The stare and chase observation strategy at the Swiss Optical Ground Station and Geodynamics Observatory Zimmerwald: From concept to implementation

A sustainable use of the outer space becomes imperative for preserving current operational missions and
enabling the placement of new space-based technology in the outer space safely. The uncontrolled growing
number of resident space objects (RSO) increases the likelihood of close conjunctions and therefore collisions
that will populate the space environment even more. To prevent such situations, orbit catalogues of RSO are
built and maintained, which are used to assess the collision risk between RSO. In order to keep the catalogues
up-to-date, a worldwide ground-based infrastructure is used to collect observations coming from different
observation techniques.
The current study focuses on the so-called stare and chase observation strategy using an active and passive-
optical system. The final aim is to correct the pointing of the telescope so that the target will be within the
field of view of the laser beam, thus enabling the acquisition of laser ranges. By doing so, objects with poor
ephemerides, available e.g. from Two Line Elements (TLE), will not pose a problem anymore for the rather
small field of view of the laser beam. The system gathers both angular and range measurements, which can be
used for an immediate orbit determination, or improvement, that will enhance the accuracy of the predictions
helping other stations to acquire the target faster and permitting the station to repeat the procedure once
more.
The development of the observation strategy is particularized for the Zimmerwald Laser and Astrometry
Telescope (ZIMLAT), located at the Swiss Optical Ground Station and Geodynamics Observatory Zimmerwald
(SwissOGS), Switzerland. Likewise, all the implemented algorithms were tested using real measurements from
ZIMLAT and the tracking camera.