_          
                                             |_|         
 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         
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 ***  N    E    W    S  ***               <)             

IMAGES!!

With fringes having popped up at all three correlators, it was only a matter of time before the first images were made. An internationally coordinated series of press releases was made over the last two days to announce and publicize the first images. The first VSOP image was made from an In-Orbit Checkout (IOC) observation on May 22nd. Several hours HALCA data (via the Green Bank tracking station) were correlated at Socorro with phased VLA data, and somewhat less than an hour of HALCA-VLA-VLBA data were also obtained of the source PKS 1519-273. The press release images (now available on the VSOP WWW site /astro/halca/vsop/) show first an image from ground telescope data only, and then an image with the addition of HALCA data. The source remains unresolved on baselines to HALCA, making the source a good test of the observation--orbit reconstruction--time correction--correlation--imaging chain.

A second image from 2.5 hours of HALCA-VLBA data has also been made. These data were obtained from observations of 1156+295 during another IOC experiment. The ground-only 18cm image shows a core and extension to the north-east. The addition of baselines to HALCA clearly resolves components in the jet.

This week has also seen the first image produced from the Penticton correlator, of 1055+018 from an IOC experiment. The Tidbinbilla 64m, Hobart 26m and phased Australia Telescope Compact Array co-observed with HALCA for four hours during this experiment, and the resulting image shows the core to be partially resolved on the longest baselines.

HALCA RECEIVER PERFORMANCE

Tests of HALCA's on-board radio-astronomy system to date have shown that the 1.6 and 5 GHz system temperatures are both almost 20K better than their nominal values of 100 K and 120 K respectively. The pointing of HALCA will be improved over the next few weeks and 5 GHz fringes are expected soon. Some limitations in the attitude control of HALCA have slowed down the IOC somewhat.

The system temperature measured at the input to the 22 GHz LNA has been found to be twice the nominal pre-launch value of 200 K. Drifts scans of the earth through HALCA's beam indicate that only about 10% of the 22 GHz signal is being transmitted between the feed and the 22 GHz LNA, resulting in an effective system temperature, in terms of antenna output, of about 4000 K. After further pointing checks this value will be determined more accurately and the impact of this increased system temperature on the 22 GHz scientific program will be assessed.

 
       Editors: Phil Edwards and Hirax Hirabayashi