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Tag Archives: JPL

Adapted from an article by Kenneth Chang published in The New York Times, September 14, 2017:

NASA’s Cassini spacecraft, the intrepid robotic explorer of Saturn’s magnificent beauty, has finally ended its 20-year journey. By design, the probe vanished into Saturn’s atmosphere, disintegrating moments after its final signal slipped away into the background noise of the Solar System. Until the end, new measurements streamed one billion miles back to Earth, preceded by the spacecraft’s last picture show of dazzling sights from around the Sun’s sixth planet.

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Credit: Credit NASA/JPL-Caltech/Space Science Institute

 

The mission for Cassini, in orbit since 2004, stretched far beyond the original four-year plan, sending back multitudes of striking photographs, solving some mysteries and upending prevailing notions about the Solar System with completely unexpected discoveries.

Even at the end, 20 years after launch, Cassini and its instruments remained in good working shape. The plutonium power source was still generating electricity. But there was not enough propellant fuel left to safely send Cassini anywhere except into Saturn.

In the very last phase of the mission, Cassini dove through the gap between Saturn and the planet’s innermost ring. This provided new, sharp views of the rings and allowed the craft to probe the planet’s interior, as another NASA’s Juno spacecraft is doing at Jupiter.

Links: read the full article; also NYT’s ‘100 Images from Cassini’ feature.

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From JPL press releases, July 4, 2016:

While Americans celebrated the evening of Independence Day, 1.7 billion miles (2.7 billion kilometres) NASA’s Juno spacecraft, launched nearly five years ago, reached its final destination: the most massive planet in our Solar System, Jupiter.

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Credit: NASA/JPL-Caltech

Juno now starts its tour of Jupiter in a 53.5-day orbit. The spacecraft saves fuel by executing a burn that places it in a capture orbit with a 53.5-day orbit instead of going directly for the 14-day orbit that will occur during the mission’s primary science collection period. The 14-day science orbit phase will begin after the final burn of the mission for Juno’s main engine on October 19.

Most of Juno’s instruments deal with Jupiter’s particles and magnetic field, which is 20,000 times more powerful than Earth’s. The main instruments are in a vault made of 400 pounds of titanium to protect them from the strong radiation. The Junocam, its imaging camera, is outside that protection, and may not last as long as other instruments; further, it will give images as it rotates that will have to be transformed to the equivalent of steady views.

Links: Full details via the JPL press release; NASA Juno mission page; NY Times: Jupiter and its moons graphic.

From a JPL news release, February 10, 2015:

Astronomers tinkering with ice and organics in the lab may have discovered why comets are encased in a hard, outer crust. Using an icebox-like instrument nicknamed Himalaya, the researchers show that fluffy ice on the surface of a comet would crystalize and harden as the comet heads toward the Sun and warms up. As the water-ice crystals form, becoming denser and more ordered, other molecules containing carbon would be expelled to the comet’s surface. The result is a crunchy comet crust sprinkled with organic dust, like a deep-fried ice cream: the crust is made of crystalline ice, while the interior is colder and more porous. The organics are like a final layer of chocolate on top.

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Credit: ESA/Rosetta/NAVCAM

The composition of comets is important to understanding how they might have delivered water and organics to our nascent, bubbling-hot Earth. New results from the Rosetta mission show that asteroids may have been the primary carriers of life’s ingredients; however, the debate is ongoing and comets may have played a role.

Links: JPL news article; Rosetta home.

NASA’s Voyager 1 spacecraft is officially the first human-made object to venture into interstellar space. The 36-year-old probe is about 12 billion miles (19 billion kilometers) from the Sun.

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Credit: NASA/JPL-Caltech

New and unexpected data indicate Voyager 1 has been traveling for about one year through plasma, or ionized gas, present in the space between stars. Voyager is in a transitional region immediately outside the solar bubble, where some effects from our sun are still evident. A report on the analysis of this new data, led by Don Gurnett and the plasma wave science team at the University of Iowa, Iowa City, is published in the journal Science.

Voyager 1 does not have a working plasma sensor, so scientists needed a different way to measure the spacecraft’s plasma environment to make a definitive determination of its location. A coronal mass ejection, a massive burst of solar wind and magnetic fields, that erupted from the Sun in March 2012 provided scientists with the data they needed. When this blast from the Sun eventually overtook Voyager 1 some 13 months later, in April 2013, the plasma around the spacecraft began to vibrate like a violin string. On April 9, Voyager 1’s plasma wave instrument detected the movement. The pitch of the oscillations helped scientists determine the density of the plasma. The particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere. This density is that which is expected in interstellar space.

Much more information is available on NASA’s Voyager page, and via this JPL press release, which includes more images and a short video. The sound of interstellar space may be heard here.

Astronomers have used data from the Spitzer Space Telescope to measure the distances, and hence temperatures, of so-called “brown dwarfs” (see Section 9.5).

These brown dwarfs, the coldest known free-floating celestial bodies, were found to be warmer than previously thought, with surface temperatures ranging from about 250 to 350 degrees Fahrenheit (125 to 175 degrees Celsius). By comparison, the Sun has a surface temperature of about 10,000 degrees Fahrenheit (around 6000 degrees Celsius).

To reach these surface temperatures after cooling for billions of years, these objects would have to have masses of only 5 to 20 times that of Jupiter. Unlike the Sun, the only source of energy for these coldest of brown dwarfs is from their gravitational contraction, which depends directly on their mass. The Sun is powered by the conversion of hydrogen to helium; these brown dwarfs are not hot enough for this type of “nuclear burning” to occur.

PIA17258_ip

Credit: NASA/JPL-Caltech

The findings help researchers understand how planets and stars form, but also present new puzzles to astronomers who study cool, planet-like atmospheres, as the observable properties don’t correlate with temperature in a straight-forward way. Ongoing studies of newly discovered brown dwarfs may shed some light (and heat) on these outstanding issues.

Read the JPL press release for more detail and additional images.