WASHINGTON — A pair of international Earth observing spacecraft will now launch six months later than planned because of a roughly $200 million cost overrun on NASA’s Ice, Cloud, and land Elevation Satellite (IceSat)-2, the agency said in a report delivered to Congress July 28.

Paying the price for IceSat-2’s long-publicized overrun are a NASA-Indian Space Research Organisation synthetic aperture radar satellite slated to launch in 2020 and the Pre-Aerosol, Clouds, and ocean Ecosystem satellite, a Franco-U.S. collaboration penciled in for liftoff in 2019 to observe global ocean color and aerosols. Funds for the missions, which are in the early planning phases, were steered into IceSat-2’s budget.

IceSat-2 is now expected to cost roughly $760 million to build and launch, about 36 percent more than the baseline estimate NASA established in 2012, when the high-priority mission entered development, according to the IceSat-2 Project Cost and Schedule Analysis Report, a copy of which was obtained by SpaceNews. NASA announced in December the mission was likely to exceed its budget by a wide enough margin to trigger this mandatory report to Congress.

Including the cost of operating the satellite in a 495-kilometer polar orbit for its three-year primary mission to measure the height of sea-ice and vegetation canopies, the total price tag will run close to $1.1 billion.

NASA has spent some $420 million on the mission already. Launch has slipped to June 2018 from May 2017, NASA said in the report.

As part of its report, NASA was required to examine alternatives to replanning the IceSat-2 mission, including finding some other way to meet its science objectives. That, NASA concluded in the report, would be impossible. Neither aircraft observations nor the radar altimetry instruments aboard a pair of European Space Agency satellites — the CryoSat-2 spacecraft that launched in 2010 and the Sentinel-3 spacecraft set to blast off in 2015 — are suitable replacements for IceSat-2, the successor to the IceSat mission that ended in 2010 after seven years on orbit, NASA said.

IceSat-2’s overrun was driven primarily by technical difficulties with the satellite’s lone science instrument, the Advanced Topographic Laser Altimeter System, which was designed and developed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with help from contractor Fibertek Inc. of Herndon, Virginia. NASA’s Earth Science Division will foot the bill for putting the laser’s development back on track, the agency told Congress.

NASA said some $180 million of the IceSat-2 overrun will be covered with savings or expected savings on missions including: the Global Precipitation Measurement core satellite that launched in February; the Gravity Recovery and Climate Experiment Follow-On slated to launch in 2017; the Orbiting Carbon Observatory-2 that launched in July; and the Soil Moisture Active Passive mission scheduled for liftoff no earlier than January.

Following a presentation on an unrelated matter at a National Research Council meeting here, Michael Freilich, director of NASA’s Earth Science Division, declined to discuss the IceSat-2 replan on the grounds that the agency had already prepared a formal report for Congress.

“I have nothing to add on IceSat,” Freilich said.

An aide for the Republican majority on the House Science Committee said committee leaders were willing to wait and see how NASA’s new plan for IceSat-2 plays out in the near-term.

“The committee will continue to monitor the status of this program,” the aide said. “Cost growth in systems like IceSat-2 remind us of the trades that have to be made between maintaining existing datasets in perpetuity versus developing new systems and sensors.  The overrun associated with the program will unfortunately come at the expense of new datasets and missions, so NASA must be mindful of additional cost growth.”

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.