The future of space exploration calls for many reliable, inexpensive spacecraft exploring our solar system and sending us vast amounts of new information about all parts of our planet's neighborhood. In the past, robotic spacecraft have been directly controlled by ground control. This limits a spacecraft's ability to react to unexpected events and to explore areas that are difficult to reach with current communications systems. Remote Agent is the newest approach to confronting these limitations by enabling spacecraft to: 1) be more autonomous, able to operate without help from Earth; and 2) use flexible, goal-based plans, plans which include general goals and windows of time in which they should happen, rather than specific tasks which must happen at specific times.Remote Agent will enable spacecraft to:
In the past, unmanned spacecraft were controlled from Earth. The spacecraft could only operate if it could communicate with Mission Control using radio signals. If a spacecraft were to enter an area to which the signals were blocked, for example by a planet or by a mass of ice, such as the oceans of Jupiter's moon Europa, the spacecraft would not be able to operate. Also, if the spacecraft was too far away from Earth, the large amount of time that it would take for the signal to travel to the spacecraft would make it very difficult to control the spacecraft from Earth. The on-board Remote Agent controls most of the spacecraft activities on its own, making the spacecraft much more autonomous. It tells the spacecraft what to do, when to do it, and makes sure its instructions are carried out successfully. It detects and fixes problems that may occur on the spacecraft. A Remote Agent-controlled spacecraft can explore areas from which communication with Earth is difficult if not impossible, greatly opening up the boundaries for space exploration.
Space missions can be expensive; therefore, the unrecoverable failure of a space mission can be a costly loss. For this reason, the reliability of both the health of the spacecraft and the accomplishment of the mission goals is very important.
Remote Agent increases the reliability of the health of the spacecraft by enabling the spacecraft to fix itself autonomously. Sometimes, the quickness with which a failure can be corrected is crucial to the survival of the spacecraft.
Apollo 13 required a failure correction in a short amount of time in order for the spacecraft and crew to make it safely back to Earth. Although they were successful, the spacecraft was almost destroyed because of the amount of time it took to fix the failure.
Communication down to Earth to report a failure, and communication from Earth back to the spacecraft with instructions on how to fix the failure both take time. By being able to do this on-board, thereby bypassing the communication delay, Remote Agent has a better chance of fixing the spacecraft in time than ground controllers.
In the past, the plan for how the spacecraft should go about accomplishing the mission goals consisted of specific tasks that were to be done at specific times. This is problematic in the face of unexpected circumstances. If a spacecraft failure occurred and by the time it was fixed, crucial parts of the plan had been missed, the entire plan would have to be scrapped and the mission goals would not be accomplished. If one task took longer than expected, so a crucial task in the plan was missed, the result would be the same. Remote Agent mitigates this problem by having flexible, goal-based plans. Remote Agent receives the general goals that should be accomplished during the mission from Mission Control; for example, to take pictures of an asteroid. Remote Agent generates a plan of the tasks necessary to accomplish this goal. The tasks are assigned varying, and sometimes very broad, windows of time during which the task must be accomplished. The plan is called flexible, because it doesn't always dictate specific times or specific ways in which the task must be completed, and instead leaves those decisions up to Remote Agent. The hope is that if a spacecraft failure occurs or a task takes longer than expected, the spacecraft will still be able to successfully continue with the plan because of the time flexibility and will therefore still be able to accomplish the general mission goals.
Although many great discoveries are made by looking for something specific, others, like the discovery of pennicillin, are made by accident. In the past, space missions were pre-programmed with exactly when, how, and from what they were going to collect information. Remote Agent has the potential to change this due to generating and executing flexible plans. Flexible plans describe varying and sometimes broad windows of time in which tasks must be accomplished, rather than exact, specific times. The hope is that in the future, this will enable Remote Agent to react to unexpected, interesting phenomena that it encounters in space. For example, an asteroid may pass that is giving off an uncharacteristic radiation. If there are large windows of time within which EXEC can carry out the tasks of the current plan, EXEC can command the spacecraft to take pictures of the asteroid, and still have time to continue with the plan as scheduled. This ability would greatly expand the opportunities for interesting scientific discoveries in deep space.
Space missions can be expensive to build and conduct. Given that NASA has a fixed budget, if each mission is less expensive, more missions can be conducted with the budget contraints. Remote Agent has the potential of greatly decreasing costs, thereby increasing the number of missions that can be conducted and the amount of knowledge that can be gained.
It is very time-consuming and therefore expensive to perform the complex task of programming flight software, which helps run the spacecraft. Remote Agent is a unique piece of software in that it is based on models. Each specialized part on the spacecraft is programmed separately with how it works, its behavior, and what happens when it fails. The model figures out how they all fit together. If there are last minute changes in the plan of the spacecraft, insteading of having to scrap the whole program, just the part that changed needs to be altered. In the same way, the program can be re-used for different spacecraft rather than having to write a new program. This can save much money in the long run by decreasing the amount of time it takes to program spacecraft software. The less time it takes for engineers to build a spacecraft, the less expensive it is.
Running a mission is also expensive. If a mission is run by ground control, it must have frequent communication with Mission Control via the Deep Space Network. (DSN) There is much demand for DSN bandwidth and therefore space on the network can be costly. In addition, using human ground controllers to keep constant watch on the spacecraft is not only expensive, but also tedious especially when routine commanding of the spacecraft could be automated. Remote Agent makes the spacecraft autonomous in that it can generate and execute its own plans, and correct many of its own failures without communicating with ground control. By cutting down on the amount of communication a spacecraft must have with Earth, the cost of the mission is greatly decreased.