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Exploring New Heights

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DQI Bureau
New Update





On July 4, 1997, NASA's Mars Pathfinder spacecraft entered the Martian atmosphere. In its
hull, the Pathfinder held a 22-pound, six-wheeled Sojourner Rover, the first robot ever to

explore the Martian terrain. Scientists used a specially designed Java interface to

designate science targets for the Rover and perform a variety of operations. At the same

time, people around the world had the opportunity to simulate their own Rover missions and

view data downlinked from Mars.






Developed for NASA's Telerobotics Program by Jet Propulsion Laboratory (JPL), with SoHaR
Inc and IA Tech Inc, the Web Interface for Telescience (WITS) enables mission participants

worldwide to collaborate and view Rover activities over the internet. JPL, the premier

center for robotic exploration of the solar system, is managed for NASA by the California

Institute of Technology. JPL's Rover and Telerobotics Program develops technology to

demonstrate how telerobotics can contribute to NASA missions.






Interested scientists and students used WITS over the internet to command the JPL Rocky 7
research Rover in a May 1997 field test in the California desert. Participants viewed the

terrain through the Rover's eyes and controlled the robot's exploration activities using a

desktop computer with a browser. "WITS is a testimony to the robustness and ease of

programming with Java," says Paul Backes, WITS team leader at JPL.






The mission


Backes and his team first envisioned a distributed interface for planetary Rovers in 1995.
Facing the challenge of accommodating growing teams of scientists, Backes sought a way to

allow large groups to collaborate easily from remote locations. Since future missions will

last up to six months or more, JPL needed a way for large science teams to collaborate

without residing there. The challenge lay in creating an interface that could be easily

loaded while running flawlessly on all user machines.






NASA awarded funding to JPL in October 1995, just as the first Java beta releases were
circulating over the internet. Backes' team began running simple tests with Java to see if

it could meet their development needs. In their first experiment, the team used Java to

command the Rover using images transmitted from space. Within one month, the team reached

its first milestone, getting a head start on creating the full WITS interface in Java.






The solution


From Backes' point of view, Java offered the crucial advantage of easy installation.
"Java's platform independence and automated downloading over the internet have been

critical," says Backes. At a test run in December of 1996, distributed teams

successfully controlled the Rover with a Java applet. "I had three test sites on

three different platforms using two browsers, all working exactly the same way," he

says. "I gave everyone a URI and bingo they were there."






Java played a key role in the development of a GUI for WITS. "I've used GUI builders
in the past and often found that they were complex and difficult to incorporate into the

underlying language," says Backes. Building the interface with Java proved so

easy-even without special GUI development tools-that Backes' team ended up writing the

interface directly in Java. "Java was simple, graphical and intuitive. I've never had

such an easy time building a GUI," he says.






With its Java interface, WITS allows the public-or scientists-to easily interact with the
sophisticated Rover. Participants click a screen image, select the Rover's position and

use command options to place an instrument or pick up a rock. Once complete, an activities

list is sent to the Rover.






Development environment


Backes and his team began writing code in November 1995. By August 1996, WITS was ready to
roll. "The speed of our development was remarkable," says Backes. Even though

the team had to learn a new language, it took JPL less than half the projected time to

develop WITS with Java. "To be honest, I would never have attempted to build a

distributed interface in time for the Mars Pathfinder mission without Java. We would have

had no chance of successfully meeting our deadlines," says Backes.






Deployment environment


The Java applet is deployed from a SPARCstation 10 Web server. Users download the applet
via a browser such as Netscape or Internet Explorer. The SPARCstation communicates with

other parts of the telerobotic system using CGI scripts.



Only the mission system is authorized to connect to the command uplink systems at JPL.
Identical mission and public versions of WITS, with alternative URLs, are used during

missions and field tests. Each database is updated with the actual mission data.






User types, passwords and IP addresses ensure optimal security for all systems.
"Security is tremendously important. When I first went to the mission planning team

and told them we would generate commands for the Rover over the net, they got quite

nervous," recalls Backes. NASA gave the go ahead only after Backes outlined a plan

guaranteeing that the system would remain secure.






Looking at the future


Reflecting on the WITS and Rover's first three-way field tests, Backes recalls, "We
knew it was going to work from JPL, and that it should theoretically work for the students

and for NASA headquarters." Still, he was ecstatic with the results. "There were

just no problems," he says. "After many years of aggravation with other

difficult systems deployment, this was so easy."






WITS has given JPL the power to generate an outreach program with the potential to connect
millions of users. Scaling the system has become top priority for Backes. The original

communications architecture prohibited use by more than 1,000 concurrent participants.

While initially the group thought this would be sufficient, it turned out to be more than

two orders of magnitude too small. "With Sun's help and technical recommendations, we

are modifying the architecture to increase capacity," says Backes. A new Sun server

and protocol will enable WITS to support millions of users.






Backes' team, whose priorities include continually enhancing the applet's functionality,
is currently developing 3D graphics for standard internet users-written entirely in Java.


































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