Beyond Mars

This month, Rosetta will shift into a series of elliptical orbits that will bring it progressively closer to the comet, in preparation for the mission's end on September 30. As mentioned on this blog earlier, the spacecraft is shutting down nonessential systems because of declining solar power; one of those nonessential systems was the package that had been used to communicate with the silent Philae lander. Last month the Rosetta blog hosted an interesting article about the origin of comets, based on research performed with Rosetta data. The latest NavCam release covers images taken through June 28. As always, check here for the latest NavCam image releases and here for the OSIRIS image of the day.

With its prime mission over and the decision made for Dawn to remain at Ceres, we're starting to see a higher rate of scientific results coming out of the mission. Two stories came out last month, about permanently shadowed regions at Ceres, and a curious lack of large craters. Regular readers will recognize the latter story, which I covered when it was presented at the Lunar and Planetary Science Conference in March. As always, check the Photojournal for the latest images!

As far as I know, Juno is doing fine; it will reach the apojove on July 31, beginning "orbit 1." It will spend almost all of August approaching Jupiter, speeding up all the way, until it executes its first close encounter with the planet with all its instruments firing at Perijove 1 on August 27. Once Juno returns the data to Earth, we should see the closest-ever images of Jupiter's clouds, and stunning pole-on views of the planet. I can't wait. JunoCam should have been shooting images continuously since July 9. After that, we're headed toward conjunction on September 26, a period when Juno will not be permitted to do much science or other activity. The science mission begins on November 9. Don't forget to visit the JunoCam website to discuss features visible in amateur astronomers' Jupiter images.

Cassini will reach apoapsis on July 30, beginning its Rev 239. There will be a targeted flyby of Titan on August 10, which will be used for gravity science, an opportunity to detect Titan's subsurface ocean. The 1600-kilometer flyby will raise Cassini's orbit inclination even more, to a very high 53.5 degrees. These high-inclination orbits are designed for studies of the rings; Cassini will be looking at "propellers" in the rings, and also observing several bright stars pass behind the rings. It will shoot a color portrait of the lit rings on August 6, and search for meteor impacts onto the C ring(!) on August 9. As always, check the raw images page for the latest views from Cassini's cameras.

I have a couple of updates on New Horizons. According to Kim Ennico they currently expect to complete the process of returning all the data from the Pluto encounter in late October or early November, but of course that depends on the schedule with the Deep Space Network and things could change. Meanwhile, they've had "a busy July" acquiring new data, according to John Spencer. He told me they've been "doing post-Pluto calibration observations of stars and so on during a brief 3-axis period, but also looking at KBOs Quaoar, 1994 JR1, Ixion, and 2002 MS4, plus Centaurs 2010 JJ124 and Chiron to get phase curves (though we don't expect to actually detect the Centaurs unless they have strongly forward-scattering rings, which is what the observations are designed to test)." The spacecraft has to be in 3-axis stabilization mode to be able to do these kinds of observations. The spacecraft has now returned to spin-stabilized mode, in which they can't point cameras but they can double their downlink rates. They'll remain spin-stabilized until January 2017, when they'll observe more Kuiper belt objects. For more on New Horizons, check out the latest team blog posts: one by Fran Bagenal on her 26 years of involvement in a Pluto mission; one by Anne Verbiscer on studying the opposition effect; and one by Cathy Olkin and Eddie Weigle on commanding spacecraft instruments.

Finally, the Voyagers are still going, going, going. Voyager 1 is at 135.7 AU from the Sun, and Voyager 2 is at 111.8 AU.

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