Members Can Post Anonymously On This Site
-
Similar Topics
-
By NASA
On Aug. 29, 1789, German-born British astronomer William Herschel observed a tiny bright dot orbiting around Saturn. His son later named the object Enceladus. Because of its distance from Earth and proximity to bright Saturn, for the next two centuries little remained known about Enceladus other than its size, orbital parameters, and that it held the honor as the most reflective body in the solar system. It took the Voyager flybys through the Saturn system in the early 1980s and especially the detailed observations between 2005 and 2015 by the Saturn orbiter Cassini to reveal Enceladus as a truly remarkable world, interacting with Saturn and its rings. Harboring a subsurface ocean of salty water, Enceladus may possibly be hospitable to some forms of life.
Left: Portrait (1785) of William Herschel by Lemuel Francis Abbott. Image credit: courtesy National Portrait Gallery, London. Middle: Drawing of Herschel’s 40-foot telescope. Right: Portrait (1867) of John Herschel by Julia Margaret Cameron. Image credit: Metropolitan Museum of Art.
Herschel’s previous astronomical accomplishments include the discovery of Uranus in 1781 and two of its moons, Oberon and Titania, in 1787. He also catalogued numerous objects he termed nebulae, but remained frustrated by the limitations of telescopes of his age. He began to build ever larger instruments, finally building the world’s largest reflecting telescope of its time. At 40 feet long, and with a 49-inch diameter primary mirror weighing a ton, it looked impressive although its optical characteristics did not advance the field as much as he had hoped. Nevertheless, Herschel used this telescope to observe Saturn and its five known moons, looking for others. On Aug. 28, 1789, he observed a bright point orbiting the planet and believed he had discovered a sixth moon. On Sept. 17, he discovered a seventh moon orbiting the ringed planet. He did not name these moons, that task fell to his son John who believed Saturn’s moons should be named after the Titans of Greek mythology. He named the first moon Enceladus and the second Mimas.
Left: Relative sizes of Earth, Earth’s Moon, and Enceladus. Right: Best Voyager 2 image of Enceladus.
For nearly two centuries, Enceladus remained not much more than a point of light orbiting Saturn, just another icy moon in the outer solar system. Astronomers estimated its diameter at around 310 miles and its orbital period around Saturn at 1.4 days, with a mean distance from the planet’s center of 148,000 miles. Enceladus has the distinction as one of the brightest objects in the solar system, reflecting almost 100 percent of the Sun’s light. Unusual telescope observations during the 20th century showed an increase in brightness on its trailing side, with no known explanation at the time. In 1966, astronomers discovered a diffuse ring around Saturn, the E-ring, and found in 1980 that its density peaked near Enceladus. The Voyager 1 spacecraft flew within 125,570 miles of Enceladus during its passage through the Saturn system on Nov. 12, 1980. Its twin Voyager 2 came within 54,000 miles on Aug. 26, 1981, during its flyby. These close encounters enabled the spacecraft to return the first detailed images of the moon, showing various terrains, including heavily cratered areas as well as smooth crater-free areas, indicating a very young surface.
Left: False color image of Enceladus from Cassini showing the tiger stripes at bottom. Middle: Limb view of Enceladus showing plumes of material emanating from its surface. Right: Cassini image of Enceladus backlit by the Sun showing the fountain-like plumes of material.
After the Cassini spacecraft entered orbit around Saturn in July 2004, our understanding of Enceladus increased tremendously, and of course raised new questions. Between 2005 and 2015, Cassini encountered Enceladus 22 times, turning its various instruments on the moon to unravel its secrets. It noted early on that the moon emitted gas and dust or ice particles and that they interacted with the E-ring. Images of the moon’s south polar region revealed cracks on the surface and other instruments detected a huge cloud of water vapor over the area. The moon likely had a liquid subsurface and some of this material reached the outside through these cracks. Scientists named the most prominent of these areas “tiger stripes” and later observations confirmed them as the source of the most prominent jets. During the most daring encounter in October 2015, Cassini came within 30 miles of the Enceladus’ surface, flying through the plume of material emanating from the moon. Analysis of the plumes revealed an organic brew of volatile gases, water vapor, ammonia, sodium salts, carbon dioxide, and carbon monoxide. These plumes replenish Saturn’s E-ring, and some of this material enters Saturn’s upper atmosphere, an interaction unique in the solar system. More recently, the James Webb Space Telescope imaged the water vapor plume emanating from Enceladus’ south pole, extending out 40 times the size of the moon itself. The confirmation of a subsurface ocean of salty water has led some scientists to postulate that Enceladus may be hospitable to some forms of life, making it a potential target for future exploration. Enceladus may yet have more surprises, even as scientists continue to pore over the data returned by Cassini.
Left: James Webb Space Telescope image of a water vapor plume emanating from Enceladus. Right: Illustration of the interaction of Enceladus and Saturn’s E-ring.
Map of Enceladus based on imagery from Cassini, turning our view of Enceladus from a small point of light into a unique world with its own topography.
Events in world history in 1789:
January 29 – Vietnamese emperor Quang Trung defeats Chinese Qing forces at Ngọc Hồi-Đống Đa in one of the greatest military victories in Vietnamese history.
March 10 – In Japan, the Menashi-Kunashir rebellion begins between the Ainu people and the Japanese.
April 7 – Selim III succeeds Abdul Hamid I as Sultan of the Ottoman Empire.
April 28 – Aboard the HMS Bounty in the Pacific Ocean, Fletcher Christian leads the mutiny against Captain William Bligh.
April 30 – Inauguration of George Washington as the first President of the United States of America.
July 14 – Citizens storm The Bastille fortress in Paris during the French Revolution.
September 15 – Birth of American writer James Fenimore Cooper in Burlington, New Jersey.
December 11 – Founding of the University of North Carolina, the oldest public university in the United States.
Explore More
11 min read 15 Years Ago: STS-128 Delivers Cargo to Enable Six-Person Space Station Crew
Article 1 day ago 10 min read 40 Years Ago: President Reagan Announces Teacher in Space Project
Article 2 days ago 12 min read 55 Years Ago: Apollo 11 Astronauts End Quarantine, Feted from Coast to Coast
Article 1 week ago View the full article
-
By Space Force
U.S. Space Force Brig. Gen. Jacob Middleton became the new commander of Space Forces in Europe – Space Forces Africa in a change of command ceremony at the Ramstein Officers Club Tuesday.
View the full article
-
By NASA
Teams with NASA’s Exploration Ground Systems Program, in preparation for the agency’s Artemis II crewed mission to the Moon, begin installing the first of four emergency egress baskets on the mobile launcher at Launch Complex 39B at the agency’s Kennedy Space Center in Florida on Wednesday, Jan. 24, 2024. The baskets, similar to gondolas on ski lifts, are used in the case of a pad abort emergency to enable astronauts and other pad personnel a way to quickly escape away from the mobile launcher to the base of the pad and where waiting emergency transport vehicles will then drive them away.NASA/Isaac Watson Recently, teams with NASA’s Exploration Ground Systems (EGS) Program at the agency’s Kennedy Space Center met with engineering teams at a central Florida amusement park to share knowledge on a new braking system NASA is using for its launch pad emergency egress system for Artemis missions.
“We have a new magnetic braking system for the Artemis emergency egress system and NASA hasn’t used this technology on the ground infrastructure side before to support launches,” said Jesse Berdis, mobile launcher 1 deputy project manager for EGS. “I realized we have neighbors 50 miles from us in Orlando that are essentially the world experts on magnetic braking systems.”
For Artemis, teams will use a track cable that connects the mobile launcher to the terminus site near the perimeter of NASA Kennedy’s Launch Pad 39B, where four baskets, similar to gondola lifts, can ride down. This is where the magnetic braking system operates to help control the acceleration of the baskets in multiple weight and environmental conditions. At the pad terminus site, armored emergency response vehicles are stationed to take personnel safely away from the launch pad to a designated safe site at Kennedy.
Many roller coaster manufacturers employ the use of an “eddy current braking system,” which involves using magnetics to help slow down a vehicle. Though the applications used on the roller coasters differ slightly from what the EGS teams are using for Artemis, the concept is the same, explained Amanda Arrieta, mobile launcher 1 senior element engineer.
However, unlike roller coasters which are typically in use daily for multiple hours on end, the Artemis emergency egress system is there for emergency situations only.
“We don’t plan to ever run our system unless we’re testing it or performing maintenance,” Berdis said.
Regardless of this, teams at Kennedy have ensured the system is able to function for years to come to support future Artemis missions.
“The maintenance crews [at the amusement park] were awesome because they showed us their nightly, monthly, and yearly inspections on what they were doing,” Berdis said. “That gave our operations teams a really good foundation and baseline knowledge of what to expect when they maintain and operate this system for the Artemis missions.”
Some of the conversations and suggestions teams shared include adding an acceleration sensor in the emergency egress baskets during testing. The sensor will help detect how fast the baskets are going when they ride down.
The emergency egress system is one of several new additions the EGS team is implementing to prepare for future crewed missions starting with Artemis II, and this system especially emphasizes the importance of safety.
“We have a mission, and a part of that mission is in case of an emergency, which we don’t expect, is to protect our astronauts and supporting teams at the launch pad,” Berdis said. “We want our teams to be safe and, for any scenario we put them in, especially on the ground infrastructure side, it’s important for us to do our due diligence. That includes talking to other groups that are the experts in their field to ensure we have looked at all possibilities across the board to ensure our mission is a safe one for our teams.”
During the Space Shuttle Program, teams used a similar system for the escape route astronauts and other personnel take in the event of an emergency during a launch countdown. However, instead of using a magnetic braking system for the baskets, teams used a mechanical braking system, which involved using a catch net and drag chain to slow and then halt the baskets sliding down the wire.
For the agency’s Commercial Crew Program, SpaceX also uses a catch net and drag chain for its slidewire cable at NASA Kennedy’s Launch Complex 39A pad and a deployable chute at Space Launch Complex 40 at Cape Canaveral Space Force Station. Boeing and United Launch Alliance also use a slidewire, but instead of baskets, the team deploys seats, like riding down a zip line, that ride down the slide wires at Space Launch Complex 41 at Cape Canaveral Space Force Station.
Under NASA’s Artemis campaign, the agency will establish the foundation for long-term scientific exploration at the Moon, land the first woman, first person of color, and its first international partner astronaut on the lunar surface, and prepare for human expeditions to Mars for the benefit of all.
View the full article
-
By Space Force
STARCOM's unit, Space Delta 10, charged with developing doctrine, tactics, wargaming, and lessons learned, was welcomed to Patrick Space Force Base with a change of command – and location.
View the full article
-
By Space Force
Col. Patrick took command of SPACEFOR-KOR from his previous assignment at Ramstein Air Base, Germany, he is a career space operations officer, with command experience at the squadron level and joint experience in both Germany and Belgium.
View the full article
-
-
Check out these Videos
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.