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Showing posts with label VLBI. Show all posts
Showing posts with label VLBI. Show all posts

Sunday, July 15, 2012

Space Geodesy



 Project manager Stephen Merkowitz talks about his work with NASA's Space Geodesy Project, including a brief overview of the four fundamental techniques of space geodesy: GPS, VLBI, SLR, and DORIS.

Learn more about space geodesy at: http://space-geodesy.nasa.gov/

This video is public domain and can be downloaded at: http://svs.gsfc.nasa.gov/goto?11031


Space Geodesy provides positioning, navigation, and timing reference systems and Earth system observations
Geodesy is the science of the Earth’s shape, gravity and rotation, including their evolution in time. A number of different techniques are used to observe the geodetic properties of the Earth including the space-geodetic techniques of Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS) like the US Global Positioning System (GPS), and the French Doppler Orbitography and Radio-Positioning by Integrated Satellite (DORIS) system. These space-geodetic observations also provide the basis for the reference frame that is needed in order to assign coordinates to points and objects and thereby determine how those points and objects move over time. See SGP Science






See Also:


Saturday, October 08, 2011

Subtly Shaded Map of Moon Reveals Titanium Treasure Troves

A map of the Moon combining observations in visible and ultraviolet wavelengths shows a treasure trove of areas rich in Titanium ores. Not only is Titanium a valuable mineral, it is key to helping scientists unravel the mysteries of the Moon’s interior.  Mark Robinson and Brett Denevi will be presenting the results from the Lunar Reconnaissance Orbiter mission today at the joint meeting of the European Planetary Science Congress and the American Astronomical Society’s Division for Planetary Sciences. >EPSC-DPS JOINT MEETING 2011 PRESS NOTICE
ISSUED 13:15 CEST ON FRIDAY 7TH OCTOBER
Ref. PN: EPSC11/14
 

It seems this Europlanet is a little bit behind the times. Check label below on Plato's Nightlight Mining Company. What more can I say?

See Also: LROC “Treasure Map” Reveals Titanium Deposits

Monday, April 25, 2011

LRO's Crater Science Investigations



If you want to learn more about the history of Earth and other rocky planets in the solar system, craters are a great place to look. Now, thanks to LRO's LROC instrument, we can take a much closer look at Linné Crater on the moon--a pristine crater that's great to use to compare with other craters! See: LRO's Crater Science Investigations



The life cycle of a lunar impact and associated time and special scales. The LCROSS measurement methods are “layered” in response to the rapidly evolving impact environment. See: Impact:Lunar CRater Observation Satellite (LCROSS)



Data from the ultraviolet/visible spectrometer taken shortly after impact showing emission lines (indicated by arrows). These emission lines are diagnostic of compounds in the vapor/debris cloud.
Credit: NASA


LCROSS Impact Data Indicates Water on Moon11.13.09






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It is important that we establish an outpost on the moon in order to progress further out into the universe. A lot of work has to be done to venture further out, so that we may explore.

Click on Image


See Also: Plato's Nightlight Mining Company

Sunday, November 14, 2010

The Lunar Far Side: The Side Never Seen from Earth

                                                            Mass concentration (astronomy)

This figure shows the topography (top) and corresponding gravity (bottom) signal of Mare Smythii at the Moon. It nicely illustrates the term "mascon". Author Martin Pauer

While article is from Tuesday, June 22, 2010 9:00 PM it still amazes me how we see the moon in context of it's coloring.
Topography when seen in context of landscape, how we measure aspects of the gravitational field supply us with a more realistic interpretation of the globe as a accurate picture of how that sphere(isostatic equilibrium)  looks.


Image Credit: NASA/Goddard
Ten Cool Things Seen in the First Year of LRO

Tidal forces between the moon and the Earth have slowed the moon' rotation so that one side of the moon always faces toward our planet. Though sometimes improperly referred to as the "dark side of the moon," it should correctly be referred to as the "far side of the moon" since it receives just as much sunlight as the side that faces us. The dark side of the moon should refer to whatever hemisphere isn't lit at a given time. Though several spacecraft have imaged the far side of the moon since then, LRO is providing new details about the entire half of the moon that is obscured from Earth. The lunar far side is rougher and has many more craters than the near side, so quite a few of the most fascinating lunar features are located there, including one of the largest known impact craters in the solar system, the South Pole-Aitken Basin. The image highlighted here shows the moon's topography from LRO's LOLA instruments with the highest elevations up above 20,000 feet in red and the lowest areas down below -20,000 feet in blue.

Learn More About Far side of the Moon

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 Credit: NASA/Goddard/MIT/Brown

Figure 4: A lunar topographic map showing the Moon from the vantage point of the eastern limb. On the left side of the Moon seen in this view is part of the familiar part of the Moon observed from Earth (the eastern part of the nearside). In the middle left-most part of the globe is Mare Tranquillitatis (light blue) the site of the Apollo 11 landing, and above this an oval-appearing region (Mare Serenitatis; dark blue) the site of the Apollo 17 landing. Most of the dark blue areas are lunar maria, low lying regions composed of volcanic lava flows that formed after the heavily cratered lunar highlands (and are thus much less cratered). The topography is derived from over 2.4 billion shots made by the Lunar Orbiter Laser Altimeter (LOLA) instrument on board the NASA Lunar Reconnaissance Orbiter. The large near-circular basins show the effects of the early impacts on early planetary crusts in the inner solar system, including the Earth. 

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 Author and Image Credit: Mark A. Wieczorek
Radial gravitational anomaly at the surface of the Moon as determined from the gravity model LP150Q. The contribution due to the rotational flattening has been removed for clarity, and positive anomalies correspond to an increase in magnitude of the gravitational acceleration. Data are presented in two Lambert azimuthal equal area projections.
The major characteristic of the Moon's gravitational field is the presence of mascons, which are large positive gravity anomalies associated with some of the giant impact basins. These anomalies greatly influence the orbit of spacecraft about the Moon, and an accurate gravitational model is necessary in the planning of both manned and unmanned missions. They were initially discovered by the analysis of Lunar Orbiter tracking data,[2] since navigation tests prior to the Apollo program experienced positioning errors much larger than mission specifications.

Friday, November 13, 2009

LCROSS Observes Water on Moon



Data from the ultraviolet/visible spectrometer taken shortly after impact showing emission lines (indicated by arrows). These emission lines are diagnostic of compounds in the vapor/debris cloud.
Credit: NASA


LCROSS Impact Data Indicates Water on Moon11.13.09


The argument that the moon is a dry, desolate place no longer holds water.

Secrets the moon has been holding, for perhaps billions of years, are now being revealed to the delight of scientists and space enthusiasts alike.

NASA today opened a new chapter in our understanding of the moon. Preliminary data from the Lunar CRater Observation and Sensing Satellite, or LCROSS, indicates that the mission successfully uncovered water during the Oct. 9, 2009 impacts into the permanently shadowed region of Cabeus cater near the moon’s south pole.

The impact created by the LCROSS Centaur upper stage rocket created a two-part plume of material from the bottom of the crater. The first part was a high angle plume of vapor and fine dust and the second a lower angle ejecta curtain of heavier material. This material has not seen sunlight in billions of years.

See more on link above.



LRO's First Moon Images

07.02.09

1994 Clementine image of moon with Mare Nubium labeled 1994 Clementine image of the moon with Mare Nubium labeled. LRO's first lunar images show an area near this region. Credit: NASA

NASA's Lunar Reconnaissance Orbiter has transmitted its first images since reaching the moon on June 23. The spacecraft's two cameras, collectively known as the Lunar Reconnaissance Orbiter Camera, or LROC, were activated June 30. The cameras are working well and have returned images of a region in the lunar highlands south of Mare Nubium (Sea of Clouds).

As the moon rotates beneath LRO, LROC gradually will build up photographic maps of the lunar surface.

"Our first images were taken along the moon's terminator -- the dividing line between day and night -- making us initially unsure of how they would turn out," said LROC Principal Investigator Mark Robinson of Arizona State University in Tempe. "Because of the deep shadowing, subtle topography is exaggerated, suggesting a craggy and inhospitable surface. In reality, the area is similar to the region where the Apollo 16 astronauts safely explored in 1972. While these are magnificent in their own right, the main message is that LROC is nearly ready to begin its mission."

Sunday, March 26, 2006

On Gauss's Mountain

You must understand that any corrections necessary are appreciated. The geometrical process spoken too here must be understood in it's historical development to undertand, how one can see differently.

Euclidean geometry, elementary geometry of two and three dimensions (plane and solid geometry), is based largely on the Elements of the Greek mathematician Euclid (fl. c.300 B.C.). In 1637, René Descartes showed how numbers can be used to describe points in a plane or in space and to express geometric relations in algebraic form, thus founding analytic geometry, of which algebraic geometry is a further development (see Cartesian coordinates). The problem of representing three-dimensional objects on a two-dimensional surface was solved by Gaspard Monge, who invented descriptive geometry for this purpose in the late 18th cent. differential geometry, in which the concepts of the calculus are applied to curves, surfaces, and other geometrical objects, was founded by Monge and C. F. Gauss in the late 18th and early 19th cent. The modern period in geometry begins with the formulations of projective geometry by J. V. Poncelet (1822) and of non-Euclidean geometry by N. I. Lobachevsky (1826) and János Bolyai (1832). Another type of non-Euclidean geometry was discovered by Bernhard Riemann (1854), who also showed how the various geometries could be generalized to any number of dimensions.


These tidbits, would have been evidence as projects predceding as "towers across valleys" amd "between mountain measures," to become what they are today. Allows us to se in ways that we are not used too, had we not learnt of this progression and design that lead from one to another.


8.6 On Gauss's Mountains

One of the most famous stories about Gauss depicts him measuring the angles of the great triangle formed by the mountain peaks of Hohenhagen, Inselberg, and Brocken for evidence that the geometry of space is non-Euclidean. It's certainly true that Gauss acquired geodetic survey data during his ten-year involvement in mapping the Kingdom of Hanover during the years from 1818 to 1832, and this data included some large "test triangles", notably the one connecting the those three mountain peaks, which could be used to check for accumulated errors in the smaller triangles. It's also true that Gauss understood how the intrinsic curvature of the Earth's surface would theoretically result in slight discrepancies when fitting the smaller triangles inside the larger triangles, although in practice this effect is negligible, because the Earth's curvature is so slight relative to even the largest triangles that can be visually measured on the surface. Still, Gauss computed the magnitude of this effect for the large test triangles because, as he wrote to Olbers, "the honor of science demands that one understand the nature of this inequality clearly". (The government officials who commissioned Gauss to perform the survey might have recalled Napoleon's remark that Laplace as head of the Department of the Interior had "brought the theory of the infinitely small to administration".) It is sometimes said that the "inequality" which Gauss had in mind was the possible curvature of space itself, but taken in context it seems he was referring to the curvature of the Earth's surface.


One had to recognize the process that historically proceeded in our overviews "to non-euclidean perspectives," "geometrically enhanced" through to our present day headings, expeirmentallly.

Michelson interferometer(27 Mar 2006 wikipedia)

Michelson interferometer is the classic setup for optical interferometry and was invented by Albert Abraham Michelson. Michelson, along with Edward Morley, used this interferometer for the famous Michelson-Morley experiment in which this interferometer was used to prove the non-existence of the luminiferous aether. See there for a detailed discussion of its principle.

But Michelson had already used it for other purposes of interferometry, and it still has many other applications, e.g. for the detection of gravitational waves, as a tunable narrow band filter, and as the core of Fourier transform spectroscopy. There are also some interesting applications as a "nulling" instrument that is used for detecting planets around nearby stars. But for most purposes, the geometry of the Mach-Zehnder interferometer is more useful.


A quick summation below leads one onto the idea of what experimental validation has done for us. Very simply, the graduation of interferometer design had been taken to astronomical proportions?



Today the Count expands on this for us by showing other information on expeirmental proposals. How fitting that this historical drama has been shown here, in a quick snapshot. As well the need for understanding the "principal inherent" in the project below.

VLBI is a geometric technique: it measures the time difference between the arrival at two Earth-based antennas of a radio wavefront emitted by a distant quasar. Using large numbers of time difference measurements from many quasars observed with a global network of antennas, VLBI determines the inertial reference frame defined by the quasars and simultaneously the precise positions of the antennas. Because the time difference measurements are precise to a few picoseconds, VLBI determines the relative positions of the antennas to a few millimeters and the quasar positions to fractions of a milliarcsecond. Since the antennas are fixed to the Earth, their locations track the instantaneous orientation of the Earth in the inertial reference frame. Relative changes in the antenna locations from a series of measurements indicate tectonic plate motion, regional deformation, and local uplift or subsidence.


See:

  • Apollo Moon Measure