Curiosity

by Rod Pyle

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  Conclusion. Historically, NASA has found the probability that schedule-impacting problems will arise is commensurate with the complexity of the project. MSL is one of NASA's most technologically complex projects to date. Accordingly, we are concerned that unanticipated problems arising during final integration and testing of MSL, as well as technical complications resulting from outstanding P/FRs, could cause cost and schedule impacts that will consume the current funding and threaten efforts to complete development and launch on the current schedule. Similarly, we are concerned that the limited remaining schedule margin may increase pressure on NASA to accept reduced capabilities in order to meet the approaching launch window and avoid another 2-year delay that would require significant redesign at a cost of at least $570 million or cancel the mission.

  So there you have it…mostly. This is a very abbreviated version of just the report's overview; it goes on for another forty-two pages in excruciating detail. But that is how proper audits are done. Don't you wish that all government-procurement programs were this transparent? One of NASA's great challenges since the early days is that, being a civilian agency, everything it does is in the full glare of public scrutiny, the media limelight, and the squinty eyes of hostile congresspeople and representatives. The money that must be spent just to maintain transparency, to report on the proceedings, is in itself blinding. And while it contributes to accountability, dollars spent on audits are not spent on flying to Mars or to the space station. It can be highly frustrating, and it is never easy to be this self-critical, especially when so many others are ready to pounce on every word. “See? I told you this government bureaucracy if full of pork and waste!” and so forth, ad nauseam. Yes, there can be issues, and there may even be occasional waste (though you are very unlikely to see it when you visit JPL—trust me on this). But overall it's a pretty tightly run ship.

  Perhaps most important: if the agency was not at the whim of two- and four-year election cycles, shifting administrative priorities, and home-state-driven representatives, and if it could actually plan a decade ahead (like China's space program does, to its everlasting benefit), American space exploration would be a different story. But that is not how our system works, and until it does, agencies like NASA that run programs that span multiple presidential administrations will likely have to estimate low and then suffer the consequences. Just try not to be too alarmed when the budgets begin to pass the estimates—because those estimates were probably not realistic to begin with.

  The scope of the program had expanded and the subsequent delays had cost money. MSL had slipped by a full two-year launch cycle, and besides incurring more expense, it threw the life schedules of 480 participating scientists and countless engineers, programmers, technicians, lunch servers, and a large janitorial staff into disarray. The launch delay had a bright side too, however, as many of the critical issues that were dogging the engineers in particular now had another year plus to get ironed out. In the end, it may well have contributed to the mission's success.

  And now for some self-indulgence. I've been obsessed with space since early childhood, and with Mars just about as long. This began during the second act of the space race, the early 1960s. It was still not proven whether or not there were vast forests of lichen, leafy plants, or perhaps even evolved life on Mars. Admittedly, much had changed since the days of Percival Lowell. Others had made extensive telescopic observations, and few saw the canals or oases he and Schiaparelli did. Some used spectroscopes and found little moisture in the atmosphere, and still others determined that the air pressure there was about 1/1000 of Earth's. It was not a promising set of observations for those of us still hoping to find a Lowellian Mars.

  The Mars of Lowell, Edgar Rice Burroughs, and Ray Bradbury was rapidly vanishing. My Star Trek–inspired visions of green-skinned Orion dancing girls was, reluctantly, evaporating with them.

  Then Mariner 4 flew past the red planet and the Martian empire, whether plant or intelligent beings, was toast. What was left was a dry, forbidding expanse. I was not a happy camper.

  Of course, this was also the era of Apollo, so there were other obsessions to be indulged. But Mars was never far from my mind. It was pretty certain by then that the Victorian vision of a Venus populated with riotous jungles and dinosaurs stomping across that steamy world did not exist, and ultimately the planet turned out to be a hellhole. And long before, the other planets had been discounted as places where beings could live—Mercury was too hot, and the gas giants—Jupiter, Saturn, Neptune and Uranus—were wholly inhospitable. And poor Pluto later lost planetary status, being demoted to a “dwarf planet.” The solar system beyond Earth was rapidly becoming a lousy place for people—human or otherwise. Mars had joined the unfortunate, forbidding list.

  When I was about ten, the year after that evil Mariner 4 forever ruined Barsoom, my father took me to Griffith Observatory in the hills above Hollywood. We spent the afternoon looking through the museum and seeing the planetarium show. Then evening came, and from the building's roof, Los Angeles spread out gleaming like a bejeweled carpet. It was a magical scene, but nothing compared with was yet to come.

  Soon after dusk, the door to Griffith Observatory's telescope building opened. There were three green-patinated copper domes on the roof of the museum—one for the planetarium, one for a solar telescope, and the third for the astronomical telescope. The public was invited in—as they were every clear night except Monday—to view whatever was on the menu for the evening. The instrument was a twelve-inch-diameter refracting telescope that had been ordered from Carl Zeiss in prewar Jena, Germany, in 1930. It was among the finer instruments of its size for the time. The telescope's mount tracked the celestial motions with a rather-elaborate clock drive, electrically powered and with huge knife switches and bulky glass insulators, that strongly resembled something Dr. Frankenstein would covet. I liked it too.

  Fig. 14.1. GRIFFITH OBSERVATORY: Built by the Works Progress Administration, Griffith Observatory opened in 1935 and included a planetarium, a science museum, and two telescopes—one solar and one celestial. Griffith Observatory has inspired generations of youth toward space and astronomy. Image from klotz.

  A fine older gentleman named Gordon Mitchell was the telescope demonstrator that evening. He was very good with kids and made me feel like the most important person in the universe for a night. I was led up the wooden steps to the eyepiece, and there before me, against a deep-black field, was Mars.

  As noted previously, the best telescopes yield a hazy, wavering red orb. In a smaller instrument, above the brightly lit and smoggy LA landscape, it was definitely suboptimal viewing. But it was still Mars—my Mars—and that first viewing has become a cherished memory.

  I asked endless questions until my father took the cue and ushered me out, as there were other children, some surely as starstruck as I was, waiting in line.

  When I was eighteen, I would return to the observatory as an employee—a museum guide. Two years later I was in charge of the guide staff. It was the best part-time job I could imagine while in college, and I stayed there for almost seven years. Many others have stayed far longer; some whom I shared that time with still work there—it's that kind of place.

  As employees we had full run of the building, and we were put in charge after 6:00 p.m. I had keys to virtually everything, and the Zeiss telescope was freed up after we closed for the evening. The demonstrator from my youth, Gordon Mitchell, still worked there and would often turn the telescope to the object of our choice after hours. There we would stay, exploring the cosmos until the wee hours. It was fantastic.

  Meanwhile, I struggled through classes in UCLA's astronomy department. Then, in 1976, Viking 1 was scheduled to land on Mars on July 20th. I did not have the pull or connections to get into JPL at the time, but I did live only a few miles from Caltech, which manages JPL. I suspected that they would be hosting a live video link (quite exotic for the time), so I headed down at the requisite hour and,
um, found my way into the auditorium. As I recall, it was not open to the public, but that was not about to stop this space-obsessed young man.

  I stood near the back of the auditorium with a hundred others for whom there were not enough seats. There was a large, movie-sized video projection on the screen onstage. The room fell silent as the final minutes of the descent from orbit were relayed from JPL's mission control, a few miles to the north. We all knew that the transmissions were delayed by close to twenty minutes, and that success or failure had already occurred. But it felt live, and to a person the attendees were swept up in the moment.

  Down, down Viking went. Nobody had any real idea what awaited it in the Chryse Planitia region—the orbital mapping was just not good enough then. The area had the virtue of holding some geologic interest as well as appearing to be relatively safe, but there was really no way to know. There was a lot of guesswork involved in selecting landing sites at the time, and a thousand kinds of surface features—invisible from orbit in 1976—could destroy the spacecraft instantly. It was the era of the “Big Dumb Lander,” as JPL’ers would later refer to the Viking surface probes, and it was anybody's guess how it would end.

  A few minutes later, a safe touchdown was confirmed. Where the Soviet probes had failed just a few years prior, the United States had succeeded brilliantly, and in the year of the American bicentennial, too. It was just fantastic, as Rob Manning would later say—frequently—about his Mars missions. I couldn't agree more.

  Immediately after landing, the cameras were turned on and began sending down the first image from Mars. Contrary to the expectations of many, it would not be a magnificent color panorama of the landscape, but a black-and-white shot of a footpad on Martian soil. The engineers wanted to make certain that the spacecraft had landed level, and on solid ground.

  Strip by strip, top to bottom, the picture came in a line at a time, moving left to right. It was completed over the course of a few minutes. Though it was a monochromic image, the primitive video projectors ended up displaying it as purple. But I didn't care—I was looking at the surface of Mars!

  The next day, the first color landscape shot was delivered, and what a photo it was. Newspapers and TV reports carried it across the globe. It was amazing—deep saturated red soil and bluish sky (the image was later corrected to reflect a more accurate salmon-colored skyline, to which a few snarky reporters attending the press conference responded with the likes of “What's it gonna be tomorrow? Green?” Some people just don't appreciate the difficulties of planetary exploration).

  Over the next decade, the pursuit of girlfriends, a long trip around the world, and a career in television would pull me away from Griffith Observatory, the space program, and the red planet. But not for long. And I never forgot the Mars I was able to explore at Gordon Mitchell's telescope at the tender age of ten, nor that first image from Viking.

  We now return you to our regularly scheduled chapters. Thanks for listening.

  On November 26, 2011, at just past 10:00 a.m., the Mars Science Laboratory spacecraft departed Cape Canaveral, Florida, from Launch Complex 41. It's a pad reserved for unmanned launches, smaller and less elaborate than the one you were used to seeing the shuttle launch from in the past. The rocket was an Atlas V, and while there is one larger booster in the US arsenal (the Delta IV Heavy), the Atlas makes a heck of a racket when it departs. I watched an Atlas V launch in 2009 from about six or seven miles away with my thirteen-year-old son, and the look of shock and awe on his face was gratifying. Not as booming and grand as a shuttle launch, but plenty loud.

  There had been the usual last-minute checks and tweaks before the MSL launch, but in addition, there had been some eleventh-hour drama beyond the norm. An issue with the drill—a potential short-circuit-causing defect—had been discovered, and Rob Manning and his team had quickly designed and implemented some last-minute fixes. It was a close thing.

  The first stage burned as planned and dropped off to break up over the Atlantic. The second stage, called a Centaur, pushed MSL the rest of the way toward escape velocity. Both the Atlas and the Centaur are part of the old guard of American rockets, though the Atlas has been substantially changed since the early days (in fact, the first stage is now powered by—heavens!—Russian rocket engines). Both are reliable, proven designs, and both did their jobs that day.

  MSL shed the Centaur once it was on its way to Mars. But before it cut loose, the spacecraft was set spinning at two revolutions per minute along its center axis for its long trip. This continually changes the side of the spacecraft exposed to the sun, equalizing temperatures across the structure. It also provides stability for the craft, in the same way that imparting spin to a football when thrown causes it to fly straight.

  The entire spacecraft now consisted of the Curiosity rover and its landing rockets, enclosed in a cone-shaped aeroshell, and a cruise stage. The cruise stage was a ring-shaped unit that had its own rocket motors and power system. Its rockets, intended for course corrections, were small ones, using a nasty monopropellant (a fuel that does not require a separate tank of oxidizer like liquid oxygen) called hydrazine. Besides being highly toxic, hydrazine is, as you might imagine, highly reactive. I have heard that the engineers who worked at Grumman Aerospace in the 1960s, building Apollo's lunar module, used to show the new guys just how reactive monopropellants were with a graphic demonstration. They would take the newbie outside, preferably in the winter, squirt some hydrazine onto a frozen bush, and watch it explode. If true, this exercise would have made the point with little discussion.

  The spacecraft made the 352-million-mile crossing to Mars in just over eight months without mishap, then the cruise stage separated from the lander's aeroshell ten minutes before atmospheric entry. The spacecraft then used small rockets to cancel out the spin imparted when it left Earth. It was now flying blunt end first and heading directly for Mars. And here is where it got really interesting.

  I'm sure you have seen the “7 Minutes of Terror” video that JPL posted online before the MSL launch. It was a nicely crafted and exciting piece dramatically illustrating the entry, descent, and landing (EDL) phase of MSL. If you are one of the five or ten people with access to the Internet who have not seen it, treat yourself. Besides being highly informative, it's also fun. It will also introduce you to Adam Steltzner, the engineer in charge of the EDL sequence who became known as “NASA's Elvis” due to the pompadour he sports. Turns out he is also a highly entertaining informer.

  The main point here is that the MSL spacecraft went right from interplanetary cruise into the Martian atmosphere like a bullet. None of this “let's go into orbit, pick a nice place to set down, and then land” stuff from the Viking days. From Pathfinder onward, all the missions had simply aimed the spacecraft at where Mars would be in eight to nine months and scored a bull's-eye. The orbital missions have it a bit better: when they reach Mars, they use a technique called aerobraking, in which they go into a large, lopsided orbit, dipping into the thin atmosphere over a period of months to scrub off speed and reach a nice, stable orbit. Not so the landers—they just barrel in and land.

  When MSL reached Mars, it was traveling at over 13,000 mph. That's fast. The upper Martian atmosphere is 1/1,000 the pressure of Earth's and not dense enough to slow an incoming spacecraft anything like Earth's far thicker atmosphere slowed Apollo capsules or the space shuttle. A heat shield and parachute are not enough to slow a heavy lander to a gentle landing on Mars. Something more complex is needed.

  Fig. 15.1. NASA'S ELVIS: Adam Steltzner, who gained fame in JPL's viral video “7 Minutes of Terror,” was in charge of the entry, descent, and landing (EDL) phase of MSL's mission. Credited (along with “Mohawk Guy” Bobak Ferdowsi) with helping to make NASA “cool” again, Steltzner came to his career choice later in life after spending time in his twenties in a rock ‘n’ roll band. Image from NASA/JPL-Caltech.

  Here's where I will start to go Tom Clancy on you—so prepare yourselves.

  Anyone who
has followed the MSL mission knows that it has a high degree of autonomy in its surface operations. It was the same story in space, especially in the final phases of the journey. JPL had defined the landing zone, or “landing ellipse” in their terminology, at about twelve miles long by five miles wide. The long axis corresponds with the direction of flight. The width is determined by any deviation from the straight line as the spacecraft comes in for a landing. It was a far smaller zone than ever attempted, and it would require far greater accuracy.

  Curiosity was headed for Gale Crater. At its widest point, Gale was still twenty-five miles smaller than the MER's landing ellipse's long axis. And with Mount Sharp dominating its center, the strip of real estate deemed safe for landing was small indeed. This would require unprecedented levels of accuracy and control. A carefully controlled, guided entry through the upper atmosphere, driven by a relatively powerful computer, would be needed.

  And MSL did possess a much more powerful computer than its predecessors. Though sluggish by the off-the-shelf standards of the time, it was the most modern, affordable, radiation-hardened chip available, and it was perfect for the intended set of tasks. It was called a RAD750 PowerPC chip, a descendant of the Motorola CPUs that Apple used in its G3 Macintosh computers around the turn of the twenty-first century. It was still ten times as powerful as those used on MER, and with the highly efficient and dense software written by JPL, it would do the job handsomely. For those who enjoy the numbers, it has 10.4 million transistors (MER had 1.1 million), runs at a maximum of 200 MHz (MER ran at 20), and has access to two gigabytes of flash memory. There are two identical units on board the rover, one primary and one backup.

  For landing, the computer had a set of parameters and values preloaded and was capable of making many of its own decisions as it hurtled into the Martian atmosphere. It knew where Mars was in three-dimensional space (due to exacting and recently updated calculations provided by the ground), and it knew where it was in three-dimensional space (via Earth-based measurements and its own onboard inertial measuring systems). It also had multiple thrusters mounted to the outside of the aeroshell to give it maneuvering capability to make any needed corrections as it headed in. As the spacecraft got closer to the surface, the onboard computers were able to keep the landing zone's location in the navigational crosshairs and adjust the trajectory in real time. MSL was now headed in the right direction; all it had to do was track the target and survive the landing.