Gemini guidance and control.
Gemini guidance and control, discussing design, ground monitoring, launch and flight guidance, spacecraft instrumentation, maneuvering, etc
SPACE RENDEZVOUS MANEUVER↗
SEARCH · Search NASA
Results for “Spacecraft instruments”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Dynamics Explorer spacecraft and ground operations systems
The Dynamics Explorer program of NASA is designed to study the coupling of energy, electric currents, electric fields, and plasmas between the atmosphere, ionosphere, and the magnetosphere. The program is composed of two well instrumented polar orbiting satellites and ground operations and data handling systems which have been designed to acquire, process, and make readily available to the scientists of the program the data sets necessary for analysis to accomplish the science objectives. These systems are described with emphasis placed on the relationship of the two instrumented spacecraft and the ground systems to their roles in meeting the program requirements. In addition, the characteristics of the orbits selected are specified.
Hoffman, R. A.↗
Autonomous-Control Concept For Instrument Pointing System
Integrated payload articulation and identification system (IPAIDS) is conceptual system to control aiming of instruments aboard spacecraft of proposed Earth Observation System (EOS). Principal features of concept include advanced control strategies intended to assure robustness of performance over wide range of uncertainties in characteristics of spacecraft and instrument system. Intended originally for application to spacecraft system, has potential utility on Earth for automatic control of autonomous (robotic) vehicles or of remote sensing systems.
Mettler, Edward↗
Ultraviolet Measurements of the Sun
Wealth of experimentation with spaceborne spectroscopic and polarimetric instrument described. Instrument consists primarily of telescope, spectrometer, polarimeter, and associated electronics. Through ability of instrument possible to study evolution, in space and time, of spectral-line intensities, densities, and mass motions in preflare and flare-transistion-zone plasmas-novel feature for spacecraft instrument.
Henze, W.↗
Spacecraft Cryocooler Thermal Integration
Spacecraft instruments requiring cryocoolers to cool infrared focal plane arrays have increased complexity in the overall design with respect to power and thermal management. The use of mechanical cryocoolers can drive spacecraft solar array and thermal radiator dimensions, and spacecraft designers must be prudent in keeping these dimensions feasible.
Infrared focal plane Launch Lift Capabilities↗
A Ground Validation Network for the Global Precipitation Measurement Mission
A prototype Validation Network (VN) is currently operating as part of the Ground Validation System for NASA's Global Precipitation Measurement (GPM) mission. The VN supports precipitation retrieval algorithm development in the GPM prelaunch era. Postlaunch, the VN will be used to validate GPM spacecraft instrument measurements and retrieved precipitation data products. The period of record for the VN prototype starts on 8 August 2006 and runs to the present day. The VN database includes spacecraft data from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and coincident ground radar (GR) data from operational meteorological networks in the United States, Australia, Korea, and the Kwajalein Atoll in the Marshall Islands. Satellite and ground radar data products are collected whenever the PR satellite track crosses within 200 km of a VN ground radar, and these data are stored permanently in the VN database. VN products are generated from coincident PR and GR observations when a significant rain event occurs. The VN algorithm matches PR and GR radar data (including retrieved precipitation data in the case of the PR) by calculating averages of PR reflectivity (both raw and attenuation corrected) and rain rate, and GR reflectivity at the geometric intersection of the PR rays with the individual GR elevation sweeps. The algorithm thus averages the minimum PR and GR sample volumes needed to "matchup" the spatially coincident PR and GR data types. The result of this technique is a set of vertical profiles for a given rainfall event, with coincident PR and GR samples matched at specified heights throughout the profile. VN data can be used to validate satellite measurements and to track ground radar calibration over time. A comparison of matched TRMM PR and GR radar reflectivity factor data found a remarkably small difference between the PR and GR radar reflectivity factor averaged over this period of record in stratiform and convective rain cases when samples were taken from high in the atmosphere. A significant difference in PR and GR reflectivity was found in convective cases, particularly in convective samples from the lower part of the atmosphere. In this case, the mean difference between PR and corrected GR reflectivity was −1.88 dBZ. The PR-GR bias was found to increase with the amount of PR attenuation correction applied, with the PR-GR bias reaching −3.07 dBZ in cases where the attenuation correction applied is greater than 6 dBZ. Additional analysis indicated that the version 6 TRMM PR retrieval algorithm underestimates rainfall in case of convective rain in the lower part of the atmosphere by 30%-40%.
Schwaller, Mathew R.↗
A Ground Validation Network for the Global Precipitation Measurement Mission
A prototype Validation Network (VN) is currently operating as part of the Ground Validation System for NASA's Global Precipitation Measurement (GPM) mission. The VN supports precipitation retrieval algorithm development in the GPM prelaunch era. Postlaunch, the VN will be used to validate GPM spacecraft instrument measurements and retrieved precipitation data products. The period of record for the VN prototype starts on 8 August 2006 and runs to the present day. The VN database includes spacecraft data from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) and coincident ground radar (GR) data from operational meteorological networks in the United States, Australia, Korea, and the Kwajalein Atoll in the Marshall Islands. Satellite and ground radar data products are collected whenever the PR satellite track crosses within 200 km of a VN ground radar, and these data are stored permanently in the VN database. VN products are generated from coincident PR and GR observations when a significant rain event occurs. The VN algorithm matches PR and GR radar data (including retrieved precipitation data in the case of the PR) by calculating averages of PR reflectivity (both raw and attenuation corrected) and rain rate, and GR reflectivity at the geometric intersection of the PR rays with the individual GR elevation sweeps. The algorithm thus averages the minimum PR and GR sample volumes needed to "matchup" the spatially coincident PR and GR data types. The result of this technique is a set of vertical profiles for a given rainfall event, with coincident PR and GR samples matched at specified heights throughout the profile. VN data can be used to validate satellite measurements and to track ground radar calibration over time. A comparison of matched TRMM PR and GR radar reflectivity factor data found a remarkably small difference between the PR and GR radar reflectivity factor averaged over this period of record in stratiform and convective rain cases when samples were taken from high in the atmosphere. A significant difference in PR and GR reflectivity was found in convective cases, particularly in convective samples from the lower part of the atmosphere. In this case, the mean difference between PR and corrected GR reflectivity was -1.88 dBZ. The PR-GR bias was found to increase with the amount of PR attenuation correction applied, with the PR-GR bias reaching -3.07 dBZ in cases where the attenuation correction applied is greater than 6 dBZ. Additional analysis indicated that the version 6 TRMM PR retrieval algorithm underestimates rainfall in case of convective rain in the lower part of the atmosphere by 30%-40%.
Schwaller, Mathew R.↗
Jet Propulsion Laboratory: Annual Report 2001
For many years before the clock counted down to midnight and the arrival of the year 2000, the world had anticipated 2001 as a special time and a new era. Now we know that 2001 will be a year none of us will ever forget. We began a new year, a new century, and a new millennium. Yet after September 11, the world in many ways seems profoundly changed. On that day we witnessed both the worst and best in human nature. Space exploration is one pursuit that points towards the best instincts in our nature. And certainly the pioneering spirit, so much a part of the American character, is a value deeply embedded into all the work we undertake at JPL. We are privileged that the nation has entrusted us with exploring space on its behalf. And we are fortunate to find ourselves part of two of the world's most accomplished institutions - NASA and the California Institute of Technology. Looking back over the past four decades, JPL has carried out an initial reconnaissance of nearly all of the solar systems planets. Today we have more than a dozen missions flying, and many more in various stages of development. Our challenge now is to create missions that help us understand these places more deeply. And in addition to exploring and understanding our solar system, we want to discover neighboring solar systems and explore them as well. The 21st century is upon us. So is a tremendous era of space exploration. There were many events in 2001 to celebrate, one being the arrival of the Mars Odyssey orbiter, which joins the Mars Global Surveyor orbiter in providing continuous coverage of the red planet. This is a major step in establishing a permanent robotic presence at Mars. Ahead for JPL will be both rewarding and challenging moments; thats the nature of being pioneers and explorers.
National Aeronautics and Space Administration (NAS↗
Magnetometer instrument team studies for the definition phase of the outer planets grand tour
The objectives of magnetic field investigations on missions to the outer planets were defined as well as an instrumentation system, a program of studies and instrument development tasks was proposed for the mission definition phase of the Outer Planets Grand Tour project. A report on the status of this program is given. Requirements were also established for the spacecraft and the mission which would insure their compatibility with the magnetic field investigation proposed for the outer planets missions and developed figures of merit for encounter trajectories. The spacecraft-instrumentation interface and the on-board data handling system were defined in various reports by the Project Team and in the reports by the Science Steering Group. The defining program for exploring the outer planets within the more restrictive constraints of the Mariner Jupiter-Saturn project included defining a limited magnetic field investigation.
Coleman, P. J., Jr.↗
The Small Spacecraft Systems Virtual Institute (S3VI) and NASA's Small Spacecraft Enterprise
The mission of the Small Spacecraft Systems Virtual Institute (S3VI) is to advance the field of small spacecraft systems and allied sciences by promoting innovation, exploring new concepts, identifying emerging technology opportunities, and establishing effective conduits for the collaboration and the dissemination of research results relevant to small spacecraft systems. The S3VI is the common portal for NASA related small spacecraft activities. The portal hosts the Small Spacecraft Body of Knowledge as an online resource for the Small Spacecraft Technology State of the Art report, and reliability processes and practices, among other small spacecraft-focused content. The S3VI's first year activities focused on development of the web portal and investment in collaborative tools to host and support working groups formed to concentrate on a variety of small spacecraft topics such as reliability and access to space. The S3VI serves as the front door for other governmental and non-governmental organizations that wish to collaborate or interact with NASA small spacecraft organizations. NASA presently has a growing number of small spacecraft related programs, projects, and efforts underway to advance the state of the art of small spacecraft instruments, technologies, and missions in order for NASA to achieve its science and exploration goals.
Small spacecraft↗
Remote sensing of soil moisture
The surface emissivity and reflectivity of soil are strong functions of its moisture content. Changes in emissivity, observed by passive microwave techniques (radiometry), and changes in reflectivity, observed by active microwave techniques (radar), can provide information on the moisture content of the 0 to 5 cm surface layer. In addition, the thermal inertia of the surface layer, which can be remotely sensed by observing the diurnal range of surface temperature, is an indicator of soil moisture content. The thermal infrared approach to remote sensing of soil moisture has little utility in the presence of cloud cover, but provides soil moisture data at high spatial resolutions and thermal data which are a potentially useful indicator of crop status. Microwave techniques can penetrate cloud covers. The passive technique has been demonstrated by both aircraft and spacecraft instruments, but spatial resolution is limited by the size of the antenna which can be flown. Active microwave systems offer the possibility of better spatial resolution, but have yet to be demonstrated from aircraft or spacecraft platforms.
Schmugge, T.↗
Numerical simulation of spacecraft charging by impact-induced plasmas during a cometary flyby
A numerical model is developed for the interaction of a cometary probe, such as Giotto, with its environment, i.e., dust particles and gas. The spacecraft was set on a course to pass the comet at a velocity of 69 km/sec, so a chance existed that a potential field would form around the spacecraft and block lower energy particles from reaching the spacecraft instruments. The motion of electrons and ions is traced as a function of time to examine the evolution of the electric field, electric potential and the total space charge distributions on the surface of the spacecraft and its environment. Account is taken of the density of the particles and gas molecules at various distances from the comet, the collision energies involved, and the Giotto geometry. A solution is defined for the Poisson equation to describe the evolution of the plasma around Giotto, including the effects of ion collisions with the Al bumper protecting the spacecraft. The simulation predicts formation of an ion wake behind Giotto and the evolution of a positive potential on the order of 10 V around the spacecraft, i.e., sufficient for a positive potential barrier near the surface of the spacecraft.
Thiemann, H.↗
Comparison of Nimbus 7 and ERBE radiation budget measurements
Correlations were sought between data sets on exitance radiance and albedos sensed by the Earth Radiation Budget Experiment (ERBE) and the Nimbus-7 spacecraft instruments. The emitted exitance (W/sq m) and the albedos measured over the ocean and the land and diurnal global averages are compared. The 5 W/sq m average difference between noon-midnight recorded by the ERBE spacecraft showed that noon-midnight averages can not be used with ERBE data as they have been with Nimbus-7 data.
Campbell, G. G.↗
Observations of gamma-ray line emission from the galactic center region
Balloon and HEAO-3 spacecraft instrumentation measurements of the .51 MeV gamma ray line arising from positron-electron annihilation near the galactic center are examined. The first balloon flights were made in 1970, and satellite data was collected in 1979. Subsequent spacecraft gamma ray spectroscopy of the region in the spring of 1980 revealed that the emission had undergone a factor of three decrease. The mean flux had displayed a value of within .19 of 1.04/1000 before the decrease was observed. The source has a luminosity of 10 to the 37th ergs/sec and an annihilation rate of 10 to the 43rd/sec. The emission region would stay within a temperature range of 100,000 K and have a diameter of 10 to the 18 cm, a mass less than 1 billion solar masses, and feature annihilations at least 10 to the 14 cm outward from the source. Further balloon flights are planned to verify the variability.
Jacobson, A. S.↗
A look at the universe in gamma rays
The scientific background and objectives, proposed instruments, spacecraft constraints, operations plans and present status and schedule of the Gamma Ray Observatory (GRO), a shuttle-launched free-flyer satellite currently planned by NASA, are reviewed. Objectives for the satellite study of the highest energy electromagnetic radiation in the cosmos discussed include the investigation of the evolution of compact objects, nucleosynthesis, gamma-ray objects whose nature is not yet known, the gamma-ray properties of the Galaxy and other galaxies, cosmological effects and intense gamma-ray bursts. The five instruments considered in the definition study which span six decades in energy are presented and proposed experiments are outlined. Although a spacecraft has not yet been selected, several feasible alternatives have been identified, and a launch in the mid-1980s is planned.
Kniffen, D. A.↗
Adding "Missed" Science to Cassini's Ops Plan
The phenomenal success of the Cassini Mission at Saturn is largely due to flagship instruments, in a target rich environment, for a long period of time, executing almost error free complex mission operations. A smooth transition from cruise operations through the prime science mission and extended science (Equinox) mission culminating in the currently executing Solstice mission has folded in necessary procedural alterations due to improved understanding of the spacecraft, instruments, uplink and planning systems as well as additional science objectives. These have come with the maturation of the mission along with management of workforce reductions. One important set of operational changes has been initiated due to scientific findings highlighting "missed" science opportunities. This is the case for the Titan Meteorology Campaigns and Saturn Storm Watch Campaigns. These observations involve long term monitoring of the atmospheres of Titan and Saturn while the spacecraft and science teams are focused on other high priority targets of opportunity (like Enceladus). Our objective in this paper is to emphasize how a non-invasive strategy to get additional remarkable science was conceived and implemented in a mission with an already well defined operational plan. To illustrate this we will detail Titan Meteorology Campaign and Saturn Storm Watch Campaign integration and implementation strategies as well as the scientific goals and achievements of both.
Roy, Mou↗
Adding "Missed" Science to Cassini's Ops Plan
The phenomenal success of the Cassini Mission at Saturn is largely due to flagship instruments, in a target rich environment, for a long period of time, executing almost error free complex mission operations. A smooth transition from cruise operations through the prime science mission and extended science (Equinox) mission culminating in the currently executing Solstice mission has folded in necessary procedural alterations due to improved understanding of the spacecraft, instruments, uplink and planning systems as well as additional science objectives. These have come with the maturation of the mission along with management of workforce reductions. One important set of operational changes has been initiated due to scientific findings highlighting "missed" science opportunities. This is the case for the Titan Meteorology Campaigns and Saturn Storm Watch Campaigns. These observations involve long term monitoring of the atmospheres of Titan and Saturn while the spacecraft and science teams are focused on other high priority targets of opportunity (like Enceladus). Our objective in this paper is to emphasize how a non-invasive strategy to get additional remarkable science was conceived and implemented in a mission with an already well defined operational plan. To illustrate this we will detail Titan Meteorology Campaign and Saturn Storm Watch Campaign integration and implementation strategies as well as the scientific goals and achievements of both.
Roy, Mou↗
Constraining the Global, Cloud-Free Reflected Solar Radiation Flux (RSRF) with Earth Observing System (EOS) Instruments
Variations in the top-of-atmosphere reflected solar radiation flux, and in the factors that determine its value, are among the most important diagnostic indicators of changes in Earth's energy balance. Data from the MISR (Multi-angle Imaging SpectroRadiometer), MODIS (Moderate-resolution Imaging Spectroradiometer), SAGE-3 (Stratospheric Aerosol and Gas Experiment), and CERES (Clouds and Earth's Radiant Energy System), all of which are spacecraft instruments scheduled for launch in 1999, will each constrain pieces of the RSRF budget. Prior to launch, we are performing studies to determine the sensitivity of these instruments to key factors that influence the cloud-free RSRF: aerosol optical depth, aerosol scattering properties, and surface visible bidirectional reflectance distribution function (BRDF). We are also assessing the ability of the aggregate of instruments to constrain the overall RSRF budget under natural conditions over the globe. Consider the MISR retrieval of aerosols: according to simulations over cloud-free, calm ocean, for pure particles with natural ranges of optical depth, particle size, and indices of refraction, MISR can retrieve column aerosol optical depth for all but the darkest particles, to an uncertainty of at most 0.05 or 20%, whichever is larger, even if the particle properties are poorly known. For one common particle type, soot, constraints on the optical depth over dark ocean are very poor. The simulated measurements also allow us to distinguish spherical from non-spherical particles, to separate two to four compositional groups based on indices of refraction, and to identify three to four distinct size groups between 0. 1 and 2.0 microns characteristic radius at most latitudes. Based on these results, we expect to distinguish air masses containing different aerosol types, routinely and globally, with multiangle remote sensing data. Such results far exceed current satellite aerosol retrieval capabilities, which provide only total optical depth for assumed particle properties; the new information will complement in situ data, which give details about aerosol size and composition locally. In addition, our team is using climatologies that reflect the constraints each instrument is expected to provide, along with ERBE (Earth Radiation Budget Experiment) data and a radiative transfer code, to study overall sensitivity to RSRF, helping us prepare for similar studies with new data from the EOS-era instruments.
Kahn, Ralph↗