As of November 2018, 789069 asteroids und 4026 comets have been discovered in our solar system and the rate of objects being discovered is ever-growing. The reason for this is the growing power of telescopes and the increasing performance of the data processing techniques dealing with the enormous amount of data which is generated with the observations. Apart from the discovery process which is performed by fully automated telescopes in large-scale all-sky surveys, continuous observations of already known asteroids and comets yield important insights of the dynamical and physical properties of these objects like size, rotational properties, shape and the nature of the surface material. Further, remote sensing of asteroids and comets is crucial for the success of space missions like Rosetta or Hayabusa2. On one hand, the observations support mission planning in terms of identifying and characterizing target objects. On the other hand they help to complement and interpret the data from the mission.
For these tasks, the department asteroids and comets performs observations from two observing stations located on Calar Alto, Spain and Sutherland, South Africa. Both telescopes are mainly used for long-term observation programs for determining the rotational properties of asteroids. Special attention is paid on Jupiter Trojan asteroids which share the orbit of Jupiter and to which the NASA space mission LUCY will set out in 2021. Further, observation of comets are performed to study their activity as a function of the distance to the sun and occultations of stars by asteroids are monitored which helps constraining the size of the asteroid.
Even though the field of view of the Calar Alto telescope, compared with those of the survey telescopes, is rather small, it frequently happens that known and unknown asteroids are serendipitously observed. Measuring the astrometric positions of all observed asteroids helps to better constrain the orbit of already known objects and contributes to discover previously unknown objects.