WASHINGTON — The U.S. National Oceanic and Atmospheric Administration requested a $165 million increase for its satellite division in 2015 to buy spare instruments for its polar-orbiting weather satellite program, speed up the launch of an international ocean topography mission and study whether to fly a climate sensor left over from a canceled civil-military program as a hosted payload.

In all, NOAA is seeking $2.25 billion for its National Environmental Satellite, Data, and Information Service next year.

The biggest chunk of the proposed increase would go toward instrument spares for the Joint Polar Satellite System (JPSS) program, which is designed to provide global coverage from polar orbit through 2025 at an estimated life-cycle cost of about $11.3 billion. NOAA wants $916 million for JPSS in 2015, about $95 million more than Congress appropriated in 2014, according to budget documents released March 13.

With the extra funding, NOAA would purchase copies of the Advanced Technology Microwave Sounder and Cross-track Infrared Sounder instruments for the planned JPSS-2 satellite. Those sensors, a subset of the JPSS-2 instrument package, are built by Northrop Grumman Electronic Systems and Exelis Geospatial Systems, respectively.

A prototype JPSS satellite, Suomi-NPP, launched on a five-year mission in October 2011. JPSS-1 is scheduled to launch by March 2017, and JPSS-2, which is not yet under contract, is scheduled to launch by December 2021, according to NOAA’s 2015 budget request.

Experts have warned of a gap in coverage should one of those satellites encounter delays or fail prematurely.

In the budget documents, NOAA ruled out the possibility of launching JPSS-1 early, but left the door open for moving up the launch date for JPSS-2. Starting work on JPSS-2 instruments now “may enable options to accelerate JPSS-2 schedules and reduce risk of a data gap between JPSS-1 and JPSS-2,” NOAA said.

NOAA also said it is considering other “potential gap mitigation missions” within the JPSS program but did not provide details.

All five JPSS-1 instruments, meanwhile, have been completed and are in environmental testing.

NOAA requested roughly $942 million for its other main satellite program, the Geostationary Operational Environmental Satellite system, an increase of nearly $39 million over the 2014 appropriation. NOAA says it needs to add 48 full-time workers to keep the first of the new-generation Geostationary Operational Environmental Satellite-R satellites on track for a March 2016 launch.

The Geostationary Operational Environmental Satellite constellation includes three spacecraft: one to watch the U.S. East Coast, one for the West Coast, and an on-orbit spare. A total of four of the new-generation satellites are under contract to Lockheed Martin Space Systems of Denver.

Meanwhile, NOAA is seeking roughly $26 million for the Jason-3 ocean altimetry satellite, some $7 million more than the 2014 appropriation. NOAA says it needs the extra money to make sure that Jason-3, slated to launch on a Space Exploration Technologies Corp. Falcon 9 rocket, lifts off by March 31, 2015.

NOAA said its European partners on Jason-3 threatened to cancel their participation if the agency could not guarantee the launch by next spring. NOAA had previously scheduled the launch by the end of next year.

But another Falcon 9 launch, of NOAA’s Deep Space Climate Observatory, is being delayed from November 2014 to April 2015 due to a shortfall in NASA’s contribution to the mission, and delays on SpaceX’s end, NOAA’s budget documents said. NOAA will use the 570-kilogram spacecraft, left over from an Earth observing mission that was conceived in 1998 by then-U.S. Vice President Al Gore but never flown, to observe space weather.

NOAA appears to have dropped plans for a so-called Polar Free Flyer satellite to host some of the instruments orphaned by the 2010 cancellation of the civil-military weather satellite program that preceded JPSS. Congress declined to fund the Polar Free Flyer this year.

But NOAA is not giving up on the instruments. The agency requested $15 million for an effort called Solar Irradiance, Data and Rescue, which is aimed at finding other ways to get these instruments — including a climate-change sensor and a search and rescue payload — to space.

One possibility is to fly the climate-change sensor, built by the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder, as a hosted payload, NOAA said.

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