NASA planetary scientists and procurement officials are doing the right thing by setting their own pace rather than rushing to meet a congressional deadline in putting together the latest proposal solicitation for the agency’s long-running series of Discovery-class missions.

James Green, director of NASA’s Planetary Science Division, said in January that while his office was working at a “brisk pace” to draft and release the announcement of opportunity (AO), the May 1 date was unrealistic and would not allow potential responders adequate time to prepare. NASA is working on a draft solicitation for public comment and has a goal of issuing the final version before October, he said.

In the report accompanying the Consolidated Appropriations Act for fiscal year 2014, signed into law Jan. 17 by U.S. President Barack Obama, Congress urged NASA to pick up the pace of activity on its Discovery program of cost-capped, principal investigator-driven planetary missions. The report urged NASA to initiate the latest AO “no later than May 1.”

To be sure, congressional interest in keeping the Discovery brand going is a very good thing. This has been a highly successful program for nearly two decades, filling gaps between so-called flagship-class missions with smaller probes that carry out exciting and meaningful science at an affordable cost. Discovery spacecraft have, among other things, landed on Mars, visited an asteroid, collected and returned sample material from the tail of a comet, and discovered hundreds of so-called exoplanets, many with the potential to support life.

But setting aside the obvious irony of the fact that Congress’ deadline was handed down in 2014 funding legislation that wasn’t passed until the fiscal year was already one-fourth over, the process of putting together a science-driven mission that draws on the best available research and ideas is not one that lends itself to randomly imposed timetables. Scientists need time to formulate their concepts and assemble industry and academic teams to execute the mission; NASA must take stock of what’s out there and determine how it fits with its priorities and available budgets.

It was encouraging to hear that preparations for the latest Discovery AO are in full swing. Equally encouraging is that NASA, while mindful of Congress’ eagerness to move ahead quickly, is taking the time to get it right.

Congressional enthusiasm and support for the Discovery program, and planetary science in general, is always welcome, and lawmakers deserve credit for wanting to keep the momentum going. But the best way to demonstrate that support is to pass targeted, detailed budgets for U.S. federal agencies like NASA before the start of each fiscal year.