  Space Object Identification is one of the cornerstones of Space Traffic
Control and a requirement for successful operation of a spacecraft.
  ELROI, the Extremely Low Resource Optical Identifier, is a new concept that
can provide a self-powered satellite identification beacon in a package the
size of a thick postage stamp. Its small size, low cost, and fully autonomous
operation make it usable by all space objects, including CubeSats and inert
debris objects.
  The beacon's signal is received on the ground using a small telescope
equipped with a photon-counting detector which can unambiguously determine the
satellite identification number during a single pass overhead. Additional
information can be included in the signal to aid in anomaly diagnosis and
resolution, further improving spaceflight reliability and safety.
  The first ELROI unit in orbit was launched December, 2018 as a payload on the
student CubeSat NMTSat. We are now searching for the identification signal.
