Orientation of the hipparcos frame with respect to the reference frames of the DE403/LE403 and DE405/LE405 ephemerides based on asteroid observations

Highly accurate observations of 116 asteroids are used to determine the orientation of the Hipparcos frame with respect to the reference frames of the DE403/LE403 and DE405/LE405 majorplanet ephemerides. These observations include the photographic observations of 15 asteroids obtained as part of the programs for observing selected asteroids and reduced to the Hipparcos frame using dependences, the space observations of 48 asteroids obtained by the Hipparcos satellite, and the presentday observations of 116 asteroid performed in the frame of the ACT catlog. The total number of observations used is more than 50 000 in the interval 1949–2007. Processing this series has yielded the following estimates of the orientation parameters: ω _x = 0.12 ± 0.08 mas yr^?1, ω _y = 0.66 ± 0.09 mas yr^?1, and ω _z = ?0.56 ± 0.16 mas yr^?1. This rotation may be attributable to a peculiarity of the transition from the reference frame of the DE200/LE200 ephemerides to that of DE403/LE403 ephemerides (since October 1, 1988, to J2000) that consists in the the assumption that the former reference frame has no rotation relative to the ICRF.