Summary of the February 2002 APT meeting


Wednesday 6 Feb. 2002, Tsukuba Epochal, 1:30 - 4:30pm


Agenda Summary
--------------
1. Welcome
2. APT Activities and Science Results
3. Observatory Reports
4. The future of the APT              



1. Welcome
----------
APT co-chair Hisashi Hirabayashi (ISAS) welcomed participants to the
meeting. APT Secretary Philip Edwards (ISAS) reviewed the aims of the
APT (http://www.vsop.isas.ac.jp/apt/DefinitionAndAims.html).

2. APT Activities and Science Results
-------------------------------------
Ed Fomalont (NRAO) described the participation of the APT in a 56 hour
observing campaign of Sco X-1 in June 1999.  The APT was used together
with the Very Long Baseline Array (VLBA) and the European VLBI Network
(EVN) to monitor this X-ray binary system at 5 GHz.  The Australia
Telescope Compact Array, and Ceduna, Hartebeesthoek, Kashima, Mopra,
Parkes, and Shanghai telescopes of the Asia-Pacific Telescope
participated in these observations. The observations were made using
the phase referencing technique, with a calibrator 70 arcseconds from
Sco X-1 (with the ATCA having to nod back and forth between the two).

The results are described in two scientific papers, "Scorpius X-1:
Energy Transfer from the Core to the Radio Lobes" by E.B. Fomalont,
B.J. Geldzahler, and C.F. Bradshaw, in ApJ 553, L27 (2001), and
"Scorpius X-1: The Evolution and Nature of the Twin Compact Radio
Lobes" by E.B. Fomalont, B.J. Geldzahler, and C.F. Bradshaw, in ApJ
558, 283 (2001).  NRAO has a press release describing the results, and
with a link to a "movie" showing the evolution of the source over the
56 hours (see http://www.vsop.isas.ac.jp/apt/science.html).

One of the main scientific activities of APT telescopes collectively
has been participation in the VLBI Space Observatory Programme (VSOP).
Philip Edwards gave a brief overview of the HALCA satellite and 
VSOP observing, and described a number of the scientific results
of the mission. The participation of APT telescopes in the all-sky
VSOP Survey Program was of particularly importance to the mission.

In the absence of Tetsuo Sasao, Philip Edwards briefly described
results of the APT 22 GHz observations conducted from October 1st to
5th, 1997. A written report is available in the Proceedings of the
GEMSTONE meeting, January 1999 (CRL) p.142-146. The observations
revealed both the strengths and weaknesses of the APT. The advantages
included the high north-south resolution, the ability to correlate
observations made in different recording formats, and the potentially
high sensitivity at 22 GHz. The disadvantages were the unstable observing
systems at some telescopes at that epoch (such as problems with PLOs
and masers), the poor calibration information for some telescopes,
and the insufficient east-west extent of the array.

3. Observatory Reports
----------------------
Observatory reports were presented for ATNF, Hobart & Ceduna by Tasso
Tzioumis (ATNF), Kashima by Yasuhiro Koyama (CRL), NAO, including
Nobeyama and VERA, by Makoto Inoue (NAO), Taeduk and the planned KVN
by Young Chol Minh (TRAO), and Usuda by Kenta Fujisawa (NAO)

Written reports were submitted for O'Higgins by Wolfgang Schlueter,
the GMRT by Ananthakrishnan, SEST by Roy Booth, Itapetinga and
Fortaleza by Pierre Kaufmann, and Russian telescopes by Igor Molotov
and Hobart and Ceduna by Peter McCulloch. There are available from
the APT web site.

4. The future of the APT              
------------------------
"Hirax" Hirabayashi described the status of planning for the VSOP-2
project and the possibilities for APT involvement in the mission.  The
VSOP-2 satellite will most likely have observing bands at 5 or 8 GHz,
22 GHz and 43 GHz, and be launched toward the end of the decade.

Philip Edwards outlined a number of items requiring action, including
updating the APT web site (the results can be seen at
http://www.vsop.isas.ac.jp/apt/) and the technical details of the
individual APT telescopes.

It was planned to hold the next APT meeting at the New Techniques in
VLBI meeting in Korea in November 2002, with the following meeting to
be held to coincide with the IAU General Assembly in Sydney in July,
2003.