WASHINGTON — NASA’s top science official reminded members of the scientific community March 6 that budgets for small, competitively selected Earth and space science missions will be among the first programs to feel the pain of across-the-board spending cuts that took effect March 1.

Speaking to members of the National Research Council’s (NRC) Space Studies Board, who met here March 6-8 as part of NRC Space Science Week 2013, John Grunsfeld, associate administrator for NASA’s Science Mission Directorate, reiterated warnings NASA Administrator Charles Bolden delivered to Congress last month: Funding for NASA’s Astrophysics Explorer and Earth Science Venture programs of competitively selected missions would be reduced 10 percent to 15 percent this year because of sequestration.

Postponing solicitations and delaying selections is more palatable to NASA than withholding funds from missions that are in development, or which have already launched, Grunsfeld said.

“When you look at where the budget lies, the only place where there are new programs that have a significant budget that can be adjusted by 10 percent to 15 percent, it’s in the start of new things,” Grunsfeld told NRC members March 6. “And we’re not starting other new things, [but we are] starting new Explorers, new Discoveries, those kind of missions.

“They’re not being singled out,” Grunsfeld added, explaining to one NRC member why small mission lines would absorb a greater cut than the blanket 5 percent reduction prescribed by the White House Office of Management and Budget for sequestration.

NASA’s Astrophysics Division had about $112 million in its budget for Explorer-class missions, prior to sequestration. A 15 percent cut to that would leave the program line with about $95 million for 2013. The same cut applied to the Earth Venture line would leave that program with $46 million for this year, down from the presequestration level of $53.6 million.

All four divisions of NASA’s Science Mission Directorate have a series of competitively selected, cost-capped missions that are led by the principal investigator who submitted the proposal. When sequestration hit March 1, The Earth Science and Astrophysics divisions had competitions under way, or were planning new competitions for later in the year. NASA’s Planetary Science Division meanwhile, selected its most recent Discovery-class mission in August and does not plan to issue a new call for mission proposals until 2015.

A NASA spokesman said cuts to the Explorer and Earth Venture lines would delay the opening of new competitions and postpone  final selections in ongoing competitions. Missions that are in development or have been selected to proceed into development would not be affected.

“The impact of a sequester would not affect any Earth Venture or Explorer missions already selected or in development,” NASA spokesman Stephen Cole said in an email. However, “a sequester could mean delaying new solicitations and selections for Earth Venture and Explorer missions.”

NASA was supposed to announce the winner of an ongoing Astrophysics Explorer-class competition this spring and begin a new competition for a Small Explorer-class mission later in the year. The current competition is down to two proposals: the Fast Infrared Exoplanet Spectroscopy Survey Explorer, which would observe the atmospheres of planets outside our solar system, and the Transiting Exoplanet Survey Satellite, an alien planet hunter similar to the Kepler telescope.

The agency was also expected to begin a competition for an Earth Venture  mission that could be conducted aboard an aircraft or suborbital rocket and solicit Earth Venture Instruments proposals for sensors that would hitch a ride satellites being built for other purposes.

Dan Leone is the NASA reporter for SpaceNews, where he also covers other civilian-run U.S. government space programs and a growing number of entrepreneurial space companies. He joined SpaceNews in 2011.Dan earned a bachelor's degree in public communications...