WASHINGTON — NASA has updated a planned call for proposals for lunar landers to enable a human mission in 2024, broadening the scope to include integrated lander concepts.

In a procurement filing issued late April 26, NASA updated an earlier notice published April 8 that announced plans to solicit proposals for an ascent stage for a human-rated lunar lander. Instead, the upcoming procurement will seek proposals for “a complete integrated lander” that includes an ascent module as well as a descent module and transfer stage.

A formal call for proposals, part of NASA’s Next Space Technologies for Exploration Partnerships, or NextSTEP, program and formally known as Appendix H, has yet to be released by the agency. NASA said on the NextSTEP website that it anticipates issuing that solicitation by the end of May, and will include both studies as well as options for vehicle development.

“NASA will seek proposals from U.S. industry for the development, integration, and crewed demonstration of these elements as a functional human landing system that can fulfill NASA and industry requirements,” including landing people on the moon by 2024, the agency stated.

Prior to the announcement by Vice President Mike Pence March 26 that called for a human lunar landing in five years, NASA was going on a two-track approach for developing human-class lunar landers. In February, it released a separate solicitation for studies of transfer vehicles and descent stages, also as part of NextSTEP and designated Appendix E. At the time, NASA said it would keep studies of the ascent stage within the agency.

However, NASA changed course after Pence’s speech, announcing plans for the ascent stage work in the April 8 presolicitation notice. NASA Administrator Jim Bridenstine, in an April 9 speech at the 35th Space Symposium in Colorado Springs, said that notice was developed within a week. He added that he expected the lunar lander systems to be built as public private partnerships.

The updated plans provide a second chance for those who did not participate in the earlier lander studies solicitation or who do not get awards. “Appendix H offerors who are not awardees on Appendix E will be afforded the opportunity to propose similar work, to the extent it is necessary for their Appendix H proposals,” NASA stated in the revised procurement filing.