WASHINGTON — The U.S. Defense Department is warning that some of the proposals contained in the House and Senate versions of the pending defense authorization bill for 2015 would delay and otherwise hinder the Air Force’s efforts to reshape its space portfolio.

In a 105-page packet of conference appeals from the Defense Department’s assistant secretary for legislative affairs and obtained by SpaceNews, military leaders asked for changes that would allow the Air Force more freedom as it investigates future potential satellite architectures. House and Senate authorizers are expected to meet in conference before the year’s end to reconcile the differences in their respective versions of the defense policy bill.

Air Force officials have argued that a new contested and congested space environment calls for a constellation architecture that is less vulnerable than the current scheme, which relies heavily on large, multimission spacecraft. But some in Congress are resisting major changes, arguing that the service has not fully maximized the capabilities on the satellites it currently has on orbit.

These differences have manifested themselves most sharply in the Air Force’s Space Modernization Initiative budget, which the service uses to explore next-generation satellite capabilities.

In marking up its version of the Defense Authorization Act for 2015, for example, the House Armed Services Committee authorized the full requested amounts for the Air Force’s Space Based Infrared System missile warning satellites, and for its Advanced Extremely High Frequency constellation of secure communications satellites. But the committee also adopted amendments targeting key modernization initiatives within those programs.

The Air Force is in the midst of an analysis of alternatives for future space-based missile warning. In the meantime, the Air Force is seeking $21 million in its SBIRS modernization budget next year for hosted payload activities and $29 million for a wide-field-of-view sensor demonstration program.

The House bill would fence off half of that modernization funding until after the analysis of alternatives is complete and the results shared with congressional defense committees.

That provision, the appeal said, “would significantly narrow the decision space for a follow-on system, restrict the future competitive environment, and delay fielding of new capabilities to meet evolving threats.”

Specifically, it could force the Air Force to delay the launch of an experimental 6-degree field of view sensor under development by a division of L-3 Communications. “Lack of data from alternatives could also lead to a decision that eliminates opportunities to mature and insert new technologies and foster competition for another generation,” the appeal said.

As a compromise, the Defense Department recommended that the House-Senate conference committee fence off just 25 percent of the requested modernization funding.

Similarly, the House bill fences off 50 percent of the money requested to demonstrate next-generation capabilities in protected satellite communications pending completion of an analysis of alternatives on the AEHF program. The Air Force requested $23 million next year for a protected tactical communications demonstration and $14 million for a protected military satellite communications testbed.

The Defense Department said these activities are “vital” to Air Force efforts to explore next-generation protected communication satellites.

In the weather arena, the House bill would limit funding for a follow-on weather satellite program until the secretary of defense submits to Congress a report on the Pentagon’s meteorological and oceanographic collection requirements, its use of weather data from outside sources and a launch plan for its legacy Defense Meteorological Satellite Program (DMSP) Flight 20 satellite.

In its appeal, the Defense Department said the data that would be collected by the proposed new weather satellites are not available from the DMSP satellites. This includes data on the space radiation environment that are necessary to protect other on-orbit assets.

“Loss of this information would drive significant operational risk to global naval and amphibious operations which depend on timely and accurate tropical cyclone and ocean wind information,” the appeal said. “Additionally, U.S. military, civil, and commercial satellites valued in the billions of dollars could be risked without critical energetic particle information required for satellite protection and anomaly attribution.”

The Air Force had requested $39 million for the new weather satellite program. The House recommended $5 million.

Meanwhile, the report accompanying the Senate version of the bill would prohibit the Air Force from storing DMSP-20 unless the defense secretary said storing the satellite until 2020 is the most cost-effective approach.

According to the Defense Department, however, any such restriction could “potentially increase the overall cost and delay the availability of Flight-20 to support a launch call-up.”

Air Force officials are considering launching the satellite in 2016.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.