  Small spacecraft now have precise attitude control systems available
commercially, allowing them to slew in 3 degrees of freedom, and capture images
within short notice. When combined with appropriate software, this agility can
significantly increase response rate, revisit time and coverage. In prior work,
we have demonstrated an algorithmic framework that combines orbital mechanics,
attitude control and scheduling optimization to plan the time-varying,
full-body orientation of agile, small spacecraft in a constellation. The
proposed schedule optimization would run at the ground station autonomously,
and the resultant schedules uplinked to the spacecraft for execution. The
algorithm is generalizable over small steerable spacecraft, control capability,
sensor specs, imaging requirements, and regions of interest. In this article,
we modify the algorithm to run onboard small spacecraft, such that the
constellation can make time-sensitive decisions to slew and capture images
autonomously, without ground control. We have developed a communication module
based on Delay/Disruption Tolerant Networking (DTN) for onboard data management
and routing among the satellites, which will work in conjunction with the other
modules to optimize the schedule of agile communication and steering. We then
apply this preliminary framework on representative constellations to simulate
targeted measurements of episodic precipitation events and subsequent urban
floods. The command and control efficiency of our agile algorithm is compared
to non-agile (11.3x improvement) and non-DTN (21% improvement) constellations.
