WASHINGTON — NASA defended the selection of two concepts for study as the agency’s first astrophysics probe-class mission amid community complaints that the two missions are not on an equal footing. NASA announced Oct. 3 that it picked two proposals for further study for its new Astrophysics Probe Explorer, or APEX, line of missions. The two proposals each received $5 million for one-year studies to refine their designs. NASA plans to pick one of the proposals in 2026 as the first probe-class mission for launch in 2032. The APEX program,…