Spirit’s First Light
First Light, Hello Mars
One of the most intriguing initial panoramas from Spirit’s new resting place shows a depression or crater in the near-center of the horizon, and hills in the distance. The site appears ‘clean’ to principal investigator, Steven Squyres, who is anxious for enough rocks to look for lake-bed sediments, but not too many for restricted driving.
The lander is currently facing south, with a 73 centimeter rock (or partially deflated airbag) butted against its nominal egress path and another semi-retracted airbag. To get off the landing petal and drive around as a robotic geologist, the team is considering a one-third turn in place or waiting for any protruding airbags to cool more at night and deflate.
The rover team indicated after landing, that in all their simulations done to date, they never have had so many things go right at once like today.
Much of the tension of one thousand days of work was seen in the faces of those who made the latest Mars rover pass successfully through its highest risk maneuver: safe landing. Three and half years of planning presented an accelerated timeline. Late changes were made to include a horizontal correction rocket, in case winds on Mars began to tilt the descent path or interfere with parachute attitudes. During the NASA press conference at JPL in Pasadena after the landing, one of the loudest cheers came when mission managers thanked all the families that weathered long hours needed to make the landing possible.
To celebrate the human side of exploration, in this fourth endeavor on Mars, the mission team gave a synopsis of their reactions, which are summarized by the faces and comments in the immediate afterwards of a long, tense waiting period. Conference articipants included NASA Administrator, Sean O’Keefe; NASA Science Administrator, Dr. Ed Weiler; JPL Center Director, Dr. Charles Elachi; JPL Mars Exploration Rover Project Manager, Pete Theisinger; Deputy Project Manager, Richard Cook; and development manager for the landing phase, Rob Manning. Most of this team held positions during the successful 1997 Pathfinder landing, but also suffered disappointments as 1999 anomalies led to an extensive review and revision of many mission planning features. Most notable among these changes was a return to airbag landings, from the 1999 rocket-fired soft landing profiles.
|Oblique view of crater ring, sometimes whimsically called the "Happy Face" crater.
Six months ago, just after Spirit launched, Weiler said: "Everytime I see the descent and landing video, I get nervous. There are too many moving parts. Too many things that can go wrong. We can do absolutely everything right…after the failure of Mars 99, but if we get a gust of wind that exceeds the limits [on descent in January], we can lose the lander."
"There was a huge boulder next to Viking," noted Weiler, as he described the 1976 rocket-powered Viking spacecrafts’ descent onto Mars. "All it takes is a boulder of the wrong size in the wrong place. Three [successes] out of 9 [attempts] aren’t good odds."
But as Rob Manning, the development manager for what is otherwise described as this landing’s ‘six minutes from Hades’–the Entry, Descent and Landing phase, or EDL–put it, their task was to ‘make sure this cannonball is shiny’.
Sean O’Keefe, NASA Administrator: We’re back. And we’re on Mars.
Ed Weiler, NASA Science Administrator: I feel speechless. It was six minutes from hell. We said the right prayers, and got up to heaven.
Charles Elachi, JPL Center Director: When I looked in the mirror this morning, I had a full head of black hair. Now I have a thin, gray cap. But in the darkest days of 1999, Congress said "don’t stop"–Keep exploring.
Pete Theisinger, JPL Mars Exploration Rover Project Manager: I told myself this morning [Saturday] that when I woke up on Sunday, the world would be different. This is a tremendous day.
Richard Cook, Deputy Project Manager: I really, really like doing it when it works like this.
Theisinger: We’ve retired alot of risks with this landing.
Cook: Seven years ago [during Pathfinder] we were young and didn’t know what wasn’t possible.
Rob Manning, EDL Dev. Manager: It’s alot of fun when it works. It is very intense. EDL is up in the war room, figuring out what happened.
Weiler: When the parachute came out, I went through my phase shift. I felt this might work.
Manning: Entry timing went perfectly. Navigation, perfect. We can’t tell any differences between predictions and what happened.
O’Keefe: Steve Squyres [Cornell's principal investigator for the science package called Athena] told me he has been thinking about this project for sixteen years now. That is the dedication it takes.
Manning: Mars is a busy place right now [approximately 2 pm Mars time]. The sun is up. Earth has set. [The landing involved] an astounding set of ‘good circumstances’. It did however appear that we had wind shear and a horizontal velocity, so we had to fire the lateral correction thrusters, or rockets, to correct. Winds at Gusev were expected. We had added self-induced velocity from Spirit’s own wake, which with the wind gave us about twenty meters per second horizontally.
O’Keefe: I’m told in a golf analogy, that landing on Mars is a hole-in-one, from Paris to Tokyo.
Weiler: With a water hazard. 380 million miles away.
Manning: We were living in near tension for three and half years. So now you think you’re in practice. But this is not a rehearsal. Our testing has always had to do double-duty. When it comes to the real McCoy, I was surprised how calm it was. But just after landing may have happened, when the signal disappeared, that caused us some…pause. For about ten minutes, we had nothing. But once we rolled to a stop, we landed base petal down [which is optimal]. That has only a one in four chance.
|Mission scientists survey first polar view which is a wrapped, 360-degree view to the horizon, but is a good approximation to looking down on the site. To the right (30 degrees) is a 73 cm rock, the largest in the landscape, and to the left (30 degrees) is a semi-retracted airbag. The combination of these will lead to maneuvers that may turn the rover in place, and also take advantage of its fortuitously low tilt, about two degrees.
Weiler: I’m buying lottery tickets.
Cook: We saw something in the data that we had landed. We celebrated. Then nothing. [The data disappeared]. In the pit of my stomach, the agony built. Then it’s very surreal.
Manning: Changes in the parachute release timing, due to the possibility of dust storms at Gusev, that is one of the key questions for the EDL reconstruction [for Opportunity]. We want to make sure this cannonball is shiny.
Theisinger: This shows the design is solid for Opportunity [landing in three weeks]. It is a confidence builder. We can still change things at very subtle levels. The two rovers are identical as can be. They were built at the same time. They broadcast at different frequencies for Deep Space Network [DSN] reasons.
Manning: I’m excited about seeing the [three] descent images [used to gauge horizontal speed as in a time-lapse]. We have 7 minutes of data from then, and we will be listening for that bounce data. The [betting] pool [to guess the exact landing position] has begun. There are people who will race to know where we are. But we are probably in the middle of the [landing] ellipse. There will be one big crater to the south. And more mesas to the south.
Cook: It’s an inspiring thing.
Elachi: Don’t forget we are roving. Everyday now we get the equivalent of a new lander in a different location.
Manning: We appear to have bounced for quite awhile. [Remember this landing involves]: 8 thrusters, 37 pyrotechnic devices, 8 cable-cutters, 4 sensors, 2 radios, 1 computer—and airbags. And they work!
Theisinger: We have added a fourth place to land on Mars. The scientists selected a safe site. It has the potential to answer questions about Mars’ past.
Manning: I use the analogy of building bicycles in the 1800’s. We have even stranger ideas about how to land. Our inexperience needs practice to progress. But I’m not sure how many more times I could do this.
Cooke: At least one more time….[Opportunity is three weeks away.]
Manning: [Mars] is not that far away. It is not cheap. We don’t visit too often. But when you see these pictures, it will be familiar.
JPL, a division of the California Institute of Technology, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Additional information about the project is available from JPL and from Cornell University, Ithaca, N.Y.