www.thespacewriter.com/wp

New Horizons at Pluto — New Horizons, Pluto, and Charon (artist’s concept). Courtesy NASA.

Our favorite outer solar system spacecraft is back on the job! New Horizons woke up from a five-month hibernation on its way to the distant world 2014 MU69. It’s still more than a year before the spacecraft gets to its next target, but it has a lot of work to do in the meantime. The current plan is to have it look at objects in the Kuiper Belt, measure the radiation environment it’s passing through, and check out the distribution and density of dust and gas. These are all “first-time” measurements of a regime of the solar system planetary scientists are eager to study.

New Horizons isn’t the first to transit the Kuiper Belt. The Voyagers and Pioneers passed through the same region and returned some data as their instruments would allow. Today, the Voyagers continue to measure the outermost region of the solar system and have crossed the heliospheric boundary to interstellar space. The Pioneers haven’t communicated back to Earth since 1995 and 2003, respectively. New Horizons is on a similar headlong trajectory out of the solar system and will return data for at least a couple of decades if all the instruments continue to work.

Mission Operations for New Horizons

New Horizons next target — The Kuiper Belt object 2014 MU69 may be a double-lobed object or possibly a more spherical one with a chunk missing. The New Horizons spacecraft will fly by this object in January 2019. Courtesy JHU/APL/SWRI/Alex Parker

Now that New Horizons is up and ready for a few months of work, the mission team will be outfitting it with new software packages and getting ready for a trajectory course correction. That will help refine its path toward its next target. This kind of “maintenance” is important. We want a healthy working spacecraft. By all accounts, New Horizons is functioning right on the nominal. Each week it has been sending back a little “I’m here” signal to let controllers know it’s doing okay. That beacon, speeding across more than 3.6 billion kilometers of space, is a signal from our planetary probe scout. It’s checking out the territory ahead and sending back critical updates along the way.

Next Up

In December, New Horizons slips into sleep again (still sending out its little signal). That happens December 9th. This time the spacecraft will snooze until June 4th. At that point, controllers will begin prepping it for the close flyby of 2014 MU69, which will take place on January 1, 2019. It’ll be another high-speed flyby, this time of a much smaller, dimmer world than Pluto. Nothing is known first-hand about any other Kuiper Belt world than Pluto and its moons. Pictures and data will really open a window into the kinds of worlds that populate this distant region of space. There are

There are many more M69-type worlds out there, and the next flyby is sure to provide some surprises about what they look like. There’s so much to learn about the Kuiper Belt — from the compositions of distant KBOs — to their origins and evolution. Sure, planetary scientists have a good general idea of how these places formed and changed over time, but actual images and data will help cement that understanding.

Exploring Distant Reaches

We’ve come a long way in our perception of the solar system since the first time Galileo trained a telescope on Jupiter in 1610. Today, the Kuiper Belt is the third regime of the solar system and it’s huge. Its inner boundary is at 30 astronomical units and stretched out to beyond 50 astronomical units. In linear measure, that’s a range of 20 astronomical units, covering a straight-line distance of 2,980,000,000 kilometers. Another way to think of it is about the distance between the Sun and planet Uranus. The Kuiper Belt surrounds the Sun at that far distance. It’s the vast wilderness of the solar system, compared to the better-explored areas of the terrestrial and gas giant planets. Who knows how many worlds are out there? For now, we have New Horizons to explore it, along with a cadre of Earth-based (and orbiting) telescopes. Stay tuned!

The time is coming when we will all say goodbye to Cassini, the spacecraft exploring Saturn since it first turned its cameras to stare at the planet in 2002. It began its Grand Finale activities some months ago with final orbits, final images, and other “last” looks at the Saturn system. The last pass around the moon Titan is done. The spacecraft got a gravitational kick from that loop that sends it right into Saturn’s northern hemisphere clouds on Friday. The last command sequences are sent. All controllers can do now is wait, monitor transmissions coming back from Cassini, and make any last-minute changes as necessary.

Cassini Opened New Windows on Saturn

As I look over the many, many images and other data reports from the mission, it’s hard to select a “favorite” result. It continues to show us way more than simply a ringed planet with a bunch of moons and some gorgeous rings. Granted, we are used to seeing great images of the system from the Voyager spacecraft in the 1980s. But, Cassini did it in high-res for years.

One of the great truisms about planetary science tells us that while it’s good to take snapshots of a target, it’s even better to study how that target changes over time. It’s the difference between taking a baby picture of someone and having a series of pictures taken during their lifetimes. You get to see how they grow and change. Cassini opened windows of opportunity to watch the Saturn system change over time — from its storms and cloud belts and zones to activities on some of its moons and within its rings.

Encountering Enceladus

cassini — A 14-hour image sequence of Enceladus made by Cassini shows plumes spewing ice crystals out to space. Courtesy NASA/Cassini Mission.

Still, if I had to select just one result that’s really important, I’d go with the discovery and long-term study of the moon Enceladus and its jets. Those geysers spew out to space and create the E ring. Their ice particles told scientists about the ocean hidden beneath the icy crust of that little moon. The fact that there’s an ocean there at all is a major surprise. The finding that it’s salty and “warm” (i.e. not frozen) indicates conditions could be hospitable to life.

Now, to be clear, life hasn’t been discovered there. But, the conditions exist. For a world that far from the Sun’s heat, that’s a tantalizing finding. It rewrites what we know about frozen worlds in the outer solar system.

After Cassini, What Happens?

Saturn propellor — A “propeller” of ring material swirling around a tiny moonlet near the Encke Gap in Saturn’s rings. This one is named “Earhart” after Amelia Earhart, a famous aviator in the early 20th century. Courtesy Cassini mission.

The Enceladus discoveries are enough to start people looking at future missions to Saturn. Those will follow up on Cassini’s accomplishments. While we’re thinking about sending more spacecraft to Saturn, it wouldn’t be a bad idea to check out Titan again. That world was another surprise, with its frigidly weird landscapes and lakes. The rings could use some more study, too. Those tiny little ‘propellers’ that interact with ring particles in an intricate dance are intriguing.

Both worlds merit closer looks and in-depth surveys, if not landers. It may be many years before those missions happen. NASA might not be leading those missions. Perhaps other countries will see what the international Cassini team has achieved and will launch probes to these worlds. However we get back to this system (and who ever does it next), Cassini made it possible.

Follow the final few days of Cassini’s historic mission as it sails into the clouds. NASA’s Cassini link is your best source of info.

The Spacewriter's Ramblings

New Horizons Wakes Up