Long-time readers know that This is True was created while I still had a Day Job. It was a very cool job: I was on the engineering staff at NASA’s Jet Propulsion Laboratory (1986-1996 — True was started in 1994, so there was a two-year overlap).
Shortly after I left to pursue True full time, a friend of mine there took over a public outreach program: the “Solar System Ambassadors” who help educate the public about what NASA (and JPL in particular) are doing.
Kay reached out to me, and I’ve been an Ambassador ever since. It doesn’t change what I share with the public — I’ve been writing about space topics on the side anyway, but this way, I get some special access to make my reports to you even better, and Kay gets “outreach credit” for the people I reach: a nice win-win.
As a NASA Center, the Jet Propulsion Laboratory’s main mission is to manage the robotic (vs astronaut) exploration of the solar system, and beyond. They’re the ones that send probes out to other planets, and the rovers on Mars.
In 2012, the Curiosity rover, more formally known as the Mars Science Laboratory, landed on Mars. How do you safely land a 2,000-lb. (900kg) rover on the surface of another planet with a very thin atmosphere? With an audacious landing like this (5-minute summary):
Now, I really like working for myself, but if I “have to” have a Day Job, well, JPL is about the coolest place on Earth to work. I got to work with the kind of people who figured stuff like this out. I watched it live. Here’s what it looked like in Mission Control (2-1/2 minute summary):
Behind the Scenes
And all this ties together to explain why I was in California: that “special access” I get as an Ambassador turned into a behind-the-scenes, VIP tour of the Lab and what they’ve been working on lately, being briefed by the scientists who are working on the missions. The idea: to celebrate the Ambassador program’s 25th Anniversary, and brief the Ambassadors on what’s going on so we can all explain it to the public better. I also got to bring Kit; she’s bit of a science nerd too (hey: it’s one of the reasons why we got together!) Here are just a few of the highlights.
Welcome to the Solar System
They started us out in Mission Control. Just like there’s a Mission Control in Houston for the astronaut-led missions, there’s one at JPL for the robotic missions — as seen in the second video above. There’s a gallery window above Mission Control that I used to go to all the time: I’d always take visitors there to see it. But even as an employee, I never got to go inside Mission Control. On the VIP tour, we did:
There are multiple spacecraft in the sky currently, and Mission Control is in operation 24 hours a day, every day. At JPL, it’s known as SFOF (which yes, they pronounce: “ess-foff”), for its more formal title: the Space Flight Operations Facility. It was built to support the unmanned (Ranger and Surveyor) missions to the moon in preparation for the Apollo moon landings. So it’s been running 24x7x365 since the early 1960s!
The on-duty engineers put up with all of us geeky types running around taking pictures:
In that last photo, you can see what looks like big dish antennas with radio waves. To talk to spacecraft that are sometimes billions of miles away, you need a big antenna system. More on that in a moment.
We popped up to the “Mars Yard” to see where they test the rovers. There’s a full size copy of Curiosity there, so if the real rover gets into any sort of a jam, they can replicate what’s going on at JPL and decide how to get the rover out of that jam. Here’s the full-size replica:
Notice the holes in the wheels? That’s not just to let dust out of the wheels as they turn. It’s hard to see here, but as they roll through the Martian dust, they stamp out a pattern. That helps create milestones for the cameras to get very specific measurements. It’s also Morse Code ( · – – – · – – · · – · · ) …which just happens (cough) to spell out “JPL”.
They didn’t start out with Morse Code: they started with regular letters as part of the treads, which you can see here, on an early version of the wheel:
Note the holes punched into this wheel: that’s how they were able to tell they were making the wheels too thin. Six wheels support the rover’s 2,000-lb. (900kg) weight. Even though the gravity on Mars is less, and thus the weight isn’t as much there (about 750 lbs.), Mars rocks are known to be sanded by the winds into sharp points. When they ran these wheels over simulated Mars rocks, they punched through. They fixed that well before launch.
But that, as mentioned, wasn’t the only change in the wheels. When NASA headquarters saw the “JPL” on them, they said there’s no way they were going to allow JPL’s rover to stamp “JPL” all over Mars. That’s when the engineers got more creative, and came up with the Morse Code alternative.
The Next Mars Mission
So Curiosity has been motoring around for five years now. What’s next? Mars 2020. You can read about that mission at the link (Wikipedia article), but here’s what I didn’t know about this new rover mission until we got a briefing from one of the engineers: it’s going to drive around Mars to gather samples from the planet. They’ll drill into things that look interesting, and then seal the samples into tubes. The engineer who was telling us about that has the job of figuring out how the rover itself will deposit the samples into metal tubes, and then seal them so there’s no possibility of contamination between Mars and Earth.
So the obvious question is, how the heck are they going to get the tubes back to Earth for analysis? Here’s the wild part: that’s beyond the scope of the Mars 2020 mission! The mission after that will have the job of following in the “footsteps” of the Mars 2020 rover, pick up the tubes that it dropped, and send them back to Earth! They don’t want all their mission eggs in one basket, so they’re making that a separate mission. Wild!
Here’s what the tubes look like:
Once fully boggled by that, we then headed for the High Bay. To get there, we had to walk by the building where I had my first office:
The High Bay is a giant clean room, where spacecraft are built. I used to go down there all the time during lunch to watch the Cassini spacecraft being built. It launched the year after I left (1997), and took seven years to arrive at Saturn, where it is still doing science …until September 15, 2017, when it will have a very decisive end of mission (details at the link).
ECOSTRESS doesn’t have a Wikipedia page, but JPL has one for it. Briefly, it will measure the temperature of plants and use that information to better understand how much water plants need, and how they respond to stress, to answer three main science questions:
- How is the terrestrial biosphere responding to changes in water availability?
- How do changes in diurnal vegetation water stress impact the global carbon cycle?
- Can agricultural vulnerability be reduced through advanced monitoring of agricultural water consumptive use and improved drought estimation?
Getting All the Data Back
I mentioned above that the spacecraft JPL sends out can be billions of miles away. They’re not going out there just to go, they’re out there to do science, including sending back photos. We have to get the data and photos back …somehow.
The twin Voyager probes, launched in 1977, are the farthest away — specifically, Voyager 1 is the farthest. As of this writing, it’s about 12.85 billion miles (20.7 billion km) from Earth. It’s so far away that a radio signal, which travels at the speed of light, takes more than 19 hours to get there. Send a command and wait for a reply? Twice that for the round trip.
Then consider the transmitter power on the spacecraft is just 25 watts. The typical radio transmitter in a police car or ambulance generally puts out 50-75 watts of signal. (Power is very scarce on a spacecraft, so they use as little as they think they can get away with.) So if the spacecraft is putting out a feeble signal from very far away, how do you receive it? With a BIG antenna.
Because JPL is the lead NASA center for interplanetary spacecraft missions, it created and operates the Deep Space Network, which uses three ground stations around the world so that at any specific time, at least one of them can “see” any probe out in space. Those three ground stations are located in Madrid, Spain; Canberra, Australia; and the Mojave Desert in Southern California. So after a day of touring JPL’s main campus, the next day we drove out to the “Goldstone” tracking stations, which are located within the confines of the U.S. Army’s Fort Irwin, a major training base.
It was a fairly typical 112 degrees there (44.5C) that day. And oh, “You can’t wear shorts.” (The supposed reason: the rattlesnakes. Our suspected reason: the army brass don’t want the trainees to be too jealous.)
So now wrap your mind around this: the spacecraft is billions of miles away, and has a transmitter putting out less power than the light bulb in your refrigerator. So you have this huge antenna to receive that signal, but to do that it has to be really carefully pointed toward that spacecraft. So you not only have to know exactly where that spacecraft is, you have to point right at it. Which means that this antenna, which is 70m (230 feet) in diameter, not only moves, but very, very precisely!
I worked on a project for the DSN when I worked at JPL, and had been here before. We didn’t have to drive: since several of us were going, we got to fly on a NASA aircraft. (And we not only got to wear shorts, we were told to!)
That time, we went into the control room at the bottom of the dish. We could see the platform was turning, so we just had to be careful as we transitioned onto the stairs. We climbed up to the control room, got to see everything, and came back out. When we climbed on, the antenna was pointed up, as in this photo. When we came back out, it was pointed horizontally — a 90-degree movement. And we had no idea it was doing that — it was that smooth. Astounding.
Each of the three stations around the world has one of those big dishes. For less demanding communications (such as closer spacecraft), they have several smaller (34m) antennas at each station too. And consider that the Earth is spinning on its axis, so for a “long pass” (lengthy download), the antenna has to move constantly to stay directly pointed.
And that’s why we popped out to California. We Ambassadors soaked up a lot of new information to help explain things, which will certainly inform my upcoming space-related blog posts. (See the full menu of past space-related posts here.)
While I left JPL to work on True full time, it’s still in my blood — officially, even, as an Ambassador (thanks, Kay!) It was an amazing place to work, and I’m glad I’m still welcome back from time to time.
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