_                   
                                                         |_|                  
      V   V   SSSS   OOO   PPPP                 \__      |_|      __/         
      V   V  S      O   O  P   P                   --____/ \____--            
      V   V   SSS   O   O  PPPP                    _ _ _ --- _ _ _            
       V V       S  O   O  P                      |_|_|_|  @|_|_|_|           
        V    SSSS    OOO   P                             o-o                  
                                                          /                   
      ***  N    E    W    S  ***                        <)                    

HALCA STATUS

As mentioned in the last issue, pointing tests were carried out for HALCA at 1.6 and 5 GHz last month. Initial results indicate that there has been no significant deterioration in pointing since the last check. More recently, HALCA experienced attitude control anomalies twice in the last few weeks. During the recovery of the first of these it became necessary to fire HALCA's Reaction Control System (RCS) hydrazine thrusters -- their first use since December last year. Firing the thrusters produces a small but noticeable change in HALCA's orbit, and the impact on this on the long-term observing schedule is now being checked.

VSOP DATA ARCHIVE

As mentioned in VSOP news 136 (which, like all previous issues, is available from the VSOP website), an archive of the correlator output from VSOP observations is being established at ISAS as part of the Data ARchive and Transmission System (DARTS). A test archive has been established, which presently includes only data from VSOP test observations, but which will be expanded in coming months to include data from General Observing Time (GOT) observations for which the 18 month proprietary period has elapsed. The test archive can be accessed from http://www.darts.isas.ac.jp/ .

VSOP STAFF

Zhi-Qiang "Eric" Shen left ISAS at the beginning of this month to take up a visiting scholar position at the Institute of Astronomy and Astrophysics of the Academia Sinica in Taiwan. Eric spent two years with the VSOP team at the National Astronomical Observatory in Mitaka, before moving to ISAS for a similar length of time. Eric's contributions included regular operations work at the VSOP correlator and for HALCA tracking, maintenance of the VSOP Survey Program data-base, and data reduction of both VSOP Survey and GOT data.

RECENT PUBLICATIONS

The paper "Engineering Accomplishments of the space-VLBI satellite HALCA and the VLBI Space Observatory Programme (VSOP)", by Hirosawa and Hirabayashi, is the very first article to appear in the new journal Recent Research Developments in Electronics and Communications: vol. 1, pp. 1-23. Reprints are available on request.

"The parsec-scale structure and evolution of PKS0521-265" by Tingay & Edwards appears in the Astronomical Journal, vol. 124, p. 652. Multi-epoch and multi- frequency VLBI data, including VSOP observations, are used to that show that any apparent motion of components in the jet must be less than 1.2c. This, together with the core brightness temperature and jet to counter-jet ratio, suggest PKS0521-365 is not highly beamed, and constrains previous modeling of the source. Evidence for evolution internal to a jet component is seen, similar to that seen on the sub-parsec-scale in Centaurus A and M87.

                Editors: Phil Edwards and Hirax Hirabayashi