The Delta 4-Heavy rocket launches at 9:47 p.m. EST on January 17. Credit: Chris Miller/Spaceflight Now

The NRO payload on the Delta 4-Heavy is a 5-to-6 ton eavesdropping spacecraft with a high tech deployable antenna as wide as 350 feet.

The spacecraft is to enhance the capability for the U.S. to listen in on communications in hostile governments like Iran and terrorist organizations like Al Qaeda.

The NROL-26 mission has worried NRO officials and other intelligence professionals because of concerns about flying the critical satellite on the new Delta 4-Heavy.

If the mission was to fail, it would spark another crisis in the U. S. intelligence community, already burdened with growing tasks from an increasingly dangerous world.

The satellite is likely an "Advanced Mentor" design, according to GlobalSecurity.Org, a military think tank. Earlier versions were designated Orion.

Due to satellite development delays and a 1998 Titan launch failure involving an earlier "Mercury" eavesdropper design, the U.S. has fallen as much as one or two spacecraft behind its original 10-year schedule to launch such giant eavesdroppers. These spacecraft provide the kind of information the White House, State Dept. and Pentagon need to make military and national foreign policy decisions.

It is also likely a "broad spectrum" satellite that can update key frequency information on hostile radars and other detection systems that could threaten U.S. forces.

The three earlier Mentor spacecraft introduced a very large 'wrap-rib' deployable antenna design spanning up to 350 feet, says GlobalSecurity.Org.

The Delta 4-Heavy rocket launches at 9:47 p.m. EST on January 17. Credit: Chris Miller/Spaceflight Now

The National Security Agency will be the prime distributor of the spacecraft's data, sending information from the satellite to the other 15 agencies and organizations that now make up the intelligence community.

It has been five years since a large geosynchronous orbit eavesdropping satellite has been launched from Cape Canaveral. That earlier satellite, believed to have been a less capable version of the Mentor, was lofted on board a Titan-Centaur booster in September 2003.

Over the last two-and-a-half years, however, two different eavesdropping satellites have been launched on smaller Delta 4-Medium and Atlas 5 rockets from Vandenberg Air Force Base, Calif. These spacecraft, with smaller antennas, are in highly elliptical orbits of roughly 700 x 23,500 miles.

Instead of remaining parked over one location above the equator, these Vandenberg-launched satellites travel up and down over the northern hemisphere. They can listen into radio communications from different locations or radio waves monitored from different angles, compared with geosynchronous orbit satellites.

The data from these different eavesdroppers is then combined and assessed with other sources of information including that obtained by aircraft such as advanced versions of the U-2.

Additional coverage for subscribers:
VIDEO: FULL LAUNCH EXPERIENCE PLAY
VIDEO: LAUNCH PAD CAMERA NO. 1 PLAY
VIDEO: LAUNCH PAD CAMERA NO. 2 PLAY
VIDEO: THE DELTA 4-HEAVY ROCKET LIFTS OFF PLAY
VIDEO: LAUNCH AS SEEN FROM PRESS VIEWING SITE PLAY | HI-DEF
VIDEO: TIME-LAPSE MOVIE OF THE GANTRY RETRACTING PLAY | HI-DEF
VIDEO: LAUNCH PAD'S MOBILE GANTRY ROLLED BACK PLAY | HI-DEF
MORE: PREVIOUS DELTA 4-HEAVY COVERAGE
SUBSCRIBE NOW