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Emily Lakdawalla • April 7, 2011

365 Days of Astronomy Podcast: What's up in the second quarter of 2011

Regular readers of this blog will find the content of today's 365 Days of Astronomy Podcast familiar, because it's an update on what the solar system exploration spacecraft are up to, based on my monthly "what's up" updates. For 365 Days of Astronomy I am doing audio versions these updates on a quarterly basis, so I'm looking ahead to April, May, and June. For more details on what's been going on in planetary exploration you might want to look back at my April, March, February, and January updates!

Solar system exploration missions in April 2011

Olaf Frohn

Solar system exploration missions in April 2011
Solar system exploration missions in April 2011, by Olaf Frohn

And now, the transcript of the podcast

I'm Emily Lakdawalla and I keep an eye on the robots that are exploring our solar system for the Planetary Society blog. Today I'm going to take a look at what we can expect from the planets, moons, and other stuff during the second quarter of 2011, April, May, and June.

With the Shuttles making their final launches here's a lot of concern right now about the present and future of human space exploration. Most people don't realize that at the same time, we're living through the greatest age of robotic space exploration, ever. I count ten spacecraft that are gathering scientific data from other worlds. These are MESSENGER, Venus Express, Chang'E 2, Lunar Reconnaissance Orbiter, Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, the Mars rover Opportunity, Dawn, and Cassini. We're orbiting every one of the terrestrial planets, including the honorary terrestrial planet (by which I mean the Moon), plus Saturn, and we're creeping up on an asteroid.

Let me give you the rundown on what all these spacecraft are doing. MESSENGER went into orbit at Mercury in March, and as of a couple of days ago has officially begun its one-year mission at Mercury. It's gathering four main types of data. It's taking color photographs of the surface to build up the first complete global map of Mercury. It's using a laser altimeter to make precise measurements of the altitudes of ridge peaks and crater floors, which will be used to build the first global topographic map of Mercury. It's gathering data with ultraviolet, visible, and infrared spectrometers to study the composition of the surface and atmosphere, and how they both are affected by the solar wind, which is blasting Mercury with more and more force now that the Sun is finally crawling out of its prolonged period of minimum activity. Finally, MESSENGER is mapping out Mercury's magnetic field. Already the mission has released several images of places never before seen from spacecraft, areas near Mercury's north and south poles.

Moving outward from the Sun, we get to our sister planet, Venus. The European Space Agency's Venus Express has, as of this month, been in orbit at Venus for five years. It's continuing to gather photos of Venus's swirling clouds, trying to see through them to the hot volcanic rocks below. Europe plans to continue operating Venus Express for at least another four years.

Next out from the Sun is our own planet and its companion, the Moon. There's currently two spacecraft in lunar orbit. NASA's Lunar Reconnaissance Orbiter has been up there for nearly two years, and in that time it's assembled a nearly complete map of the entire globe at a resolution of 100 meters per pixel, and it's imaged large swaths of the Moon at much higher resolution of only 50 centimeters per pixel, small enough to spot most of the human-built artifacts that have landed or crashed to the lunar surface over the past five decades of lunar exploration. You can go to their website to browse through these amazing maps and sharp images of weird landscapes.

The other lunar orbiter is China's Chang'E 2, which was sent to the Moon to scope out sites for their first lunar lander to touch down. It has just completed its primary mission, which included some orbits of the moon as low as 15 kilometers -- that's not a lot higher than a jet plane's cruising altitude! China's space agency reports the spacecraft to be in good condition, and a variety of options are being discussed for an extended mission. It could stay in lunar orbit or it could be sent beyond the Moon, perhaps to one of the Lagrangian points where the gravity of Earth and Moon balance out.

Mars, of course, has been the most active place for planetary exploration for nearly two decades now, and there are currently four active spacecraft there. Mars Odyssey, the longest-surviving spacecraft ever to explore Mars, is still gathering photos and also serving as the main data relay for the rovers. Europe's Mars Express also continues its mission to get 3D color images of the Martian surface, even as it is exploring Mars' inner moon Phobos to help Russia determine where its Phobos-Grunt sample return mission will touch down.

Mars Reconnaissance Orbiter is continuing its mission to map the planet in both spatial and temporal detail. Its HiRISE camera produces amazingly detailed views of the surface at a resolution of only 25 centimeters per pixel -- that's about the length of an adult's foot, and it's not hard to imagine hiking across the ridges and valleys in those HiRISE images. In fact, one of Mars Reconnaissance Orbtier's main goals right now is to map out the possible future landing sites for NASA's next Mars rover, Curiosity. Meanwhile, the longer the mission lasts, the closer it gets to imaging the whole planet at a lower resolution of about 6 meters per pixel with its Context Camera Even as it maps the surface in spatial detail, the orbiter also images the whole planet with its MARCI weather camera. MARCI and all the other Mars observers will see the planet go through its solstice in a couple of days, the darkest days of winter at Mars' north pole and brightest summer Sun in the south.

On the ground, the Opportunity rover is on the final leg of its trek toward the rim of Endeavour crater. About six kilometers remains. This is no small distance -- Opportunity's covered a total of 17 kilometers in 7 years of operations -- but the driving has been getting easier and easier and the rover routinely covers more than 100 meters per driving sol, averaging out to about 300 meters per week. So she could well reach the rim by the fall. She's headed to Endeavour to study some mineral deposits that may record the effects of long-lasting liquid water on the surface, including clay minerals. Studying these minerals is the goal also of the next Mars rover, and Opportunity's drivers are motivated to beat Curiosity to the clays. At her current rate of driving, Opportunity could get there before Curiosity even launches. Meanwhile, Opportunity's sister Spirit has not been heard from for more than a year. With the solstice passing, hope is fading that we'll hear from her again, but NASA's still trying.

Going further outward from Mars, we get to the asteroid belt. Throughout April. May, and June, Dawn will be sloooowly approaching its first target, Vesta, the second most massive object in the asteroid belt. Vesta is regarded by many scientists to be a protoplanet, a planetary seed that never grew, a relic of the formation of the solar system. By early June, Dawn's photos of Vesta will achieve better resolution on the surface than our best views from Hubble, and by the end of June, Dawn will be slipping gently into orbit, ready to start systematic mapping.

Finally, at Saturn, Cassini will pass through its 150th orbit of the planet in the coming months. Its orbit changes shape with time as it's sent to explore different aspects of the planet, its rings, its magnetosphere, its space environment, and its moons. Throughout April, May, and June Cassini will be orbiting Saturn in the same plane as the rings, a perspective that makes the rings nearly vanish but which makes it easy to study the planet's atmosphere. But the orbit will shift with time. Right now Cassini spends most of its time in a position far from Saturn where it sees the planet lit at about half-full phase. Over these months the orbit will swing around toward the Sun, and Cassini will be imaging a more gibbous Saturn. There will also be three flybys of Titan, and one of Helene, the little moon that sits in the lagrangian point that's ahead of the much bigger Rhea's orbit around the planet.

While these ten spacecraft are doing their things, eight more are cruising toward distant destinations. New Horizons has recently passed the orbital distance of Uranus, but it'll be three more years until it reaches Pluto. Rosetta is looping deep into the asteroid belt; it, too, has to wait three more years to reach its goal, comet Churymov-Gerasimenko. Japan's Akatsuki and IKAROS are both in solar orbit; Akatsuki will hopefully return to Venus five or so years from Now. A couple of old spacecraft, Deep Impact and ICE, are awaiting further instructions. And then there's Voyager 1 and 2, both exploring the distant reaches of the solar system.

Another five spacecraft are scheduled to launch later this year, toward Jupiter, the Moon, and Mars. I hope this update has given you a sense of what an exciting time it is in planetary exploration. And all of this doesn't even count any of the dozens of missions that are studying the Sun, Earth, stars, or extrasolar planets. Stay tuned to planetary dot org slash blog to hear the latest from our robot explorers! This has been Emily Lakdawalla for the Planetary Society. Thank you for listening.

Read more: IKAROS, Lunar Reconnaissance Orbiter, Titan, Saturn's small moons, Akatsuki (Planet-C), Venus Express, MESSENGER, Dawn, Chang'E program, Saturn's moons, Saturn, Mars Odyssey, Opportunity, Mars Express, Venus, Mars Exploration Rovers, the Moon, Mars, New Horizons, Cassini, Mercury, podcasts and videos, Mars Reconnaissance Orbiter, Rosetta and Philae, Deep Impact, mission status

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Emily Lakdawalla

Senior Editor and Planetary Evangelist for The Planetary Society
Read more articles by Emily Lakdawalla

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