Through an agreement for scientific cooperation with the German-Spanish Astronomical Center at Calar Alto – Spain –, the DLR Institute of Planetary Research operates the 1.2-m telescope of the Observatory for a total of 100 nights a year. During these observations, the German-mounted, Ritchey-Chretien telescope is fully remotely operated from our control room in Berlin via the internet. The telescope, which is equipped with a large-size CCD, is mainly used for photometry, spectrophotometry and astrometry of asteroids and comets in the visible spectral range.
The 1.23m Telescope of the German-Spanish Observatory at Calar Alto.
Studying the enormous amount of asteroids and comets plays an important role in understanding the formation and development of our solar system. Unfortunately almost no telescope on earth is able to resolve these objects, which makes their examination a difficult task. Despite that limitation there are methods for determining the physical properties even without resolving the objects. A powerful method for this is the interpretation of light curves (periodic variations of the brightness) from which the rotational properties and even a simplified assumption of the objects shapes can be derived. Using more complex models it is also possible to discover and characterize asteroid systems (asteroids with satellites). We mainly use the 1.2-m telescope at calar alto to study Jupiter Trojans, a special group of asteroids in resonance with Jupiter.
Another method for determining the physical properties of asteroids is to observe occultations of stars caused by asteroids. By measuring the length of the occultation event and with precise knowledge of the objects orbit it's size can be determined quite well despite the enormous distance between the observer and the object.
Distribution of Jupiter Trojans in the solar system.
Beside these main tasks the telescope is used to observe comets to study their coma and to observe NEOs (Near Earth Objects).
To maximize the scientific benefit of the data obtained from calar alto the images are also searched for serendipitously observed asteroids. Sending the astrometry of these objects to the minor planet center helps to refine orbits of already known objects. Sometimes even new Asteroids are found.
In some cases the telescope is also used to observe events outside our solar system like transits of extrasolar planets (passages of the planet in front of the star it orbits) to study their physical properties and determine the orbits on which they circle around their host star. Furthermore the telescope is part of a network for fast optical observations of gamma ray bursts, a phenomena caused by supernovae, visible over distances of many thousand light years.