What's up in the solar system in April 2012

Welcome to my monthly roundup of the activities of our intrepid robotic emissaries across the solar system! I count 16 spacecraft that are actively performing 13 scientific missions at Mercury, Venus, the Moon, Mars, Vesta, Saturn, and at the edge of the heliosphere, while another 9 are cruising to future destinations. And my count doesn't include all the spacecraft observing Earth, Sun, and points beyond our Sun's reach.

So, what highlights do we have to look forward to in April 2012? The Cassini Saturn orbiter is in the middle of a busy stretch of several orbits that take it close by Saturn's icy moons, offering lots of opportunities for great images, which get posted (as always) to JPL's Cassini Raw Images website almost as soon as they arrive on Earth. It's Mars' southern winter solstice today, so Opportunity's power levels are beginning to pick up again. Ebb and Flow are in the full swing of science operations at the Moon, and will be streaming thousands of MoonKAM photos to Earth over the coming months. And MESSENGER will shortly start lowering its orbit at Mercury.

Below I'll get to much more detailed summaries of each mission's activities, but first, here's Olaf Frohn's diagram of where all our wandering spacecraft are as of April 1. Compare it to last month's to see how things have moved.

Exploring the inner solar system:

NASA's MESSENGER Mercury orbiter announced a few weeks ago that they've been granted a one-year mission extension, doubling their operational time at Mercury. They'll be adjusting their elliptical orbit from its current 12-hour period to a faster, lower 8-hour one, giving them much more time close to the planet for their fields and particles instruments to gather data on the composition of the planet and its atmosphere, the structure of the magnetic and gravity fields, and the shape of its interior. The lower orbit will also allow an incremental improvement to their topographic maps, allowing them to be extended a little farther south. But the most important reason to extend the mission is that the Sun is moving to a much more active phase of its 11-year cycle, and MESSENGER will get to watch how the Sun's changing activity changes the environment around Mercury. Last month the team released a huge amount of data to the Planetary Data System, as well as an iOS app that makes it easy to find the latest photos and to find out where MESSENGER is. I have tried out the app and actually find it to be an easier way of browsing their image releases than their web gallery is. This possibly volcanic collapse pit in Tolstoj is pretty cool.

ESA's Venus Express Venus orbiter remains in orbit on a mission that has been extended through 2014. After a long hiatus, ESA has resumed posting mission updates to the Venus Express Science & Technology site. These updates are extremely detailed and worth reading for the insight they provide into routine operations on an orbiting mission. The latest update describes the preparations Venus Express had to perform to be ready for its 20th "eclipse season," when its orbit around Venus takes it into Venus' shadow. Eclipses are challenging for spacecraft both because conditions suddenly get very chilly and because most spacecraft are solar-powered; they must rely on batteries to survive through each eclipse.

Ebb and Flow, the twin spacecraft of NASA's GRAIL mission, are now mapping the Moon's gravity. Last month the MoonKAM project also got underway; check the MoonKAM website for the latest student-requested images from the tiny cameras on the two spacecraft. I like shots across the lunar limb. I've inquired with the MoonKAM team about whether they plan to provide a facility to batch download their images, and they do not; their site also blocks wget. So it's hard to grab a lot of images to make animations or mosaics, unfortunately. There are other tools out there that can download all the images from the site, and I have found one, but I don't want to mention it here for fear they'll block that one too!

NASA's ARTEMIS spacecraft are presumably still orbiting the Moon, but there's no recent mission status information available. They were sent into lunar orbit in 2011 to study the Moon's magnetic field, and should last for at least seven years.

China's Chang'E 2 lunar orbiter is now at L2, the Lagrange point on the far side of Earth from the Sun, having arrived there in August 2011. According to this Xinhua article, the plan is for it to stay there for a year. I'm eager to receive more information on the status of this mission!

NASA's Lunar Reconnaissance Orbiter is busily mapping the Moon from its science orbit, producing insane quantities of data (their latest data release, issued on March 16, uncludes 9.6 Terabytes of raw data and brings their image total to 667,572). Browsing their photo gallery is always rewarding; here's a lovely recent oblique view of Ryder crater.

On to Mars:

Out at Mars, today is the southern winter solstice. (It's currently Ls 89.8 of Mars Year 31.) The Mars Exploration Rover Opportunity's sol 2908 is drawing to a close. We're now past the winter solstice, so Opportunity's power levels are picking up (her panels are producing 306 watt-hours, 30 more than last month). They're still parked at the north edge of Cape York on the rim of Endeavour crater, keeping still in order to perform careful radio tracking of the rover's position, an operation that should allow them to determine whether Mars has a liquid outer core like Earth's. They're also occupied with trying to figure out why the left-front wheel suddenly shifted position and the robotic arm stalled on sol 2899. According to the last report, everything is fine with the arm. Here is Eduardo Tesheiner's latest route map and Google Earth kml file for Opportunity (three months old now).

ESA's Mars Express is carrying on with an extended mission, planned to run through 2014. Their website carries a cool story from last month about simultaneous observations of the recent solar storm by Cluster at Earth and Mars Express at Mars, showing that Mars lost oxygen from its atmosphere at a rate ten times Earth's.

NASA's Mars Reconnaissance Orbiter is keeping an eye on Mars' weather with MARCI. As is usual for this time of Mars' year, near northern summer solstice, which coincides with aphelion, the atmosphere is stuffed with water from the endlessly illuminated northern polar cap, so there are clouds everywhere. As always, check in on the latest captioned image releases from HiRISE for your dose of spectacular photos, and make sure you follow the links at least as far as the browse versions of the images, because the thumbnails that are automatically posted with their voluminous image releases routinely fail to convey the awesomeness hidden in each photo. Enlarge this one, showing "some of the best exposures of ancient bedrock on Mars," within a region called Nili Fossae.

NASA's Mars Odyssey is now the longest-lived spacecraft ever to operate at Mars. You can see the latest from its THEMIS instrument here. Here's a nify photo from the flank of a Martian volcano, Apollinaris Mons, where wind has eroded deeply into the (likely) ashy deposits around the mountain, except where impact craters splatted out ejecta that formed an armor atop the ash.

In the Asteroid Belt:

NASA's Dawn asteroid orbiting spacecraft is still in Low Altitude Mapping Orbit around Vesta, averaging 210 kilometers' elevation. As stated in Marc Rayman's latest Dawn Journal, the spacecraft will pass through solar conjunction this month, and reach its farthest separation ever from Earth, at 520 million kilometers. Keep watching their daily image releases; here's a cool photo of two typical Vestian craters, with a rim sharp on one side and hummocky on the other. Once the Low-Altitude Mapping Orbit phase is complete, Dawn will raise its orbit to a second High-Altitude Mapping Orbit phase. By summer, Dawn will be able to see the north polar areas of Vesta that were in winter darkness during the previous mapping cycle. And in July, Dawn will depart Vesta for Ceres, which it will reach in early 2015. Here's a timeline summarizing the Vesta phase of the Dawn mission.

Exploring Saturn:

The NASA-ESA-ASI Cassini Saturn orbiter is now wrapping up its Rev 163. It has just completed very close flyby of the geyser moon Enceladus, and performed some very cool imaging of moons Janus and Dione at nearly the same time. Cassini will perform two more close flybys of Enceladus on April 14 and May 2, also passing pretty close to Tethys on the first one. These will be Cassini's last targeted flybys of moons other than Titan until March 2013, as Cassini's orbit will be dropping away from the ring plane after the May 2 encounter. To see what Cassini's doing when, check out my long and detailed page on Cassini's tour of the Saturn system, and look to the Looking Ahead page for more detailed information.

Cruising from here to there:

NASA's New Horizons has 9.61 AU to go to reach Pluto. There are 1200 days left until Pluto closest approach. New Horizons is on course for a January to July 2015 encounter with the Pluto and Charon system. Cosmoquest has recently started a new citizen science project, the successor to IceHunters, called Ice Investigators. The goal is still to discover a good Kuiper belt target for the New Horizons mission.

NASA's Juno spacecraft is outbound from the Sun, heading way beyond Mars' orbit before heading sunward again. An Earth flyby in August 2013 will send it on to a July 2016 Jupiter arrival.

NASA's next great Mars rover, Curiosity, or Mars Science Laboratory, is now 53 million kilometers from Mars and closing. A recent status report says that their second trajectory correction maneuver was successful, and that nine of Curiosity's instruments have been powered on and checked out. All of the instruments have passed their checkouts. Curiosity will be landing in Gale crater, next to a mountain that's recently been (informally) named Mount Sharp, on August 6, 2012, just after 5:00 UTC (August 5, after 10:00 p.m. here in Los Angeles). On Mars, it will be in the midafternoon of a late winter day in the southern hemisphere at the landing site at 4.49°S, 137.42°E. Its nominal mission will last one year but it should go on much longer.

NASA's Deep Impact is in solar orbit, awaiting further instructions for a possible second mission extension. But a course has been set for a possible January 2020(!) encounter with near-Earth object 163249 (2002 GT).

JAXA's Akatsuki is now in solar orbit, on its long cruise to a second encounter with Venus.

JAXA's IKAROS is now hibernating. It has nearly exhausted its maneuvering fuel, so can no longer maintain a minimum solar incidence angle on its solar cells, reducing available power. It was last heard from on December 24, 2011.

ESA's Rosetta is now on the final, long leg of its cruise to its target comet. It's been placed into hibernation and will not communicate with Earth again until January 2014. The next object it'll encounter will be its goal, comet 67/P Churyumov-Gerasimenko; rendezvous is set for May 2014.

The International Cometary Explorer remains on course for a return visit to Earth in 2014. When it does, ICE can be returned to a Sun-Earth L1 halo orbit, or can use multiple Earth swingbys to encounter Comet Wirtanen during its near-Earth apparition in December 2018.

Finally, NASA's Voyager 1 and 2 spacecraft are still going strong. Follow the current position of both using the NASAVoyager2 twitter feed. (This is not an official NASA account, but it's the one with the most information.)
Finally, a few random items, mostly from JPL's Space Calendar:

• Yuri's Night is on April 12. Space party!
• Saturn is at opposition on April 15.
• The USA Science and Engineering Festival is in Washington, DC. on April 28 and 29, and the Planetary Society will have a large presence. I'll be there! I hope to meet many of you!