  We have conducted a data study of leadership and participation in NASA's
Astrophysics Explorer-class missions for the nine solicitations issued during
the period 2008-2016, using gender as a marker of diversity. During this time,
102 Principal Investigators (PIs) submitted Explorer-class proposals; only four
of these PIs were female. Among the 102 PIs, there were 61 unique PIs overall;
of these, just three were female. The percentage of females in science teams in
these proposals ranges from a low of 10% to a high of 19% across the various
solicitations. Combining data from all these Explorer-class proposals, we find
that the overall participation by females in science teams is 14%. Eighteen of
the Explorer-class proposals had zero females in science roles, and this
includes science teams with as many as 28 members. These results demonstrate
that participation by women in the leadership of and, in many cases, on the
science teams of proposals for Explorer-class missions is well below the
representation of women in astronomy and astrophysics as a whole. In this white
paper, we present our data and a discussion of our results, their context, and
the ramifications for consideration by Astro2020 in its study of the state of
the profession.
