U.S. dependence on its satellites for purposes ranging from national security to widespread use of civilian satellites throughout the economy makes it essential that the U.S. military prepare to employ a variety of measures to protect those vital asset and ensure that they are not attacked or interfered with, Ellis said. He stressed that the techniques that must be developed cover a wide range of offensive measures and more likely countermeasures such as moving a satellite out of range.

Ellis said the most critical need is understanding exactly what is going on in space and on the ground that might affect U.S. satellites -- something the military calls situational awareness.

Potential enemies are aware of the importance of satellites to the United States, and will attempt to deny their use, Ellis said. Clear evidence of this was demonstrated when the Iraqi military attempted to jam the GPS navigation signals during battle last year, he said.

Over the past 10 years, more than 400 reports have addressed the issue of U.S. satellite vulnerability to enemy attack, Ellis said.

"We have admired the problem long enough, and now it is time to act," Ellis said. "Enemies cannot pursue any action that threatens our space assets without an immediate response from the United States of America."

One of the first priorities in this area is improving the Pentagons ability to keep tabs on its own satellites and others in space, Ellis said. The Pentagon must be able to determine whether one its satellites is under attack, or if it is being disrupted by a factor like a space weather disturbance or a normal satellite failure, he said. "We need to define what constitutes a threat," he said.

Protecting satellites is a mission that will take place in space, as well as on the ground, as enemies may seek to attack U.S. satellite ground stations, Ellis said. The battle may also extend to cyberspace if enemies attempt to disrupt satellite operations through hacking into computer networks, he said.

In addition to protecting its own satellites, the Pentagon must also be prepared to respond to enemy use of satellites ranging from GPS to commercial remote sensing spacecraft against U.S. forces, Ellis said. But in preparation for those capabilities, Ellis noted that a lot of work needs to be done so that the Pentagon understands the rules of engagement and the consequences and potential collateral damage issues if the U.S. takes steps to protect its satellites.

The Pentagon also needs to devote significant attention to its space modernization plans, Ellis said. The military cannot afford failure as it moves forward on programs like the Space Based Infrared System (SBIRS) High, which is intended to begin replacing the Defense Support Program missile warning satellites later this decade.

While programs like SBIRS High have experienced significant cost growth and schedule delays, the military should not be overly critical of program officials who are often not given the tools and resources they need to deal with complex programs, Ellis said. As the military moves forward on SBIRS High and other space programs, it must recognize the processes that have gone wrong in the past and make changes, he said.