Dear Colleague:

NASA has initiated a community-based process to identify Mission Concepts for candidate large missions to follow the James Webb Space Telescope (JWST) and the Wide-Field Infrared Survey Telescope (WFIRST). For details on the process, please refer to "Planning for the 2020 Decadal Survey: An Astrophysics Division White Paper," available at NASA Astrophysics Documents. As a result of this process, the community identified four candidate missions for prioritization by the 2020 Decadal Survey:

• The Far Infrared (IR) Surveyor
• The Habitable-Exoplanet Imaging Mission
• The Large Ultraviolet (UV), Optical, and Infrared Surveyor
• The X-ray Surveyor

These are the mission concepts that NASA will study, as candidates for the missions to follow JWST and WFIRST, in preparation for the 2020 Decadal Survey.

In this letter, NASA is soliciting applications from interested individuals in the community for participation as members of Science and Technology Definition Teams (STDTs) for the four mission concepts. The STDTs will provide science parameters, investigation approaches, key mission parameters, and any other scientific studies needed to support the definition of a space mission concept (Design Reference Mission). The STDTs will document their findings in final reports (one for each of the four STDTs), which will be used by NASA as input to the 2020 Decadal Survey. The Charter for the STDTs and related documents are available at Decadal Survey Planning.

Applications for the STDT memberships are due to NASA no later than February 1, 2016. Only E-mail applications of a single PDF file will be accepted. Please submit your application via E-mail to the NASA contact for the mission concept of choice listed in the Table below.

The application material should consist of:

• A two-page cover letter including (1) identification of the STDT of choice, (2) the reasons for the applicant's interest in the STDT, and (3) the capabilities and experience that the applicant brings to the STDT;
• A short statement of commitment to perform the tasks assigned to the STDT within the allocated timeframe, and
• A one or two-page resume, including relevant activities and publications.

Applications are solicited from individuals at U.S.-based research and academic institutions, Government laboratories, and industry, and from private individuals.

STDT members will be selected so that the STDT has members with expertise in relevant science areas, relevant hardware and technology, optics, detectors, and both ground- and space-based approaches to the implementation of the science priorities. NASA will accept additional suggestions for STDT membership from the community at large, including NASA Centers. The NASA Astrophysics Division Director will appoint the members of the STDTs after consulting with the Headquarters, program, and study scientists involved. The STDT Chairs will be appointed from the STDT membership.

Applicants are allowed to apply for simultaneous membership on more than one STDT, provided that a compelling rationale is provided in the application.

NASA reserves the right to cancel this Dear Colleague Letter at any time should programmatic and/or other reasons warrant it.

Questions about the specific STDT may be addressed to the corresponding Program Scientist at NASA Headquarters as listed in the Table below.

Surveyor / STDT	NASA HQ Program Scientist	Contact Information
Far IR Surveyor	Dr. Kartik Sheth	kartik.sheth@nasa.gov 202-358-4805
Habitable Exoplanet Imaging Mission	Dr. Martin Still	martin.still@nasa.gov 202-358-4462
Large UV, Optical, IR Surveyor	Dr. Mario Perez	mario.perez@nasa.gov 202-358-1535
X-ray Surveyor	Dr. Daniel Evans	daniel.a.evans@nasa.gov 202-358-3882