Lagerkvist, in collaboration with G. Hahn, S. Mottola M. Lundström and U. Carsenty at DLR, Berlin, and A. Doppler and A. Gnaedig (Berlin) have started to study the distribution of the Trojans in the preceeding Lagrangian cloud, L4. In September and October/November 1996 the Schmidt telescope at ESO was used to cover about 900 square degrees twice centered on L4. The Bochum telescope was used in September for additional observations of positions and magnitudes. Totally about 400 Trojans were found on the September films and accurate positions of these have been obtained with the Optronic machine at ESO. Additional observations were made in October 1996. In October 1997 and November 1998 a large area of the sky centered on L4 was again observed with the ESO Schmidt telescope. So far 34 of the found Trojans have been permanently numbered. The result, "The Uppsala-DLR Trojan Survey of L4, the preceding Lagrangian cloud of Jupiter", from the 1996 observations were published in Astronomische Nachrichten, vol. 323, no. 5, p. 475-483. The size distribution of L4 trojans is shown below. The orbital elements will be used to study the existence of asteroid families in this population.
The image shows the trail of a typical Trojan (to the left of the ink mark) on one of the Schmidt films.