On April 3, 2019, the National Aeronautics and Space Administration (NASA) Science Mission Directorate (SMD) is releasing two solicitations for Astrophysics Explorers Science Investigations.

1. Solicitation Number: NNH19ZDA011O (Small Explorer AO) 
2. Solicitation Number: NNH17ZDA004O-APEXMO (Amendment 14 to the SALMON-3 AO: NNH17ZDA004O)

Mandatory Notice of Intent Due: May 15, 2019;   Proposals Due: August 1, 2019

NASA released concurrently the 2019 Astrophysics Small Explorer Announcement of Opportunity (NNH19ZDA011O), and the 2019 Astrophysics Explorers Mission of Opportunity (MO) Program Element Appendix (PEA) (NNH17ZDA004O-APEXMO) as Amendment 14 to the NASA Third Stand Alone Missions of Opportunity Notice (SALMON-3) Announcement of Opportunity NNH17ZDA004O.

NSPIRES is the official NASA source for the full text of the solicitations and all appendices, therefore please visit: http://nspires.nasaprs.com/.

A joint Preproposal Conference will be held via teleconference/WebEx in early May, 2019. The forthcoming date, agenda, and logistical information for this session maybe found by searching the Acquisition Homepage: https://explorers.larc.nasa.gov/2019APSMEX/.

The Astrophysics Explorers Program conducts Principal Investigator (PI)-led space science investigations relevant to SMD's astrophysics programs. Astrophysics Explorers investigations must address NASA’s strategic objective to discover how the universe works, explore how it began and evolved, and search for life on planets around other stars.

Prospective investigators from any category of organizations or institutions, U.S. or non-U.S., are welcome to respond to this solicitation. Specific categories of organizations and institutions that are welcome to respond include, but are not limited to, educational, industrial, and not-for-profit organizations, Federally Funded Research and Development Centers (FFRDCs), University Affiliated Research Centers (UARCs), NASA Centers, the Jet Propulsion Laboratory (JPL), and other Government agencies. Non-U.S. organizations may participate on a no-exchange-of-funds basis.

NASA expects to select two to three Astrophysics Explorers Small Explorer missions for Phase A studies, and down select one to proceed into Phase B and subsequent mission phases. NASA expects to select two or more Astrophysics Explorers Missions of Opportunity for Phase A studies, and down select one or more to proceed into Phase B and subsequent mission phases.

The 2019 Small Explorer AO incorporates a number of changes relative to the previous Explorers Program AO and to the Draft 2019 Small Explorer AO. All proposers must read the AO carefully, and all proposals must comply with the requirements, constraints, and guidelines contained within the AO.

The 2019 Mission of Opportunity SALMON-3 PEA incorporates a number of changes relative to the previous Astrophysics Explorers Mission of Opportunity solicitation and to the Draft 2019 Astrophysics Explorers Mission of Opportunity PEA. All proposers must read the SALMON-3 AO and PEA O carefully, and all proposals must comply with the requirements, constraints, and guidelines contained within them.

Comments and questions may be addressed by E-mail to the Astrophysics Explorers Program Scientist Dr. Linda S. Sparke, at linda.s.sparke@nasa.gov (subject line to read "Astrophysics Explorers SMEX AO" or "Astrophysics Explorers MO PEA" as appropriate). Proposers are encouraged to send comments and questions early, so that they may be addressed at the Preproposal Conference.