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Headshot of Emily Lakdawalla

Fun with a new image data set: Mars Orbiter Mission's Mars Colour Camera

Posted By Emily Lakdawalla

06-10-2016 18:16 CDT

Topics: Mars Orbiter Mission (MOM), pretty pictures, amateur image processing, Mars, Phobos, explaining image processing, Deimos

It's always a delight to sink my teeth into a new data set, and I have spent this week playing with one I've been anticipating for a long time: ISRO's Mars Orbiter's Mars Colour Camera, or MCC. Last week, they released the first year's worth of mission data, up to September 17, 2015. In this post I'll show you some highlights of the data set, then go into more detail about how you can access the data and some of the things I learned about the data set while I was playing with it.

MCC is different from most recent Mars cameras in that it has a very wide field of view, designed so that it is capable of imaging all of Mars' disk when the spacecraft is near the apoapsis of its highly elliptical orbit. It doesn't take crisp high-resolution views of Mars; instead, MCC's value lies in its ability to capture beautifully colored, regional views of the planet that can serve as context images for other missions' more detailed but much more narrowly focused pictures. Its detector is 2048 pixels square, so its images have plenty of pixels for print publication. For instance, here is a lovely view of a hemisphere of Mars that contains many past and future landing sites:

Global view of Mars from MOM: Chryse and Acidalia Planitiae and Kasei, Mawrth, Tiu, and Ares Valles

ISRO / ISSDC / Emily Lakdawalla

Global view of Mars from MOM: Chryse and Acidalia Planitiae and Kasei, Mawrth, Tiu, and Ares Valles
This global view of Mars contains the landing sites of Viking 1, Mars Pathfinder, Opportunity, and Schiaparelli, as well as the future landing site of the ExoMars rover. It was taken by Mars Orbiter Mission on October 1, 2014, from an altitude of 76,247 kilometers.

Before I write anything else in this blog post, I want to deliver a message to the Mars Orbiter Mission team:

Your full-globe images of Mars are amazing and unique. Please consider shooting more at any phase angle, not just fully-lit ones. No spacecraft has ever captured beautiful, high-resolution images of Mars at a crescent phase. You can. Please shoot more global views at all possible phases that your spacecraft may see: crescent, half-full, gibbous, or full. Such images would be published in books for decades to come.

So now let's get to the good stuff. First: here is every full-globe image that MCC took, all of them from October, 2014. A remark in the documentation for the data set suggests that they stopped shooting global views after that because they only take full-globe images when they see a nearly fully-lit Mars at apoapsis. Several of these images have been released before, but processed in a way to make them garish and strangely colored. I found that it wasn't at all hard to produce more realistically colored views from MCC.

Global view of Mars from MOM: Meridiani Planum

ISRO / ISSDC / Emily Lakdawalla

Global view of Mars from MOM: Meridiani Planum
Mars Orbiter Mission caught this global view of Mars soon after arriving in orbit, on September 28, 2014, from an altitude of 74582 kilometers.
Global view of Mars from MOM: Syrtis Major and Hellas #1

ISRO / ISSDC / Emily Lakdawalla

Global view of Mars from MOM: Syrtis Major and Hellas #1
Mars Orbiter Mission captured this photo on October 4, 2014, from an altitude of 72,935 kilometers.
Global view of Mars from MOM: Syrtis Major and Hellas #2

ISRO / ISSDC / Emily Lakdawalla

Global view of Mars from MOM: Syrtis Major and Hellas #2
Mars Orbiter Mission took this photo on October 7, 2014 from an altitude of 70,325 kilometers.
Global view of Mars from MOM: Elysium Planitia and Gale Crater

ISRO / ISSDC / Emily Lakdawalla

Global view of Mars from MOM: Elysium Planitia and Gale Crater
This view of Mars includes the landing sites of Viking 2, Beagle 2, Spirit, and Curiosity, and the future landing site of InSight. Mars Orbiter Mission took this photo from an altitude of 66,552 kilometers on September 30, 2014.
Global view of Mars from MOM: Tharsis Montes and Valles Marineris

ISRO / ISSDC / Emily Lakdawalla

Global view of Mars from MOM: Tharsis Montes and Valles Marineris
Mars Orbiter Mission took this photo on October 4, 2014, from an altitude of 76,680 kilometers.
Mars and Phobos

ISRO / ISSDC / Emily Lakdawalla

Mars and Phobos
Phobos makes a guest appearance in this nearly global view of Mars taken by Mars Orbiter Mission on October 31, 2014.

That last image contains Phobos. Even better, there was another set taken on a different date that showed Phobos transiting Mars over four different photos:

Phobos crossing Mars' disk (animation)

ISRO / ISSDC / Emily Lakdawalla

Phobos crossing Mars' disk (animation)
Mars Orbiter Mission took the four photos in this animation, showing Phobos transiting Mars' disk, over a period of 35 seconds beginning at 3:02:41 on October 7, 2014.

Here's a higher-resolution view of Phobos. Again, this image has been released before, but it was stretched in a way that turned Phobos into a black hole. In my version, you can distinctly see the difference between Phobos' dark gray dayside and black nightside.

Phobos over Mars from MOM

ISRO / ISSDC / Emily Lakdawalla

Phobos over Mars from MOM
Mars' inner moon Phobos appears far darker than the bright clouds of Mars in this view taken by Mars Orbiter Mission on October 14, 2014.

Here's a zoom in on Phobos.

Phobos over Mars from MOM (detail)

ISRO / ISSDC / Emily Lakdawalla

Phobos over Mars from MOM (detail)
Taken October 14, 2014.

In the data released to date, there's only one view that I can find of Deimos. It's one that was released before, but in a weird color; in my processing, I find that it comes out the right color, a brownish gray. It's a little hard to discern its shape because it is nearly fully lit (that is, the image was taken at a very low phase angle).

Deimos from Mars Orbiter Mission

ISRO / ISSDC / Emily Lakdawalla

Deimos from Mars Orbiter Mission
Mars Orbiter Mission shot this photo of Mars' outer moon Deimos on October 14, 2014. The view is onto Deimos' concave south pole.

After October 2014, they quit taking the global views and switched to taking higher-resolution images from vantage points closer to the planet. The field of view is still quite broad, which is great because it means MCC can encompass all of some rather large geologic terrains in a single field. For instance, there's Valles Marineris:

Valles Marineris

ISRO / ISSDC / Emily Lakdawalla

Valles Marineris
Mars Orbiter Mission captured this expansive view of the solar system's largest canyon on October 20, 2014.

Here's a view centered on Gale crater, Curiosity's landing site, showing it in context with some of the steep topography of Mars' hemispheric dichotomy boundary:

Gale Crater regional context

ISRO / ISSDC / Emily Lakdawalla

Gale Crater regional context
Gale Crater -- Curiosity's landing location -- is easy to spot in wide-angle views of Mars because of its dark "beard" and the black sand dunes that form outlines around Gale's central mound. This view was taken by Mars Orbiter Mission on January 17, 2015.

How about a volcano? I always have to look up which of the Tharsis montes is which. The big one in this picture is Arsia, the southernmost. I love the high cloud, and the fact that you can see its shadow cast on the surface.

Arsia Mons and cloud, Mars

ISRO / ISSDC / Justin Cowart

Arsia Mons and cloud, Mars
Mars Orbiter Mission took this photo on January 4, 2015, from an altitude of 10,773 kilometers. The image covers an area about 1100 kilometers wide. Arsia is the southernmost of the three Tharsis Montes.

In fact, speaking of the Tharsis Montes, here's a lovely atmospheric view of all of them (with bonus Uranius and Ceraunius Tholi). I turned it sideways from its original format because I thought it'd make a nice page banner this way.

Tharsis Montes

ISRO / ISSDC / Emily Lakdawalla

Tharsis Montes
At far left are the small Uranius Tholus and the conical Ceraunius Tholus, close together. Then, from left to right (northeast to southwest) are the three Tharsis Montes: Ascraeus, Pavonis, and Arsia Mons. Arsia has a bit of early morning cloud to the southwest of its peak. The photo was taken by Mars Orbiter Mission on December 13, 2014.

Here's a much closer view of a bit of Valles Marineris. Pick your favorite chasma and you can find a nice regional view from MOM, I think.

Candor and Ophir Chasmata, Mars

ISRO / ISSDC / Justin Cowart

Candor and Ophir Chasmata, Mars
Candor Chasma (bottom right) and Ophir Chasma (center), two large canyons in the north-central portion of the Valles Marineris system. Taken by Mars Orbiter Mission on July 19, 2015, from an altitude of 1858 kilometers. The image shows a region about 200 kilometers across.

I'll finish my tour of the data set with this more atmospheric view. Crop it to a rectangle and I think it'd make another terrific page header!

Syrtis Major and the Martian limb from Mars Orbiter Mission

ISRO / ISSDC / Justin Cowart

Syrtis Major and the Martian limb from Mars Orbiter Mission
Three frame Mars Orbiter Mission Mars Color Camera mosaic of the Syrtis Major region on September 24, 2015. The first frame was taken while MOM was at an altitude of 7200 km, and the final frame was taken at an altitude of 8300 km 10 minutes later.

Okay. Enough playing around; let's talk a bit of technical details about the data set.

The official way to access it is through this site. It requires registration for access, but I never received the promised email saying I got access; eventually I got a login to work without it, and was able to get in to get the data. I find that logging in the first time typically does not work; I have to wait for the site to throw an error and then try logging in again. Sometimes I close my browser after a login attempt and then open it again and try logging in again and it tells me I'm already logged in, and then I can access the data through the menus at the top of the page. Whatever works!

Downloading images is time-consuming, because the site limits you to five images at a time (though in practice I never got it to download more than one at a time), and each time you request an image download it takes a minute or two to zip together two versions of the image, one 16-bit and one 32-bit, along with various ancillary data, making for typically 30 Megabytes of downloading for each image.

Over the last two days, I downloaded all 517 images, one by one, so you don't have to.

I collated the ancillary data from the image headers and assembled my own browse page to the data, which you can access here. For each image you can click a thumbnail to get to a 512-pixel-square browse version of the image, or download the 16-bit or 32-bit versions, along with detached text labels. For 42 of the images, there are two versions of the same photo, downlinked through different ground stations, so the data set actually contains 375 unique images. I highlighted in yellow the ones that are duplicates.

My favorite batch-converting software, IMG2PNG, does not yet handle this data set, so in order to open them I began with the 16-bit image and changed its file extension to ".raw". Then I opened it in Photoshop, setting its size to 2048 by 2048 pixels, 3 channels, not interleaved, 16-bit, IBM PC byte order, and the image opened fine. Invariably, the image appears black, because most of the data are crowded into the low end of the histogram, so I stretched the levels to make the image visible. I found that the images all appear orange; the green and blue levels are way too low. By adjusting the levels of a full-globe image so that the south polar clouds are white, I find that assigning an input value of 211 in the green channel and 144 in the blue channel to white makes the color balance look much more like published Hubble photos -- and then the same proportion applies to all of the rest of the images in the data set.

The images benefit from a little unsharp masking. Reading the documentation for the data set (PDF), I see they used bilinear interpolation to demosaic the images from the raw Bayer filter frames. If you really want to try to get more detail out of the photos, it could be worthwhile to go back to the ISSDC (if you can manage to log in), download the raw frames, and try some other demosaicking schemes to see if you can get better results.

Most of the images are targeted at Mars, but there are several images taken between 18 and 21 October 2014 that were attempts at targeting Comet Siding Spring. From April to mid-July 2015, there was no imaging due to Mars passing through solar conjunction.

One final, stray observation: This is the first data set I've encountered where the ground station that received an image is noted in the image's filename: D18 and D32 for the Indian Deep Space Network antennas in Bangalore, CNB for Canberra, and GDS for Goldstone. As I mentioned before, some images exist in two versions, each transmitted to a different ground station. The only other archival data set where I've seen two versions of single images received through different ground stations is Mariner 10. Most other missions handle this by choosing one or the other to archive, whichever has fewer or no errors, or by creating a product that merges the good parts of two or more error-ridden images to produce the best possible product. It's a funny little quirk of the data set.

Please go forth and process the Mars Orbiter Mission images, and use them in good health! Many thanks to ISRO for designing a camera that takes such unique regional-context images of Mars!

 
See other posts from October 2016

 

Read more blog entries about: Mars Orbiter Mission (MOM), pretty pictures, amateur image processing, Mars, Phobos, explaining image processing, Deimos

Comments:

Alterra: 10/07/2016 06:37 CDT

Nicest!!! For planetary astrophotographers all over the world, it is a treasure trove! Thanks for pointing at it. Since Mars is receding fast from us, spanning a mere 8 arcsec diameter, imaging it is geting harder by the day, and it is amazing how these images are so much similar to Earth´s point of view. One of the above - from October 6th - is almost dead on identical to the one I took last night, using a 11" SCT, from my backyard in Brazil! :)

Alterra: 10/07/2016 06:58 CDT

lol I just realized: "identical" is an superoverstatement on my part... sorry... Mine is a tiny little Mars... here: http://astrob.in/267206/0/

Foz: 10/07/2016 07:29 CDT

Dear Emily. Thank you so much for posting these amazing images- really beautiful. Whilst currently following the current Mars apparition as comprehensively as possible, to compare our own earth based captures, and the Hubble image of May 12, with the MOM images is just amazing. In the meantime, monitoring Mars at every opportunity and waiting patiently for the next major dust storm....! Regards

LocalFluff: 10/07/2016 08:02 CDT

That's a great image, Alterra! And because of it, I understand why MOM's images have that vintage science fiction feeling about them: Because they show entire Mars, like in a telescope, like in War of the Worlds 1896.

Alterra: 10/07/2016 08:44 CDT

And for the complete set, as a five frame animation. Mars showing almost the same CM as of the oct 6th image you shown above. At just 8,5" there is little to see, but Hellas is very prominent, and Syrtis major planum too. The bright SPC and some nebulosity over NPR compares nicely with the MOM image.

Alterra: 10/07/2016 08:45 CDT

forgot the link... :) http://astrob.in/267206/B/

Alterra: 10/07/2016 09:20 CDT

lol LocalFluff! WoW they are! Including the departing spaceship in the animation! Run for the hills!!!

tvs: 10/09/2016 08:17 CDT

Thanks for the amazing post! I hope MOM team considers your suggestions for the Mars phases. Those would be incredible.

Ryan: 10/11/2016 03:26 CDT

@Alterra awesome pictures you took, nice - love the animation, than's crazy.

Michael Oghia: 10/28/2016 08:36 CDT

You're amazing. Thank you for this!

Anirban: 10/30/2016 09:04 CDT

Thank you for this wonderful effort of yours, Emily, and others at the Planetary Society. The images look stunning! Full thanks to ISRO as well! Login attempts on the ISSD website are indeed quite hard. The odd colour scheme images released by ISRO that you have referred to over here were ones they released early into the mission .... over time ISRO too have processed and released images with a natural looking colour scheme like the ones you have processed and posted on here. Examples: http://isro.gov.in/pslv-c25-mars-orbiter-mission/arena-dorsum-region-of-mars http://isro.gov.in/pslv-c25-mars-orbiter-mission/mars-full-disc-image-momhttp://isro.gov.in/pslv-c25-mars-orbiter-mission/mars-full-disc-image-mom https://www.facebook.com/photo.php?fbid=10152832247323688&set=a.10152774229748688.1073741837.620983687&type=3&theater https://www.facebook.com/photo.php?fbid=10152832251168688&set=a.10152774229748688.1073741837.620983687&type=3&theater http://www.isro.gov.in/pslv-c25-mars-orbiter-mission/olympus-mons-large-shield-volcano-planet-mars

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