Mapping Mars

The European Space Agency (ESA) embarked on its first-ever mission to another planet with the Mars Express. One of the orbiter's key onboard instruments is the so-called High Resolution Stereo Camera (HRSC), which Gerhard Neukum, German scientist based at Berlin’s Free University, helped develop. Trying to find a lost lander unit Beagle 2, the HRSC took its first close-ups of the red planet on Friday. While there’s little hope to locate the tiny probe on the Martian surface, there are still big plans for the coming years: Neukum wants to use his camera to map at least half the planet at a resolution never achieved before.

DW-WORLD recently sat down with Neukum to discuss his project, its significance and possible commercial uses for the camera in the future.

In laymen's terms, what does the camera actually do?

The camera is a CCD (a charge-coupled device – a silicon chip whose surface is divided into light- sensitive pixels) camera similar in a way to commercially available systems that many people use in their daily lives to take pictures. It's a lense optics system, on a very large focal plain, about 14 cm wide, and there in parallel are nine CCDs mounted to take individual line images of the scene through this one single optics. There are different angles in terms of looking at the surface. This has the advantage that one can have a stereo angle right away in flying over the scene. And so the camera works in a way that nine individual image strips on the surface are build up in flying over Mars. In a push broom way, line images are taken and the camera moves forward on its trajectory in orbit and so the images build up in a swath, and so we will have nine individual image swaths. Since there are angles between the different swaths, you get a very good 3D impression of the surface after processing the data. It's not just a nice view, we'll make very precise measurements from that and we'll be able to interpret the data for what is there in terms of geologic structures and in terms of processes that formed the surface in the past. And in addition to that we will have four additional swaths for color images, three of them in the normal red, yellow and blue colors that we also use on our television and one scientifically very important one in infrared that will give us very important information about the composition of the surface materials.

Mars Express failed to contact Beagle 2 so far and there is some fear that it might actually have crashed when it landed on Mars. Is that having any effect on your work?

Not any great effect except that we will look now at the Beagle landing site very early. On Jan. 9, there will be an imaging sequence of the Beagle landing site. We will fly directly over the site and we will have highest resolution possible, that means 10 meters in the HRSC proper and about 2.3 meters per pixel in the additional, sort of tenth, channel of the HRSC, the so-called super resolution channel that is an addition to the camera proper, which functions like a magnifying glass right in the center of this swath. There we will even have 2.3 meters per pixel, so there's a chance to even see parts of the landing equipment, maybe the parachute or the air bags (of Beagle 2).

The camera actually hasn't started this mapping of the planet yet?

No. Apart from an approach image that has gone through the media from 5.5 million kilometers away, the camera has not been switched on for real data taking. We made a “go, no-go” test, that means we switched the camera on to see whether it's still alive and it's in very good health. But the real imaging sequence will start with the Beagle 2 landing site.

How long will the entire mapping take?

The whole mission time officially is two years and we will be able to cover about 50 percent of the Martian surface in that time at a resolution of 10 to 20 meters per pixel by the HRSC and a few percent of the surface in super resolution by the super resolution channel, that means around 2.3 meters resolution.

What are the challenges you face?

One challenge will be to keep up with the amount of data that would be coming in. Let's put it this way, one data take is on the order of a few giga byte of data. Compressed data, which then will have to be transferred to the Earth and will be received by the big stations, the ESA station in Australia or by the deep space network stations of NASA and then the data will be transferred from ESOC, the European Space Operations Center, to DLR (German Aerospace Center), my former institute in Berlin Adlershof, where some first processing of the data will be carried out. The data will be decompressed and then raw images will be produced.

What do they look like?

You will already see what there is on the surface, but not in the correct geometry necessarily, not necessarily in color, but individual swaths of the nine CCD channels will be visible. Then the data will be transferred to me here at the university, then validated and then further processed by me and will be given to the 43 co-investigators from 10 countries involved. We have to produce certain products from the overall data, that means 3D views or digital terrain models in general terms, color images and a number of others like thematic maps or topographic maps and so on, so there will be a multitude of individual tasks. The decompressed data will be very many gigabytes, it comes up to terabytes in the end. That is a data amount never handled before. So this is a huge task and one has to imagine sort of what it means in covering Mars. The total surface of Mars is quite comparable to the total land surface of the Earth, excluding the oceans, so it's a huge task. Not even done for the Earth. Ever. To cover this land surface at that resolution in stereo and color.

Why is it such an important thing to do?

Oh, scientifically it’s a tremendously interesting object. Mars is the most Earth-like planet among the planets on the inner solar system. Mars shows signs of formally flowing water. It may have had even oceans. It has even now gigantic volcanoes that may be even active now, we don't know really yet. But they were active until a few tens of millions of years ago. We know that already from looking at the previous images. That means from the data one can also get time information, how old Mars is. That means looking at the images and looking at the amount of superimposed impact craters give you a means of determining even the absolute age of the surface structures. And so the data are also important in this respect that we get the context of what happened when, how much water for instance was there, when in the Martian history. We'll be able to extract that from the images directly.

The Americans with their mission right now have been producing some pictures that people have said are spectacular. Are your pictures going to be as spectacular and what's the difference between them?

The pictures taken by the “Spirit” camera on the ground are quite different, even up to millimeter resolution per pixel. From the orbit we will have quite a distance, 250 km, so we will have a highest resolution of close to 2 meters. Of course we will coordinate with NASA and take highest resolution images of their landing site to see what is there in terms of geologic structures. But you cannot compare them. They’re different kind of pictures, but equally spectacular.

You said earlier that the mission lasts two years , how long will it take you then to evaluate the pictures and have them ready for presentation?

The follow-up processes that produce specific higher level products will take days normally. On Jan. 13, the real mission science phase will start and then we will plan a month ahead and of course we have a coarse plan for a two year period. We even have a coarse plan for a four year period, because we have already talked about extending this mission for another two years..

Are there any commercial uses for this camera, the data that you get?

No. Of course one can image commercial uses further down stream in the mission. You know, 3D data are very exquisite data, so the Mars fans would like to look at such data, but we are not a commercial enterprise, we will not produce such data for the commercial market, but one can imagine that in cooperation with some companies or so this could be of interest sometime downstream. But the camera itself, the hard-ware, that is a more concrete thing. It was planned by me and also by the board of DLR that the camera should be used commercially for earth remote sensing and for geometric applications on aircraft.

What would you do with those pictures?

There is quite an industry for photographing the earth, for generating 3D models, models of the topography of the earth. For instance, in the telecom industry you have to know where the mountains are or the buildings (to choose spots for cell phone antennae.) Or urban planning. The camera was used for taking sharp images of Ground Zero in Manhattan. Film-based system are not capable of doing that, so the HRSC was the only one to be used and to produce good results. We have flown the camera on aircraft over five years now. A company was founded by me and a few others from my former institute but this came to an abrupt end by a contrary decision of the DLR board and this was one of the reasons why I thought I should leave DLR and go back to the university. It's not dead yet, the idea to commercialize the HRSC, but it will certainly not be done by my former organization DLR, because it was stopped there.