tracking the Tracking and Data Relay Satellite System (TDRSS) geostationary orbiters. One uses GLT with a global network; the other relies on a small 'connected element' ground network with a distributed clock for short-baseline differential carrier phase (SB Delta Phi). We describe an experiment planned for late 1993, which will combine aspects of both GLT and SB Delta Phi, to demonstrate a new approach for tracking the Tracking and Data Relay Satellites (TDRSs) that offers a number of operationally convenient and attractive features. The TDRS demonstration will be in effect a proof-of-concept experiment for a new approach to tracking spacecraft which could be applied more generally to deep-space as well as near-Earth regimes.

Lichten, S. M.↗

NASA NTRS1988

The role of GPS in precise earth observation

The potential of the Global Positioning System (GPS) for precise earth observation is evaluated. It is projected that soon GPS will be utilized to track remote-sensing satellites with subdecimeter accuracy. The first will be Topex/Poseidon, a US/French ocean altimetry mission to be launched in 1991. In addition, it is suggested that developments planned for future platforms may push orbit accuracy near 1 cm within a decade. GPS receivers on some platforms will track the signals down to the earth limb to observe occultation by intervening media. This will provide comprehensive information on global temperature and climate and help detect the possible onset of a greenhouse effect. It is also projected that dual-frequency observations will be used to trace the flow of energy across earth systems through detection of ionospheric gravity waves, and to map the structure of the ionosphere by computer tomography.

Yunck, Thomas P.↗

NASA NTRS2024

Impacts of an Early Morning Low Earth Orbit Observing Platform in A Future Global Observing Network Scenario

Significant changes to the global observing network are expected in the coming decades including the launch of a global ring of geostationary satellites and a reduction in the number of low earth orbit (LEO) platforms. It is anticipated that there may be a gap in the LEO coverage between the planned mid-morning and early afternoon orbits. Here, the utility of an early morning LEO orbit for numerical weather prediction is considered using an observing system simulation experiment (OSSE). A global observing network with two LEO platforms including microwave and hyperspectral infrared instruments and three geostationary hyperspectral infrared platforms is considered for a future baseline scenario. Two instruments, a microwave radiometer modeled on the Advanced Technology Microwave Sounder (ATMS) and a hyperspectral infrared radiometer modeled on the Cross-track Infrared Sounder (CrIS), are tested both individually and in conjunction on a new early morning orbit in addition to the future baseline scenario. The microwave instrument is found to have beneficial impacts for up to 4–7 days in the medium range forecast period with beneficial impacts for the infrared instrument for up to 3–5 days. Short-range forecast impacts estimated with Forecast Sensitivity Observation Impacts (FSOI) over the conterminous United States for the early morning orbit are somewhat weaker than for the same instruments in the early afternoon orbit due to the orbital passage being coincident with rawinsondes while the afternoon orbit is coincident with the minima of both rawinsondes and aircraft.

Nikki C Prive↗

NASA NTRS1983

Status of the geopotential

Satellite laser ranging, satellite altimetry, and improved measurements of surface gravitational anomalies have broadened the data base on intermediate and short wavelength regions of the earth gravity field. The global data set served to develop new geopotential models with a resolution in spherical harmonics out to degree 180. The resolution was made possible using Seasat altimetry data containing 56,761 values of 1 x 1 deg gravity anomalies. Satellite-to-satellite tracking techniques involving the Geos-3 and Apollo spacecraft data for the sea surface temperature have yielded accurate intermediate wavelength gravity variations which correlate well with residual depth anomalies. Oceanic gravity anomalies have been computed directly from satellite altimetry or through statistical estimation using oceanic geoid heights. The data sets for gravimetric geoids have been compared with altimetric surfaces to identify areas which were of interest for geophysical investigation. Future data sets could become available from a proposed satellite-to-satellite Doppler tracking system (Gravsat) launched by NASA.

Lerch, F. J.↗

NASA NTRS2016

Modeling of the Orbital Debris Environment Risks in the Past, Present, and Future

Despite of the tireless work by space surveillance assets, much of the Earth debris environment is not easily measured or tracked. For every object that is in an orbit we can track, there are hundreds of small debris that are too small to be tracked but still large enough to damage spacecraft. In addition, even if we knew today's environment with perfect knowledge, the debris environment is dynamic and would change tomorrow. Therefore, orbital debris scientists rely on numerical modeling to understand the nature of the debris environment and its risk to space operations throughout Earth orbit and into the future. This talk will summarize the ways in which modeling complements measurements to help give us a better picture of what is occurring in Earth orbit, and helps us to better conduct current and future space operations.

Matney, Mark↗

NASA NTRS1983

Forecasting tropical cyclone recurvature with upper tropospheric winds

Data from 17 tropical cyclones during the 1974 through 1979 hurricane seasons are used to investigate whether the high level winds far to the northwest, north and northeast of the hurricane center can be used to predict hurricane track recurvature. When the man 200-mb winds 1500 to 2000 km northwest and north of the storm center equal or exceed 20 m/s, 80 per cent of the storms recurved before traveling as much as 12 degrees of longitude farther west. The high winds were also used to predict change in direction of forward motion during the next 72 hours. The regression equations developed explain up to 41 per cent of the variance in future direction. In addition to the geostrophic winds used, winds were also obtained by tracking clouds with successive satellite imagery. The u-components of the satellite winds are highly correlated with the geostrophic winds at 200-mb and could probably be used instead of them when available. The v-components are less highly correlated.

Gentry, R. C.↗

NASA NTRS2015

Risky Business

During my internship I worked on two major projects, recommending improvements for the Center's Risk Management Workshop and helping with the strategic planning efforts for Safety and Mission Assurance (S&MA). The risk management improvements is the key project I worked on this semester through my internship, while the strategic planning is the secondary assignment. S&MA Business Office covers both aspects in its delegation, getting both spans some of the work done in the office. A risk is a future event with a negative consequence that has some probability of occurring. Safety and Mission Assurance identifies, analyzes, plans, and tracks risk. The directorate offers the Center a Risk Management Workshop, and part of the ongoing efforts of S&MA is to make continuous improvements to the RM Workshop. By using the Project Management Institute's (PMI) Standard for Risk Management, I performed a gap analysis to make improvements for our materials. I benchmarked the PMI's Risk Management Standard, compared our Risk Management Workshop materials to PMI's standard, and identified any gaps in our material. My major findings were presented to the Business Office of S&MA for a decision on whether or not to incorporate the improvements. These suggestions were made by attending JSC working group meetings, Health, Safety and Environment (HSE) panel reviews and various risk review meetings. The improvements provide better understanding of risk management processes and enhanced risk tracking knowledge and skills. Risk management is an integral part of any engineering discipline, getting exposed to this section of engineering will greatly help shape my career in the future. Johnson Space Center is a world leader in risk management processes; learning risk management here gives me a huge advantage over my peers, as well as understanding decision making in the context of risk management will help me to be a well-rounded engineer. Strategic planning is an area I had not previously studied. Helping with the strategic planning efforts in S&MA has taught me how organizations think and function as a whole. S&MA is adopting a balanced scorecard approach to strategic planning. As part of this planning method strategic themes, objectives, and initiatives are formed. I attended strategic theme team workshops that formed the strategy map for the directorate and gave shape to the plan. Also during these workshops the objectives were discussed and built. Learning the process for strategic planning has helped me better understand how organizations and businesses function, which also helps me to be a more effective employee. Other assignments I had during my internship included completing the Safety and Mission Assurance Technical Excellent Program (STEP) Level 1, as well as doing a two week rotation through the Space Exploration division in S&MA, specifically working with a thermal protection systems (TPS) engineer. While working there, I learned about the Orion capsule and the SpaceX Dragon cargo capsule. I attended meetings to prepare the engineers for the upcoming Critical Design Reviews for both capsules and reviewed test data. Learning risk management, strategic planning, and working in the Space Exploration division has taught me about many aspects of S&MA. My internship at NASA has given me new experiences and taught me numerous subjects that I would have otherwise not learned. This opportunity has expanded my educational horizons and is helping me to become a more useful engineer and employee.

Yarbrough, Katherine↗

NASA NTRS1999

The Past, Present, and Future of Ground Station Automation within DSN

This paper describes an architecture for an autonomous Deep Space Tracking Station (DS-T).

ground↗

NASA NTRS1978

Calibration standards and field instruments for the precision measurement of insolation

The design of a fieldworthy survey instrument based on a developed radiation calibration standard is discussed. The radiometer system, a fieldworthy modification of Pacrad, is an all-weather solar radiometer, and a field test is described which demonstrates the instrument's stability in severe environments over an extended period of time. It is suggested that the instrument may be considered a transfer standard as well as a radiometer. It is hoped that future modifications might reduce the 15-deg view angle and improve the tracking system to eliminate weekly manual declination adjustments.

Reid, M. S.↗

NASA NTRS1978

An extension of the quickened display for manual control

It is very difficult (or even impossible) for a human to control plants of third order or more with little or no damping by just knowing the instantaneous error. It has been shown that adding first and/or higher order derivatives to the error signal and displaying the combined signal are effective in facilitating human control over such plants. This signal quickening technique by Birmingham and Taylor is further extended to incorporate the future trajectory variation into the displayed signal so as to minimize the tracking error. A method for tuning free parameters in ordinary and extended quickening is established by applying discrete-time optimal control. Experimental results for a triple integrator plant indicate the effectiveness of the proposed method to achieve high quality tracking.

Tomizuka, M.↗

NASA NTRS1985

Determining Availability Characteristics of DSN Data Systems Using Discrepancy Report Data

A reasonably economical way was developed to determine availability characteristics of Deep Space Network (DSN) data systems, subsystems, and assemblies using the DSN discrepancy report (DR) data base and DSN operating schedule and history data bases. Operating mean time between failures (OMTBF), operating mean time to restore service (OMTTRS), and operating functional availability (OFA) can be computed by year, by system, by subsystem, by assembly, and by station. The effort required to produce the desired reports is described, specific data on the telemetry, command, and tracking systems are presented, and major contributors to system outages are identified. Future improvements in preparing and analyzing DR data are also outlined to enhance their use in correcting conditions that lead to outages.

Ruskin, A. M.↗

NASA NTRS2009

SPACE MEDICINE and Medical Operations Overview

This presentation is an overview of the function of the work of the Space Medicine & Health Care Systems Office. The objective of the medical operations is to ensure the health, safety and well being of the astronaut corps and ground support team during all phases of space flight. There are many issues that impact the health of the astronauts. Some of them are physiological, and others relate to behavior, psychological issues and issues of the environment of space itself. Reviews of the medical events that have affected both Russian, and Americans while in space are included. Some views of shuttle liftoff, and ascent, the medical training aboard NASA's KC-135 and training in weightlessness, the Shuttle Orbiter Medical system (SOMS), and some of the medical equipment are included. Also included are a graphs showing Fluid loading countermeasures, and vertical pursuit tracking with head and eye. The final views are representations of the future crew exploration vehicle (CEV) approaching the International Space Station, and the moon, and a series of perspective representations of the earth in comparison to the other planets and the Sun, the Sun in relation to other stars, and a view of where in the galaxy the Sun is.

Dervay, Joe↗

NASA NTRS2011

Uplink Array Technology Development

Objective: Develop and demonstrate Uplink Array CALIBRATION and BLIND TRACKING TECHNOLOGIES at X-band, under realistic operational conditions relevant to future DSN uplink arrays

planetary radar↗

NASA NTRS2014

Assessment of the Pseudo Geostationary Lightning Mapper Products at the Spring Program and Summer Experiment

Since 2010, the de facto Geostationary Lightning Mapper (GLM) demonstration product has been the Pseudo‐Geostationary Lightning Mapper (PGLM) product suite. Originally prepared for the Hazardous Weather Testbed's Spring Program (specifically the Experimental Warning Program) when only four ground‐based lightning mapping arrays were available, the effort now spans collaborations with several institutions and eight collaborative networks. For 2013, NASA's Short‐term Prediction Research and Transition (SPoRT) Center and NOAA's National Severe Storms Laboratory have worked to collaborate with each network to obtain data in real‐time. This has gone into producing the SPoRT variant of the PGLM that was demonstrated in AWIPS II for the 2013 Spring Program. Alongside the PGLM products, the SPoRT / Meteorological Development Laboratory's total lightning tracking tool also was evaluated to assess not just another visualization of future GLM data but how to best extract more information while in the operational environment. Specifically, this tool addressed the leading request by forecasters during evaluations; provide a time series trend of total lightning in real‐time. In addition to the Spring Program, SPoRT is providing the PGLM "mosaic" to the Aviation Weather Center (AWC) and Storm Prediction Center. This is the same as what is used at the Hazardous Weather Testbed, but combines all available networks into one display for use at the national centers. This year, the mosaic was evaluated during the AWC's Summer Experiment. An important distinction between this and the Spring Program is that the Summer Experiment focuses on the national center perspective and not at the local forecast office level. Specifically, the Summer Experiment focuses on aviation needs and concerns and brings together operational forecaster, developers, and FAA representatives. This presentation will focus on the evaluation of SPoRT's pseudo‐GLM products in these separate test beds. The emphasis will be on how future GLM observations can support operations at both the local and national scale and how the PGLM was used in combination with other lightning data sets. Evaluations for the PGLM were quite favorable with forecasters appreciating the high temporal resolution, the ability to look for rapid increases in lightning activity ahead of severe weather, as well as situational awareness for where convection is firing and for flight routing.

Stano, Geoffrey T.↗