On Friday, HiRISE released over 1200 color observations. This was our first large release of the color products (not counting the 140+ images of MSL candidate sites released back in October). I was asked recently if our images look fairly similar to one another, or if they are all completely different. Well, you can now judge that for yourselves, but I feel the answer clearly tends toward the latter. The variety of terrain types on Mars is wider than you might have expected, and everywhere you look you’ll find something spectacular.

But I’d like to showcase one image in particular. Within this single image, there is a remarkable progression of landforms, in a view running down a small portion in the interior of Valles Marineris, the “Grand Canyon of Mars.” Here are a selected set of sub-images from the RGB color product; each thumbnail links to a larger view. All of the original products are available at our website.

At the top of the image is a flat, cratered plain, very much what one thinks of as typically Martian. The edge is abrupt, leading immediately to a steep descent crossing multiple layers of bedrock. The accumulating aprons of debris are channeled down between rocky ridges.

A number of boulder tracks are visible, remnants of mighty tumbles. You can follow one of these tracks for something like a kilometer down into the middle portion of the image. Here is a small part of this track.

Farther down, a network of scalloped terrain has formed in what must be a transition zone from the upper, steeper section and the lower, flatter step. What’s interesting to me about this section is, as shown in the image below, the scalloped edges form a stunning pattern of bifurcation.

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Lately we’ve been working hard dealing with a LOT of extra data. Because Mars is getting closer to the Earth (you can visualize that in this view of the solar system), we are approaching the peak data rate for the entire primary mission. Not that we’re complaining! This just means the Targeting Specialists are planning many more images, and we’re making those images as big as we can.

Unfortunately, we can’t just make them all the largest size the instrument is capable of taking, because our camera will get too hot. If it overheats, the instrument will shut itself off in order to prevent any damage to the electronics. So we have to be careful, and only plan images that won’t overheat HiRISE. In order to predict those temperatures, we use a tool called HiTemp (of course!). Here’s what it looks like (click on the image to see a bigger version).

This program reads in our planning files, and then models the temperatures of two key spots on the focal plane of the camera. It’s our job to make sure we don’t go above the dotted red line – this gives us a comfortable buffer below the scary solid red line. That’s when HiRISE would shut off, or safe. We know from experience by now that this is a big pain in the neck – a lot of work is required to get us back up & running, and we miss observations while we’re turned off. So we watch our HiTemp plots!

Each HiRISE image has a color strip in the central portion of the image. That strip is comprised of three color wavelengths, blue-green, red and near infrared. Let’s clarify some terms first. RED refers to the visible wavelength portion of the spectrum in which the full-width HiRISE images are taken. These look black and white, not red, because they are displayed in grayscale. But we call them RED images. The other two colors seen by the HiRISE camera are in the visible blue-green (called BG) and invisible near infrared (often called NIR, but we refer to it here as IR).

The magic happens when we succeed at coregistering the IR and BG to the RED parts of the image to produce the center strip, false color images. More about this in an upcoming post. The maximum width of a color image is 4048 pixels. Some HiRISE images are 100,000 pixels long, which makes for a very long skinny image. These are affectionately dubbed “color noodles” by the HiPI (PI=Principle Investigator).

The image below illustrates where the color portion of the image is located. The zoomed in part of the same image just shows more clearly how the colors can offer more detailed geologic information than is available in the RED (black and white) image. For detailed information about the use of the color products and how they can be interpreted for scientific purposes, please refer to “Information for Scientific Users of HiRISE Color Products”

Is this what Mars really looks like? The images are not true color. The three color images taken by HiRISE are coregistered and stacked on top of each other. Then each color layer is assigned to red, blue or green, because those are the colors that are projected on your screen. So you can see how the word “color” becomes quite confusing. First, red is black and white. Then, we have all those I’s R’s and G’s and B’s! The color in HiRISE color products is really false color, because we are assigning a visible color to one that is invisible to human eyes. Also, there are only three wavelengths of light, not the full visible spectrum we are used to seeing. The RGB products are more similar to “natural” color. Even with HiRISE’s limited color capability, there is still an incredible amount of information gained by having the two extra wavelengths.

Why is there a garish green strip along the right side of the color image (left side in the nomap products)? You will notice this in some of the HiRISE color products. It will be apparent in the IRB, but not the RGB products. This is due to one half of the IR10 CCD having electronics issues during the earlier part of the mission. This problem was resolved for most cases, so that later images have both channels of IR10 — no green strip. Some of the earlier images were also able to be reprocessed to restore the missing IR information.

What is the difference between “RGB” and “IRB”? The RGB products are different than the IRB products in that the IR channel has been replaced by a “synthetic blue” layer that creates an image that is somewhat closer to natural color. In many of the images, the infrared band does not contribute a lot of information. The bands in this product have also been stretched to provide better contrast. In other words, the RGB images are more aesthetic. The IRB product is a science product. It contains the IR, RED and BG layers.

In the IAS viewer, you can turn the bands on and off to see what information each one contributes to a particular image. Use this button to switch from color to grayscale. This dialogue will also allow you to switch the color assigned to each band. The way the images are stacked in the HiRISE images goes like this:

Changing two bands to display the same color will show what kind of information is contributed by each band.

Below is a detail from PSP_004052_2045 showing the IRB color overlaid on the RED image. It is a beautiful example of how the color available in HiRISE images gives us new information that aids in interpreting the images. They are also just plain beautiful.

With the color images, dynamic range becomes more important then ever before. The DRA (Dynamic Range Adjustment) options of the IAS viewer are a great boon when looking at these images.

DRA performs what image processing folks call a “stretch.” A stretch takes some range of pixel values from the file and maps it onto a new range for the screen. To take an example, consider an image that appears over-exposed: much of the information is in the upper range of pixel values and you will have trouble distinquishing any detail. If the over-exposed pixels are not completely saturated (i.e. they don’t all have the maximum value) then a stretch that reduces brightness can reveal this otherwise hidden detail.

HiRISE has a very high signal-to-noise ratio, and our targeting specialists do a very good job choosing camera settings (which they do individually for each and every image) so completely saturated pixels are very rare.

But this also means that a stretch that works well over the entire image (a global stretch) may not be the best, the optimal stretch, for any one sub-image area that you are viewing. This is where the Auto DRA function in IAS becomes critical.

The button (shown below) is located on the right-hand side of the toolbar. A single click will do a stretch based only on the pixels you are viewing. This can bring out detail in shadow–amazingly, there is enough ambient light scattering around in the thin atmosphere to illuminate those scenes (and HiRISE is sensitive enough to pick enough of it up). It can also bring out detail in bright areas of over-exposure. For the color images in particular this can make things look a whole lot better.

Another factor plays a part in this. By default, the IAS viewer performs a global DRA when the image is loaded. As seen in the screenshot below, there are areas in our image that can skew the stretch. The large red rectangle is an area where the red CCDs start imaging before the blue-green. The IRB images often will have a cyan region where one of the IR CCDs was too noisy. We have elected to keep these areas in our images.

When in a sub-area, hit the Auto DRA button and the image should be drastically improved, as you can see in this final screenshot.

DRA early and often!

Starting with the 10/10 release, color images are included for the first time. We’ll describe how we process these in the days and weeks to come. But what I’d like to do first is give a brief description of all our product types as they currently are available. You’ve no doubt noticed a mind-boggling array of new options on our product pages. They now include what we call our “NOMAP” products; NOMAP means that they are not map-projected. In other words, not rotated to the direction of north, not mapped to a coordinate system, and not scaled to any particular geometric resolution.

I’ve prepared this ugly table that outlines each of the products now available (excluding the raw EDRs). So reading the columns from left to right: there are three types of “NOMAP” products, two types of lossy “QLOOK” (Quicklook) RDRs, and two types of lossless RDRs.

HiRISE Products	“NOMAP”	RDR
		“QLOOK”
Grayscale	RED	RED	RED
Color	RGB	COLOR	COLOR
	IRB
JP2	Lossy		Lossless

With that as a reference, now I’ll try to define everything more precisely.

“NOMAP”

Non map-projected product. Always lossy compressed for smaller size and quicker viewing. These are not formal Planetary Data System products; they’re “special”, meaning there is no PDS label and no Software Interface Specification describing them. Available for IRB, RGB and RED.

RDR

Reduced Data Record: reduced in the sense of refined or processed, not raw data. Formal PDS products with accompanying labels and a detailed SIS document describing their format and processing steps. Available both in lossless and quicklook formats for both RED & COLOR.

“QLOOK”

Quicklook: a special product that is a lossy compressed version of the RDR. In a normal RDR, all of the original data is retained. But with a quicklook, some of the highest resolution detail is discarded to make for quicker viewing.

RED

The image obtained by the red-filtered CCDs. It will be over the full swath width, typically data from all ten red CCDs. Covers the visible wavelength band from 550 to 850 nanometers.

IR

Infrared. Covers the near-IR wavelengths from 800-1000 nanometers.

BG

Blue-Green, visible wavelengths from 400-600 nm.

COLOR

A color RDR. It contains data from the IR, BG and center RED ccds. Typically this will be a skinny strip (”center swath”) inside a skinny strip, or as I like to say, the bacon-strip effect.

IRB

An enhanced color NOMAP. It has the same color bands as the RDR: IR, RED and BG.

RGB

An enhanced color NOMAP. It contains only data from the RED and BG. The blue is derived from the difference between the RED and BG. The color bands are RED, BG and the synthetic blue.

EDR

Experiment Data Record, a formal PDS product that is raw uncompressed data with a label header.

Note: we will be working towards making all of these products available for all prior releases.

Yesterday morning we turned the MRO spacecraft around to see our point of origin – the Earth. We took a special calibration image of the Earth and Moon. HiRISE isn’t the first to take a picture of the Earth from Mars, but we’re hoping ours will be even more detailed. We expect the Earth to be about 90 pixels across its diameter, and the Moon about 24 pixels. So it won’t be a big beautiful clear image like you’re used to looking at from our weekly releases, but we should be able to resolve features like continents!

This diagram simulates of what the inner solar system would look like if it were being viewed from above right now. MRO is looking from Mars (orange) towards Earth (purple). You can see from this geometry that we’ll only see the sunlit part of the Earth and Moon as a crescent. They’ll look somewhat less than half full.

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Last week we had a rare event: HiRISE turned off! We call this safe mode, because it’s a safety measure built into the instrument’s software. Whenever any of the sensors starts going out of bounds, like temperatures or voltages, the instrument powers down to prevent damage to the electronics. In this case, one temperature sensor went over its upper limit of 35 degrees Celsius. It’s pretty disconcerting when something unexpected like this happens, but at least we know the instrument is protected.

We had the difficult detective job of figuring out what went wrong. It was clear early on that the instrument overheated, but we couldn’t figure out why. Our tool that predicts the temperatures (”HiTemp”) didn’t predict anything that hot. We didn’t take a really large image, which would heat us up (at least, nothing bigger than normal! ). The local operations team worked with the health & safety people, the spacecraft engineers at LMA, and some of the software developers at Ball Aerospace that originally designed HiRISE. Together we all investigated the problem.

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On this NPR Science Friday episode, HiRISE Principal Investigator Alfred McEwen and M.I.T. planetary geophysicist Maria Zuber discuss new results that illuminate the story of water on Mars with host Ira Flatow.

Also, available free on iTunes, are a collection of videos from the Phoenix Mission’s Open House, highlighting the University of Arizona’s Mars-related projects including UofA speakers McEwen, Phoenix P.I. Peter Smith, GRS and TEGA P.I. William Boynton, and planetary geologist Vic Baker.

Finally, during last week’s UofA football game, our marching band played a tribute to Mars and in particular Phoenix with a little ditty written by band director Jay Rees. I don’t know if a recording of the performance is available online, but here’s a snippet of the song:

“Follow the water” is NASA’s song,
UA’s happy to sing along.
We shall see what we shall see.
We might find biology!

Three HiRISE papers are coming out in a special issue of the journal Science today. Our science team has been working hard on analyzing the images we take, and they’ve discovered some interesting things.

One paper talks about a few aspects of the history of water on Mars: HiRISE images of “rock glaciers” and bright deposits in gullies that might be extremely recent. HiRISE observations of an area called Athabasca Valles were used to show that it is actually covered with a thin veneer of lava. A third paper discusses thin layers in the North Polar cap. HiRISE is able to discern very fine layering (seen in an excerpt of image PSP_001636_2760 at left), as well as the color and thickness of each layer. Since these layers were laid down over hundreds of thousands of years of Martian history, they provide a record of climate change on the planet.

You can find a lot of things on the HiRISE website that are impossible to include in a print journal – like full-resolution color versions of the images from the papers, and (my favorite) cool 3-D flyover movies of the stereo observations. Our webmaster designed this lovely page for accessing these special products. Have fun flying over Mars!

Wednesday September 19th, we are posting our first student suggested and captioned image on the website. Last spring, students in grades 3 to 14 in schools from around the world, including Hungary, Nepal, Curaçao, India, Arizona, and New Jersey, participated in the first HIRISE Image Targeting Challenge. They suggested target locations that they thought might hold evidence of water at or near the surface of Mars in the recent past. Then the students had to analyze the returned images, submit a report as a class, and write a figure caption. It often takes a long time to get an image after it has been suggested, even for the team members, because of all of the different constraints, including the season, the roll angle limits, and because there are other instruments on MRO that we coordinate with. However, we got very lucky and were able to get twelve of the student suggested images during the spring semester. Tomorrow we are releasing the first of these images that a third grade class in Arizona suggested and analyzed. It is so exciting to me that 8 and 9 year olds are doing science, not just reading it in a textbook. Each week we will release another student image. Hopefully this has gotten some of the students excited about possibly becoming scientists when they grow up. One day some of them may become team members on a space mission.

We are starting the Fall challenge right now. If you know of a school group that might want to participate, check out the HiRISE Challenge website at: http://quest.nasa.gov/challenges/hirise/
Our first live online chat will be on September 25th.