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Showing posts with label Satellites. Show all posts
Showing posts with label Satellites. Show all posts

Saturday, June 07, 2014

Lifi and 5g: Optical Communications


Visible light is only a small portion of the electromagnetic spectrum.

I have been away a while getting caught up on some work and enjoying some vacation time. I am always exciting about where we are going next in terms of communication development. Some of these previews  have been show here in various blog posts, that you can preview with label access.

The United States 700 MHz FCC wireless spectrum auction was started by the FCC on January 24, 2008 for the rights to operate the 700 MHz frequency band in the United States. The details of process were the subject of debate between several telecommunications companies, including Verizon Wireless, AT&T, and startup Frontline Wireless, as well as the Internet company Google. Much of the debate swirled around the "open access" requirements set down by the Second Report and Order released by the FCC determining the process and rules for the auction. All bidding must be commenced by January 28 by law. The auction was named Auction 73.[1]


The interesting thing here in terms of development is that the industry is still in a sort of infancy where those who are quite brave in terms of their science and knowledge back ground can contribute and create a different type of communication base that is current residing outside of government regulations right now. The spectrum allocation is currently not licensed and using that platform if you can develop it create the possibility of networks that do not currently reside in spectrum allocation that are being sold.?


Li-Fi, or "light fidelity", is a technology, that can be a complement of RF communication (Wi-Fi or Cellular network), or a replacement in contexts of data broadcasting. Li-Fi, like Wi-Fi, is the high speed, bidirectional and fully networked subset of visible light communications (VLC). It is wireless and uses visible light communication (instead of radio frequency waves), which carries much more information, and has been proposed as a solution to the RF-bandwidth limitations.[1]

 While we know the ground rules of communication are limited in terms of wifi, the future is quite as to how information can be disseminated and how much of it can be accessed through new technology that will reside outside of the devices that currently are being adapted too, to use that type of communication. So I encourage new development here if you have the brains and brawn in order to tackle that new fledgling business of the future.

 It is a 5G[2] visible light communication system that uses light from light-emitting diodes (LEDs) as a medium to deliver networked, mobile, high-speed communication in a similar manner as Wi-Fi.[3] Li-Fi could lead to the Internet of Things, which is everything electronic being connected to the internet, with the LED lights on the electronics being used as Li-Fi internet access points.[4] The Li-Fi market is projected to have a compound annual growth rate of 82% from 2013 to 2018 and to be worth over $6 billion per year by 2018.[5]

It is a sobering thought to thing of the optical side of things of having such a wide market growth, with the potential of money development, but at the same time brings to light the development that is currently and has yet to become marketable through innovation and technological design. So I encourage the young folk coming out of universities to explore at least from their educative perspective and expertise this area of communication and technological design..



pureLiFi is at the forefront of research and commercialisation into Li-Fi, an industry expected to grow from $100 million to $6 billion by 2018. Visible Light Communication (VLC) is the use of light to transmit data wirelessly. Li-Fi - a term coined by pureLiFi’s Chief Science Officer and co-founder, Professor Haas – is a technology based on VLC that provides full networking capabilities similar to Wi-Fi, but with significantly greater spatial reuse of bandwidth. See: pureLiFi to demonstrate first ever Li-Fi system at Mobile World Congress

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Wednesday, February 19, 2014

OPAL

OPALS is manifested to launch on the third ISS resupply mission by a SpaceX Falcon 9 Dragon in February 2014.
This artist's concept shows how the Optical Payload for Lasercomm Science (OPALS) laser will beam data to Earth from the International Space Station. Credit: NASA. 
"OPALS represents a tangible stepping stone for laser communications, and the International Space Station is a great platform for an experiment like this," said Michael Kokorowski, OPALS project manager at JPL. "Future operational laser communication systems will have the ability to transmit more data from spacecraft down to the ground than they currently do, mitigating a significant bottleneck for scientific investigations and commercial ventures." SEE: NASA's OPALS to Beam Data From Space Via Laser


OPALS will be mounted externally on the International Space Station (ISS) in a nadir position on an ExPrESS Logistics Carrier (ELC). Image is credited to NASA/JPL-Caltech.

 The fastest commercial communication links on Earth use optical (or laser) fiber to transmit information. Using laser in space without this fiber is another method.  Fast laser communications between Earth and spacecraft like the International Space Station or the Mars rover Curiosity could enhance their connection to the public.  OPALS is also used to educate and train NASA personnel. See: Optical PAyload for Lasercomm Science (OPALS) - 01.09.14
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OPALS Concept of Operations



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Monday, February 17, 2014

Lunar Atmosphere and Dust Environment Explorer spacecraft


See:
NASA Ames LADEE Mission: NASA Briefing Previews Lunar Mission 
 


NASA's Lunar Atmosphere and Dust Environment Explorer, or LADEE, spacecraft has completed the check-out phase of its mission and has begun science operations around the moon. All the science instruments on-board have been examined by the LADEE team and have been cleared to begin collecting and analyzing the dust in the exosphere, or very thin atmosphere, that surrounds the moon.

NASA's Ames Research Center designed, developed, built, and tested the spacecraft and manages mission operations.

For more information about the LADEE mission, please visit http://www.nasa.gov/ladee
For more information about NASA Ames, please visit http://www.nasa.gov/ames
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Communications Demonstration.
This is NASA's first high-data-rate laser communications system used on a deep space mission. It will enable communications similar to the capabilities found in high-speed fiber optic networks.
Take note of communications technique.
 Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking. "Free space" means air, outer space, vacuum, or something similar. This contrasts with using solids such as optical fiber cable or an optical transmission line. The technology is useful where the physical connections are impractical due to high costs or other considerations.

Wednesday, February 05, 2014

Landsat Science



The Landsat Program provides repetitive acquisition of high resolution multispectral data of the Earth’s surface on a global basis. The data from Landsat spacecraft constitute the longest record of the Earth’s continental surfaces as seen from space. It is a record unmatched in quality, detail, coverage, and value.Landsat Data Continuity Mission Overview
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Landsat Eight Bands

Urban areas and some kinds of soil are pink. In the true-color image, wild vegetation is almost uniformly olive-colored, but here we see a distinction between peach-colored scrubland, mahogany-colored woodland, and so on. Cooling onshore breezes appear as a slight purple gradient along the coast of the city. The colored strips on either side of the image are areas where not all sensors have coverage.
 
 Landsat 8 measures different ranges of frequencies along the electromagnetic spectrum – a color, although not necessarily a color visible to the human eye. Each range is called a band, and Landsat 8 has 11 bands. Landsat numbers its red, green, and blue sensors as 4, 3, and 2, so when we combine them we get a true-color image such as this one:

Friday, January 31, 2014

Unleashing the Power of Earth Observations: Barbara Ryan



Unleashing the Power of Earth Observations

 Jan 21, 2014 • In December 2013, the Secretariat Director of the Group on Earth Observations gave a TEDx talk in Barcelona, Spain making the case that all Earth-oberservation data collected from governments and institutions should be open and available to everyone. She illustrates how this could reduce hunger and improve the quality of life of all Earth’s inhabitants. Ryan emphasizes that Earth observation data show Earth without political boundaries, as an entire system. See: The Landsat Program

Thursday, December 19, 2013

Gaia in Space

Soyuz VS06 with Gaia space observatory blasts off from Europe's Spaceport
ESA PR 44-2013: ESA’s Gaia mission blasted off this morning on a Soyuz rocket from Europe’s Spaceport in Kourou, French Guiana, on its exciting mission to study a billion suns. 

Gaia is destined to create the most accurate map yet of the Milky Way. By making accurate measurements of the positions and motions of 1% of the total population of roughly 100 billion stars, it will answer questions about the origin and evolution of our home Galaxy. 

The Soyuz launcher, operated by Arianespace, lifted off at 09:12 GMT (10:12 CET). About ten minutes later, after separation of the first three stages, the Fregat upper stage ignited, delivering Gaia into a temporary parking orbit at an altitude of 175 km. See: LiftOff for ESA's billion-dollar star surveyor

Space is not flat.

Tuesday, November 26, 2013

Swarm



ESA's magnetic field mission Swarm. A European Space Agency mission to investigate the Earth's magnetic field in unprecedented detail is due to be launched later this year. Without our planets protective magnetic field, life on our planet would struggle to survive. The Swarm mission consisting of three identical satellites will be used to study all aspects of the Earth's magnetic field and assess whether it is weakening. This report outlines the science of the mission and includes interviews with a project scientist and project manager. More backgroud information can be found on: http://www.esa.int/esaLP/ESA3QZJE43D_LPswarm_0.html


 


Swarm is a European Space Agency (ESA) mission to study the Earth's magnetic field. High-precision and high-resolution measurements of the strength, direction and variations of the Earth's magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide data essential for modelling the geomagnetic field and its interaction with other physical aspects of the Earth system. The results will offer a unique view of the inside of the Earth from space, enabling the composition and processes of the interior to be studied in detail and increase our knowledge of atmospheric processes and ocean circulation patterns that affect climate and weather.




Friday, June 28, 2013

NASA | IRIS: The Science of NASA's Newest Solar Explorer



At the end of June 2013, NASA will launch its newest mission to watch the sun: the Interface Region Imaging Spectrograph, or IRIS. IRIS will show the lowest levels of the sun's atmosphere, the interface region, in more detail than has even been observed before. This will help scientists understand how the energy dancing through this area helps power the sun's million-degree upper atmosphere, the corona, as well as how this energy powers the solar wind constantly streaming off the sun to fill the entire solar system.

Data visualizations courtesy of Mats Carlsson and Viggo Hansteen, University of Oslo, Norway

This video is public domain and can be downloaded at: http://svs.gsfc.nasa.gov/goto?1125611



See:

Friday, March 22, 2013

Our Baby Universe with Ed Copeland and Planck Satellite


Where do the seeds of structure in our Universe come from, and why does our Universe appear the way it does? In this talk, Ed explores what happened in those earliest moments that lead to the Universe forming itself into what it is today. He also tells us a bit of a story about how the theories were developed, and who the scientists were behind them.Our Baby Universe: Ed Copeland at TEDxUoN



Cosmic microwave background seen by Planck


 The ESA's Planck satellite, dedicated to studying the early universe, was launched on May 2009 and has been surveying the microwave and submillimetre sky since August 2009. In March 2013, ESA and the Planck Collaboration publicly released the initial cosmology products based on the first 15.5 months of Planck operations, along with a set of scientific and technical papers and a web-based explanatory supplement. This paper describes the mission and its performance, and gives an overview of the processing and analysis of the data, the characteristics of the data, the main scientific results, and the science data products and papers in the release. Scientific results include robust support for the standard, six parameter LCDM model of cosmology and improved measurements for the parameters that define this model, including a highly significant deviation from scale invariance of the primordial power spectrum. The Planck values for some of these parameters and others derived from them are significantly different from those previously determined. Several large scale anomalies in the CMB temperature distribution detected earlier by WMAP are confirmed with higher confidence. Planck sets new limits on the number and mass of neutrinos, and has measured gravitational lensing of CMB anisotropies at 25 sigma. Planck finds no evidence for non-Gaussian statistics of the CMB anisotropies. There is some tension between Planck and WMAP results; this is evident in the power spectrum and results for some of the cosmology parameters. In general, Planck results agree well with results from the measurements of baryon acoustic oscillations. Because the analysis of Planck polarization data is not yet as mature as the analysis of temperature data, polarization results are not released. We do, however, illustrate the robust detection of the E-mode polarization signal around CMB hot- and cold-spots. See: Planck 2013 results. I. Overview of products and scientific results

ESA and the Planck Collaboration





Cosmological parameters from 2013 Planck results[18]
 
Parameter Symbol Planck - Best fit
(CMB+lensing)
Planck - 68% limits
(CMB+lensing)
Planck - Best fit
(Planck+WP+highL+BAO)
Planck - 68% limits
(Planck+WP+highL+BAO)
Age of the universe (Ga) t_0 13.784 13.796±0.058 13.7965 13.798±0.037
Hubble's constant ( kmMpc·s ) H_0 68.14 67.9±1.5 67.77 67.80±0.77
Physical baryon density \Omega_b h^2 0.022242 0.02217±0.00033 0.022161 0.02214±0.00024
Physical cold dark matter density \Omega_c h^2 0.11805 0.1186±0.0031 0.11889 0.1187±0.0017
Dark energy density \Omega_\Lambda 0.6964 0.693±0.019 0.6914 0.692±0.010
Density fluctuations at 8h−1 Mpc \sigma_8 0.8285 0.823±0.018 0.8288 0.826±0.012
Scalar spectral index n_s 0.9675 0.9635±0.0094 0.9611 0.9608±0.0054
Reionization optical depth \tau 0.0949 0.089±0.032 0.0952 0.092±0.013
Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; et al. (Planck Collaboration) (20 March 2013). "Planck 2013 results. I. Overview of products and scientific results". Astronomy & Astrophysics (submitted). arXiv:1303.5062.




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Saturday, October 13, 2012

When You Look at the Cosmos......?


Scientists have turned up rare evidence that space-time is smooth as Einstein predicted, while pushing closer to a complete theory of gravity. From NASA Goddard Space Flight Center, Fermi Gamma Ray Space Telescope. See: SpaceRip.com




.....you might be enamored with how you might see the cosmos as I am.

The question of continuity of expression as some mathematical construct with out seeing the uniqueness of  lets say lensing....how might we associate with such dynamics of that continuity?

According to Einstein's theory of general relativity, the sun's gravity causes starlight to bend, shifting the apparent position of stars in the sky.


It's the way in which the Lagrangian expressions are understood or how satellite travel helps to denote the pathways throughout our universe. Are traverse pathways being suggested as we might see the holes in the cosmos as unique just to satellite travel alone? Ask yourself how the photon is influenced then? What pathways are traveled that we may see the evidence on the screen that such association measure in the spectrum are revealing of events across space and time.

Astronomers use the light-bending properties of gravity to view very distant galaxies--such as the arc shapes in this image--in a technique called "gravitational lensing.





This book describes a revolutionary new approach to determining low energy routes for spacecraft and comets by exploiting regions in space where motion is very sensitive (or chaotic). It also represents an ideal introductory text to celestial mechanics, dynamical systems, and dynamical astronomy. Bringing together wide-ranging research by others with his own original work, much of it new or previously unpublished, Edward Belbruno argues that regions supporting chaotic motions, termed weak stability boundaries, can be estimated. Although controversial until quite recently, this method was in fact first applied in 1991, when Belbruno used a new route developed from this theory to get a stray Japanese satellite back on course to the moon. This application provided a major verification of his theory, representing the first application of chaos to space travel.




See Also:

Thursday, August 30, 2012

Radiation Belt Storms Probes Launched



 NASA hosted a two-day event for 50 social media followers on August 22-23, 2012, at NASA's Kennedy Space Center in Florida. NASA's twin Radiation Belt Storm Probes (RBSP) are scheduled to lift off aboard a United Launch Alliance Atlas V rocket at 4:08 a.m. on August 23. Designed for a two-year primary science mission in orbit around Earth, RBSP will provide insight into our planet's radiation belts, and help scientists predict changes in this critical region of space.

 http://youtu.be/w0SaKPuocRA 


NASA's Radiation Belt Storm Probes blasted off from Cape Canaveral on August 30th, 2012. Bristling with sensors, the heavily-shielded spacecraft are on a 2-year mission to discover what makes the radiation belts so dangerous and so devilishly unpredictable.
"We've known about the Van Allen Belts for decades yet they continue to surprise us with unexpected storms of 'killer electrons' and other phenomena," says mission scientist David Sibeck, "The Storm Probes will help us understand what's going on out there." 


RBSP (instruments, 200px)

Each of the two Storm Probes is bristling with sensors to count energetic particles, measure plasma waves, and detect electromagnetic radiation. Learn more
See: The Radiation Belt Storm Probes


See also

Tuesday, August 28, 2012

Grail At the Moon



 Grail Recovery and Interior Labratory
NASA's Gravity Recovery And Interior Laboratory (GRAIL)-A spacecraft successfully completed its planned main engine burn at 2 p.m. PST (5 p.m. EST) today. As of 3 p.m. PST (6 p.m. EST), GRAIL-A is in a 56-mile (90-kilometer) by 5,197-mile (8,363-kilometer) orbit around the moon that takes approximately 11.5 hours to complete.


Visualisation of the “Geoid” of the Moon

Sunday, August 26, 2012

Radiation Belt Storm Probes (RBSP)



The launch of an Atlas V carrying NASA's Radiation Belt Storm Probes (RBSP) payload was scrubbed today due to weather conditions associated with lightning, as well as cumulus and anvil clouds. With the unfavorable weather forecast as a result of Tropical Storm Isaac, the leadership team has decided to roll the Atlas V vehicle back to the Vertical Integration Facility to ensure the launch vehicle and twin RBSP spacecraft are secured and protected from inclement weather. Pending approval from the range, the launch is rescheduled to Thursday, Aug. 30 at 4:05 a.m. Eastern Daylight Time. SeeRBSP Launch Targeted for No Earlier Than Aug. 30



RBSP is being designed to help us understand the Sun’s influence on Earth and Near-Earth space by studying the Earth’s radiation belts on various scales of space and time. 

The instruments on NASA’s Living With a Star Program’s (LWS) Radiation Belt Storm Probes (RBSP) mission will provide the measurements needed to characterize and quantify the plasma processes that produce very energetic ions and relativistic electrons. The RBSP mission is part of the broader LWS program whose missions were conceived to explore fundamental processes that operate throughout the solar system and in particular those that generate hazardous space weather effects in the vicinity of Earth and phenomena that could impact solar system exploration. RBSP instruments will measure the properties of charged particles that comprise the Earth’s radiation belts, the plasma waves that interact with them, the large-scale electric fields that transport them, and the particle-guiding magnetic field. 

The two RBSP spacecraft will have nearly identical eccentric orbits. The orbits cover the entire radiation belt region and the two spacecraft lap each other several times over the course of the mission. The RBSP in situ measurements discriminate between spatial and temporal effects, and compare the effects of various proposed mechanisms for charged particle acceleration and loss. See: RBSP



Credit: NASA/Johns Hopkins University Applied Physics Laboratory
Engineers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., prepare to place Radiation Belt Storm Probes spacecraft "B" in a thermal-vacuum chamber, where they can make sure the propulsion system will stand up to the range of hot, cold and airless conditions RBSP will face in outer space. This round of testing took place in late October-early November 2010.



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Saturday, August 25, 2012

Sampex

SAMPEX, the Solar Anomalous and Magnetospheric Particle Explorer, was successfully launched by a Scout rocket on July 3, 1992. It is investigating the composition of local interstellar matter and solar material and the transport of magnetospheric charged particles into the Earth's atmosphere.

SAMPEX is a momentum-biased, sun-pointed spacecraft that maintains the experiment-view axis in a zenith direction as much as possible, especially while traversing the polar regions of the Earth. It points its solar array at the Sun by aiming the momentum vector toward the Sun and rotating the spacecraft one revolution per orbit about the Sun/spacecraft axis.




The Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellite was launched in July 1992 into a low earth orbit at an altitude of 520 by 670 km and 82 degrees inclination. The satellite far exceeded its expected three-year lifetime. It has primarily operated in a three-axis stabilized mode but has also been spun for limited periods. The satellite carries four instruments designed to measure the radiation environment of the Earth's magnetosphere.

SAMPEX was an international collaboration between NASA of the United States and Germany.[2] It was part of the Small Explorer program started in 1989[2]
SAMPEX science mission ended on June 30, 2004.[3]


Sunday, January 24, 2010

Interplanetary Transport Network




This stylized depiction of the ITN is designed to show its (often convoluted) path through the solar system. The green ribbon represents one path from among the many that are mathematically possible along the surface of the darker green bounding tube. Locations where the ribbon changes direction abruptly represent trajectory changes at Lagrange points, while constricted areas represent locations where objects linger in temporary orbit around a point before continuing on




This book describes a revolutionary new approach to determining low energy routes for spacecraft and comets by exploiting regions in space where motion is very sensitive (or chaotic). It also represents an ideal introductory text to celestial mechanics, dynamical systems, and dynamical astronomy. Bringing together wide-ranging research by others with his own original work, much of it new or previously unpublished, Edward Belbruno argues that regions supporting chaotic motions, termed weak stability boundaries, can be estimated. Although controversial until quite recently, this method was in fact first applied in 1991, when Belbruno used a new route developed from this theory to get a stray Japanese satellite back on course to the moon. This application provided a major verification of his theory, representing the first application of chaos to space travel.

Since that time, the theory has been used in other space missions, and NASA is implementing new applications under Belbruno's direction. The use of invariant manifolds to find low energy orbits is another method here addressed. Recent work on estimating weak stability boundaries and related regions has also given mathematical insight into chaotic motion in the three-body problem. Belbruno further considers different capture and escape mechanisms, and resonance transitions.

Providing a rigorous theoretical framework that incorporates both recent developments such as Aubrey-Mather theory and established fundamentals like Kolmogorov-Arnold-Moser theory, this book represents an indispensable resource for graduate students and researchers in the disciplines concerned as well as practitioners in fields such as aerospace engineering.


See:Interplanetary Superhighway Makes Space Travel Simpler
July 17 2002

Friday, January 18, 2008

MESSENGER Reveals Mercury’s Geological History

Stefan of Backreaction posted a blog entry called,"Mercury looks like the Moon, nearly... that brought me up to speed on what the planet actually looks like.

His article provides for the links here in this entry, as well sets the stage for the culminating vision I have of our solar system. Looking at the solar system in the processes I outline are important point of seeing the gravitational aspects of the universe as we have come to know it.

I had never considered what the actual surface of Mercury would look like, other then what I had thought it to be, when told as a child. A molten surface.

Using the laser altimeter, MESSENGER will verify the presence of a liquid outer core in Mercury by measuring the planet's libration. Libration is the slow 88-day wobble of the planet around its rotational axis.


Seeing Mercury the way it is below provides for some thought about Mercury facing toward the Sun. It's surface looking at the picture below, I was wondering if facing directly in opposition to the Sun would showing brighter spots as we look to the right of this image.

This also raised an interesting question on my mind about how the uniformity of the surface could retain it's moon like look while undergoing the passage of "increased heat" as it faced the sun at anyone time through it's rotation.

Question 4 : What is the structure of Mercury's core?


Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

More recently, Earth-based radar observations of Mercury have also determined that at least a portion of the large metal core is still liquid to this day! Having at least a partially molten core means that a very small but detectable variation in the spin-rate of Mercury has a larger amplitude because of decoupling between the solid mantle and liquid core. Knowing that the core has not completely solidified, even as Mercury has cooled over billions of years since its formation, places important constraints on the thermal history, evolution, and core composition of the planet.




Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

This MESSENGER image was taken from a distance of about 18,000 kilometers (11,000 miles) from the surface of Mercury, at 20:03 UTC, about 58 minutes after the closest approach point of the flyby. The region shown is about 500 kilometers (300 miles) across, and craters as small as 1 kilometer (0.6 mile) can be seen in this image.


The Gravity Field



Clementine color ratio composite image of Aristarchus Crater on the Moon. This 42 km diameter crater is located on the corner of the Aristarchus plateau, at 24 N, 47 W. Ejecta from the plateau is visible as the blue material at the upper left (northwest), while material excavated from the Oceanus Procellarum area is the reddish color to the lower right (southeast). The colors in this image can be used to ascertain compositional properties of the materials making up the deep strata of these two regions. (Clementine, USGS slide 11)

This is always of interest to be because it is an accumulation of the synthesis of views we gain as we come to understand not only the views of on the Window of the universe, as we look at the Sun under information obtain in the neutrino laboratory's and information modelling of how we can now look at the sun with this new view.

But the truth is, the Earth's topography is highly variable with mountains, valleys, plains, and deep ocean trenches. As a consequence of this variable topography, the density of Earth's surface varies. These fluctuations in density cause slight variations in the gravity field, which, remarkably, GRACE can detect from space.

Well, by adding the label of Grace and Grace satellite systems, it is important to me that not only is gravity considered in context of the exploration of space in terms of Lagrangian, but of viewing how we map the earth and the views we obtain of that new gravity model of earth. This application then becomes of interest as we understand how we see the gravity model of Mercury and how the geological structure of Mercury will be reflected in that gravity model.

The Culminating Vision

Fig. 1. Story line showing the principle of least action sandwiched between relativity and quantum mechanics See A call to action

See:
  • The Periodic Table of the Moon's Strata
  • Time-Variable Gravity Measurements

  • Andrew Wiles and Fermat