Welcome to my monthly roundup of the activities of our intrepid robotic emissaries across the solar system! Probably the most anticipated celestial event of the month is not happening on a spacecraft; it's the June 5/6 transit of Venus, which I think I may watch from the Griffith Observatory. On Mars, Opportunity is finally covering new ground again, as Curiosity is barreling toward its August 5 landing. At Saturn, Cassini is getting its first good views of Saturn's rings for two and a half years, and will have good imaging encounters with Mimas and Tethys as well as RADAR observations of Titan this month. GRAIL has completed its prime mission and is beginning to set up for its extended mission, while Dawn's climbing to a higher altitude above Vesta. For other missions, it's business as usual, exploring alien worlds.
Here's Olaf Frohn's diagram of where all our wandering spacecraft are as of June 1. Compare it to last month's to see how things have moved. 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.
Exploring the inner solar system:
NASA's MESSENGER Mercury orbiter is working steadily from its new 8-hour orbit at Mercury. As always, check out their image gallery for the latest goodies. They announced last month a new Deputy Principal Investigator, Larry Nittler, which is notable because this mission has clearly been Principal Investigator Sean Solomon's favorite child since its inception. Solomon is going to become the director of Lamont-Doherty Earth Observatory in July. Honestly, it's really hard to imagine him handing the reins over to anyone else.
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. The most recent one, posted on May 4, has a welcome new section, which I'm going to post in its entirety here because it provides fresh new insight into the science being performed by this long-running mission:
The status reports will henceforth include a scientific overview of operations carried out during each medium term plan (MTP), a four-week period made up of 28 days, consisting of four seven-day periods. The current report falls under MTP 76, 5 February to 3 March 2012.
The twentieth eclipse season began on 8 February. The Local Time at Ascending Node (LTAN) ranged from 20:40 hours at the start to 23:40 hours. Many observations are performed when the spacecraft is in nadir pointing mode (pointing towards the surface of the planet directly below the spacecraft). The angle of the Sun on the planet's surface is therefore the same as the angle of the Sun on the spacecraft. This Sun angle means that this was a cold period: a nadir observation did not illuminate any of the thermally restricted faces on the spacecraft, allowing long, unrestricted nadir observations.
During MTP 76, science targets included: Ishtar Terra in the Northern Hemisphere and Central Eistla Regio, which has been identified as a ‘hotspot' — a surface manifestation of a mantle upwelling. The area observed in the Southern hemisphere hosts ground features that have been observed in the past by the imaging spectrometer (VIRTIS) and which are of interest to look at again.
Venus Express flew over Bereghinia Planitia on 18 February during an eclipse. Situated at 28°E, 39°N, this area was identified as the location of a possible cooling lava flow by Bondarenko et al (GRL, 2009), using the atmospheric spectrometer (SPICAV infrared nadir observations) as well as the monitoring camera (VMC).
Ebb and Flow, the twin spacecraft of NASA's GRAIL mission, announced yesterday the completion of their prime mission at the Moon, way ahead of schedule. GRAIL is not a mission whose results appear instantaneously; it'll be a while before the data set is processed and prodded and compared to other data sets to yield the science. But the data are on the ground and it looks great so far. GRAIL's science instruments are now turned off, awaiting the lunar eclipse on June 4. After that, they'll readjust their orbit and begin their extended mission on August 30. The MoonKAM website now lists almost 72,000 images.
NASA's ARTEMIS spacecraft are presumably still orbiting the Moon. 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! Anybody got anything? I don't.
NASA's Lunar Reconnaissance Orbiter is quietly continuing its mission at the Moon, producing insane quantities of data and occasional cool departures from the Moon like the photo I featured last week of Earth during the solar eclipse. One of the reasons I do these monthly updates is to remind myself to go check all the different spacecraft image galleries once in a while. I got several emails last month about this spectacular oblique view of the central peak of the crater Tycho. I thought I'd seen it before; it wasn't until I read the caption just now that I understood that the new image views Tycho's peak from the opposite side to that seen in Lunar Reconnaissance Orbiter's June 2011 view. I've been to a couple of science conferences since then, and the Lunar Reconnaissance Orbiter Camera team always brings massive printouts of oblique views like this one, which gather crowds of scientists, whose mouths are often open in amazement at the dramatic perspective and fascinating geological detail visible. Check out the photo gallery for more lunar amazement.
On to Mars:
Out at Mars, days are lengthening in the south as winter presses on. (It's currently Ls 117.8 of Mars Year 31.) The Mars Exploration Rover Opportunity is in the middle of sol 2968. In the past month, Opportunity's finally shaken off her winter stasis and started rolling again. (I wonder what kinds of creaking noises accompanied her first motion in six months?) There have been some good drives recently, and Opportunity's moving toward the northern end of Cape York to investigate some tantalizing bright veins in the rocks. As usual, you can follow her daily activities along with other rover huggers at unmannedspaceflight.com. And I am really, really happy to be able to update the route map for the first time since winter came; here is Eduardo Tesheiner's latest route map and Google Earth kml file for Opportunity, up to date as of sol 2965. She's driven a good 70 or 80 meters in the last week.
ESA's Mars Express is carrying on with an extended mission, planned to run through 2014.
NASA's Mars Reconnaissance Orbiter is keeping an eye on Mars' weather with MARCI. Still lots of water ice clouds especially around the peaks of the great volcanoes, as is usual for this time of Mars' year. As always, check in on the latest captioned image releases from HiRISE for your dose of spectacular photos. Here's a neat one with three dust devils. I find this one especially compelling, with sharp ridges of folded and broken rock.
In the Asteroid Belt:
NASA's Dawn asteroid orbiting spacecraft has spent the last month spiraling upward toward High-Altitude Mapping Orbit 2. As of yesterday's status report, it was at 590 kilometers, approaching its final altitude of 680 kilometers; I suspect there'll be a new Dawn Journal update soon, informing us about the plans for arrival in HAMO 2. Keep watching their daily image releases for cool new views of the lumpy world. This image is notable because its strange pattern of some areas with no shadows and some areas with extreme shadows make it clear that the photos being released here have been heavily processed. I think, but am not sure, that the processing being performed by the imaging team is to attempt to remove (or at least reduce) topographic shading effects from the images, which makes albedo differences (changes in the brightness or darkness of the surface) clearer. However, sometimes processing of this type produces odd artifacts. This is no better or worse than releasing "raw" images as the Cassini and Opportunity missions do; it's just different. Cassini raw images are full of artifacts -- horizontal banding, dust donuts, other stuff -- that would be reduced or removed during the sort of calibration or processing that has produced the images released by the Dawn team. Anyway, back to Dawn: In August, 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.
The NASA-ESA-ASI Cassini Saturn orbiter has just begun its Rev 167. (Yay: for once, the calendars have aligned so that the Looking Ahead article for the current orbit got published just days before I write my monthly update, which means this will be an unusually detailed one!) Cassini's orbit inclination has started pumping upward; now at about 16 degrees, Cassini is getting the first open views of Saturn's rings since late in 2009. The season has advanced a great deal since then; gone is the dim light of the equinox season. Now the north face of Saturn's rings shine brilliantly in sunlight. The equatorial phase of the mission has been fun for moon imaging, but it is very nice to see those rings surrounding Saturn again. Moon imaging isn't entirely impossible; in fact, there'll be a very good Mimas encounter on June 5, which should help fill in a gap in Cassini's image coverage over Mimas' north pole. (The advancing season has made northern polar territory newly visible on all of Saturn's moons.) There'll also be searches for "propellers" in the A ring on the same day. A Titan flyby on June 7 features some RADAR imaging of previously unimaged areas as well as more distant repeat views of some lakes and areas that received rainfall in the past. At the very end of the month, on the next rev, Cassini will get a good nontargeted view of Tethys. Between now and then, expect lots and lots of ring imaging! 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 9.11 AU to go to reach Pluto. There are 1139 days left until Pluto closest approach. Alan Stern's latest blog entry mentions that they have not yet discovered a good candidate for the Kuiper Belt phase of the mission; but the search continues, and there's still time. (Of course, discovering a good candidate tomorrow would be better than discovering it next year.) You can join the search at Cosmoquest's Ice Investigators site. New Horizons is on course for a January to July 2015 encounter with the Pluto and Charon system.
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. Last month its camera, JunoCam, took a picture of the Big Dipper. Why? Well, if you were hanging out in the outer solar system with a really nice camera, what would you do?
NASA's next great Mars rover, Curiosity, or Mars Science Laboratory, is now 22 million kilometers from Mars and closing. Only 67 days remain until landing. Just writing that sentence makes my heart jump. I think I'll be promoting Curiosity to the "active" section of this update next month, because I'll sure be actively thinking about it. Curiosity's microscopic camera, MAHLI, took a photo from its position tucked inside the cruise configuration of the spacecraft early last month. Curiosity will be landing in Gale crater, next to a mountain that's was informally called Mount Sharp by the science team but is now formally named Aeolis Mons, while the name Robert Sharp has been given to a nearby large crater. The landing will happen 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 mid-afternoon 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. On Earth, the Planetary Society will be hosting a huge Planetfest event, gathering thousands of space fans to celebrate this momentous event together! I'll be putting in brief appearances at Planetfest but will be spending most of my time having an anxiety attack about the impending landing up at JPL.
JAXA's Akatsuki is now in solar orbit, on its long cruise to a second encounter with Venus.
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.