_                   
                                                         |_|                  
      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 RE-BOOTED

As reported in the last issue, HALCA suffered a recurrence of the Data Handling Unit (DHU) problems last month just before observing was going to restart. It was originally planned to wait until the next eclipse season, beginning in late January 1999, to reboot HALCA, as an eclipse pass provides the safest way for this operation to be performed. However, it was realized that keeping HALCA in its safehold attitude until then would possibly use up all the RCS thruster fuel, used to put HALCA in, keep HALCA in, and take HALCA out of, safehold -- but not for routine maneuvering between sources which is done with the Reaction Wheel system. In safehold, HALCA is in a slow spin about the sun-satellite axis, with one revolution taking about 12 minutes.) Rather than run the risk of loss of the RCS fuel, it was decided to let the spin axis drift away from the sun, and to tilt the solar panels so that HALCA effectively experienced an eclipse for some of its 12 minute spin cycle.

On November 30th the first attempts were made to re-boot HALCA. The DHU was successfully restarted, and downlink telemetry was able to be read again, but there was a synchronization problem between elements of the on-board system which meant that HALCA could not be restored to its full operating mode. HALCA was re-booted a number of times during the same tracking pass to try and fix this word offset, but without success. Nevertheless, the fact that telemetry could now be monitored was a big step forward.

On December 10th, further attempts were made to re-boot HALCA to try and start up with the word-offset problem solved. After several tries: success! Since then, contact has been re-established with the ku-band (15 GHz) tracking stations, the batteries have been reconditioned, the observing system checked, and pointing tests for the satellite are scheduled for next week. A first interferometric test run will be conducted at the end of December, with full observing scheduled to restart in the second week of January.

HAPPY BIRTHDAY!

Our congratulations to the Australia Telescope Compact Array and the VLBA Array Operations Center, both of which celebrated their 10th birthdays recently! The AT Compact Array was given a big birthday present: its party coincided with the commemoration of the construction work on the northern spur to the (currently east-west) array.

PRESS RELEASE

A joint press release was made in Japan and Australia this month to promote the recent determination of the Hubble constant using the gravitational lens PKS 1830-211. VSOG team member Jim Lovell led a team that derived a time delay for the lens from radio monitoring of 26 days. Several teams have used lenses recently to derive values for the Hubble constant (see the note added in proof to ApJ 508, L51) which all cluster around 65 km/s/Mpc. The press release generated a lot of interest, with most media reporting the result from the point of view of the age of the Universe.

 
                Editors: Phil Edwards and Hirax Hirabayashi