July 2, 1997:
Out at JPL, getting ready for the Pathfinder landing. Things are still relatively mellow here-- there's really nothing we can do. The spacecraft seems to be perfectly on target, and they are contemplating skipping the final trajectory correction maneuver, since it looks like it won't be needed. Keeping my fingers crossed, and trying not to be nervous--
July 4 1997:
Yahoo! It worked! Pathfinder is down; it's working great! You couldn't believe the pandemonium here in the science working area when the first images came down-- everybody here went nuts. It was absolutely spectacular-- this landing is great! -- the area we landed on Mars is a lot more exciting than anybody had a right to imagine.
For more information, here are my e-mail answers to some questions posed by school kids, forwarded from Janet Kretschmer (a schoolteacher in southern Ohio):
>the kids are hilarious...they are only first through 4th grade, so it took us a
>while to help some of them understand that there were no men on Mars, no women
>either, and that JPL is not on Mars. (the child who believed that saw the JPL
>letters on the side of the lander and thought ..honest!.. that you were all
>living in the lander.)
>we got that untangled. Scale is so hard.
>They cannot conceive of how far away it is, have it mixed up with shuttle a
>bit, and thought that if the rover tipped over, someone could (depending on
>the age level of the student) 1) step out of the lander and tip it back right
>side up 2) take the next shuttle (!) and go tip it back over 3) push a
>James Bond-type lever and have it just flip back over.
>The Hotwheels are perfect, but the scale, because it is not consistent,
>makes them quite confused. We are having trouble imagining how big things are.
>Could the lander rest in the library with all of its petals open. (I think it
>might be able to.) Is the Pathfinder the size of a small car? We could use
>some real life, very familiar size references.
>You must be high on adrenaline and busy as hell. We don't expect instant
>answers, and know that net access and free time are at a premium.
>Thank you so much for being willing to answer at all.
Sorry it's taken me so long to get back to you; as you can imagine, it's been very hectic, and a lot of stuff is just piling up.
Anyway, some quick answers to your questions. It bothered me that the scale of the Hotwheels was inconsistent too. Not much I can do about it, though! The rover is about two feet long; it would come to about knee-level if you were on Mars with it. The way we usually describe it to the outside is "about the size of a microwave oven".
The Pathfinder spacecraft is a little smaller than a very small car. Sitting on Mars, it is about four feet tall (not counting antennas and the camera, which sticks up).
We work on Mars time. The Mars day (called a "sol") is about 40 minutes longer than the Earth day, so this means that for us the working day begins about 40 minutes later every day.
I have a hotel room that I go back to when it's night on Mars and the mission isn't sending back information. When the mission is sending back information, I usually bring in something to eat.
The "Carl Sagan Memorial Base" (which is what the lander was named after it landed) has the main camera, the weather station, and the radio, so it's still sending back information.
It took about seven months. It was launched December 4, 1996.
We're going to use it to design better solar arrays for upcoming Mars missions. In particular, we're going to find out whether dust is a problem, and we need to invent some way to sweep the solar arrays clean of dust.
There doesn't seem to be much extra dust when it moves around. We did see a bunch of dust when the petal got lifted up and put back down.
It has a tiny little on-board computer that is working furiously calculating whether there are any obstacles that it is going to hit.
That wasn't in the design, but it's always possible that something might have gone wrong. I'm glad it didn't!
That's why the antenna doesn't get put up until it is on Mars and the camera has looked around and seen that there's nothing that it might hit.
Well, if it lost a tire it would probably be dead. But the tires are made out of steel, so they should be pretty sturdy!
This would have been a real problem. This was one of the things that the science team thought about when we selected the landing site. We wanted a site with rocks, but without BIG rocks that the petal might have been wedged against.
No. Once it's deployed, it's deployed.
They are made of steel. They're not actually "filled" with anything.
Low cost to make it and to get it to Mars. We wanted to use the smallest rocket we could to launch it, because rockets are very expensive.
That would end the rover mission, because there is nobody there who can turn it right side up again. That's why the rover moves so slowly, so we can be very very careful that this doesn't happen.
Sojourner has a height of 28 centimeters and is 63 centimeters long and 48 centimeters wide. That's 11 inches by 25 inches by 19 inches.
Slightly faster; it's about one centimeter per SECOND, not per minute.
Actually, I named a bunch of rocks. There's a big one off to the right side of the ramp that looked (from the undeployed position, anyway) like a cartoon bear with a bow-tie, so I named that one "Yogi Bear" (which seems to have been shortened to just "Yogi" by the geologists.) This has been an APXS target recently.
I also named quite a few more-- chimp, wedge, the dice-- all based on their shapes-- and a few others. I tried naming one "tip of giant buried pyramid", but that one got shortened to just "pyramid". I also got Mike Malin to change the name of "double hill" to "Twin Peaks", but I don't think I can claim exclusive credit for that-- several people other than me had been calling it Twin Peaks.