Tag Archives: Moon

Cassini’s Solar System Scrapbook

Cassini has completed its second-to-last ring plane crossing.  There’s only one more left before the final and fatal atmospheric entry.  But before it goes, Cassini completed a sort of family scrapbook of the solar system, by adding Neptune.  Here are some highlights of Cassini’s solar system scrapbook (which skips Mercury because it’s far too close to the Sun for Cassini to photograph):

Venus, Earth, and Mars

Venus, Earth and Mars, the only rocky planets easily observable from Saturn, as seen during the equivalent of a total solar eclipse around Saturn — Saturn is backlit by the Sun here. This was captured July 19, 2013.

Earth (and Moon), closeup from last image

This is a mega huge zoom in on the picture above.

 

Captured just before an Earth gravity assist maneuver, this is the Moon as seen on August 17, 1999. The spacecraft did not attempt to photograph the Earth during closest approach.

It’s worth also adding this. It’s the last image Cassini will ever take of Earth, captured April 12, 2017.

Jupiter

This was captured on December 29, 2000, while Cassini was grabbing a gravity assist boost from the giant planet.

Saturn

There’s really no end of good Saturn pics, but I quite like this one, taken last year as Saturn approached the summer solstice in its northern hemisphere.

Uranus

This blue planet against Saturn’s rings is not Earth. That little blue dot is the larger of the two “ice giants”, Uranus. I sincerely hope this is not the closest we’ll get to it in the 21st Century; it’s an astonishingly bizarre world that would seriously test a lot of basic science about planetary formation, magnetospheres, and so forth. This was captured April 11, 2014.

Neptune

This is the most recent addition to the scrapbook, a zoom-in enhanced version of an image taken Aug. 10, 2017, commemorating Voyager 2’s flyby on August 25, 1989 and the 40th anniversary of the mission’s launch on August 20, 1977. This is Neptune and its largest moon, Triton.

Pluto

Call it a consolation for not nabbing Mercury; Cassini captured this image of the dwarf planet Pluto on July 14, 2015, just as New Horizons was making its closest approach. (Naturally, New Horizons got much better pictures!)

 

It’s bittersweet, waiting for the end, but it helps to remember the amazing things Cassini has been doing.  Like Voyager 1 before it, Cassini is leaving behind portraits of our solar system.

Advertisements

Leave a comment

Filed under Space

Cassini’s Grand Finale Has Begun

In the wee hours of the morning today, Cassini made its 127th and final close flyby of Saturn’s giant moon Titan, the second largest satellite in the solar system.  There were many targeted observations planned on this final encounter, including radar studies of the “magic island”, a landform that has appeared and disappeared in Ligeia Mare, one of Titan shallow methane seas.  It’s presumed this disappearing trick is the work of changing levels in the sea, but more data is needed.

But there’s more to this flyby than just some great science.  Cassini has relied heavily on Titan’s mass to adjust its trajectory for very little fuel expenditure, and today was no exception.  Today, Cassini used Titan’s gravity to lower its orbit significantly, bringing the periapsis (the low point) within the rings, and shortening the entire orbit to just about a week.  Cassini will make twenty two dives into the area within Saturn’s rings, low enough to begin to directly sample some of Saturn’s tenuous upper atmosphere, gradually sinking on each closest approach until finally, next September, its predicted to impact the giant planet’s cloud decks and burn up.

It’s bittersweet, to be sure.  Cassini has functioned like a champ, long past its original design life.  But all things must come to and end, and Cassini will go out with a bang.

So as we prepare to say farewell in a few months, here’s a parting shot from Cassini: the last photograph it will be able to take of the Earth and Moon.  This was taken on April 12, taking advantage of a viewing geometry that will not occur again on the mission, where Earth peeked through the gap between the A ring and the F ring:

Leave a comment

Filed under Space

Chandrayaan-1: the Lost and Found Lunar Orbiter

This is pretty cool.  😉

On October 22, 2008, India joined the elite group of nations which have successfully sent spacecraft to orbit the Moon.  The mission was successful, conducting joint operations with NASA’s Lunar Reconnaissance Orbiter and LCROSS impactor, deploying an impactor of its own to help search for lunar ice (and making India only the fourth country to place its flag upon the Moon), and providing the first definitive proof of water ice in the lunar soil.  The mission was cut short, however, when the spacecraft abruptly stopped responding to ground commands on August 29, 2009.  The cause of the failure was never determined, but it had been experiencing issues in several systems, including the star tracker that keeps its antenna aligned with Earth.

Like other deep space spacecraft, the moment it stopped transmitting it became impossible to track from Earth — the Moon is much too far away to track such small objects (in Chandrayaan-1’s case, about 1.5 meters by 1.5 meters) by radar.

Or is it?

As international governmental and private space programs grow at an astonishing rate, it has become clear that space traffic will increasingly become a problem not just in Low Earth Orbit (LEO) and in the immensely valuable Geostationary Earth Orbit (GEO, the province of most communications satellites) but in deep space as well.  The recent move of the MAVEN spacecraft to dodge Mars’ innermost moon, Phobos, also underscores the hazards.  So JPL conducted a study to see whether lunar spacecraft actually could be tracked from Earth. And guess what — they can!

JPL’s first target was LRO, because it’s an active spacecraft and therefore its real position is known with exquisite precision.  Having located it with ground-based radar, the team moved on to something trickier: the Chandrayaan-1 spacecraft.  Lunar spacecraft are difficult, because the Moon is so lumpy that a) dead spacecraft don’t stay long unless their orbits are fairly high, and b) orbits can be difficult to predict over long timescales.  Nevertheless, they found it.  Chandrayaan-1 is dead, but not gone, and certainly not forgotten.

Leave a comment

Filed under Space

SpaceX could be the next to send humans to the Moon???

Yes, you heard that right.  They have yet to launch their crewed spacecraft as far as the ISS, but this week they announced that two undisclosed wealthy individuals have approached them about riding a Dragon capsule, boosted by their soon-to-fly Falcon Heavy, in a trip around the Moon.  (I’m betting they’re talking a lunar swingby mission, not an orbital mission.)  They plan on conducting this mission by the end of 2018.

For perspective, there are only two flights of Falcon Heavy currently on the manifest (the demo launch and a USAF experimental mission, one this year and one the next), and the crewed Dragon isn’t set to fly to the ISS until the fourth quarter of 2018 as it is.  (And the GAO recently expressed serious doubt about that even happening.)  So this is pretty ambitious.  Exciting, and very very cool, but certainly a stretch goal.

Who are the two individuals?  SpaceX isn’t saying.  They did, however, say they’d be happy to give NASA dibs on flying to the Moon aboard Dragon first — an announcement which came as a great shock to NASA, since they found out about all of this the same time the rest of us did.

This is sure to shake things up, and I’d not put odds on whether or not they’ll manage this.  I do have to wonder whether they’re overextending themselves.  They have put a lot of very ambitious challenges in front of themselves.  From a program risk perspective, this doesn’t seem like a good idea.  But if they pull it off . . . hoo boy.  There’s quite a payoff in terms of bragging rights, and it’s definitely a strong step towards their ultimate goal: Mars.

Leave a comment

Filed under Space

GOES-16 catches the Moon

I have a particular fondness for pictures of the Earth and Moon together.  NOAA’s latest weather satellite, the ground-breaking GOES-16, produced this particularly stunning example.  It’s currently in its commissioning phase, so it isn’t yet contributing to weather forecasting.  But it will, and when it does, it will be spectacular.  This image was taken from geosynchronous orbit — 22,000 miles away.  Earth and Moon are natural color, and this is not a composite — this is the image it actually took.  It can be surprising to see the Moon look so dark; we’re used to seeing it so bright in our night sky.  But it’s really because the Earth is so much brighter.  The Moon is of course not a usual target for a GOES satellite; but it still will take pictures of the Moon every now and again for calibration purposes, since unlike the Earth, the Moon looks very much the same from one orbit to the next.  For now, though, this image exists mostly to be beautiful.  Enjoy it!

ab_moon_from_geo_orbit_med_res_jan_15_2017

Leave a comment

Filed under Space

Earth, from Mars

Here’s the latest view of our blue marble from Mars, courtesy of Mars Reconnaissance Orbiter:

pia21260

It’s a composite image, merging images taken through different filters to produce color (although not “true” color, since MRO can see in infrared — vegetation shines very brightly in infrared, which makes Earth redder than it would be to the human eye), and processing Earth and Moon separately so that Moon can be bright enough to see without making the Earth just a big white smear.  The Earth is one of the brightest objects in  the solar system, and while the Moon looks really bright from here, it’s actually much darker than the Earth.

Believe it or not, the Moon was the real target of this image.  MRO isn’t really equipped to take this kind of picture, since it has what’s called a “pushbroom” camera (great for mapping, terrible for portraiture or landscapes), but once every now and again it does — for calibration purposes.  When this image was taken, the Moon was almost directly opposite the Earth from Mars’ perspective.  That means it’s the Earth-facing side of the Moon that we can see — the same side of the Moon we’ve all grown up seeing.  The lunar nearside is the best-known celestial object, and therefore a perfect calibration target.  😉  They know precisely how bright it should be.

Pretty neat, huh?

Leave a comment

Filed under Space

RIP, Jade Rabbit

“Yutu”, the Jade Rabbit rover, delivered to the Moon by the Chang’e 3 lander, the first lunar lander sent by any nation other than the USA or the USSR and the first sent by anyone at all since 1976, has now officially ended its mission.  The little rover survived a harrowing failure early on, but recovered (albeit without the ability to move anymore) and endured repeated long lunar nights (lasting almost half a month).  But now, after an incredible 31 months, the rover can no longer survive.  It’s well past its primary mission, which was only slated for three months.  I haven’t been able to find out whether Jade Rabbit is succumbing to the environment or to a lack of funding — ten times past the original mission length, it’s often hard for any space agency to justify continued funding — but either way, it’s dang impressive.  The mission team signed off by posting one final message on behalf of Jade Rabbit to Weibo: “I’m a rabbit that has seen the most stars!”

jade-rabbit-1

Leave a comment

Filed under Space, Uncategorized