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The Planetary Society Weblog

By Emily Lakdawalla

Mars Renaissance Orbiter

Oct. 4, 2006 | 18:37 PDT | Oct. 5 01:37 UTC

Weblog Archive

by Doug Ellison

No, not a typo! Mars Reconnaissance Orbiter (MRO) is the renaissance man of Mars exploration -- defined as "a modern scholar who is in a position to acquire more than superficial knowledge about many different interests". A good description of MRO -- with three ticks under ‘high resolution' for special, spectral, and temporal study of Mars. Tuesday saw Jim Graf's presentation about the "Status of Mars Reconnaissance Orbiter Mission." Jim is the MRO Project Manager, so it was a packed session in the largest technical session lecture room. This glog-entry is an overview of Jim's paper and MRO in general over the past year or so.

As most of you will know, MRO launched in August 2005 and successfully arrived in orbit in March 2006. This initial orbit was highly elongated -- 400 km by 45,000 km and 35 hours long. Before starting the aerobraking process to reduce that to the final science orbit, four of the six instruments onboard were checked out -- the three cameras HiRISE, CTX, and MARCI all functioned well and those results have been public since late March/early April. The Mars Climate Sounder was the last of the four to be checked out before aerobraking. MCS has a very long and tortured history. It was first designed to be flown on the Mars Observer mission in 1992 which was lost due to a failed launch. A new instrument was built for the Mars Climate Orbiter, but that was also lost. The new version, Mars Climate Sounder, was a considerably lighter and more accurate instrument than the first and was fitted onboard MRO and finally delivered safely into Mars orbit. It was checked out before aerobraking and took an ‘image' of Mars that again, you will have seen previously but also an unreleased image that I thought was fantastic when I saw it in Jim's paper -- a self portrait of the spacecraft science deck!

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MRO Self Portrait
The Mars Climate Sounder aboard Mars Reconnaissance Orbiter took this "self portrait" of the suite of instruments on the science deck. Three other science instruments are visible -- HiRISE, CRISM, and MARCI as well as the Electra UHF relay antenna, one of the two solar panels, and a cluster of thrusters on a corner of the spacecraft. Credit: JPL / NASA

Not the prettiest image you'll ever see, but I think it's great -- in the same way I loved the reflection of one of the front Hazcams onboard one of the Mars Exploration Rovers as seen in the metallic electronics box of the Microscopic imager and the Mars Global Surveyor MOC images of Mars Odyssey and Mars Express. Not pretty, but pretty awesome. The MCS image shows some great detail -- even the spider that holds the secondary mirror at the top of the optical tube assembly for HiRISE. The same technique has since been used to partially verify the deployment of the SHARAD antenna.

After that checkout of four instruments -- the periapsis of the spacecraft was lowered to "brush" the atmosphere. Aerobraking is HUGE benefit for missions like this, and we can thank the Magellan mission which first tested the technique around Venus nearly 15 years ago. Aerobraking actually saved the spacecraft 1184 m/sec of "delta v" (the measure of a spacecraft's ability to change its speed) -- or to put it another way, the orbit insertion burn used 777 kg of fuel and aerobraking effectively did the work of a further 600 kg of fuel. They had 426 passes at around 100 km altitude over a period of 5 months. This wasn't a cake walk -- the atmosphere of Mars is a changeable beast and from one aerobraking pass to another they observed changes in the density of the atmosphere and thus the amount of braking they received each time around. However, a few weeks ago, the orbit had been reduced enough to raise the spacecraft out of the upper atmosphere and finish up the process of putting the spacecraft into its final science orbit of 255 x 320 km using the onboard thrusters.

By mid September, the spacecraft was ready to do two final deployments and instrument checkouts. Firstly, the SHARAD instrument, a shallow radar relative of the MARSIS instrument onboard Mars Express. SHARAD has a pair of antennae that total 10 m in length that "ping" the surface of Mars and listen for the radio reflection from not only the surface but also any subsurface layers. There were a lot of worries about the MARSIS deployment in 2004, and it was delayed significantly. SHARAD would have wobbled around and could well have been damaged if it was deployed before aerobraking, so it was done after aerobraking was finished. It deployed successfully, and Jim was able to show one of the first "traces" by SHARAD over an area of Mars near to where MARSIS had observed a subsurface layer under a polar icecap. I can't share the image with you, but it looked very similar to the MARSIS pass and I am sure the SHARAD team will be releasing their initial few passes in the next few weeks. SHARAD does not penetrate as deeply as MARSIS but has better resolution in the depth it can see -- the two instruments complement each other well and are made by the same team from JPL and Italy.

Finally, the CRISM spectrometer which is a very high resolution instrument that samples pixels of around 15-20 metres on the ground in nearly 500 wavelengths from the visible through to the infrared to identify mineral signatures got its "first light" moment. It had a cover over its 10-cm wide optical tube to protect the instrument during aerobraking, but it has now successfully deployed and has started returning data. Here's the first targeted observation by CRISM, taken at 1511UT on Sept 29th.

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CRISM "First Light"
This CRISM targeted observation of Ius Chasma was acquired on September 29, 2006 and covers an area of 8 by 5 miles (13 by 9 kilometers). Credit: NASA / JPL / JHUAPL / Brown University

Now that image in itself doesn't look like much -- typical Marsey colours of a typical Marsey terrain, all a bit beige and boring -- but that's the visible range. When you go into the infrared, you get a lot more variety and variation, and you can begin to tell something about the minerals on the ground. The initial plan is to do a global survey using only about an eighth of the wavelengths, and then revisit the interesting areas with all 544 wavelengths to get an even better look at what is on the ground.

Jim was able to present other images from MRO taken from the science orbit within the past week -- MARCI produces daily colour images of the entire planet and is, in effect, a Mars weather satellite. A stunning image at around 1km/pixel of one of the poles was presented, as well as come fantastic images from CTX -- the context imager that comes from the same stable as MARCI: Malin Space Science Systems (MSSS). I hope they will release these soon as they truly are beautiful images which I only wish I could share with you now.

With all this great news, I was particularly disappointed to see that Malin Space Science Systems have stopped doing their daily image releases from the MOC camera on Mars Global Surveyor. MOC has been producing extraordinary images of Mars for nine years and has revolutionised our understanding of the planet, and it's a pity that at the same time its contribution might be overshadowed by a bigger more modern spacecraft, it's continuing contribution to our understanding of Mars may become overlooked and it will not get the credit it deserves because of the tight budget the mission is running on. I thought it right to show what the MOC team consider one of their favourite images as a firm doff of the cap to all that MGS and MOC have shown us and will continue to show us about Mars.

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Fine Layering in Martian Crater
Subframe of a Mars Global Surveyor Mars Orbiter Camera image of very fine layering in a crater floor in western Arabia Terra. Image approx 1.5 km on a side and 1.5 m/pixel. Read more about this image. Credit: NASA/JPL/MSSS

What I CAN share with you -- and in fact I am sure most of you have been abusing your internet connection in downloading these already -- are the utterly astonishing images from HiRISE. Jim showed a few bits and pieces from HiRISE now that it is in its final science orbit. I'm just going to show you my two favourite little pieces of HiRISE imagery from the first dozen or so that have been released so far, but I urge to run, not walk, to the HiRISE website and look at all of them for yourself. Both of these are just 100 x 100 metres on the surface -- about the size of a couple of football/soccer/athletics fields side by side. The first is a 50cm/pixel image (which I've blown up to 200%) of a segment of the Cerberus Fossae rift system. The rift itself is 300 metres across and 90 metres deep -- this is just part of its northern edge. The dynamic range of the camera really shows here -- look how well it can still see fine detail in the shadow of the cliff wall -- and we have incredibly fine details of a dune system at the bottom -- dunes about 2 metres across -- the sort of size of many of the ripples and dunes we've seen at Meridiani Planum

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HiRise Examines Cerberus Fossae
Small 100 x 100 metre subframe of an early Mars Reconnaissance Oriber HiRISE image of a segment of the Cerberus Fossae rift system. Credit: JPL / NASA / U. of Ariz HiRISE Team

The second subframe is the full-fat, double espresso, make mine a double, 25cm/pixel resolution that HiRISE can manage. This is actually part of the very first science orbit HiRISE image taken of Ius Chasma, part of the Valles Marineris network and target of that CRISM image I showed you above. Again – 100 x 100 metres, but a genuine 25cm/pixel (not resized). I picked this one because it really shows the resolving power of HiRISE. See the bright boulder with a shadow on the right hand side of the image about a third of the way from the bottom? That boulder is about 1.2 metres across and is casting a shadow 2 metres long. So why do I care about that boulder? That shadow is about the same size as a Mars Exploration Rover would appear from HiRISE -- an MER is approx 1.6 x 2.3 metres seen from above. When HiRISE images an MER, we should even be able to see a little bit of structure. The MGS MOC team did an awesome job of capturing both rovers several times as a dark pixel or two -- but that was more of a point on a map rather than a feature we can identify and relate to -- perhaps even a shadow that will show the camera mast and quite probably some wheel tracks as well.

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HiRise's Close Eye on Mars
Small 100 x 100 meter subframe of an early Mars Reconnaissance Orbiter HiRISE image showing meter-scale boulders on the floor of Ius Chasma. Credit: JPL / NASA / U. of Ariz HiRISE Team

I can't wait to see places I know so well -- Gusev crater and the Columbia Hills, Meridiani Planum, Endurance Crater, Eagle Crater, VICTORIA CRATER for goodness sake. That first subframe the HiRISE team released covered an area of only 600 x 400 metres and whilst putting my jaw in the full dropped position, I realised that Victoria Crater would not even fit into that field of view. Every image is going to be a little adventure of exploration scrolling around the terrain at a level that is one can relate to more easily.

Today ( Wednesday ) lunchtime my "not-stalking-Jim-Graf" plan paid off and I resorted to basically ambushing him as he was walking through the central lobby of the conference venue with two very large tubes under an arm. I wanted to ask two things….could I grab that great MCS image from his paper and include it here (he said yes…thank you Jim) and also, I wanted to know how much of that bandwidth I talked about yesterday is occupied by HiRISE images. I automatically thought, as I'm sure many of you might, that a camera that can take an image of 1,200 Megapixels very easily would be the big fat greedy instrument of the payload, stealing all the bandwidth and leaving the others to pick up whatever it left. However, this is far from the truth! SHARAD and CTX are about 20% of the data budget each and for the top-honours it's a close call between HiRISE and CRISM, with CRISM probably taking just a little bit more than HiRISE -- 25 or so percent each -- MARCI and MCS consume the rest of the budget, very little compared to the others. They were to be the primary payload for the lost Climate Orbiter, so it just goes to highlight how big a jump in downlink capacity MRO is when the primary two instruments of a mission find themselves very much the little guys of this new mission. MARCI and MCS will, perhaps for that reason, be left running during the next few weeks as solar conjunction brings this initial exciting glut of data to a close until the science campaign starts in earnest in November.

For those who like analogies, solar conjunction is when the Sun gets in the way of the line of sight between Mars and Earth so using radio communications for around two weeks at that time is a little like trying to whisper across a loud dance floor…you're just not going to be heard. For that reason, all spacecraft on Mars (or indeed anywhere when they experience conjunction) tend to be put into a quiescent mode to look after themselves whilst they're out of touch. As a Mars enthusiast, the second half of October will be a fortnight of cold turkey with nothing from Spirit or Opportunity OR our new big shiny orbiter. But with the images we already have and whatever other images they reveal at two NASA press conferences I've seen scheduled on NASA TV for Friday and Monday (these are a must see and I will try and report on Friday's before heading home from Valencia) -- I think I'll manage. Under his arm, Jim had a print out of just ¼ of that first science orbit image printed out about 1.5 x 1.5 metres. I helped him find somewhere to hang it up as the conference organisers were not being too helpful -- but they should have been…all afternoon there were two or three people just staring at it for minutes and minutes and minutes. HiRISE has been described as "the people's camera" as they intend to release most of the images quite quickly onto the web and even schedule a few observations a month based on public suggestions -- something pioneered by MGS MOC.

So far, the people very much approve. My advice is to buy stock in hard drive manufacturers because if MRO can last as long as MGS…we'll all need much MUCH bigger hard drives.