Tag Archives: NASA Dawn Spacecraft

Old Space Probes Fade, New Probes Scream Into View

As our old friends Rosetta and New Horizons head out of the Solar System, and Dawn continues to image Ceres, we have a new spacecraft to watch: Juno arrived at Jupiter this week. (Some PR genius at NASA managed to fiddle the trajectory to arrive on the US Independence Day holiday—give that person a cookie!)

Juno is an interesting and ambitions mission, because it aims to get close to Jupiter, inside the intense radiation and magnetic fields. The spacecraft and instruments had to be really, really rugged and radiation hardened. The spacecraft has entered an elliptical polar orbit, which is designed to swoop in via the reduced radiation, and back out to a “cooler” distance.

Animation of Juno 14-day orbits starting in late 2016. Credits: NASA/JPL-Caltech

Assuming that the spacecraft and instruments survive, which is far from certain, Juno will collect some of the first data about the structure, composition, and dynamics of Jupiter. Jupiter is huge, darn near a star, and it has been around since the solar system condensed. So we will get some more insight into the early solar system, including more information about where the water we find everywhere came from.

Fingers crossed, Juno will do 37 orbits over the next 20 months. When the mission is over, the spacecraft will be deliberately crashed into Jupiter. Unlike Rosetta’s planned crash into 67P/CG, which will collect data, Juno’s dive is intended to destroy any possible biological contamination from Earth. This precaution recognizes the possibility of habitable (if not necessarily inhabited) moons in the area. Future expeditions do not want to find “life” on Europa that somehow managed to ride there on Juno.   However unlikely this scenario, Juno will burn up to avert it.

Let’s stay tuned!


Space Saturday

Ceres Close Ups, and Waiting for Philae

In the solar system this week, the New Horizon probe is swooping in on Pluto, for a screaming flyby, with closest approach on 14 July. In the past month, the probe has seen several moons, albeit briefly.

Data from the New Horizon probe has been augmented by observations from the Hubble Space Telescope, which is obviously closer to Earth, but also way larger and more capable. This study has indicted that the smaller moons of Pluto / Charon have quite chaotic orbits around the twin planets. I guess that’s not too surprising, though I wonder if these moons are recent acquisitions. I mean, Pluto has been there a long time, so things should have settled down by now, no?  I expect we’ll learn more from the flyby.

Meanwhile, Rosetta is still looking for the little lost Philae lander. The Rosetta orbiter took imagery in December that should cover Philae’s location, but the lander has not been picked out. As the comet heats up, the gasses boiling off the comet have been too much for Rosetta’s navigation system, so the probe has not been able to swoop lower for closer looks.  (This is an interesting, if inconvenient finding that we’d never know without actually visiting a comet close up.)

In the coming weeks, the sunlight on 67P/CG will be increasing even more, and it is possible that Philae will be able to charge its batteries. If that happens, and the systems have survived months of extreme cold, then Philae will wake up and try to contact the Rosetta orbiter. Even if we don’t get any science, I think we all want the lander to wake up, and show us just how well it was built!

Out at Ceres, “deep into the main asteroid belt between Mars and Jupiter”, the Dawn spacecraft has been orbiting and amassing images and measurements for the past month. Last week, Dawn completed a maneuver into a lower “survey orbit”, about 4400 KM altitude. It is recording and transmitting images from this second orbit, and later it will move lower still.

Dawn’s spiral descent from its first mapping orbit (RC3) to its second (survey). The two mapping orbits are shown in green. The color of Dawn’s trajectory progresses through the spectrum from blue, when it began ion-thrusting on May 9, to red, when ion-thrusting concludes on June 3. The red dashed sections show where Dawn is coasting, mostly for telecommunications. The first two coast periods include OpNav 8 and 9. Image credit: NASA/JPL-Caltech

I would note that the Dawn team is rightly proud of their ion propulsion system, which has made possible this incredible feat.


Space Saturday

Awesome Mercury Mission Ends (And A Ceres Guessing Game)

And yet another space probe:  NASA’s “Messenger” spacecraft will end it’s voyage today with a crash landing on Mercury.  Like the other spacecraft in the news this year, Messenger has been a long, slow mission, slinging around the Solar system, and visiting Earth and Venus before swooping by Mercury three times.  I love these elegant, low energy trajectories!

Among other interesting findings, Messenger discovered ice in deep cracks on Mercury, demonstrating that there is a huge range of conditions on the surface of the tidal locked planet.

Of course, unlike the outer solar system, there is no shortage of sunlight near Mercury.  In fact, the spacecraft needed to be well shielded.  But Messenger also employed the solar wind and solar sails to help guide and propel the spacecraft, saving fuel (and just beinge awesome about it).  Cool!

Meanwhile, in another part of the solar system….

The Rosetta project released a large batch of images captured last fall. These are NAVCAM images, so they are good for movies and posters but have only a little value as data.

I’m sure we’ll get lots of data eventually, but ESA is working hard to publish the data.

Back on Earth,  JPL is trying to rev up interest in the Dawn spacecraft, orbiting Ceres. So far, the most interesting thing we’ve seen at some unexplained bright spots.

While the spacecraft is collecting more data about the dwarf planet and the bright spots, we can only guess what they are.

In keeping with the spirit of the times, JPL is “gamifying” this guessing game, and attempting to do a social media “thing”, to keep people interested.

What’s the spot on World Ceres?” is an interactive “poll”, which invites everyone to record a guess.  The choices offered cover the most plausible guesses from scientists (along with may favorite,  “other”).


I’m all in favor of engaging public interest in science of all types, and this page is the germ of a good idea. But really, this isn’t representative of how science works, or what we mean to be teaching people. Figuring out Ceres isn’t a popularity contest, and thousands of people making uninformed guesses is pointless.

What I would like to see is for each of the buttons link to a short, coherent summary of the arguments pro and con. Before you vote, you can read the “voter’s guide”—and learn what we do and don’t know about asteroids.

Furthermore, there should be a “what it means if this is true” section. For example, if the spots are due to volcanism, this means there must be a liquid interior. What would that imply about the history and structure of Ceres?

And so on.

Finally, everyone who votes should be able to sign up to get updates on data and analysis as they come in, and a special report (“suitable for framing”) on what is ultimately concluded.



Space Saturday

What Are The Sparkly Spots On Ceres?

The “Dawn” spacecraft has finished downloading the navigation images, and has now begun systematic imaging of Ceres from a circular 13,500 KM polar orbit.

This animated sequence of images from NASA’s Dawn spacecraft shows northern terrain on the sunlit side of dwarf planet Ceres. Dawn took these images on April 14 and 15 from a vantage point 14,000 miles (22,000 kilometers) above Ceres’ northern hemisphere. The spacecraft was settling into its first circular orbit, called RC3 (for “rotation characterization 3”), which it will begin on April 23. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

These images were captured a week ago—it takes a while to transmit them back, and to process the data. A reminder of the magnitude of the enterprise: this is pretty far away from home. The fact that the software is still working after years untended is amazing.

So far, Ceres is not an especially photogenic destination. The main point of interest so far are the mysterious “bright spots”, visible in this week’s images. It isn’t known what they are, so we’ll all be looking to the upcoming observations for more clues.

Speaking of huge undertakings, we commenmorating the 25th anniversary of the Hubble Space Telescope.  Though now superceded by technical advances, this has been one of the most significant scientific instruments ever.

And, by the way, there are gazoogabytes of data from Hubble available for anyone who wants it. E.g., start with the Hubble Legacy Archive.  (Astronomers are some of the original and most consistent practitioners of true Open Data policies.


Space Saturday

Real Life For Solar System Probes

As we follow our space probes this spring, we are reminded how much we are all spoiled by Hollywood spaceships that not only make cool “whoosh” sounds, but magically pop between interesting places in minutes without spending any boring time getting there.

Unfortunately, real space travel is much slower and trickier, and robot spacecraft aren’t as magical as seen on TV. In the past few months, we have seen NASA’s Dawn probe arrive at Ceres and ESA’s Rosetta at comet 67P/CG, both of which took a decade to get there. And even now that they have “arrived”, things are still “exotic” by Earthbound standards.

Dawn’s slow looping progress…

Dawn arrived at Ceres last month, achieving gravitational capture on 6 March. But this is a long, slow mission, and the spacecraft has been slowly looping around in a long spiral in, to a target 15KM circular orbit in a few weeks. Furthermore, it has been on the dark side of Ceres which, out there, is really, really dark! So no imagery until the mapping orbit is achieved.

Dawn’s final swoop down to RC3 orbit. The sun is off the figure far to the left, and Ceres’ north pole points up. The farther Dawn is to the right side of Ceres here, the smaller a crescent it sees, because the illumination is from the left. The white circles are at one-day intervals. The trajectory is solid where Dawn is thrusting with its ion engine, which is most of the time. The labels show four optical navigation sessions, where it pauses to turn, point at Ceres, conduct the indicated observation, turn to point its main antenna to Earth, transmit its findings, turn back to the orientation needed for thrusting, and then restart the ion engine. Dawn was captured into orbit on March 6. Note the periods on the right side of the figure between OpNav 5 (on March 1) and OpNav 6 (on April 10) when Dawn pauses thrusting for telecommunications and radio navigation but does not take pictures because it would have to point its instruments too close to the sun. Apodemeter is the Dawn team’s word for the highest altitude in orbit, in analogy with the more common term apogee, which applies for Earth orbits. (Demeter is the Greek counterpart of the Roman goddess Ceres.) Dawn was at its apodemeter of 46,800 miles (75,400 kilometers) on March 18. For more on Dawn’s approach trajectory, see the overall description and figures from other perspectives in November (including the motion into and out of this flat depiction), further details (including the OpNavs) in February and an animation in March. Credit: NASA/JPL


Marc Rayman gives us a ton of cool information about real life out there in Ceres orbit: reconfiguring the spacecraft from travel to observation mode, dealing with the loss of 2 of 4 maneuvering flywheels, calibrating the camera and so on.

Now that Dawn is there, it will begin a long campaign of observations, spiraling in to successively closer orbits as the months go by. And this will be the end of the mission: she will fade out and someday fall onto Ceres.

Rosetta’s navigation woes…

The Rosetta spacecraft has been swooping in for close passes to comet 67P/CG, which is heating up and developing an atmosphere as the ice steams off. This means that these passes are actually quite dangerous for the deep space adapted Rosetta: she’s not intended to operate in an atmosphere.

Example of Rosetta’s recent flyby trajectories at Comet 67P/C-G. Credit: ESA.

The mission has reported on problems they have had, which are kind of interesting. The big problem has been that the automated star finder system has been confused by all the ‘bright spots’ from the escaping gasses. The star finders continuous watch the sky for familiar groups of stars, which are used to keep the spacecraft on course and oriented correctly. The latter involves, critically, pointing the antenna at Earth.

Apparently the last pass encounters so many false “sightings” that the star finders got lost and the antenna skewed away from target Earth. The signal was lost for a while and data could not be transmitted.

The spacecraft recovered, though not before entering a “safe mode” partial shutdown.

(“Safe mode” sounds warm and cuddly to me, but I know that space scientists hate safe modes—they are what happens when all else has failed.)

I don’t know about you, but I’ve always be awed by guide star astrogation—it is so elegant and so universal. The spacecraft knows exactly where everything is….

And for that matter, orienting spacecraft with flywheels just blows my mind–again, so elegant, so flat out Newtonian.


Space Saturday

Following Our Space Probes: “Dawn” Approaches Ceres

The NASA spacecraft, “Dawn”, will enter first orbit around the asteroid/dwarf planet Ceres next week. Cool!

This week images were taken to, among other things, figure out exactly how Ceres rotates. I hadn’t thought about it, but if you want to survey a planetoid you want to use a polar orbit—which requires knowing where the darn poles are. Duh! And that isn’t easy to tell until you get close enough.

Once in orbit, Dawn will image the whole surface of Ceres in a range of frequencies. From the recent observation of unexplained bright patches, as well as earlier hints of water vapor, the team will be looking for evidence of a subsurface ocean. That would be kind of interesting.

By the way, NASA has released a 3D printable model of Vesta, mapped by the Dawn mission on its way to Ceres, and also a 3D printable model of the spacecraft itself.

There is also a 3D model for the “New Horizons” spacecraft closing in on Pluto, and a bunch of other models, all at: http://nasa3d.arc.nasa.gov/models/printable

Our other friends at ESA has posted an interesting discussion of the recent flyby, which was trickier than I realized. “Doing science during a close flyby like this is not easy,”

Meanwhile, at NASA posted a nice piece about the current activities of the New Horizons mission team as the spacecraft closes on Pluto.  This also sketches the geological studies that are planned.  (An earlier post explained the atmospheric studies.)


Cool NASA Spacecraft Approaches Ceres

What a year for planetary exploration! ESA’s Rosetta diving into the atmosphere of a comet, NASA’s fly by of Pluto, and now NASA’s “Dawn” spacecraft will reach Ceres in the next month.

After visiting Vesta for months on its way out in 2012, the Dawn spacecraft is approaching Ceres. It will spiral in towards the asteroid/mini planet during March, and reach a close orbit (375 km) and return visible and IR imagery and gamma ray data starting in April.

Dawn’s approach trajectory. We are looking down on the north pole of Ceres. The sun is off the figure far to the left. The spacecraft flies in from the left and then is captured on the way to the apex of its orbit. It gets closer to Ceres during the first part of its approach but then recedes for a while before coming in still closer at the end. Lighting by the sun is not depicted here, but when Dawn is on the right side of the figure, it only sees a crescent of Ceres, which is illuminated from the left. (The white circles are at one-day intervals.) Credit: NASA/JPL

This exploration is a groundbreaking use of an ion drive, which has enabled unprecedented periods of (low) thrust, many years worth. It also made it possible to reach Vesta, maneuver into orbit, and then depart orbit and reach Ceres, where it will orbit. All on one voyage!

These planetary missions share several very impressive features. They are long time scales (a decade and more), which require the spacecraft to hibernate for long times and then wake up. In deep, deep cold, far, far from home. Awesome!

And they are semi-autonomous systems, working beyond any hope of human assistance. The fact that the software actually still works in this situation is just plain miraculous.