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[Feature Story]

An Interview with Richard Pavlovsky of the MPF Web Development Team

Chuck Toporek
Asst. Managing Editor,
Web Review
We've all been pretty amazed lately at the wonders coming from the Jet Propulsion Laboratory in Pasadena, California. As the Mars Pathfinder mission steams full-speed ahead, we've been dazzled by the imagery that the Sojourner rover has been taking and sending back to Earth. But pulling all of the information together and disseminating it to the masses has been a major chore to the Mars Pathfinder (MPF) Web development team at JPL's Public Information Office.

The main problem that they've managed to overcome has been how to manage a site that will be seen by tens of millions of people per day. And since JPL's site could only handle about 5 million hits per day, the MPF site development team, headed by Kirk Goodall, set out to find secure mirror sites to provide global coverage of the event. The network of 21 mirrors (12 U.S. and 9 international) has the potential of handling over 87 million hits per day -- which is close to the daily average of 40-50 million hits they've been receiving.

RealAudio Interview
Listen to the RealAudio interview with JPL's Richard Pavlovsky.

Web Review had the opportunity to interview one of the three members of the MPF Web development team, Richard Pavlovsky, who give us a look behind the scenes of the Web site. In addition to the text below, the interview is also available for download in RealAudio format for your listening pleasure.

Web Review (WR): Web Review is talking today with Richard Pavlovsky of the Jet Propulsion Laboratory in Pasadena, California.

Richard is a Web programmer for the JPL home page, and a member of the development team that has built what is now probably one of the most famous Web sites in the world.

Leading up to last Friday's landing on Mars, we've heard a lot about the technological breakthroughs that the Mars Pathfinder project team at JPL have had to accomplish -- from building the lander and rover "faster, cheaper and better" to actually landing on the surface of Mars and having everything work.

But on the other side of the coin, the Mars Pathfinder Web site development team have had their own set of technology hoops to jump through. Could you share with us some of the successes, and in particular, how you set up all of the mirror sites?

Richard Pavlovsky (RP):

We have about 20 mirror sites right now, and we were expecting being hit hard by the public in terms of accesses to the home pages. We set up the mirror sites so that people from all over the world can get the information without having to hit a slow Web page.

Some of the successes that we've had is we've set up the mirror sites in other countries to handle the load internationally [for] requests for information.

WR: When I last checked the list of mirror site at Sun Microsystems, there were 12 U.S. mirrors and nine international. From what I could tell, it looked like there was a possibility of handling 87 million hits a day.
RP: We currently get about 45 million hits a day and our hit count for today is 220 million from July 4th 'til today. And then by the end of today it should be 265 million.
WR: So is that what your initial projections were? or is it better?
RP: We projected that we'd get about 50 million hits at our Web site. And the JPL Web site could not handle all the load, and the Mars Pathfinder Web site could not handle that much load, so we had to set up all the mirror sites.
WR: How far in advance did you have to arrange for the mirror sites?
RP: We were working on that for months, and it took a while to get all of the mirror sites set up. And it takes a lot of hard work to keep them up to date.
WR: So how does that actually work?
RP: We were worrying a lot about security, and we thought people might crack into our pages and change the content. So what happens when we update the pages on the mirrors is that we get the entire Web site, compress it into one file, send it out to all of the mirror sites and uncompress it and overwrite everything. So if somebody's hacked into our Web site, everything will be fixed everytime the Web site is updated.
WR: Is there any particular criteria that you looked for when you were setting up the mirror sites?
RP: High bandwidth, and a good location on the Internets' backbone. In the beginning, we just mirrored to government sites since they were the easiest to mirror to since we're a government institution. Then we had to draft some legal aspects to get on the corporate mirror sites.
WR: And how do you find the corporate affiliations have been working?
RP: Very well. They've been handling the load very well. I think SGI's mirror site has been getting on average about 9 million hits a day.
WR: So they're taking the brunt of your traffic?
RP: They're taking a lot. The JPL Web page is getting about 4.5 million hits a day, and the Mars Pathfinder page has been getting 9 million hits a day.
WR: How many people are on your Web development team?
RP: Three.
WR: Just three people? So what kind of schedule are you running? 24/7's?
RP: I haven't had a day off since two weeks ago. I'm working fairly long yours, yeah.
WR: How long do you foresee that going on for?
RP: We're working long hours until after the press room here closes; it's going to close Friday (July 11th), and then I think we're going to take a much needed break this weekend. And then next week, we're going to post all of the data, but we're not going to wait for the press conferences to do that, we're just going to put everything online, and that shouldn't take as long.
WR: We've seen all of the imagery that's on your site. Could you tell us, in short, the path that the telemetry data takes from Soujourner to the lander, to JPL and actually ends up on your site, and what image format are they received in?
RP: The rover has three black and white cameras and one color camera that takes pictures. But the main camera is the IMP (Imager for Mars Pathfinder) on the lander. The data and the images are taken and they're sent as JPEG. They're sent to the Deep Space Network (DSN), the three large stations of radio antennas that can communicate with the Pathfinder on Mars. One's located in Goldstone near Barstow, California; one's in Madrid, Spain; and one's in Australia. So the information is sent across to one of those antennas, whichever one can see Mars at the current time, and then the information is sent to JPL.
WR: And then you just take the JPEGs and put them up on the site?
RP: The data comes back as little postage stamp frames and they need to be mosaic'd together. That's why, in some of the pictures, things don't align properly. And so our image processing lab has to mosaic all of the images together.
WR: And then they send them over to you?
RP: Yeah.
WR: Now are the images that are on the site available for the general public to download and use?
RP: Yeah. The media downloads their images from our Web site, too.
WR: Is there a special path for the media to get to?
RP: There's two mirror sites that are secret that only the media has knowledge of.
WR: Who decides on which photos make it online?
RP: It's a combination of our image processing team and Peter Smith -- he okay's everything before we put it online.
WR: And as far as the textual content that provided by the scientists?
RP: The text is provided by the scientists and then it's re-written in laymens' terms, I guess you would say, by our Public Information Office.
WR: Everybody tends to design their sites for a particular audience. Who did you have in mind as the primary audience for the Mars Pathfinder site? Was it primarily for scientists? media? kids? or just a general public site?
RP: A general public site, I would say. We try to keep everything not too technical so that people can understand the information. This Web site is targeted for the public, but we also have the media access it as well.
WR: Do you have any advice for Webmasters who might be handling a site that's going to experience huge fluxes in traffic in the future?
RP: Prepare for it. Set up mirror sites if you can. Make sure that your server is capable of handling large numbers of accesses, and make sure that you have high-bandwidth to your server. If you've got a low-bandwidth connection to the server, your server might be very powerful, but the bottleneck is in the Internet and your connection to the Internet.
WR: And one final question: How does if feel to be involved in what's probably one of the most important uses of a Web site on the Net so far?
RP: It feels great! It's really awesome -- putting all of these images online, I'm usually one of the first people to see them. I get sort of a sneak peak at all of the images before anybody else. It's really great.

Also, the media coverage of the Internet has been great. I guess through the weekend -- July 4, 5, and 6 -- the news story was, Pathfinder, its mission and how it was going. And then on Monday, the story's switched and it became how the Internet helped [the] Mars Pathfinder distribute their information -- it's pictures and stuff. We've been doing many, many interviews. People seem to love the fact that we're putting all that information out for them to get for free.

WR: I know what piqued my interest in the whole story was during the initial press conference, when the director of NASA congratulated the Web development team on the ability to hook up with all of the mirror sites to be able to handle the traffic of more than 5 million hits a day. So that, coming from the director of NASA, speaks volumes to the amount of work that you guys have been doing. I know, everybody appreciates all of the work you've been doing, so congratulations from all of us.

For those who haven't been to the Mars Pathfinder site yet, you can get there by going to

Other articles in the Webmastering Mars series:

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