Archive for the ‘ Cassini ’ Category

Behind the scenes @ Cassini – A guided tour with Sarah Milkovich

I have a multiplanetary working life.  It’s gotten rather complicated.

Half of my time, I am a science planning engineer on Cassini, and the other half of my time I am the Investigation Scientist for the HiRISE camera on the Mars Reconnaissance Orbiter.  (Sometimes it seems like the hardest part of operating spacecraft is getting the work done in between all the meetings.)

Today I’m going to talk to you a little bit about some of my work for Cassini.  I hope you’ve been following along with us last year as we observed the Saturn equinox (check out all our great images on the Astronomy Photo of the Day archives!) and had some fabulous moon flybys.

Cassini is a hugely complicated spacecraft to operate, and there are a large number of people who work behind the scenes to get the stunning data that you see online.  I want to give you a taste of the amount of effort, and the many decisions, that get made by a lot of people who you rarely ever hear about in the press releases.

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JPL Open House

Go visit Sarah!

sarahThe JPL Open House is a huge annual event. Scientists and engineers will be staffing the information displays, ready to show demos and answer questions about the spacecraft and instruments that they design, build, and operate, and the data that they analyze. Info, including hours and directions as well as links to videos from last year, can be found here.

Now, we know that not everyone can hop over to Pasadena for a weekend.

 There will be an online live video chat at various times both days: http://www.jpl.nasa.gov/news/news.cfm?release=2009-073

The chats will also be archived, so you can email in a question ahead of time and watch the video later for an answer. You can also follow along on http://search.twitter.com/search?q=%23jplopen.

There are pictures from this week’s set-up on various JPL Twitter feeds, including the full-scale model of the next Mars rover, MSL, and ATHLETE, a 6-legged robot which is being developed for the moon. I saw a demo of it last fall, it was really awesome.

I’ll be at the Cassini exhibit, next to the giant inflatable Saturn, on Sunday morning!

Titan from Cassini RADAR – Rosaly Lopes

Beyond the Cradle collaborator Rosaly Lopes starts her contribution to this blog with some words about Titan that will act as a teaser for the upcoming Cassini flyby of Saturn’s moon, to take place on April, 20 when the spacecraft will be at only 3600kms from the enticing moon. 

 

Understanding the geology of Titan is not easy. We mostly have low resolution data, the  Synthetic Aperture mode in the RADAR instrument gets down to about 350 m, but that is about it.

Compare that with Mars, where we can almost see the ants on the ground, if there were any… 

We have limited topographic data for Titan, and camera and VIMS instrument images are mostly low resolution. We don’t know the composition of the surface. So, there is still a lot we don’t know. But what we do know, thanks to Cassini, is very exciting. Titan is more Earth-like than anywhere else in the solar system. It has an atmosphere and a weather system, a “hydrological” cycle, only it’s not driven by water. It is driven by methane. Titan has methane rain, methane lakes and seas. We also see craters, but not many, indicating that the surface is young. We see river beds, and some rivers may still have liquid methane in them. We see dunes like those in the Namibia desert (where I’m hoping to go later this year).  

 

Scientists have used data from the Cassini radar mapper to map the global wind pattern on Saturn’s moon Titan using data collected over a four-year period, as depicted in this image. Image credit: NASA/JPL/Space Science Institute 

And we see volcanic features! They are not like those on Earth, they are cryovolcanic features, and the “magma” is water with probably ammonia or methane. We see craters that look like calderas, with flows coming out of them. We see many flows, though it can be difficult to tell which ones are volcanic and which ones are fluvial. Titan may even have active cryovolcanism. Three papers published recently (I was co-author of two of them) argue that brightness changes detected using the VIMS instrument are due to cryovolcanic activity. 

 

This infrared projection map of Titan was composed from images taken by NASA’s Cassini spacecraft, visual and infrared mapping spectrometer. The location of two regions that changed in brightness are labeled. These regions are hypothesized by some to be areas of cryovolcanic activity on Titan. Credit: NASA/JPL, University of Arizona 

RADAR sees flow features on these two areas. The correlation between the flows and the brightness changes makes a good case for cryovolcanism. We have not seen a thermal signal yet, so the flows may not be active. Maybe what we have is some kind of degassing or fumarolic activity that is causing the brightness changes. I hope that before Cassini is over we will see a thermal signal in one of the areas that are thought to be cryovolcanic. That would be really great!

 

For more information visit the mission’s website.

Moonlets shadow

cassini_m

Do you want to see discovery as it happens?

And how YOU can make the difference?

Run to the unmannedspaceflight forum where one of its members has spotted the shadow of, not one, not two but thousands of moonlets in one of Saturn’s rings.

Great catch Floyd!

 

[EDITED] Beyond the Cradle most recent collaborator, Sarah Milkovich, Cassini Science Planning Engineer, provided us with some context for the current situation:

 

Currently, we are approaching Saturn’s equinox.  Like the Earth, Saturn’s spin axis is tilted, so as Saturn moves through its orbit, the sun shines on different portions of the planet.  The sunlight is in the process of moving from the southern to the northern hemisphere, and at equinox it will cross the rings.  The sun will shine on the edge of the rings, casting a very thin shadow onto Saturn, and the rings themselves will be dark.

So right now, the sun is getting lower with respect to the rings, which means that the shadows cast by the moons are getting longer, (which you can see in these images and movies on the imaging team’ website), and if there’s enough vertical relief within the rings we can see shadows from that as well. All of this will allow us to see more of the structure and variations within the rings themselves.

We’re also going to be looking at how the changing illumination conditions (and therefore changing temperature distributions) affect the moons and the atmosphere of Saturn itself. We’ve already begun to see some changes in the color of Saturn’s northern hemisphere – this is a mosaic of images taken in 2004, and you can see that the northern hemisphere (where it isn’t covered in shadows from the rings) is blue.  Compare that to this image taken in 2008, and you can see how the northern hemisphere is more golden, with a hint of blue at the pole. 

The Saturnian equinox will occur in August, so expect to see more changes in the future!

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