by Roger Wiens
With five days to go, the entry, descent, and landing (EDL) team radiated the command for Curiosity to execute its autonomous entry. Because the spacecraft had to complete the whole sequence on its own, all the actions were bundled into a single command called “Do_EDL.” After the last trajectory correction maneuver had been made, there was nothing more the EDL crew could do except to sit back and watch. When we heard that the command had been sent, it gave us the sense that the landing, the event we had been anticipating for so long, was imminent. Even if we did nothing in the next five days, Curiosity would land on its own.
Given the size and importance of this mission, news about the Curiosity landing was making strong competition for the summer Olympics. The event would not happen at prime time in the Western world. It would take place at 10:30 P.M. Pacific Time. On the East Coast of the United States, that would be in the middle of the night, and early morning in Europe. In spite of that, the whole world seemed interested in “watching” the landing.
There would in fact be almost nothing to see from Mars, as Curiosity would not be able to take any pictures for the first part of EDL. It would be protected inside the capsule at that time. The pictures taken during the parachute release and Sky Crane descent would not become available until several days later, after the rover’s high-gain antenna was deployed. The main information available during descent would be a continuous radio signal. In itself this signal would carry little information, except that the spacecraft was alive. It was referred to as a “heartbeat” because of this role. However, by carefully measuring the radio signal frequency, engineers could also determine the exact speed of Curiosity relative to the receiving antennae on Earth. And from that they could tell whether its trajectory, its parachute deployment, its Sky Crane maneuvers were proceeding as planned. Embedded in this signal were also a few bits of data on critical events. The signals would take long enough to travel to Earth that the rover would have already touched the ground in one way or another before we ever received the signals that it had started the entry sequence—a 13.8-minute time delay.
Of course, a continuous heartbeat all the way to the surface of Mars didn’t guarantee success. The rover could land upside down by some malevolent quirk of fate, like a dying beetle with its feet in the air. Or it could end up on the ground without its wheels locked into position, crippled in place. As soon as it landed, Curiosity had instructions to snap a couple of pictures to show its wheels on the ground. These pictures would be taken with the rover’s Hazcams (short for Hazard Avoidance Cameras), which were designed to provide images of any hazards Curiosity encountered so the vehicle could navigate around them. Thumbnails of the images would be uplinked before the Odyssey spacecraft, the relay satellite, passed below the horizon. The uplink would use a low-gain antenna, that is, an antenna with a broad radiowave beam width. Only about 1 megabyte of data could be sent this way—less than an iPhone could send in a single image—but it would be enough to get a couple of fuzzy pictures of wheels on the ground. Better images would have to wait until the next day, when the high-gain antenna, with its narrower beam and much higher data rate, would be deployed.
In spite of the paucity of data on landing night and the late hour of the event, places around the United States, Canada, and Europe were planning live events. In Los Alamos, Sam Clegg was standing by to host a crowd at the local science museum, where a new exhibit was opening. There, a live NASA feed would be shown on a big screen. In New York City, the NASA feed would be displayed on the big screen in Times Square. Anyone interested in watching at 1:30 A.M. would be able to do so. A friend of mine was ready to Skype back to an auditorium filled with Mars enthusiasts in London, where the landing would take place at 6:30 A.M. A thousand people ended up watching in Toulouse, France, where it was 7:30 A.M.
In Los Alamos, the original plan had been to seat friends and family members of our team in the museum’s thirty-seat theater, which had a big screen. But with a couple of weeks to go, it seemed like more people would show up, so the museum director decided to open the one-hundred-seat auditorium as well. Eventually, several more rooms were filled. By the time of the landing, the place was mobbed with over four hundred Mars enthusiasts. People had serious trouble finding a place to park in downtown Los Alamos.
NASA was pulling out all the stops for the landing publicity. With a month to go, JPL released Seven Minutes of Terror, a video highlighting the tricky landing, and interviewing people from the EDL team. It was released around Independence Day, emphasizing the seventy-six pyrotechnic devices that would have to go off perfectly to guarantee a landing. Additional videos followed, with celebrities talking about the amazing landing being planned. Invitations went out to public dignitaries and to foreign space-agency leads. By the day of the landing, JPL was thick with dignitaries.
Team members handled the stress and anticipation in different ways. French engineer René Perez, who had stayed in Los Alamos for six months to assist in the integration and testing of our instrument, showed particular spunk. He was usually quick to pooh-pooh anything religious, but now the whole ChemCam team suddenly received an e-mail showing him praying at a chapel near his ancestral home. The text explained that he was going all-out to ensure success.
Ten days later we all received an invitation to view a YouTube video of René’s own personal “seven minutes of terror.” We couldn’t guess what it would be. The video began with René strapping a small camera on the end of a short boom in front of his chest, so it could capture his face. We could see in the background that he was at a small airport. Next, he was taking off in a propeller plane, gaining altitude. Now we could see that the cargo door was open. Someone wearing a helmet was strapped onto him from behind. Next, he and his partner were jumping from the plane. Excitement beamed across René’s face as he fell. The wind was soon pushing at his face, curling his lips open, and causing his cheeks to flap uncontrollably. Arm and hand motions, like small wings, caused various changes in attitude and elevation angles as the ground approached. Then René’s companion pulled a cord on his pack, and a huge jolt followed as the parafoil opened. The two applauded as they circled slowly toward the ground. A minute later they landed in the grass, and René’s wife ran up to welcome him back to Earth. According to René, if he could survive his seven minutes of terror, Curiosity could, too. René would of course be with us at JPL for the landing.
JPL was bustling with activity on the night of the landing. The science and operations teams for all of the payload instruments gathered in a large auditorium in the basement of the Flight Projects Building. Members of the ChemCam team—Sylvestre, Bruce, René, Steve, me, and many others—all took our places in different parts of the room along with people from other instrument teams. All the teams of the different instruments were there in number. Most people came in a festive mood. Various instrument teams took group photos. Scientists and engineers alike were bouncing with nervous energy. As for me, I couldn’t help but think about Genesis, and how this mission might end up in a similar fate.
The crowd swelled to over three hundred scientists and engineers. Big screens at the front of the room showed a simulated view of Curiosity, the capsule and cruise vehicle spinning slowly, approaching the Red Planet against a starry background. To one side, the distance, speed, and time to landing were displayed. The spacecraft was still over 25,000 miles from its destination, but with a speed approaching 9,000 miles per hour, the distance numbers were flipping rapidly. The next time I entered the room, I could see that Mars was visibly closer and larger on the screen. The numbers showed that the craft was accelerating and being drawn in.
John Grotzinger called the meeting to order. He reminded us what a privilege it was to be a part of this historic mission, the biggest such undertaking since Viking. He mentioned the fact that ours would be a long and glorious adventure. The many instruments and the capable rover were just about to begin their work. He gave the floor for a few moments to Steve Squyres, leader of the twin MERs, who enco
uraged us to enjoy this once-in-a-lifetime event and the days and weeks to follow. John then directed our attention to several of the videos, one new, the others recent, talking about the mission. Finally, there was nothing to do but wait.
Now, along with the simulation on one screen, another screen was showing the EDL team in the control room seated in front of computers tracking the data. All were wearing special blue polo shirts with a logo showing the Sky Crane lowering the rover to the ground. One of the EDL team members, Allen Chen, had been selected to announce the events to NASA TV and to the world.
Our room began quieting down as people took their places. With seventeen minutes to go, the cruise stage separation was announced, eliciting a boisterous cheer throughout the auditorium. Next, weights were jettisoned, allowing the capsule to approach with an off-axis center of gravity. This would allow it to steer itself as it traversed the skies above Gale Crater. The capsule’s slow spin was now halted, and it turned with a slight angle to the planet, business-end first. The crowd became fidgety, as we had another eight minutes to go before the entry would occur. Curiosity was now less than 1,000 miles above the surface of Mars and had surpassed 13,000 miles per hour.
I looked at my watch and realized that at this very moment, Curiosity was already on the ground in one way or another, even though the signals would take another fourteen minutes to reach Earth. The thought gave me a funny feeling. Whatever the future held, it had already happened! I stood up and yelled to the crowded room that the Curiosity had, in fact, already touched the surface. People nodded in thought, then went back to watching the delayed Earth-time events.
Our attention was suddenly grabbed by the next announcement, that the capsule was now encountering the upper reaches of the atmosphere. From the control room, Allen counted up the deceleration g’s, which peaked near 10 only about a minute later; the peak heating occurred slightly later. The spacecraft was executing its steering maneuvers. The control room assured us that the craft was behaving nicely and everything was nominal. After another wait, “Parachute deploy” was echoed over the speaker. Both the control room and the auditorium erupted with ecstatic cheers. I waited and watched the faces of the EDL personnel for any signs of trouble. Almost immediately, the heat shield was released, eliciting more cheers. The radar was now on. Within a few seconds, ground acquisition of the radar was announced—earlier than expected, it turned out. The crowd was getting very animated now. About a minute later the EDL stage was activated and released from the capsule. Again I watched the expressions of the people in the control room. Their faces were strained with tension, but all seemed to be going okay.
Allen began reading off the altitude: Curiosity was down to 500 meters from the Mars surface, 100, then 40, and the Sky Crane maneuver began. It would only take a few seconds for Curiosity to reach the ground if all went well. The room was silent and the clock was ticking: it was fifteen, twenty, then twenty-five seconds after the Sky Crane had started. One EDL person pumped his fists in victory, but no one else cheered. Others started gesturing uncertainly to each other. This was the moment I feared the most—we were so close, yet everything could still go terribly wrong! But suddenly the landing confirmation was announced, and both rooms erupted in wild cheers. Scientists and engineers hugged each other and danced around the room. René wiped tears from his eyes. Curiosity’s seven minutes of terror were more emotional for him than his own skydiving adventure had been.
We were all congratulating each other joyously. A bit of doubt still lingered in my mind—how did we know that Curiosity hadn’t ended up on its side or upside down? Had there really been a clean touch-down? Then, in the middle of the celebration, everyone paused as the first image came down. All we could see at first was that the light part of the image was up and the dark part was down. It was enough to confirm that Curiosity had landed right-side up. There was more wild cheering, and this time my whole heart was in it. A second image quickly followed. Now we could actually make out wheels on the ground at the edges of the picture. It was unbelievable—everything had worked perfectly!
As the engineers adjusted the image contrast and brightness, we started to make out more details. We crowded as close to the projection screen as we could. It was our first view of the surroundings of the new world: the surface was soil and gravel, not rocks. Almost immediately we could make out an uneven horizon—the edge of the crater some miles away. This was going to be a very different place from the flatlands of Spirit and Opportunity. The shadow of the rover could clearly be seen in the foreground of the second image.
Now that we had a clearer image, though, we noticed a strange feature some distance away in the middle of the picture. Something rather formless was protruding from the landscape. Was it dust on the lens? That night it remained an enigma. Only by comparing another photo several days later was the team able to confirm a most amazing fact: the very first Hazcam image had caught the plume of the descent-stage crash about half a mile away. The retro-rocket package had been instructed to fly off to a safe distance and ditch. It was only by chance that the picture had been snapped at the right moment and in the right direction.
A few minutes after the landing, I ran to the press area. The media had set up shop in the Von Kármán Auditorium near the entrance to JPL. My path took me down a dark alley that went past the large Assembly Building that had housed Curiosity for three years. During all that time I had been able to go in, climb the stairs to the viewing gallery, and look out on the big white rover, which sat at times like a shiny new car in a showroom. Now this vehicle was sitting on another planet, getting ready to roll. It was incredible.
The press conference was a raucous affair. Charles Bolden, the head of NASA, gloated about American ingenuity. He noted that no other country had landed on the Red Planet, while the United States had successfully landed seven craft there, including this behemoth. Bolden’s speech was almost cut short by a rowdy mob outside the door loudly and persistently chanting, “E-D-L! E-D-L!” Every single EDL engineer from the control room and others who had been involved was there shouting—over fifty of them. They were eventually quieted long enough for Bolden to finish his speech. After that, they burst through the doorway and attempted a victory lap through the heavily overcrowded room.
Eventually, as the press conference wound down, operations people made their way back to their places. A small room on the fourth floor of Building 264 was set aside for the NASA and mission leads to watch the next set of images, which were beamed down during the next pass of the Odyssey orbiter after midnight. A few ChemCam team members snuck past the guard and happily reported that our instrument had successfully turned on and passed its electrical checkout within an hour of the landing. Temperatures were stabilizing, and all was well. Many of the scientists were now speculating about exactly where the rover had touched down. A day later, the spot was determined to be a mile and a half downrange from the target point, almost exactly where the EDL team had predicted based on telemetry. The next day the Mars Reconnaissance Orbiter team released a photo snapped from orbit showing Curiosity’s capsule parachuting down over Gale Crater. The picture went to the media before anyone discovered that the heat shield was also in the picture, falling away from the descending capsule—it had been caught in the act right after jettison.
We all stayed up late that night, some well past the morning light, taking in all the new data and savoring the experience. This was just the beginning of our exploration in a brand new place, a fascinating place, on the Red Planet.
EPILOGUE
SOL 74. IT IS A FEW MINUTES PAST MIDNIGHT AND I AM sitting among sixty scientists and engineers in the same room in which we witnessed the Curiosity landing two and a half months ago. For the next hour and a half the team of scientists will analyze and discuss the latest batch of Curiosity’s images and spectra until the next stream of data arrives, at around 2:30 A.M. The instrument teams will then sift through new results, while the rest of the group plans the activities for the nex
t sol. The adjustment to Mars time has been challenging for some, compounding the bewilderment of adjusting to new software packages, unfamiliar surroundings, novel instruments, and a different planet. But most of my colleagues have risen to the occasion, enjoying the time of their lives, existing vicariously on Mars.
Curiosity is now in the vicinity of Glenelg, a place where three different terrains come together near the lowest point of Gale Crater, about 400 meters northeast of the Bradbury Station landing site. The rover has stopped in a spot called Rocknest, where it is scooping sand into its mobile laboratory for the first time. Since the landing, Curiosity’s instruments have been turned on and tested one by one. It started with RAD, the Radiation Assessment Detector, which was able to operate during the flight. During the landing sequence, the Mars Descent Imager, MarDI, provided the first-ever Mars landing movie—the seven minutes of terror—making those minutes look deceivingly easy. Then Mastcam gave the world the first of many high-resolution color panoramas of the sweeping landscape. Shortly after that, before the rover began to drive, the Dynamic Albedo of Neutrons (DAN) instrument, a device for measuring water and ice on the surface, and the Rover Environmental Monitoring Station (REMS) were turned on. Eventually the arm was tested, along with its instruments, the alpha particle x-ray spectrometer (APXS) and the Mars Hand Lens Instrument (MaHLI). Lastly, the mobile laboratory instruments got their chance. SAM started sniffing the air for methane and other gases; CheMin made the first-ever mineral composition measurements of the Martian soil. These two instruments will sample the interiors of rocks, eventually. But another month of testing in JPL’s Mars yard must take place before the drill will be okayed for use.