  This paper presents initial flight results for distributed optical
angles-only navigation of a swarm of small spacecraft, conducted during the
Starling Formation-Flying Optical Experiment (StarFOX). StarFOX is a core
payload of the NASA Starling mission, which consists of four CubeSats launched
in 2023. Prior angles-only flight demonstrations have only featured one
observer and target and have relied upon a-priori target orbit knowledge for
initialization, translational maneuvers to resolve target range, and external
absolute orbit updates to maintain convergence. StarFOX overcomes these
limitations by applying the angles-only Absolute and Relative Trajectory
Measurement System (ARTMS), which integrates three novel algorithms. Image
Processing detects and tracks multiple targets in images from each satellite's
on-board camera. Batch Orbit Determination computes initial swarm orbit
estimates from bearing angle batches. Sequential Orbit Determination leverages
an unscented Kalman filter to refine swarm state estimates over time.
Multi-observer measurements shared over an intersatellite link are seamlessly
fused to enable absolute and relative orbit determination. StarFOX flight data
presents the first demonstrations of autonomous angles-only navigation for a
satellite swarm, including multi-target and multi-observer relative navigation;
autonomous initialization of navigation for unknown targets; and simultaneous
absolute and relative orbit determination. Relative positioning uncertainties
of 1.3% of target range (1$\sigma$) are achieved for a single observer under
challenging measurement conditions, reduced to 0.6% (1$\sigma$) with multiple
observers. Results demonstrate promising performance with regards to ongoing
StarFOX campaigns and the application of angles-only navigation to future
distributed missions.
