Search NASA⌕ Search

SEARCH · Search NASA

Results for “Deep Impact”

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.

At least 217 records · Page 12

Planning for Crew Exercise for Future Deep Space Mission Scenarios

Providing the necessary exercise capability to protect crew health for deep space missions will bring new sets of engineering and research challenges. Exercise has been found to be a necessary mitigation for maintaining crew health on‐orbit and preparing the crew for return to earth's gravity. Health and exercise data from Apollo, Space Lab, Shuttle, and International Space Station missions have provided insight into crew deconditioning and the types of activities that can minimize the impacts of microgravity on the physiological systems. The hardware systems required to implement exercise can be challenging to incorporate into spaceflight vehicles. Exercise system design requires encompassing the hardware required to provide mission specific anthropometrical movement ranges, desired loads, and frequencies of desired movements as well as the supporting control and monitoring systems, crew and vehicle interfaces, and vibration isolation and stabilization subsystems. The number of crew and operational constraints also contribute to defining the what exercise systems will be needed. All of these features require flight vehicle mass and volume integrated with multiple vehicle systems. The International Space Station exercise hardware requires over 1,800 kg of equipment and over 24 m3 of volume for hardware and crew operational space. Improvements towards providing equivalent or better capabilities with a smaller vehicle impact will facilitate future deep space missions. Deep space missions will require more understanding of the physiological responses to microgravity, understanding appropriate mitigations, designing the exercise systems to provide needed mitigations, and integrating effectively into vehicle design with a focus to support planned mission scenarios. Recognizing and addressing the constraints and challenges can facilitate improved vehicle design and exercise system incorporation.

Moore, Cherice↗

Radio frequency interference protection of communications between the Deep Space Network and deep space flight projects

The increasing density of electrical and electronic circuits in Deep Space Station systems for computation, control, and numerous related functions has combined with the extension of system performance requirements calling for higher speed circuitry along with broader bandwidths. This has progressively increased the number of potential sources of radio frequency interference inside the stations. Also, the extension of spectrum usage both in power and frequency as well as the greater density of usage at all frequencies for national and international satellite communications, space research, Earth resource operations and defense, and particularly the huge expansion of airborne electronic warfare and electronic countermeasures operations in the Mojave area have greatly increased the potential number and severity of radio frequency interference incidents. The various facets of this problem and the efforts to eliminate or minimize the impact of interference on Deep Space Network support of deep space flight projects are described.

Johnston, D. W. H.↗

Chemical character of the partially flooded Smythii Basin based on Al/Si orbital X-ray data

Orbital X-ray fluorescence data indicate that continuous mare-basalt flooding is confined to the northeastern quadrant of the Smythii Basin. Al/Si values for soils in the unflooded northwestern section of the Smythii Basin closely approximate those for the adjacent terra to the west. Terra soils east of Mare Smythii, however, are unusually aluminous compared to terra soils west of the basin. This pronounced contrast between Al/Si values for terra soils to the east and west of Smythii as well as the minimal difference in values between the northwestern section of the basin and adjacent terra to the west are most likely due to a chemically homogeneous layer of ejecta from a large impact event west of Mare Smythii, such as that which formed the Crisium Basin. An alternate hypothesis is that the unflooded section of the basin is predominantly original basin floor material, indicating that the impact forming the 4km deep Smythii Basin did not penetrate into a horizon chemically different from the terra west of Smythii. The chemical contrast between the terra east and west of Smythii, then, would be ascribed to lateral heterogeneity within the lunar crust

Andre, C. G.↗

Impact of an asteroid or comet in the ocean and extinction of terrestrial life

Finite difference calculations describing the impact mechanics associated with a 10 to 30 km diameter silicate or water object impacting a 5 km deep ocean overlying a silicate solid planet demonstrate that from 12 to 15% of the bolide energy resides in the water. It is speculated that minimal global tsunami run-up heights on the continents would be 300-400 meters, and that such waves would inundate all low altitude continental areas, and strip and silt-over virtually all vegetation. As a result the terrestrial animal food chain would be seriously perturbed. This could in turn cause extinction of large terrestrial animals.

Ahrens, T. J.↗

Possible world-wide middle miocene iridium anomaly and its relationship to periodicity of impacts and extinctions

In a study of one million years of Middle Miocene sediment deposition in ODP Hole 689B in the Weddell Sea near Antarctica, a single iridium (Ir) anomaly of 44 (+ or - 10) x 10 to the 12th gram Ir per gram rock (ppt) was observed in core 6H, section 3, 50 to 60 cm, after background contributions associated with manganese precipitates and clay are subtracted. The ODP Hole 689B is 10,000 km away from another site, DSDP Hole 588B in the Tasman Sea north of New Zealand, where a single Ir anomaly of 144 + or - 7 ppt over a background of 11 ppt was found in an earlier study of 3 million years of deposition. From chemical measurements the latter deposition was thought to be impact-related. Ir measurements were made, following neutron activation, with the Iridium Coincidence Spectrometer. The age vs depth calibration curves given in the DSDP and ODP preliminary reports indicate the ages of the Iranomalies are identical, 11.7 million years, but the absolute and relative uncertainties in the curves are not known. Based on the newest age data the age estimate is 10 million years. As the Ir was deposited at the two sites at about the same time and they are one quarter of the way around the world from each other it seems likely that the deposition was world-wide. The impact of a large asteroid or comet could produce the wide distribution, and this data is supportive of the impact relationship deduced for Deep Sea Drilling Project (DSDP) 588B from the chemical evidence. If the surface densities of Ir at the two sites are representative of the world-wide average, the diameter of a Cl type asteroid containing the necessary Ir would be 3 + or - 1 km, which is large enough to cause world-wide darkness and hence extinctions although the latter point is disputed.

Asaro, F.↗

An extragalactic reference frame from DSN VLBI measurements - 1989

Assessment of the impact of recent improvements Deep Space Network (DSN) instrumentation, as well as of joint data analyses, provide a prognosis for the accuracy level to be expected in future realizations of an inertial radio reference frame. Intercontinental dual-frequency radio interferometric measurements during 68 sessions (including two recent sessions employing Mark III instrumentation) from 1978 to 1989 using NASA's DSN stations in California, Spain, and Australia give 8900 pairs of delay and delay-rate observations. Analysis yields a catalog of positions of 200 extragalactic radio sources north of -45 deg declination. The resulting source-position formal uncertainty distributions peak below 1 milliarcsecond, with 75 percent being smaller than 2 mas. Comparison with independent measurements shows some evidence for systematic errors at the milliarcsecond level.

Sovers, O. J.↗

Oceanic Impact: Mechanisms and Environmental Perturbations

The contents include the following: Oceanic impacts-a growing field of fundamental geoscience. Shock metamorphism on the ocean floor (numerical simulations). Numerical modeling of impact-induced modifications of the deep-sea floor. Computer modelling of the water resurge at a marine impact: the Lockne crater, Sweden. Experimental investigation of the role of water in impact vaporization chemistry. Calcareous plankton stratigraphy around the Pliocene Eltanin asteroid impact area (SE Pacific): documentation and application for geological and paleoceanographic reconstruction. Composition of impact melt debris from the Eltanin impact strewn field, Bellingshausen Sea. Iridium concentrations and abundances of meteoritic ejecta from the Eltanin impact in sediment cores from Polarstern expedition ANT XII/4. Unmelted meteoritic debris collected from Eltanin ejecta in Polarstern cores from expedition ANT XII/4. Impact tsunami-Eltanin. Ancient impact structures on modern continental shelves: The Chesapeake Bay, Montagnais, and Toms Canyon craters, Atlantic margin of North America. The Mjolnir marine impact crater porosity anomaly. Kardla (Hiiu-maa Island, Estonia) - the buried and well-preserved Ordovician marine impact structure. Long-term effect of the Kardla crater (Hiiu-maa, Estonia) on Late Ordovician carbonate sedimentation. The middle Devonian Kaluga impact crater (Russia): new interpretation of marine setting.

Gersonde, Rainer↗

Astronaut Exposures to Ionizing Radiation in a Lightly-Shielded Spacesuit

The normal working and living areas of the astronauts are designed to provide an acceptable level of protection against the hazards of ionizing radiation of the space environment. Still there are occasions when they must don a spacesuit designed mainly for environmental control and mobility and leave the confines of their better-protected domain. This is especially true for deep space exploration. The impact of spacesuit construction on the exposure of critical astronaut organs will be examined in the ionizing radiation environments of free space, the lunar surface and the Martian surface. The computerized anatomical male model is used to evaluate astronaut self-shielding factors and to determine space radiation exposures to critical radiosensitive human organs.

Wilson, J. W.↗

Offshore Breaking of Impact Tsunami: Van Dorn was Right

Tsunami generated by the impacts of asteroids and comets into the Earth s oceans are widely recognized as a potentially catastrophic hazard to the Earth s population (e.g. Chapman and Morrison 1994, Nature, 367, 33; Hills et al. 1994, in Hazards Due to Comets and Asteroids, (ed. T. Gehrels), 779; Atkinson et al. 2000, Report of the UK Task Force on Potentially Hazardous NEOs; Ward and Asphaug 2000, Icarus, 145, 64). A peculiarity of ocean impacts is the potential global effects of an impact that would otherwise be of only regional or local importance should it occur on land. This is, of course, due to the ability of waves to propagate globally, as seen by the terrible effects of the recent earthquake off the coast of Sumatra. The overall process of an impact tsunami is complex and falls into several distinct phases: 1) initial impact of the bolide into the ocean and formation of a transient cavity in the water, 2) collapse of the cavity and propagation of large waves from the impact center outward over deep water (typically several km in depth), 3) initial effects on wave amplitude as shallower water of the continental slope is reached ("wave shoaling"), possible breaking of waves in relatively shallow water (less than 100 m depth), on continental shelves, and 5) final contact of waves with the shore and their progression onto dry land ("run-up" and "run-in"). Here we report on numerical calculations (and semi-analytic theory) covering phases 3 and 4.

Korycansky, D. G.↗

A Goddard Multi-Scale Modeling System with Unified Physics

A multi-scale modeling system with unified physics has been developed at NASA Goddard Space Flight Center (GSFC). The system consists of an MMF, the coupled NASA Goddard finite-volume GCM (fvGCM) and Goddard Cumulus Ensemble model (GCE, a CRM); the state-of-the-art Weather Research and Forecasting model (WRF) and the stand alone GCE. These models can share the same microphysical schemes, radiation (including explicitly calculated cloud optical properties), and surface models that have been developed, improved and tested for different environments. The following is presented in this report: (1) a brief review of the GCE model and its applications on the impact of aerosols on deep precipitation processes, (2) the Goddard MMF and the major difference between two existing MMFs (CSU MMF and Goddard MMF), and preliminary results (the comparison with traditional GCMs), and (3) a discussion on the Goddard WRF version (its developments and applications).

Tao, Wei-Kuo↗

The Regolith of 4 Vesta - Inferences from Howardites

Asteroid 4 Vesta is quite likely the parent asteroid of the howardite, eucrite and diogenite meteorites - the HED clan. Eucrites and diogenites are the products of igneous processes; the former are basaltic composition rocks from flows, and shallow and deep intrusive bodies, whilst the latter are cumulate orthopyroxenites thought to have formed deep in the crust. Impact processes have excavated these materials and mixed them into a suite of polymict breccias. Howardites are polymict breccias composed mostly of clasts and mineral fragments of eucritic and diogenitic parentage, with neither end-member comprising more than 90% of the rock. Early work interpreted howardites as representing the lithified regolith of their parent asteroid. Recently, howardites have been divided into two subtypes; fragmental howardites, being a type of non-regolithic polymict breccia, and regolithic howardites, being lithified remnants of the active regolith of 4 Vesta. We are in the thralls of a collaborative investigation of the record of impact mixing contained within howardites, which includes studies of their mineralogy, petrology, bulk rock compositions, and bulk rock and clast noble gas contents. One goal of our investigation is to test the hypothesis that some howardites represent breccias formed from an ancient, well-mixed regolith on Vesta. Another is to use our results to further understand regolith processing on differentiated asteroids as compared to what has been learned from the Moon. We have made petrographic observations and electron microprobe analyses on 21 howardites and 3 polymict eucrites. We have done bulk rock analyses using X-ray fluorescence spectrometry and are completing inductively coupled plasma mass spectrometry analyses. Here, we discuss our petrologic and bulk compositional results in the context of regolith formation. Companion presentations describe the noble gas results and compositional studies of low-Ca pyroxene clasts.

Mittlefehldt, D. W.↗

A Review of Global Satellite-Derived Snow Products

Snow cover over the Northern Hemisphere plays a crucial role in the Earth's hydrology and surface energy balance, and modulates feedbacks that control variations of global climate. While many of these variations are associated with exchanges of energy and mass between the land surface and the atmosphere, other expected changes are likely to propagate downstream and affect oceanic processes in coastal zones. For example, a large component of the freshwater flux into the Arctic Ocean comes from snow melt. The timing and magnitude of this flux affects biological and thermodynamic processes in the Arctic Ocean, and potentially across the globe through their impact on North Atlantic Deep Water formation. Several recent global remotely sensed products provide information at unprecedented temporal, spatial, and spectral resolutions. In this article we review the theoretical underpinnings and characteristics of three key products. We also demonstrate the seasonal and spatial patterns of agreement and disagreement amongst them, and discuss current and future directions in their application and development. Though there is general agreement amongst these products, there can be disagreement over certain geographic regions and under conditions of ephemeral, patchy and melting snow.

Frei, Allan↗

A Review of Global Satellite-Derived Snow Products

Snow cover over the Northern Hemisphere plays a crucial role in the Earth s hydrology and surface energy balance, and modulates feedbacks that control variations of global climate. While many of these variations are associated with exchanges of energy and mass between the land surface and the atmosphere, other expected changes are likely to propagate downstream and affect oceanic processes in coastal zones. For example, a large component of the freshwater flux into the Arctic Ocean comes from snow melt. The timing and magnitude of this flux affects biological and thermodynamic processes in the Arctic Ocean, and potentially across the globe through their impact on North Atlantic Deep Water formation. Several recent global remotely sensed products provide information at unprecedented temporal, spatial, and spectral resolutions. In this article we review the theoretical underpinnings and characteristics of three key products. We also demonstrate the seasonal and spatial patterns of agreement and disagreement amongst them, and discuss current and future directions in their application and development. Though there is general agreement amongst these products, there can be disagreement over certain geographic regions and under conditions of ephemeral, patchy and melting snow

Frei, Allan↗

A Review of Global Satellite-derived Snow Products

Snow cover over the Northern Hemisphere plays a crucial role in the Earth's hydrology and surface energy balance, and modulates feedbacks that control variations of global climate. While many of these variations are associated with exchanges of energy and mass between the land surface and the atmosphere, other expected changes are likely to propagate downstream and affect oceanic processes in coastal zones. For example, a large component of the freshwater flux into the Arctic Ocean comes from snow melt. The timing and magnitude of this flux affects biological and thermodynamic processes in the Arctic Ocean, and potentially across the globe through their impact on North Atlantic Deep Water formation. Several recent global remotely sensed products provide information at unprecedented temporal, spatial, and spectral resolutions. In this article we review the theoretical underpinnings and characteristics of three key products. We also demonstrate the seasonal and spatial patterns of agreement and disagreement amongst them, and discuss current and future directions in their application and development. Though there is general agreement amongst these products, there can be disagreement over certain geographic regions and under conditions of ephemeral, patchy and melting snow.

Frei, Allan↗

Observation of Mountain Lee Waves with MODIS NIR Column Water Vapor

Mountain lee waves have been previously observed in data from the Moderate Resolution Imaging Spectroradiometer (MODIS) "water vapor" 6.7 micrometers channel which has a typical peak sensitivity at 550 hPa in the free troposphere. This paper reports the first observation of mountain waves generated by the Appalachian Mountains in the MODIS total column water vapor (CWV) product derived from near-infrared (NIR) (0.94 micrometers) measurements, which indicate perturbations very close to the surface. The CWV waves are usually observed during spring and late fall or some summer days with low to moderate CWV (below is approx. 2 cm). The observed lee waves display wavelengths from3-4 to 15kmwith an amplitude of variation often comparable to is approx. 50-70% of the total CWV. Since the bulk of atmospheric water vapor is confined to the boundary layer, this indicates that the impact of thesewaves extends deep into the boundary layer, and these may be the lowest level signatures of mountain lee waves presently detected by remote sensing over the land.

satellite remote sensing↗

Assessment of MODIS and VIIRS Calibration Consistency for Reflective Solar Bands Using Vicarious Approaches

The Moderate-Resolution Imaging Spectroradiometer (MODIS) is the key instrument of the NASA’s Earth Observing System (EOS) Terra and Aqua missions, launched in December 1999 and May 2002, respectively. The Visible Infrared Imaging Radiometer Suite (VIIRS) expands the MODIS legacy, launched onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite in October 2011 and NOAA20 satellite in November 2017, respectively. The MODIS and VIIRS sensors have a similar design with spectrally matched reflective solar spectral bands (RSB). Their on-board calibration components include a solar diffuser and a solar diffuser stability monitor for RSB, a V-grooved blackbody for the thermal emissive bands (TEB), and a space view as a background reference. This study evaluates the calibration consistency of the Terra and Aqua MODIS RSB based on the current Collection 6.1 L1B data products generated by the NASA MODAPS, which have used consistent calibration coefficient look up tables (LUT) for the entire data-record. In the case of SNPP and NOAA20 VIIRS, the latest L1B data produced by NASA Land SIPS are used. Several independent vicarious approaches are used to examine the stability and consistency of the at-sensor reflectance among MODIS and VIIRS instruments. Vicarious approaches include observations from simultaneous nadir overpasses (SNO), the Libya-4 desert and Dome C snow sites, as well as deep convective clouds (DCC). Impact of existing band spectral difference on the reflectance is corrected using hyperspectral observations provided by Europe Space Agency’s SCIAMACHY sensor. Results of this study provide comprehensive assessments of calibration performance, radiometric agreement and associated uncertainties.

MODIS↗

An Assessment of SNPP and NOAA20 VIIRS RSB Calibration Performance in NASA SIPS Reprocessed Collection-2 L1B Data Products

Two VIIRS sensors onboard the SNPP and NOAA20 satellites have been successfully operating for over 10 and 4 years, respectively, providing the worldwide user community with high-quality imagery and radiometric measurements of the land, atmosphere, cryosphere, and oceans. This study provides a temporal radiometric stability and calibration consistency assessment of the SNPP and NOAA20 VIIRS reflective solar bands using the latest NASA SIPS C2 L1B products. Several independent vicarious approaches are used to examine the stability of SNPP VIIRS and consistency of the at-sensor reflectance between the two VIIRS instruments. These approaches include observations from simultaneous nadir overpasses, the Libya-4 desert and Dome C snow/ice sites, and deep convective clouds. The impact of existing band spectral differences on the reflectance measurements is accounted for utilizing scene-specific hyperspectral observations provided by the SCIAMACHY sensor onboard the ENVISAT platform. Results indicate that both SNPP and NOAA20 VIIRS reflectances are stable within 1% over their mission periods for all bands, except for a few bands in the visible range from SNPP VIIRS that show more upward drifts at high radiances. NOAA20 VIIRS reflectances are systematically lower than SNPP by 2 to 4% for most bands, with the exception of few short wavelength bands where it is seen to be up to 7%.

VIIRS↗