Using the HiRISE camera to take a special observation of a non-Mars target is a difficult but always interesting event for HiRISE Operations. While we have developed somewhat of a routine for regular imaging of the Martian surface, special observations require additional work that impacts our normal workflow as well as the science gathering of the other instruments onboard the Mars Reconnaissance Orbiter. Targeting specialists from Uplink already have so much work to do on a routine basis; adding in a special observation adds that much more work. Special observations are selected because they offer some scientific value that warrants the extra time, effort, and delay in routine science gathering.

We do not accept requests from the public directly regarding special observations.  Our very knowledgeable science team determines months in advance that the right geometry for a unique observation of a non-Mars target with scientific value is coming up. Over several iterations between Uplink and the science team, the target is planned in detail. For a target like Deimos, the smaller and more distant moon of Mars, the spacecraft needs to slew away from Mars to point the camera correctly. This is a dance that requires coordination between HiRISE, the other instruments (who will generally not be observing during this period), and the MRO platform.

For this opportunity,  we took two images of Deimos. The plan was to capture Deimos in the center of our CCD array so that the satellite would fall across our RED, BG, and IR color filters.  Uplink did a fantastic job with their targeting!  In the first observation – ESP_012065_9000 – Deimos lay across two channels of each color filter at the center of our array: RED4_0 and RED5_1, BG12_0 and BG13_1, and IR10_0 and IR11_1.  In the second observation – ESP_012068_9000 – Deimos was fully contained within RED5_1, BG13_1, and IR11_1. You can find more information about these observations here.

What did it take for Downlink to put these images together?  Well, Audrie and I came in on a Sunday (!) to wait for the observations.  Then I spent some time putting together preliminary images to send out to the team. During the following week I worked on registering the color filters to create the false color images.  See both images side by side here. Notice that green fringe around the first observation on the left? That is a bit of misregistration, something I could not seem to correct despite tweaking the position of the three color layers a pixel at a time. The first observation also required two separate stacks: (1) RED4_0, BG12_0, and IR10_0, and (2) RED5_1, BG13_1, and IR11_1.  After registering the two sides separately, I stitched them together using an ISIS tool called hiccdstitch.  That little notch you see at the top of the first observation is how the two sides almost but not quite line up. The two sides are slightly offset because their geometry is just slightly different.

Compared to the first observation, the second observation, confined to one channel each in the color filters, was wonderful to work with: no color balancing required, no stitching, and a relatively easy registration process!

GuyMac also helped make these Deimos observations a little easier to deal with than past special observations: he created a custom version of one of our processing pipelines that sharpens the image and brings out the colors a little bit. Once I had the observations registered, all I had to do was run them through his script for the really nice false color products you are now enjoying!

A while ago we posted a list of Frequently Asked Questions: http://hirise.lpl.arizona.edu/faq/ (There are also links to this over on the right of the HiBlog, and on the menu at the top of all of our HiRISE pages.)

A lot of these FAQ have to do with the different data products we release, and how we plan and process the images. There are also definitions of some of the terms we use, which we know can be confusing! Hopefully you’ll find these helpful. If you have questions about HiRISE images, how we work, or anything else, check out our FAQ. If your question isn’t answered in there, please ask us your questions below in the comments. We’ll try our best to answer them, and the FAQ will grow!

One FAQ I’d like to address is, “Why don’t you take an image of X?” where “X” is the asker’s favorite spot on Mars or other celestial body. My answer:

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It seems that things are (dare I say?) settling down into a routine here at HiROC. As the cycles progress, we get a little better with each one: software tools are being developed, our procedures are being refined, and we’re becoming more adept and making fewer mistakes (hopefully!). Of course, there are always little interruptions and semi-emergencies that preclude relaxing too much.
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Sorry we haven’t been posting much lately!

To tell the truth, some of us are experiencing a little bit of a lull. We’re in conjunction right now — this means that the Sun is directly between Earth and Mars, so we can’t communicate with the spacecraft. (Here’s a link with a few diagrams to illustrate this.)

The HiRISE instrument is turned off, and we’re not taking any images. However, there are other activities going on at HiROC….

We start imaging again on November 8, and a few of us are already planning for that. PSP, the Primary Science Phase, is divided into two-week cycles. The first cycle is rm001, the second rm002, etc. Each cycle has a Targeting Specialist assigned to it (this one isn’t me, or I wouldn’t have time to write this!). The Targeting Specialist works with a member of the science team, the “Co-Investigator of the Pay Period,” (”pay period” because of the two-week cycle) or CIPP. The CIPP helps to choose scientifically important targets, and the Targeting Specialist does the scheduling and commanding. They work together on coordinating with other teams, choosing camera parameters, etc. There are a lot of details that need to be worked out!

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Let us speak of HiRISE image names…

Every HiRISE image (or “observation”) is identified by a unique ID. Think of this observation ID as the name of the image. The basic form of the ID has three parts: a mission phase, an orbit number, and a target code. Our first transition phase image, for example, is TRA_000823_1720.

The mission phase is a three-letter abbreviation. “TRA” is the transition phase. Starting in November, you’ll be seeing “PSP” for “primary science phase,” which lasts for two Earth years.

The orbit number is a six-digit, zero-padded number. “000823″ is the eight hundred twenty-third orbit of MRO around Mars. MRO is in a roughly polar orbit around Mars, meaning the orbit is nearly perpendicular to the planet’s equator; this sort of orbit is typical of missions designed for mapping, because it provides coverage of the entire planet. The orbit number increments by one whenever we cross the planet’s equator on the nighttime side.

The target code indicates the target of the observation. If the number is between 0000 and 3595, it is the angle between the nighttime equator and the latitude of the center of the observation, multiplied by 10. It is measured to the nearest half-degree. The nighttime equator is 0000, the south pole is 0900, the daytime equator is 1800, and the north pole is 2700. 1720 is at latitude 8° S.

If the target code is between 9000 and 9303, it indicates an off-planet target, such as Deimos, Phobos, or a star.

And that’s how you identify a HiRISE image. In practice, the HiRISE team talks about them by dropping the mission phase code and the orbit number padding. Our first image is simply “823 1720″ amongst the team. Formally, however, it will always be TRA_000823_1720.