NASA's Interface Region Imaging Spectrograph (IRIS) spacecraft captured this image of several large solar prominences on the edge of the sun. Credit: NASA

WASHINGTON — NASA plans to start its competition for a $115 million heliophysics mission — which would notionally launch in 2022 — in the spring or early summer of 2016, according to a note posted on the agency’s procurement website.

As usual for NASA’s series of competitively awarded, principal investigator-led missions, the cost cap for the upcoming Heliophysics Small Explorer mission excludes launch. NASA expects to release a draft solicitation by the end of the year, according to an undated advance procurement notice posed by the agency.

Proposals are due 90 days after the final solicitation drops, according to NASA’s note. The agency will spend about a year grading proposals before selecting two or three finalists in early 2017, each of which will get one-year, $1 million study grants to refine their proposals. NASA plans to make a final down-select in 2018.

NASA’s most recently launched Heliophysics Small Explorer mission was the Interface Region Imaging Spectrograph, which lifted off in 2013 on a two-year primary mission that wrapped up in June. The mission was approved for a two-year extension in April as part of the biennial NASA Senior Review of Heliophysics Operating Missions.

NASA’s Heliophysics Division, like the Astrophysics Division, funds both small- and medium-sized Explorer missions.

The last Heliophysics Explorer competition was for a medium-sized mission whose cost was capped at $200 million, excluding launch. NASA in 2013 selected the Ionospheric Connection Explorer, which is now under construction and slated to launch in 2017 aboard an Orbital ATK Pegasus XL rocket.

NASA’s Heliophysics Division, which has a roughly $660 million annual budget under the stopgap U.S. federal spending bill approved Sept. 30, studies the sun and its interactions with Earth.

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.