Emily LakdawallaDec 30, 2016

Spaceflight in 2017, part 2: Robots beyond Earth orbit

What's ahead for our intrepid space explorers in 2017? It is with great sadness that I write that this year will be the last for Cassini. But the Saturn orbiter will be sending back spectacular ring science between now and its September end. Also in September, OSIRIS-REx will return to Earth for a flyby, enjoying the opportunity to test out its science suite on our home planet and Moon while getting an assist on to asteroid Bennu. At the end of the year, Chang'e 5 is expected to launch to the Moon to perform a robotic sample return, and there might be a Google Lunar XPRIZE launch or few. Meanwhile, a ton of other missions continue exploring the solar system from Venus to the Kuiper belt, returning routine science or cruising to new destinations. For a rundown of what's happening closer to home, read Jason Davis' post from yesterday.

Here's Olaf Frohn's chart of active space missions to get you oriented to the busy solar system.

What's Up in the Solar System diagram by Olaf Frohn (updated for July 2019)
What's Up in the Solar System diagram by Olaf Frohn (updated for July 2019) A diagram, updated once a month, of active space missions traveling beyond Earth orbit. Contains links to past diagrams.Image: Olaf Frohn

Inner Solar System

Akatsuki is returning routine science data from Venus, having now been in orbit there for more than a year -- an accomplishment that still amazes me. According to project manager Masato Nakamura, no trajectory correction maneuvers will be needed until 2018. The mission is particularly focused on understanding what drives Venus' atmospheric super-rotation. For updates, check the mission's Twitter feed and website.

Earth's Neighborhood

There are no total lunar eclipses in 2017; there's a penumbral one on February 11, and a partial one on August 7. The two solar eclipses of 2017 happen on February 26 over the south Atlantic and August 21 across North America. The path of totality for the February one only makes landfall in a few locations in southernmost Chile/Argentina and across Angola, spending most of its time crossing the ocean, but the partial eclipse will be visible across the southern half of South America and southwestern Africa. The path of totality for the August eclipse will cross the United States from Oregon in the west to South Carolina in the east. The partial eclipse will also be visible from Canada, Central America, the Caribbean, and northernmost South America. I know many people in the U.S. who are planning to travel to see the path of totality, but I always like sharing eclipses with people in my community, even if it means I miss totality. Buy some eclipse glasses to share, or plan to play with pinhole projectors at a school or public library.

Lunar Reconnaissance Orbiter "is in awesome shape, performing nominally on all counts," deputy project scientist Noah Petro tells me. He says 30 kilograms of fuel remains, of which only a few kilograms are needed every year for reaction wheel momentum dumping. (When spacecraft use spinning wheels to point their instruments and antennae, the wheels build up too much speed over time; they brake the wheels and fire the thrusters to counter the braking in order to reduce the spinning speed.) While still planning full science campaigns with all 7 of its instruments, the mission is also putting out a lot of publications. Volume 2 of a special issue of Icarus is coming out in February, and Volume 3 later in 2017. "I’m told it’s the largest special issue Icarus has ever published," Petro says. Be sure to check out their recently posted images.

China's Chang'e 3 lander will, amazingly, continue functioning into 2017; it last woke up on December 9, for its 38th lunar day of operations. Chinese space program watcher Andrew Jones told me to expect some Chang'e 3 science in March, around the time of the Chinese parliamentary session. Yutu's status is unclear.

The Chang'e 5 robotic sample return mission is currently planned for launch on a Long March 5 rocket toward the end of 2017.

2017 is the final year for Google Lunar XPRIZE contestants to make it to the Moon.

OSIRIS-REx is now in its Outbound Cruise phase. The most exciting event the OSIRIS-REx mission has planned in 2017 is its Earth flyby on September 23, passing over Antarctica at an altitude of about 17,000 kilometers. The spacecraft successfully performed a deep space maneuver on December 28 in order to line it up for this flyby. According to principal investigator Dante Lauretta, other planned activities include a search for Trojan asteroids of Earth February 9-20; two instrument calibration phases in March and July; and an Earth-Moon observing campaign running from September 22 through October 7. Today it is 89 million kilometers from Earth. Keep up with the mission via Twitter.

Near-Earth Asteroids

Hayabusa2 should have a relatively quiet 2017 as it slowly cruises toward asteroid its July 2018 rendezvous with asteroid Ryugu. As of today, it is 166 million kilometers from Earth and 57 million kilometers from Ryugu.


Summer solstice has been and gone in Mars' southern hemisphere. The Sun is beginning to return to winter-darkened northern regions. The equinox comes on May 5; southern winter solstice is on November 20. It's now dust storm season and it could be a bad one this year, according to JPL.

The Mars fleet is mostly way beyond its prime but they all keep going and going. Every January I predict that we'll finish the year having lost at least one of our aged Mars robots, and every year I'm wrong. I am always very happy to be wrong.

It's now Opportunity sol 4598. Opportunity will spend the first part of 2017 making its slow way up to and along the rim of Endeavour crater. Opportunity's goal is the top of an ancient, now-dry gully that could have been carved by water or debris flows. The climb uphill from Spirit Mound is steep, but the rover has made it halfway up already. Once at the top of the rim, it'll drive about a kilometer south to the gully, and then drive down the gully to explore its morphology and also try to get to more ancient rocks within Endeavour crater. Later in the year, it will have to find north-facing slopes to aim its solar panels at the winter sun. You can learn a lot more about Opportunity's next mission plans here. Next month will be the 13th anniversary of Opportunity's landing -- she's old enough for a bot mitzvah. (I wish I could claim that joke as mine, but it's Sondy Springmann's.)

On the other side of Mars, it's now Curiosity sol 1565. Lauren Edgar summarized the rover's eventful 2016: "We have drilled six holes, performed two scoops, driven 3 km, and climbed 85 vertical meters!" The team hopes for an equally productive 2017, heading southward toward Hematite Ridge, drilling every time they have climb 25 meters in elevation through the Murray formation. The rover and its instruments are in very good shape as the mission enters its second extension. There are problems with the wind sensors, but a voltage problem on the neutron detector seems to have gone away, deputy project scientist Joy Crisp told me. Unfortunately, they're dealing with a new problem with the drill. According to an update at Spaceflight Now, it may be caused by internal debris within the drill. Like Curiosity's past drill problems, this one is intermittent, which makes it incredibly hard to troubleshoot.

Mars Odyssey is heading into 2017 recovering from a safe mode event that happened on December 26: "The Odyssey project team has diagnosed the cause -- an uncertainty aboard the spacecraft about its orientation with regard to Earth and the sun -- and is restoring the orbiter to full operations. Odyssey's communication-relay service for assisting Mars rover missions is expected to resume this week, and Odyssey's own science investigations of the Red Planet are expected to resume next week." Despite being the oldest member of the Mars fleet, Odyssey is still doing great science from its new morning orbit, is the main data relay satellite for Opportunity, and is relied upon by the Curiosity team for timely relay of data critical for planning operations. Check out the THEMIS website for its latest image releases.

Europe's venerable Mars Express is in its sixth extended mission, doing new science observations by coordinating work on the Martian atmosphere with NASA's MAVEN; both high-flying spacecraft are doing radio occultations, probing Mars' atmosphere in different locations with their radio signals. They have also improved their ability to use MARSIS to image the subsurface of Mars.

I still think of Mars Reconnaissance Orbiter as the "new" Mars orbiter, but I need to stop doing that; it has been at Mars for a decade now, and is the third-oldest of the six active orbiters. Like Mars Express and Odyssey, it is aging, but its instruments are enormously capable and its relatively huge radio dish is continuously sending back vast amounts of data from all instruments. The theme of its current mission extension is "Mars in transition," and many of its observations are focused on seasonal changes in the atmosphere and on the surface, as well as longer-term changes involving subsurface ice. Its rapid data releases are forming the basis for countless scientific papers.

MAVEN's mission to understand the upper Martian atmosphere and its interaction with the solar wind is well into its second Mars year of observations, principal investigator Bruce Jakosky told me. They're doing the same kinds of observations they did in the first year, looking for changes now that the Sun is in a different part of its cycle. They've also begun new kinds of observations, "including radio occultations, high-resolution ultraviolet imaging, and focused observations over crustal magnetic anomalies." Look for lots of science publications from the team over the next year. Finally, as of a month ago they have begun regular activity supporting the rover missions, with communications passes scheduled roughly once per week (so each rover gets one every other week, on average). That may not sound like much but because MAVEN usually moves slowly across the rovers' skies, it can retrieve a pretty high data volume, up to 700 Megabits for one recent pass for Curiosity.

Mars Orbiter Mission is still returning data, though there was sad news last month that its methane sensor data is not likely to tell us anything about Mars' methane. Science was never really the point of this mission, and now ISRO is planning a second Mars orbiter, with a proper science package, to be launched in 2018.

ExoMars Trace Gas Orbiter successfully tested out its science instruments in November, and received a flight software update on November 30. It will perform no science in 2017, because the year (plus some of 2018) is devoted to aerobraking the spacecraft into a circular, 400-kilometer-altitude orbit, a feat that ESA has not performed before. Read this informative ESA post for details. The gist: Its orbit currently has an apoapsis of 98000 kilometers and a periapsis of 250 kilometers. A thruster firing on January 19 will set the angle of ExoMars' orbit at 74 degrees. Two more maneuvers on February 3 and 9 will reduce the size of the orbit to 200 by 33475 kilometers. Beginning March 15, ExoMars will perform seven maneuvers, spaced three days apart, to lower the periapsis to 114 kilometers. That's low enough for Mars' atmosphere to exert a tiny amount of drag on the spacecraft with every orbit; each passage through periapsis will slow the spacecraft and reduce the altitude of its apoapsis very slightly. Follow @ESAoperations and @ESA_TGO for updates. Here's a visualization of the upcoming orbit changes.

Beyond Mars

Dawn is now well into its extended mission at Ceres, and has transitioned to a sixth science orbit that's quite different to ones it's traveled in before, in which it will gather measurements useful for calibrating data acquired at lower altitudes. The orbit is elliptical and slow, taking eight days to travel from 7520 to 9350 kilometers above Ceres. The orbit is also nearly aligned with Ceres' terminator, so its views of the dwarf planet's surface will show dramatic lighting once imaging resumes this month. Seasonal change has brought sunlight to the south polar regions, and Dawn will begin mapping craters there to find permanently shadowed regions that may trap water and other volatile molecules. Learn more in Marc Rayman's latest Dawn Journal.

The Juno mission is not using its main thrusters for the foreseeable future, as engineers continue to investigate a problem with its valves. If it does not switch to its planned two-week science orbit, Juno will have seven perijove science passes over Jupiter's poles in 2017, on February 2, March 27, May 19, July 11, September 1, October 24, and December 16. JunoCam has begun allowing public voting on Jupiter image targeting, with voting periods about two weeks before each perijove pass. The next one opens on January 19. This image of a white storm on Jupiter was one result of the first round of public voting at the December 11 perijove pass.

Ah, Cassini. I don't want to accept that this will be Cassini's last year, but it is. Cassini is now in its F-ring orbit phase, passing through the gap between F and G rings on each periapsis pass. As with Juno, the best stuff comes during the brief period around each periapsis; periapses happen roughly weekly for the rest of the mission. The orbit is giving Cassini fabulous views of the north polar hexagon and ring structures and will also afford the best-ever opportunities to image the tiny moons that are embedded in the ring system. Highlight ring-moon images include Daphnis on January 16; Epimetheus and Mimas on January 30; Epimetheus and the propeller Santos-Dumont on February 21; Pan on March 7; the propeller Earhart on March 22; and Atlas on April 12. On April 22, Cassini changes its orbit periapsis, beginning the proximal orbits, with its periapsis passing in between the D ring and the planet's cloud tops. Saturn will reach northern summer solstice on May 24, and opposition on June 15, giving us spectacular open views of its rings through Earth-based telescopes. On September 15, Cassini will plunge into Saturn's atmosphere, ending the mission.

Having completed transmission of all the Pluto data to Earth, New Horizons is now focused on Kuiper belt and heliosphere science. Principal investigator Alan Stern gave me the rundown on its planned activities. It will have two main phases of distant Kuiper belt observations this year, one in January and one toward the end of the year. January targets include Pholus, Huya, 2002 KX14, Haumea, and Makemake. End-of-year targets include 2012 HZ84, 2011 HJ103, 2012 HE85, 2014 OE394, 2002 MS4, and Quaoar. In between the two science phases, from March to September, the spacecraft will hibernate, but it will still be collecting dust and plasma data even while in hibernation, as it did on its cruise to Pluto. The spacecraft is now 37.3 AU from the Sun, 4.3 AU beyond Pluto, and 6.1 AU away from 2014 MU69.

Finally, the Voyagers are still going, going, going. Voyager 1 is at 137.2 AU from the Sun, and Voyager 2 is at 113.9 AU.

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