LOS ANGELES — A decision is expected soon on whether to turn over the U.S. Air Force’s experimental TacSat-3 satellite to the military’s combatant commands for operational use. But users of the $60 million spacecraft’s hyperspectral data say aerial vehicles remain more useful because of the large areas of coverage they provide.

TacSat-3 was built by the Air Force Research Laboratory (AFRL) as part of a technology demonstration program that includes a wide variety of military and civil space agencies. Launched in May 2009, TacSat-3 is unlike traditional military satellites because it is directly tasked by users on the ground and returns processed imagery to those users during the same pass overhead.

Its primary sensor collects images of the Earth and breaks down reflected light into hundreds of spectral bands. These bands can be analyzed to determine the elemental composition of surfaces or objects on the ground. The payload was built by Raytheon Space and Airborne Systems of El Segundo, Calif.

TacSat-3 so far has collected some 1,600 hyperspectral images and is working its way through 90 different experiments, AFRL’s TacSat-3 program manager, Tom Cooley, said March 10 at the Responsive Space Conference here.

Data from the satellite have been used in operational missions, and the Pentagon in April will decide whether to hand the spacecraft over to the combatant commands to use full-time starting in May, said Air Force Lt. Col. Ryan Pendleton, who is leading a TacSat-3 follow-on capability planning effort. Air Force Gen. Kevin Chilton, commander of U.S. Strategic Command, directed in 2008 that the ground architecture to support TacSat-3 operations be put in place, and those systems are now ready, Pendleton said.

“Performance of the system has been verified. All systems are go from an engineering perspective,” Pendleton said. “There is no doubt that having an on-orbit spectral analyzer that works very well has direct military utility.”

But one set of users that has been involved in the TacSat-3 experiments found collecting hyperspectral imagery from space has a ways to go before it can be very useful to soldiers on the battlefield. Army Maj. Kenneth Nickerson was involved with the satellite’s first experiment, in which TacSat-3 imagery was used to search for the signature of nitric acid, which can be combined with fertilizer to create homemade explosives.

Because the substance is highly caustic, it is typically cured for several days outdoors, and normal electro-optical photography is not able to distinguish the substance from any other, he said during a March 11 panel here.

The soldiers tasked TacSat-3 seven times in a week to look for the substance. TacSat-3 was able to produce operationally useful data, but each swath of imagery covered an area only 2 kilometers by 10 kilometers. By comparison, an aerial vehicle outfitted with a similar sensor can collect 600 square kilometers an hour and fly 10-hour missions, Nickerson said.

“TacSat-3 can do in a year what an aerial sensor can do in a day, and I don’t know how to solve that,” Nickerson said. “It’s the big problem we have. It has good promise, but until we can figure out how to get more than 20 square kilometers, we’re not going to get a lot out of this technology.”

Joe Rouge, director of the National Security Space Office, defended TacSat-3 in a later panel, saying that although it has not worked perfectly, it has proved to be a worthwhile capability.

“Let me give you a little different view on TacSat-3,” Rouge said. “You’re right, if you’ve got [an Unmanned Aerial Vehicle (UAV)] in the area, you ought to use the UAV. But do we think we will be able to fly a UAV over Iran prior to a war kicking off, or China or North Korea or somewhere else? The real key to space systems is their ability to operate in denied areas. TacSat-3 is demonstrating that capability.”