WASHINGTON — The U.S. National Oceanic and Atmospheric Administration and Taiwan’s Ministry of Science and Technology agreed this month to scrap plans for a second set of next-generation GPS radio occultation weather satellites after determining the joint project faced an unwinnable battle to secure funding.

In a joint memorandum obtained by SpaceNews, the two agencies concluded that they would not pursue development of a second set of six Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) 2 satellites, known as COSMIC-2B, citing challenges to secure support in both countries.

COSMIC-2, also known as FORMOSAT-7, was originally planned to feature two sets of six satellites to collect GPS radio occultation data used in weather forecasting. An initial set of six satellites, known as COSMIC-2A, has been built and is scheduled for launch as part of the U.S. Air Force’s Space Test Program 2 mission, launching on a SpaceX Falcon Heavy in early 2018.

The COSMIC-2A satellites, operating in low-inclination orbits, were to be complemented by six satellites collectively known as COSMIC-2B that would operate in highly-inclined orbits. COSMIC-2B would be a replacement for the original COSMIC satellites, launched into high-inclination orbits in 2006.

The satellites measure signals from GPS and other navigation satellites as they skim through the atmosphere, using them as a probe of temperature and humidity conditions that fed into weather forecast models. Studies have concluded that GPS radio occultation data is among the best sources of data for improving the accuracy of forecasts.

However, the memo, prepared by a joint Executive Steering Committee of U.S. and Taiwanese officials, found that both countries were finding problems financing the payloads, satellites and launch of the COSMIC-2B system.

“At the senior-level meetings on June 19-20, 2017, NOAA and NSPO both acknowledged the difficulty in finding a viable path forward in exercising the option for COSMIC-2B,” the memo stated. NSPO is Taiwan’s space agency, the National Space Organization.

NOAA, responsible for the COSMIC-2 payloads, did not receive any funding for the COSMIC-2B payloads in the fiscal year 2017 omnibus appropriations bill enacted in May. The agency’s fiscal year 2018 request, released several weeks later, also requested no funding for COSMIC-2B payloads.

Uncertainty about funding for those payloads, in turn, created problems for NSPO, responsible for the satellites. “NSPO has had difficulty to secure the 2nd set of FORMOSAT-7 from the Ministry of Science and Technology (MOST) budget since 2014 because the funding of the second set of mission payloads remains uncertain,” the memo stated.

Launch options for the COSMIC-2B mission were also an issue. NASA had proposed flying four the satellites as secondary payloads on the launch of the agency’s Surface Water Ocean Tomography mission, scheduled for April 2021 on a SpaceX Falcon 9. However, NSPO “would face technical, schedule and resource challenges” in getting the satellites ready in time for that launch. The memo didn’t state what plans, if any, existed for the other two COSMIC-2B satellites.

NSPO added that its ministry had given direction “not to pursue FORMOSAT-7 Launch #2 given new priorities,” which were not stated in the memo.

That memo concluded that the Executive Steering Committee “decided not to exercise the option for COSMIC-2B/FORMOSAT-7.” The joint program would proceed with the six COSMIC-2A satellites but “will not pursue additional FORMOSAT-7/COSMIC-2 satellites” beyond them. The memo was signed by NOAA officials Oct. 6 and by their Taiwanese counterparts Oct. 16.

COSMIC-2 had become controversial in the U.S. because of perceptions by companies developing their own GPS radio occultation (RO) systems that the government was competing with them. NOAA, under pressure from Congress, started a pilot program in 2016 to purchase commercial GPS radio occultation data, awarding contracts to GeoOptics and Spire that concluded earlier this year.

In report language accompanying the 2017 omnibus appropriations bill, Congress indicated that it wanted to NOAA to consider commercial sources of that data alongside development of the COSMIC-2B satellites.

“Within 90 days of enactment of this Act, NOAA shall submit an analysis of options for acquiring polar RO data that includes a cost analysis of all alternatives and demonstrates that NOAA has thoroughly reviewed potential commercial RO sources,” the act stated in the section discussing the lack of funding for COSMIC-2B.

“If the plan proposes moving forward with additional COSMIC-2 satellites,” it continued, “the plan shall include the total cost to the U.S. government of developing, procuring, launching, and operating COSMIC-2 polar orbiting satellites, including how they would be launched and what Federal agency would incur that cost.”

NOAA has not disclosed the outcome of analysis of data collected in the initial phase of the pilot program, where only Spire was able to provide GPS RO data. The memo, though, stated that NOAA didn’t yet believe commercial data was ready for routine use.

“While the commercial sector is not at present a viable source for [GPS radio occultation] data for operational use, NOAA will continue to evaluate it as a potential source for the future,” the memo stated.

The Weather Research and Forecasting Innovation Act of 2017, signed into law in April, authorized continued development of a government-funded satellite system to collect GPS radio occultation data. The bill calls on NOAA to “complete and operationalize” the COSMIC-2 mission, placing satellites into both equatorial and polar orbits.

NOAA spokesman John Leslie did not immediately respond to an Oct. 17 email requesting comment on the status of COSMIC-2B.

Brian Berger contributed to this article.