On Easter Sunday, HiRISE took two observations of the Martian satellite Phobos. This is the larger of the red planet’s two satellites. We took two color images at slightly different angles, so we could combine them to make a three-dimensional stereo image.

It was another special sequence that had to be specially designed, commanded, tested and re-tested before it executes on board the spacecraft. Many people from JPL and LMA worked to make this happen, as well as almost everyone on the uplink team here at HiROC. In addition, the date chosen meant that people had to come in and work on a holiday to support it. So we were thrilled when the images arrived Sunday night, and we saw that they are PERFECT! The focus, timing, and pointing were bang-on, and we got a beautiful exposure of the satellite in both images.

I wish I could give you a sneak peak, but we’re still processing the images. The downlink group has to do a lot of work on special images like these. Because they’re not normal Mars images, the normal calibration routines and processing pipelines can’t be used. Much of this work has to be done by hand. We’re also trying to get some additional products together that we don’t usually release; I think you’ll like them!

So this is really just a teaser. We’re planning on releasing the Phobos images next week, so keep an eye on the website! In the meantime, here’s a warmup act: views of Phobos from previous missions, MGS (above right) and Mars Express (left).

ETA: The data are now available here: http://www.uahirise.org/phobos.php

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.