After arriving at our host's house yesterday afternoon, I took the time to get caught up on emails and so forth and to download some satellite imagery, mainly radar imagery. Then last night some colleagues of our host (Dr. Wolfgang Rack) invited us over for a BBQ. This was really really nice, I had some fantastic New Zealand wines, excellent steak.
As some of you may remember, Christchurch was hit by several earthquakes since September 2010, with earthquakes also happening in February 2011 and again in June 2011. Driving through Christchurch you can easily see the damage, empty lots, some rubble and in some places the road is warped. The people who invited us for the BBQ yesterday lived in an area that occurred a lot of damage. Luckily their house is on bedrock and seems to show less structural damage, though they did lose basically everything inside the house, not just once. In places the road is bent and warped, houses have been lifted up and slammed back to the earth or have moved down hillsides. Many homes and businesses have been condemned and there are still a lot of issues with safety. Some places only recently have had sewage connections restored and you can still find lots of portable toilets all over the place. Wolfgang's house lost its chimney and several bookcases,cabinets and their contents were knocked down or broken.
Pretty incredible stuff, I cannot even imagine the forces at work, the amount of energy and how frightening it would be to experience an earthquake. I think it would also be quite demoralizing to have so many earthquakes.
As I have mentioned a few times, I want to bring in a bit more of the basic science we do and information on the tools of our research into my blog. So today I thought I would discuss radar images. We use satellite images for many purposes: planning, monitoring and actually get data from them as well.
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| Satellite radar image from the ASAR sensor aboard the Envisat satellite. Image Courtesy of Polar View (http://www.polarview.aq) |
Just like a camera, a radar image gives us a picture of an area. An optical sensor essentially takes a picture and is measuring the amount of sunlight being reflected from objects in your picture. Optical refers to the visible light spectrum, what you and I can see with our eyes. I've used some optical images in earlier blog posts regarding this trip.
In contrast to an optical image, A radar image sensor actually sends out its own energy (think sunlight) and measures how much of it is returned from each point in the image. Radar sensors use energy from a different part of the electromagnetic spectrum so not blue, green, or red like a camera but actually use microwave wavelengths (1-100 Giga Hertz(GHz). The image above is from Envisat, a European Satellite mission that carries a microwave imaging sensor called ASAR (Advanced SAR). The sensor sends C-band 5.3GHz microwaves to Earth's surface and measures the energy that is returned to it.
Satellite radar imagery is extremely important to our work for several reasons:
1) We like to plan where we are going and what the conditions on the surface are.
2) Unlike a camera picture, radar images actually see through clouds(*for the most part at most frequencies below 10GHz). This is really handy since the polar regions often have cloud cover.
3) Rapid availability with good resolution and good areal coverage. Some of the images we get are available to us just a few hours after they have been collected. The delay is due to the time it takes to get an image downloaded from the satellite to the ground and then for the ground station to process the image.
4) Can actually get useful information from the images such as relative ice thickness, ice age, find areas of rough ice and actually record the values recorded from each pixel to try to relate to other parameters.
You can get free radar images from sites like Polar View (see SAR photo caption for link). Images from optical sensors like MODIS and Landsat are also available for free (i.e. the NASA MODIS Rapid Response System or GLOVIS.
Well that wraps up this blog post. Another one should come up later this evening after the "kitting out" and with some more details on my trip south tomorrow. As usual if you have any comments or questions just post below and I'll try to answer.
In contrast to an optical image, A radar image sensor actually sends out its own energy (think sunlight) and measures how much of it is returned from each point in the image. Radar sensors use energy from a different part of the electromagnetic spectrum so not blue, green, or red like a camera but actually use microwave wavelengths (1-100 Giga Hertz(GHz). The image above is from Envisat, a European Satellite mission that carries a microwave imaging sensor called ASAR (Advanced SAR). The sensor sends C-band 5.3GHz microwaves to Earth's surface and measures the energy that is returned to it.
Satellite radar imagery is extremely important to our work for several reasons:
1) We like to plan where we are going and what the conditions on the surface are.
2) Unlike a camera picture, radar images actually see through clouds(*for the most part at most frequencies below 10GHz). This is really handy since the polar regions often have cloud cover.
3) Rapid availability with good resolution and good areal coverage. Some of the images we get are available to us just a few hours after they have been collected. The delay is due to the time it takes to get an image downloaded from the satellite to the ground and then for the ground station to process the image.
4) Can actually get useful information from the images such as relative ice thickness, ice age, find areas of rough ice and actually record the values recorded from each pixel to try to relate to other parameters.
You can get free radar images from sites like Polar View (see SAR photo caption for link). Images from optical sensors like MODIS and Landsat are also available for free (i.e. the NASA MODIS Rapid Response System or GLOVIS.
Well that wraps up this blog post. Another one should come up later this evening after the "kitting out" and with some more details on my trip south tomorrow. As usual if you have any comments or questions just post below and I'll try to answer.
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