Category Archives: Space Science

The Cassini spacecraft made its final orbit of Saturn this morning:

NASA’s Cassini Spacecraft Ends Its Historic Exploration of Saturn

A thrilling epoch in the exploration of our solar system came to a close today, as NASA’s Cassini spacecraft made a fateful plunge into the atmosphere of Saturn, ending its 13-year tour of the ringed planet.

“This is the final chapter of an amazing mission, but it’s also a new beginning,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at NASA Headquarters in Washington. “Cassini’s discovery of ocean worlds at Titan and Enceladus changed everything, shaking our views to the core about surprising places to search for potential life beyond Earth.”

Telemetry received during the plunge indicates that, as expected, Cassini entered Saturn’s atmosphere with its thrusters firing to maintain stability, as it sent back a unique final set of science observations. Loss of contact with the Cassini spacecraft occurred at 4:55 a.m. PDT (7:55 a.m. EDT), with the signal received by NASA’s Deep Space Network antenna complex in Canberra, Australia.

*Saturn’s active, ocean-bearing moon Enceladus sinks behind the giant planet in a farewell portrait from NASA’s Cassini spacecraft. Credits: NASA/JPL-Caltech/Space Science Institute*

“It’s a bittersweet, but fond, farewell to a mission that leaves behind an incredible wealth of discoveries that have changed our view of Saturn and our solar system, and will continue to shape future missions and research,”

said Michael Watkins, director of NASA’s Jet Propulsion Laboratory in Pasadena, California, which manages the Cassini mission for the agency. JPL also designed, developed and assembled the spacecraft.

Cassini program manager at JPL, Earl Maize, left, and spacecraft operations team manager for the Cassini mission at Saturn, Julie Webster, right, embrace after the Cassini spacecraft plunged into Saturn, Friday, Sept. 15, 2017 at NASA’s Jet Propulsion Laboratory in Pasadena, California. Since its arrival in 2004, the Cassini-Huygens mission has been a discovery machine, revolutionizing our knowledge of the Saturn system and captivating us with data and images never before obtained with such detail and clarity. On Sept. 15, 2017, operators will deliberately plunge the spacecraft into Saturn, as Cassini gathered science until the end. The “plunge” ensures Saturn’s moons will remain pristine for future exploration. During Cassini’s final days, mission team members from all around the world gathered at NASA’s Jet Propulsion Laboratory, Pasadena, California, to celebrate the achievements of this historic mission. Photo Credit: (NASA/Joel Kowsky)

Cassini’s plunge brings to a close a series of 22 weekly “Grand Finale” dives between Saturn and its rings, a feat never before attempted by any spacecraft.

“The Cassini operations team did an absolutely stellar job guiding the spacecraft to its noble end,” said Earl Maize, Cassini project manager at JPL. “From designing the trajectory seven years ago, to navigating through the 22 nail-biting plunges between Saturn and its rings, this is a crack shot group of scientists and engineers that scripted a fitting end to a great mission. What a way to go. Truly a blaze of glory.”

As planned, data from eight of Cassini’s science instruments was beamed back to Earth. Mission scientists will examine the spacecraft’s final observations in the coming weeks for new insights about Saturn, including hints about the planet’s formation and evolution, and processes occurring in its atmosphere.

“Things never will be quite the same for those of us on the Cassini team now that the spacecraft is no longer flying,” said Linda Spilker, Cassini project scientist at JPL. “But, we take comfort knowing that every time we look up at Saturn in the night sky, part of Cassini will be there, too.”

Cassini launched in 1997 from Cape Canaveral Air Force Station in Florida and arrived at Saturn in 2004. NASA extended its mission twice – first for two years, and then for seven more. The second mission extension provided dozens of flybys of the planet’s icy moons, using the spacecraft’s remaining rocket propellant along the way. Cassini finished its tour of the Saturn system with its Grand Finale, capped by Friday’s intentional plunge into the planet to ensure Saturn’s moons – particularly Enceladus, with its subsurface ocean and signs of hydrothermal activity – remain pristine for future exploration.

While the Cassini spacecraft is gone, its enormous collection of data about Saturn – the giant planet, its magnetosphere, rings and moons – will continue to yield new discoveries for decades to come.

“Cassini may be gone, but its scientific bounty will keep us occupied for many years,” Spilker said. “We’ve only scratched the surface of what we can learn from the mountain of data it has sent back over its lifetime.”

An online toolkit with information and resources for Cassini’s Grand Finale is available at: https://saturn.jpl.nasa.gov/grandfinale

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL, a division of Caltech in Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington.

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Gas giants Saturn, Jupiter, et al, Space Science, Space Systems

Videos: Cassini nears its final orbit around Saturn

September 14, 2017 TopSpacer

On Friday, the Cassini probe will end its 13 year mission at the ringed planet when its final orbit takes the spacecraft into Saturn’s atmosphere: Cassini Spacecraft Makes Its Final Approach to Saturn | NASA

NASA’s Cassini spacecraft is on final approach to Saturn, following confirmation by mission navigators that it is on course to dive into the planet’s atmosphere on Friday, Sept. 15.

Cassini is ending its 13-year tour of the Saturn system with an intentional plunge into the planet to ensure Saturn’s moons – in particular Enceladus, with its subsurface ocean and signs of hydrothermal activity – remain pristine for future exploration. The spacecraft’s fateful dive is the final beat in the mission’s Grand Finale, 22 weekly dives, which began in late April, through the gap between Saturn and its rings. No spacecraft has ever ventured so close to the planet before.

*Milestones in Cassini’s final dive toward Saturn.*

The mission’s final calculations predict loss of contact with the Cassini spacecraft will take place on Sept. 15 at 7:55 a.m. EDT (4:55 a.m. PDT). Cassini will enter Saturn’s atmosphere approximately one minute earlier, at an altitude of about 1,190 miles (1,915 kilometers) above the planet’s estimated cloud tops (the altitude where the air pressure is 1-bar, equivalent to sea level on Earth). During its dive into the atmosphere, the spacecraft’s speed will be approximately 70,000 miles (113,000 kilometers) per hour. The final plunge will take place on the day side of Saturn, near local noon, with the spacecraft entering the atmosphere around 10 degrees north latitude.

When Cassini first begins to encounter Saturn’s atmosphere, the spacecraft’s attitude control thrusters will begin firing in short bursts to work against the thin gas and keep Cassini’s saucer-shaped high-gain antenna pointed at Earth to relay the mission’s precious final data. As the atmosphere thickens, the thrusters will be forced to ramp up their activity, going from 10 percent of their capacity to 100 percent in the span of about a minute. Once they are firing at full capacity, the thrusters can do no more to keep Cassini stably pointed, and the spacecraft will begin to tumble.

Graphic showing the relative altitudes of Cassini’s final five passes through Saturn’s upper atmosphere, compared to the depth it reaches upon loss of communication with Earth. Credits: NASA/JPL-Caltech

When the antenna points just a few fractions of a degree away from Earth, communications will be severed permanently. The predicted altitude for loss of signal is approximately 930 miles (1,500 kilometers) above Saturn’s cloud tops. From that point, the spacecraft will begin to burn up like a meteor. Within about 30 seconds following loss of signal, the spacecraft will begin to come apart; within a couple of minutes, all remnants of the spacecraft are expected to be completely consumed in the atmosphere of Saturn.

Due to the travel time for radio signals from Saturn, which changes as both Earth and the ringed planet travel around the Sun, events currently take place there 83 minutes before they are observed on Earth. This means that, although the spacecraft will begin to tumble and go out of communication at 6:31 a.m. EDT (3:31 a.m. PDT) at Saturn, the signal from that event will not be received at Earth until 83 minutes later.

“The spacecraft’s final signal will be like an echo. It will radiate across the solar system for nearly an hour and a half after Cassini itself has gone,” said Earl Maize, Cassini project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “Even though we’ll know that, at Saturn, Cassini has already met its fate, its mission isn’t truly over for us on Earth as long as we’re still receiving its signal.”

Cassini’s last transmissions will be received by antennas at NASA’s Deep Space Network complex in Canberra, Australia.

Cassini is set to make groundbreaking scientific observations of Saturn, using eight of its 12 science instruments. All of the mission’s magnetosphere and plasma science instruments, plus the spacecraft’s radio science system, and its infrared and ultraviolet spectrometers will collect data during the final plunge.

*Cassini’s path into Saturn’s upper atmosphere, with tick marks every 10 seconds.*
*Credits: NASA/JPL-Caltech*

Chief among the observations being made as Cassini dives into Saturn are those of the Ion and Neutral Mass Spectrometer (INMS). The instrument will directly sample the composition and structure of the atmosphere, which cannot be done from orbit. The spacecraft will be oriented so that INMS is pointed in the direction of motion, to allow it the best possible access to oncoming atmospheric gases.

For the next couple of days, as Saturn looms ever larger, Cassini expects to take a last look around the Saturn system, snapping a few final images of the planet, features in its rings, and the moons Enceladus and Titan. The final set of views from Cassini’s imaging cameras is scheduled to be taken and transmitted to Earth on Thursday, Sept. 14. If all goes as planned, images will be posted to the Cassini mission website beginning around 11 p.m. EDT (8 p.m. PDT). The unprocessed images will be available at: https://saturn.jpl.nasa.gov/galleries/raw-images

*This unprocessed image of Titan was taken by NASA’s Cassini spacecraft during the mission’s final, distant flyby on Sept. 11, 2017. Credits: NASA/JPL-Caltech/Space Science Institute*

Live mission commentary and video from JPL Mission Control will air on NASA Television and the agency’s website from 7 to 8:30 a.m. EDT (4 a.m. to 5:30 a.m. PDT) on Sept. 15. A post-mission news briefing from JPL is currently scheduled for 9:30 a.m. EDT (6:30 a.m. PDT), also on NASA TV.

A new NASA e-book, The Saturn System Through the Eyes of Cassini, showcasing compelling images and key science discoveries from the mission, is available for free download in multiple formats at: https://www.nasa.gov/ebooks

An online toolkit of information and resources about Cassini’s Grand Finale and final plunge into Saturn is available at: https://saturn.jpl.nasa.gov/grandfinale

Follow the Cassini spacecraft’s plunge on social media using #GrandFinale, or visit:

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More about the Cassini mission and its ending:

Events, Space Science, Space Systems

Videos: 40th Anniversary of the Voyager missions

September 12, 2017 TopSpacer

To mark the 40 years of the flights of the two Voyager spacecraft through the solar system and into interstellar space, NASA held an event with several of the scientists involved in the project to discuss what it has accomplished:

This segment with William Shatner is about public messages transmitted to Voyager 1:

From the caption:

On Sept. 5, 2017—the 40th anniversary of Voyager 1’s launch—NASA revealed the winning #MessageToVoyager and beamed it into space. “Message to Voyager” is a social media campaign inspired by the messages of goodwill carried on the Golden Record aboard each Voyager spacecraft.

NASA invited the public to submit short, uplifting messages to the Voyager 1 spacecraft and all that lies beyond it. These messages were a maximum of 60 characters and were tagged #MessageToVoyager. NASA tracked more than 30,000 submissions. The Voyager team together with JPL and NASA headquarters selected their 10 favorites, which were then put to a public vote. The winning message was sent into interstellar space by a command that originated from the Deep Space Network (DSN) mission control at NASA’s Jet Propulsion Laboratory with help from the original Captain Kirk, actor William Shatner; Tracy Drain, Juno mission deputy chief engineer; Jeff Berner, DSN chief engineer; and Annabel Kennedy, DSN command engineer.

To see all 10 finalist messages and get more details about the #MessageToVoyager campaign, visit https://voyager.jpl.nasa.gov/message/

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Astronomy, SETI, Space Science

Project Blue: Crowd-funding a telescope to find habitable worlds

September 12, 2017 TopSpacer

The BoldlyGo Institute and several other institutions are supporting Project Blue, a private initiative to develop a space telescope specialized to look for habitable planets around other stars. The Project has opened a crowd-funding campaign to pay for the design of the spacecraft: Project Blue: A Telescope to Find Habitable Worlds | Indiegogo

Our generation has a unique opportunity to discover Earthlike planets around other stars, and Project Blue could make this breakthrough. We’re creating detailed plans for the spacecraft, and we want you to be a part of advancing our mission to the Launchpad!

We believe a sister Earth could exist not too far from the place we call home and, thanks to recent breakthroughs, the technology now exists to find out. We at Project Blue aim to search the Alpha Centauri system for planets like Earth, and we want your help to launch our engineering design effort, like creating blueprints for a house before construction begins. We are looking to raise $175,000 to complete this engineering phase and to establish our industry partnerships. And we want to get you involved in the mission right at the start so that, together, we can all take a bold leap into shaping humanity’s future!

The observatory would be much smaller, and much cheaper, than the Hubble or similar big science spacecraft:

Project Blue is a space telescope mission that seeks to find and photograph a habitable world, another Earthlike planet where life can potentially thrive. Our goal is simple — to build & launch a telescope so powerful it can detect a blue planet in the nearby Alpha Centauri star system. Thanks to recent technological innovations, our telescope is small enough to fit on a coffee table, but powerful enough to pick up a planet over a billion times dimmer than its star — from four light years away! With this telescope we aim to take the first ever optical image of a potentially habitable exoplanet, and the team hopes that the results will show a ‘pale blue dot’ similar to the famous photo of Earth taken by the Voyager probe.

With sufficient public support, the spacecraft could go into orbit by 2023:

Gas giants Saturn, Jupiter, et al, Space Science

Cassini nears journey’s end + The plume of Enceladous + The rings in hi-res

September 9, 2017 TopSpacer

The Cassini mission to Saturn will end on September 15th when the spacecraft’s orbit will take it into the gas giant’s atmosphere. This video shows some of the spectacular imagery of the Saturn system sent back by the probe since it went into orbit there in 2004.

** Here is a video clip showing the plume of water vapor emitted at the pole of Saturn’s moon Enceladus: Cassini: The Grand Finale: Last Enceladus Plume Observation

This movie sequence of images is from the last dedicated observation of the Enceladus plume by NASA’s Cassini spacecraft.

The images were obtained over approximately 14 hours as Cassini’s cameras stared at the active, icy moon. The view during the entire sequence is of the moon’s night side, but Cassini’s perspective Enceladus shifts during the sequence. The movie begins with a view of the part of the surface lit by reflected light from Saturn and transitions to completely unilluminated terrain. The exposure time of the images changes about halfway through the sequence, in order to make fainter details visible. (The change also makes background stars become visible.)

The images in this movie sequence were taken on Aug. 28, 2017, using Cassini’s narrow-angle camera. The images were acquired at a distance from Enceladus that changed from 684,000 to 539,000 (1.1 million to 868,000 kilometers). Image scale changes during the sequence, from 4 to 3 miles (7 to 5 kilometers) per pixel.

** Sharpest images yet of Saturn’s rings: Cassini: The Grand Finale: Colorful Structure at Fine Scales

These are the highest-resolution color images of any part of Saturn’s rings, to date, showing a portion of the inner-central part of the planet’s B Ring. The view is a mosaic of two images that show a region that lies between 61,300 and 65,600 miles (98,600 and 105,500 kilometers) from Saturn’s center.

The first image (Figure A, above) is a natural color composite, created using images taken with red, green and blue spectral filters. The pale tan color is generally not perceptible with the naked eye in telescope views, especially given that Saturn has a similar hue.

The material responsible for bestowing this color on the rings—which are mostly water ice and would otherwise appear white—is a matter of intense debate among ring scientists that will hopefully be settled by new in-situ observations before the end of Cassini’s mission.

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More about Cassini’s final days and its legacy: