GSFC: LISA Pathfinder -- 'Comet Crumb' Detector

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GSFC: LISA Pathfinder -- 'Comet Crumb' Detector

Postby bystander » Mon Apr 17, 2017 6:16 pm

NASA Team Explores Using LISA Pathfinder as 'Comet Crumb' Detector
NASA | GSFC | 2017 Apr 17

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LISA Pathfinder, a mission led by the European Space Agency (ESA) with contributions from NASA, has successfully demonstrated critical technologies needed to build a space-based observatory for detecting ripples in space-time called gravitational waves. Now a team of NASA scientists hopes to take advantage of the spacecraft's record-breaking sensitivity to map out the distribution of tiny dust particles shed by asteroids and comets far from Earth.

Most of these particles have masses measured in micrograms, similar to a small grain of sand. But with speeds greater than 22,000 mph (36,000 km/h), even micrometeoroids pack a punch. The new measurements could help refine dust models used by researchers in a variety of studies, from understanding the physics of planet formation to estimating impact risks for current and future spacecraft. ...

The mission's primary goal was to test how well the spacecraft could fly in formation with an identical pair of 1.8-inch (46 millimeter) gold-platinum cubes floating inside it. The cubes are test masses intended to be in free fall and responding only to gravity.

The spacecraft serves as a shield to protect the test masses from external forces. When LISA Pathfinder responds to pressure from sunlight and microscopic dust impacts, the spacecraft automatically compensates by firing tiny bursts from its micronewton thrusters to prevent the test masses from being disturbed. ...

In response to an impact, LISA Pathfinder fires its thrusters to counteract both the minute "push" from the strike and any change in the spacecraft's spin. Together, these quantities allow the researchers to determine the impact's location on the spacecraft and reconstruct the micrometeoroid's original trajectory. This may allow the team to identify individual debris streams and perhaps relate them to known asteroids and comets. ...
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LISA Pathfinder -- 'Zodiacal Gegenschein' Detector

Postby neufer » Tue Apr 18, 2017 2:21 pm wrote:
<<Zodiacal light is a faint, roughly triangular, diffuse white glow seen in the night sky that appears to extend up from the vicinity of the Sun along the ecliptic or zodiac. It is caused by sunlight scattered by space dust in the zodiacal cloud. It is best seen just after sunset in spring, and just before sunrise in autumn when the zodiac is at a steep angle to the horizon, but is so faint that either moonlight or light pollution renders it invisible.

The zodiacal light decreases in intensity with distance from the Sun, but on very dark nights it has been observed in a band completely around the ecliptic. In fact, the zodiacal light covers the entire sky and is responsible in large part for the total skylight on a moonless night. Another phenomenon—a faint, but slightly increased, oval glow directly opposite the Sun—is called the gegenschein.

The dust forms a thick pancake-shaped cloud in the Solar System collectively known as the zodiacal cloud, which occupies the same plane as the ecliptic. The dust particles are between 10 and 300 micrometres in diameter, most with a mass around 150 micrograms [i.e., approximately a billionth the LISA Pathfinder mass of 125 kg such that a 30 km/s impact imparts a 30 micron/sec push].

In 2007, Brian May, lead guitarist with the band Queen, completed his PhD thesis A Survey of Radial Velocities in the Zodiacal Dust Cloud 36 years after having started and abandoning it to pursue a career in music. He was able to submit it only because of the minimal amount of research on the topic undertaken during the intervening years. May describes the subject as being one that became "trendy" again in the 2000s.>> wrote:
<<Nicolas Fatio de Duillier (26 February 1664 – 12 May 1753) was a Swiss mathematician known for his work on the zodiacal light problem, for his role in the Newton v. Leibniz calculus controversy, and for originating the "push" or "shadow" theory of gravitation. (Fatio assumed that the universe is filled with minute particles, which are moving indiscriminately with very high speed and rectilinearly in all directions except when shadowed by a nearby planet to which it is thereby attracted.)

Fatio was born in Basel, Switzerland, in 1664, the seventh of fourteen children of Jean-Baptiste and Cathérine Fatio. The family moved in 1672 to Duillier. Before he was eighteen, Fatio wrote to the astronomer Giovanni Domenico Cassini, suggesting a new method of determining the Sun's distance from the Earth and an explanation of the form of Saturn's ring. Encouraged by Cassini's reply, he went to Paris in the spring of 1682, and was kindly received. Fatio began astronomical studies under Cassini at the Parisian observatory. In 1683, Cassini presented his theory of the zodiacal light. Fatio followed his observations, repeated them at Geneva in 1684, and gave in 1685 new and important developments of this theory. They were published in his Lettre à M. Cassini … touchant une lumière extraordinaire qui paroît dans le ciel depuis quelques années.

In London in 1687, Fatio made the acquaintance of John Wallis and Edward Bernard (1638-1697) and worked out a solution of the inverse tangent problem. In 1690, he wrote a letter to Huygens, in which he outlined his own gravitational theory, which later became known as Le Sage's theory of gravitation. Soon after that, he read its content before the Royal Society. This theory, on which he worked until his death, is based on minute particles which push gross matter to each other.

Fatio alleged that he had convinced Newton of certain mistakes in the latter's monumental work Philosophiæ Naturalis Principia Mathematica. He put himself on a par with Newton, and in a letter to Huygens, dated 1691, wrote that it was really unnecessary to ask Newton to prepare a new edition. "However," he adds, "I may possibly undertake it myself, as I know no one who so well and thoroughly understands a good part of this book as I do." Huygens wrote on the margin of this letter ‘"appy Newton".

When Leibniz sent a set of problems for solution to England, he mentioned Newton and failed to mention Fatio among those probably capable of solving them. Fatio retorted by sneering at Leibniz as the "second inventor" of the calculus. In replying to Fatio, Leibniz appealed to Newton himself as having admitted the independent discovery. Fatio stirred up the whole Royal Society to take a part in the dispute.

Fatio retired to Worcester, where he formed some congenial friendships and busied himself with scientific pursuits, alchemy, and the mysteries of the cabbala. In 1732, through the influence of John Conduitt, Newton's nephew-in-law, he endeavoured without success to obtain some reward for having saved the life of the Prince of Orange. He assisted Conduitt in planning the design and writing the inscription for Newton's monument in Westminster Abbey.>>
Art Neuendorffer

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