Date: June 1, 2011
Title: Taking Pictures of Mars with the Mars Reconnaissance Orbiter
Podcaster: Tanya Harrison
Organization: Malin Space Science Systems: www.msss.com
Link: NASA’s Mars Reconnaissance Orbiter mission page: www.nasa.gov/mro
Description: Taking pictures of Mars involves meticulous planning. This podcast will give you a quick summary of what goes into acquiring these images.
Bio: Tanya Harrison is a planetary scientist on the science operations team for the Mars Reconnaissance Orbiter Context Camera (CTX) and Mars Color Imager (MARCI) at Malin Space Science Systems: http://www.msss.com/about-us/tanya-harrison.php
Sponsor: This episode of the “365 Days of Astronomy” is sponsored by Neil McIvor.
Hello, my name is Tanya Harrison, and I am a planetary scientist at Malin Space Science systems in San Diego, California. We build and operate cameras for various NASA missions, predominantly at Mars, and so today I’m going to be talking to you about how we go about acquiring images of Mars and how we get them out to you, the public, to enjoy.
I’ll give you a bit of background information in case you’ve never heard of Malin Space Science Systems, known short-handedly as “M-S-cubed.” MSSS is comprised of several small groups which all contribute to designing, building, and operating cameras on orbiters and rovers at other planets. We currently have several cameras operating at Mars: the Thermal Emission Imaging System Visible Focal Plane, or THEMIS-VIS, camera operating on Mars Odyssey and the Mars Color Imager (also known as MARCI) and Context Camera (CTX) aboard the Mars Reconnaissance Orbiter. In addition, MSSS has two cameras operating on the Lunar Reconnaissance Orbiter at the Moon. In the upcoming months, the next orbiter to Jupiter will launch with MSSS’s JunoCam, and the next rover to Mars, Mars Science Laboratory, will have three MSSS cameras onboard – the Mast Cameras, the Mars Hand Lens Imager (MAHLI), and the Mars Decent Imager (MARDI). Today we’ll be focusing on CTX and MARCI on board the Mars Reconnaissance Orbiter.
CTX takes images of Mars that are up to 30 km wide and over 300 km long at a resolution of 6 meters per pixel. This is a pretty big footprint with a relatively high resolution compared to previous cameras! The size of that footprint has allowed us to cover over 60% of Mars at 6 meters per pixel in the 5 years MRO has been orbiting Mars. In addition to mapping, we use CTX to acquire stereo coverage of key areas, as well as to monitor hundreds of locations on Mars for changes such as new impact craters and dust activity.
MARCI is used to monitor the weather on Mars on a daily basis. It acquires images of the entire planet every day at 5 visible wavelengths and 2 ultraviolet wavelengths. MARCI actually picks up where the wide-angle Mars Orbiter Camera (MOC WA, which was also built and operated by MSSS) aboard Mars Global Surveyor (MGS). The MOC wide-angle began acquiring daily global mosaics of Mars in mid-March 1999 until November 2006, when MGS was lost. MRO went into orbit of Mars in March of 2006, so combining the MOC WA with MARCI gives us over 12 Earth years of continuous monitoring of martian weather. This is important for planning rover and lander missions to Mars, as well as for targeting orbital cameras, which we will discuss a bit later.
Two groups at MSSS see to the operations of the cameras: Science and Operations (“Ops”). The Science group is responsible for selecting targets for CTX and keeping track of the martian weather with the images from MARCI. The Operations group plans, commands, retrieves, processes, logs, and archives instrument images. In addition, Ops is responsible for monitoring the health and safety of the flight instruments.
Taking an image at Mars is not a simple or short process. Planning a cycle, or 2-week period, generally starts 3 weeks before the first image is taken in a given cycle. This process of image selection starts with the Operations group creating files called products. Products incorporate initial input files that include orbits, spacecraft info, limitations, and opportunities over a cycle. All this information is ingested and processed. Using that output, coupled with the database of options, produces product files that have several hundred possible imaging opportunities over a given cycle. Products are then handed off to the Science group.
Now, in the science group, we target the CTX camera, and this is the group that I’m actually in. I think some people are under the impression that we just take pictures of whatever the spacecraft happens to be flying over at the time, but that’s not the case at all. The Mars Reconnaissance Orbiter was specifically designed with slewing in mind, so we can point the spacecraft off nadir to acquire images. Every image is carefully planned, taking a number of factors into account, including:
-Weather (because you don’t want to take pictures in dusty areas or the image quality will be very poor, if you can see the surface at all)
-Sun angle (because you don’t want to try to take pictures of a feature that would be in deep shadow at that particular time of year)
-Downlink availability (because when Mars is farther away from the Earth, the “downlink” (which is akin to bandwidth for your internet connection) is lower, so we can’t take as many images)
-Target priority (since we have to operate under the assumption that the spacecraft could fail any day, we image parts of Mars in order of priority—for example, Valles Marineris would be more important than some featureless locale in the northern plains)
Once the files are completed on the targeting side they are returned to the Operations group. Files are converted into a text-formatted file in a process called sequencing. Several checks are done on this file in order to eliminate any possible errors or mistakes. This file is then sent to JPL, or the Jet Propulsion Laboratory. Using specific MRO tools, JPL integrates files from all instruments on MRO—HiRISE, CRISM, CTX, MARCI, SHARAD, and Electra—to produce a final file that contains all the observations that will be commanded within a cycle.
This final file is returned to the instrument teams for checking. The Operations group verifies that the final file contains all the observations for the instrument for a given cycle. After it passes this stage, the file is converted into spacecraft commands and submitted to Lockheed Martin Aerospace, who operates the actual MRO spacecraft vehicle, for radiation to the spacecraft through the Deep Space Network.
After an image executes onboard, the data is sent back to Earth, arriving at a server at JPL. Operations at MSSS queries for the data as soon as it is available. Images are viewed, logged, any possible problems are noted, then passed back to the Science group. Here, images are analyzed to see if they met their scientific goals, and if they don’t, they go back into the database as possible targets for upcoming cycles.
I hope this gives you some insight into the involved process that is required to take pictures of Mars. For more information about the Context Camera and the Mars Color Imager, check out the Malin Space Science Systems website at www.msss.com, and for more information on the Mars Reconnaissance Orbiter
End of podcast:
365 Days of Astronomy
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