  Secondary school teachers often lack the necessary content background in
astronomy to teach such a course confidently. Our theory of change postits that
an increased confidence level will increase student retention in astronomy and
related STEM fields. Beyond the science content knowledge though, teachers need
opportunities to embed the content in pedagogically sound practices, and with
appropriate technology tools. We report on our interdisciplinary approach to
designing, developing, fielding, and iteratively improving the San Antonio
Teacher Training Astronomy Academy (SATTAA), an annually offered Teacher
Professional Development program. In particular, we present how our separate
areas of expertise, in content and in STEM pedagogy, led to a synergistic
process of teacher professional development that has now resulted in three
cohorts of alumni. In this paper, we share our interdisciplinary processes and
lessons learned; program metrics are described elsewhere in detail.
