Guest Post: A lifelong dream of Mars realized

A week ago I wrote a post about one of Northeastern’s art, media and design stu­dents spending her summer at the Jet Propul­sion Lab­o­ra­tory. As I men­tioned, Maddy San Martin’s father was instru­mental in the recent Curiosity rover landing. Miguel San Martin, Chief Engi­neer for Guid­ance, Nav­i­ga­tion & Con­trol on the Curiosity mis­sion, was kind enough to share his story with us today. Read on to learn how he became inter­ested in the work he does, the chal­lenges he and his team encoun­tered in the design of the Sky­Crane, which suc­cess­fully low­ered the rover to Mars’ sur­face, and what it was like being part of such an intense and rewarding mission.

Miguel San Martin leading the Entry Descent and Landing team into the press con­fer­ence after the Curiosity landing. Photo by NASA/​JPL-​​Caltech.

When I was a teenager I fol­lowed the progress of Viking, the first space­craft to suc­cess­fully land on Mars,  by lis­tening to the BBC on short wave radio from my family farm in the Patag­onia. It was at that point that I decided that one day I wanted to be part of a mis­sion to Mars like that. I wanted to be part of such an adven­ture; expe­ri­ence such a moment of dis­covery. What I did not know was that fate will have it that I was going to play an inte­gral role, as the Chief Engi­neer for Guid­ance, Nav­i­ga­tion & Con­trol, in  the mis­sion that fol­lowed Viking 21 years later, Mars Pathfinder. I thought that by then we would have gone back to Mars with unmanned space­craft at least more than once. Mars Pathfinder landed the first rover, Sojourner, on Mars and was an unqual­i­fied suc­cess. Then came the rovers Spirit and Oppor­tu­nity, where I played the same role. The sci­en­tific objec­tives were to find evi­dence that in the dis­tant past Mars was a warmer and wetter planet;  that it had water in the form of rivers and lakes that might have har­bored life.  It was another unqual­i­fied suc­cess and Spirit and Oppor­tu­nity proved beyond a shadow of a doubt that water once was common on Mars.

With these suc­cesses under its belt, NASA needed to follow up with a mis­sion that rep­re­sented a quantum leap in sci­ence, and thus, of rover capa­bil­i­ties. The next rover would have to have com­plex ana­lyt­ical instru­ments that could ana­lyze soil and rock sam­ples in search of organic com­pounds, like water — another indis­pens­able ingre­dient in life. The com­plexity of these instru­ments was accom­pa­nied by their huge size. A single instru­ment, of the 10 onboard, was the size of the Spirit rover. This required the rover Curiosity itself to be the size of a small car, like a Mini-​​Cooper, and with a weight of almost 900kg com­pared to 185kg for Spirit/​Opportunity. But the sci­en­tists not only wanted lo land a huge and com­plex rover on Mars but they wanted to place it with unprece­dented pre­ci­sion near places of great sci­en­tific interest. The landing place they chose for curiosity was Gale Crater. It is a 150km diam­eter crater. That in itself doesn’t sound too dif­fi­cult were it not for the fact that in the middle of the crater there is a huge 5km high moun­tain, that leaves very little room for the rover to land between the crater’s  dan­gerous rim and Mount Sharp in its center. The prover­bial landing between a rock and a hard place.

How did we solve the chal­lenges of landing a huge rover in a small place inside a crater? Once again fate will have it that both solu­tions required the engi­neering dis­ci­pline that I had spent a life­time mas­tering: Guid­ance, Nav­i­ga­tion, and Con­trol. My appren­tice­ship of  the sub­ject started at MIT, where I studied with pro­fes­sors that devel­oped the hard­ware and soft­ware that guided and nav­i­gated our astro­nauts safely to the Moon during the Apollo era.

In order to solve the problem of the pre­ci­sion landing  we incor­po­rated what we call Entry Guid­ance. In this tech­nique, as the cap­sule pro­tecting Curiosity decel­er­ates due to the aero­dy­namic fric­tion with the atmos­phere, a series of rockets con­trols the cap­sule ori­en­ta­tion to fly the vehicle like a plane to its intended target.

Landing a rover of the size of Curiosity pre­sented immense chal­lenges. Mars Pathfinder, Spirit, and Oppor­tu­nity landed using a series of airbags to cushion their impact with the ground; not very ele­gant but it did the job. For Curiosity, how­ever, just the thought of bouncing a one tone rover with airbags was laugh­able. On the other hand, landing it the old fashion way, with rockets and a 3 legged plat­form pre­sented the very annoying problem of how to dis­mount the rover perched on top of the lander at one meter over the ground. Ramps come to mind but where we could store them during the trip? There is no room inside the cap­sule. The solu­tion came in the form of what we call the Sky­Crane. In this approach the rover is deposited over the sur­face sus­pended by bri­dles which are attached to a con­trap­tion akin to a heli­copter but that uses rockets instead of pro­pellers. The only problem? It has never been tried before. Actu­ally, the Mars landing of August 5 was the first time that this approach was ever attempted anywhere.

Cel­e­brating a deserved suc­cess. Photo by NASA/​JPL-​​Caltech.

The final days prior to landing were charged with excite­ment and anx­iety, con­fi­dence and doubt. Feel­ings that are sup­posed to be the oppo­site of each other were present simul­ta­ne­ously and in per­fect har­mony. The count­down con­tinued its relent­less and unavoid­able march to zero, the instant in time that our hard work of 8 years was going to be put to the ulti­mate test. The state of mind during those days can be sum­ma­rized by the phrase George Wash­ington used to use when asked about the like­li­hood of suc­cess during the Rev­o­lu­tionary War: “We can not guar­antee suc­cess but we can deserve it”. And come landing day, we entered the con­trol room with our heads held high based on the belief that we deserved suc­cess; that we have  done every­thing that was humanly pos­sible; that we had worked dili­gently and with integrity.  Math­e­mat­i­cally the prob­a­bility of suc­cess was excel­lent, but math­e­matics often fails to model human frailty, which is com­pounded by the impos­si­bility of testing  the full system on Earth. Finally landing day came and the  seven min­utes of terror passed in a flash. Sud­denly  the words “Touch­down Con­firmed” were announced and the Con­trol Room broke into a spon­ta­neous and mad­dening cel­e­bra­tion. We have done it! We landed the biggest rover ever on Mars at only 2.2km from the target.

So, as I look back to the early days of my youth in the Patag­onia, dreaming of Mars explo­ration with robotic space­craft, I feel  extremely for­tu­nate and very happy that I was able to realize my dreams beyond my wildest expectations.