REPORT OF THE CASCA RADIO ASTRONOMY COMMITTEE

In the past six months, the radio astronomy committee had no formal
meetings but will have one during this CASCA meeting.
The following report will try to summarize the main activities
of the radio astronomy community under the following headings:

* Future of Astronomy in Canada 
* News from the SKA
* Future of DRAO
* News from DRAO
* News from the JCMT

Future of Astronomy in Canada 

As will be discussed at this year CASCA meeting, the next year will be
very important for the future of Astronomy in Canada with a planning
exercise for the next 10 to 15 years.  The facilities for
consideration could include the following:

1) Radio Array for mm and submm wavelengths, e.g. the proposed joint
Large Southern Array and Millimetre Array (LSA/MMA) to be built in
Chile by ESO and NRAO early in the next decade.

2) Radio Array for m to cm wavelengths, e.g. the proposed Square
Kilometre Radio Telescope (SKRT) for which Canada is investigating the
Large Adaptive Reflector with airborne receivers.  If an economically
feasible technology can be found, construction could begin late in the
next decade following completion of the LSA/MMA.  Meanwhile prototype
construction could be a useful activity for HIA.

3) Replacement for the CFHT now being considered by an international
committee charged with producing a final report for the CFHT Board by
1998 November 15.  It is important that this committee advise on when
a change should occur as well as its nature.

4) Any other facilities that the panel considers worthy, including
continuation of the JCMT agreement.

5) The place of the DAO and DRAO telescopes in the broad plan.

The CASCA RA committee should play an important role in defining the
first two facilities and the possible future of the JCMT & DRAO.


News from the SKA

The 1997 URSI Large Telescope working group meeting
was held in Sydney Australia on 15 December.  Attached to the
meeting was a three day technical workshop on the Square
Kilometre Array.  The combined meeting, entitled "The URSI Large
Telescope Working Group Meeting and 1kT International Technical
Workshop" was hosted by the Commonwealth Science and Industrial
Research Organization (CSIRO). Sixty-five people attended the
meeting from nine countries, including Canada, China, France,
Germany, India, Japan, the Netherlands, UK and USA.  From
Canada were Norbert Bartel, Peter Dewdney and Russ Taylor.

The science presentations provided a good overview of science
areas in which fundamental advances will be made with the SKA;
particularly in cosmology, large scale structure, the formation
and evolution of galaxies and stars, and the search for
extraterrestrial intelligence.  Perhaps the most important
development in the science area is that there is now general
agreement among all the countries involved that the SKA should
operate up to a frequency of at least 10 GHz (thus satisfying
the minimum requirement for Canadian participation as specified
in the report of the Seaquist committee).  This is a very
different situation from only a few months ago, when Canadian
scientists stood alone in pushing the high frequency science case
(detailed in the Canadian science document distributed at the
URSI meeting in Kyoto).

There is also agreement that now is the time to develop a more
mature international science document for the SKA. It was agreed
that the he science case will assume an instrument with the
following capabilities:

1) Aeff/Tsys of about 20,000 square metres per Kelvin,

2) operating frequencies from 0.1 to 20 GHz.

3) instantaneous field of view 1 square degree at 1.4 GHz.

4) number of instantaneous beams 100.

5) angular resolution 0.1" at 1.4 GHz.

6) surface brightness sensitivity 1 K at 0.1" (continuum).

Significant technical advances were reported in several areas.  A full
report of the Sydney workshop can be found at
www.ras.ucalgary.ca/Sydneyworkshop.html.

A draft science document for the SKA is now under development. An
International SKA Science meeting will be held at Calgary on 20-22
July. The meeting will be devoted chiefly to the science case and a
mature document will be developed following the Calgary meeting.

As a result of a special grant from the National Research Council of
Canada, research and development work has begun on the Large Adaptive
Reflector (LAR). The LAR, an innovative reflector antenna design, is a
contender for the design of the elements of the SKA. The LAR is long
focal-length paraboloid which requires an air-borne platform to
support the focal package, but does not require mechanical tilting of
the reflector as in more traditional designs. A triple tethered
aerostat has been selected for the airborne platform.

Several different groups are working on different aspects of the LAR
design, building on the early investigations of P. Dewdney and
B. Veidt. At the University of Calgary, a group from the Geomatics
Engineering department (Lachappelle, Cannon, and Yang) is considering
the use of differential GPS methods to accurately determine the 3-D
position of the aerostat payload as a function of time. A joint
project between the University of B.C. and Coast Steel Fabricators
(Stiemer, Halliday, and Lo) is investigating construction methods for
the reflector surface, which must be adjustable. At the University of
Alberta (Meng and Smith) a laboratory model of the tether/aerostat
system is being constructed in order to gain insight into how the
position of the aerostat can be controlled. At HIA/Victoria,
J. Fitzsimmons is verifying aerodynamic calculations done earlier by
B. Veidt, and will soon be extending this work. At DRAO, B. Veidt is
continuing to work on the aerodynamics, and has started work on feed
designs. B. Carlson at DRAO has just started part time work on the
project. He will initially be involved in project coordination. Leonid
Belostotski, a Masters student at the University of Alberta (working
at DRAO under T. Landecker) has been designing a prototype
radio-linked Local Oscillator and distance measuring apparatus. And
very recently, a Ph.D. student from the engineering department at the
University of Manitoba (working under L. Shafai) has selected the LAR
electromagnetics as his thesis project. Several reports on this work
are available on the World-wide Web at
http://drao.nrc.ca/ska/ska.html.

Many countries are currently facing the challenge of developing a
coherent vision for development of radio astronomy facilities at mm
and cm wavelengths. It is clear that both the SKA and the large mm
array projects that are now approaching the construction phase will be
large international projects. Preliminary communications have take
place between principles in several countries toward developing an
international vision for cooperative development of cm (SKA) and mm
(MMA/LSA) facilities.  It is expected that further discussion of this
concept will take place at the Calgary meeting.

(Russ Taylor -- see Cassiopeia March 1998)


Future of DRAO

The senior management of NRC has decided that DRAO is not to be
closed in March 2001, but is to continue. The Plan Beyond March 2001 is:

1) Continue observing with the Synthesis Telescope for about 5 years.

2) Continue studies related to participation in a future radio facility.

3) Continue scientific and engineering research in the area of radio
astronomy in collaboration with our partners.

4) Continue providing technical assistance to Canadian enterprises.

5) Continue monitoring the solar radio flux.

6) Continue to work for the protection of the radio-astronomy frequency
allocations.

The observing could be an extension of the Canadian Galactic Plane
Survey or responses to specific proposals, or some of each, depending
on the wishes of the Canadian community.  By March 2001 we expect that
the consortium investigating technical approaches to the Square
Kilometre Radio Telescope (SKRT) will have selected one or more
systems for prototype tests.  If one of those is the Large Adaptive
Reflector, and it is possible to raise funds for a prototype,
considerable effort on that can be expected at DRAO until about 2005.
If the LAR is not chosen, it may be decided to direct the effort to
the technology that is selected.

In any case, this plan will ensure that the DRAO will continue to
operate beyond 2001.  The scope and timeframe of its operations then
will depend to a large extent on the decisions to be made in the next
few years by HIA, in consultation with the astronomy community,
regarding the future of radio astronomy in Canada.


News from DRAO

Christmas was an especially happy season for DRAO, with the news that the
senior management of NRC has decided that our Observatory is not to be
closed in March 2001, but is to continue (for the announcement, see the
December 1997 issue of Cassiopeia). We are now starting to plan that longer
future, and will involve our community heavily as we make plans for the
Synthesis Telescope after March 2000 (when it completes observations for
the present phase of the Canadian Galactic Plane Survey - the CGPS).

CGPS observing routines are well established, and data reduction techniques
are approaching the same state, allowing us to focus more on research with
the data. Observations for the CGPS are rolling along, with the Synthesis
Telescope working like a well-oiled machine. Over half the area projected
for observation at DRAO has now been observed with the Synthesis Telescope.
Data reduction is (not surprisingly) a little further behind. A second data
release to members of the CGPS Consortium was distributed (via CD) just
after Christmas; this is the first release of data which includes
single-antenna information.

Observations of the entire survey area with the DRAO 26-m Telescope (to
provide short-baseline information for the survey) are now complete, and
Lloyd Higgs is working on the final corrections to these data (for
telescope sidelobe responses and other small effects). More than 25,000 HI
spectra were taken, and this survey is quite an undertaking in its own
right.

The Space VLBI Correlator is a busy place. After the excitement of the
first fringes from space to ground in June last year, the correlator
is settling into a busy and productive everyday existence. A lot of
work has gone into co-ordination of the far-flung observatories which
send their data to DRAO. Brent Carlson and David Del Rizzo are working
two shifts to keep pace with the data as there are currently more than
50 observations at some stage of completion. Some involve as many as
eight stations, quite a trick for a six-station correlator. Natural
Resources Canada, a partner in the VLBI operation, has installed a
3.5-m antenna at DRAO to be used for Geodetic GVLBI measurements. Over
the summer of 1998 this system will be put through its paces by Bill
Petrachenko (seconded to DRAO from NRCan).  After about a year of
"shakedown" at DRAO, the small antenna will be on the road every
summer, making precise survey measurements of a network of sites to
help refine knowledge of the reference points on which all precision
surveying in Canada depends.

The Solar radio flux monitoring program is continuing into its sixth decade
of precise and reliable measurements. The flux density is slowly climbing
as we enter a new cycle of solar activity. The worldwide community of
users, solar astronomers, space-weather forecasters, meteorologists and
climate specialists, power companies, and satellite-communications
companies (among others), counts on the data, and its reliability is a
source of pride to the DRAO Operations Group.

Working to protect the radio astronomy allocations in the frequency
spectrum is now occupying a substantial fraction of Ken Tapping's time. He
reported in the last issue of Cassiopeia on the World Radio Conference held
in Geneva in October and November 1997. He was in Geneva again in late
February. This work is very necessary to ensure that radio astronomy has a
future. Pressure on the radio spectrum will affect astronomers at both
centimetre and millimetre wavelengths, and we are grateful to Ken for
carrying on this battle. The work has national and international
significance, with Canada playing a significant role.

The team working on the design of a new multi-beam spectrometer for the
JCMT is approaching an important deadline, the Preliminary Design Review at
DRAO in April. Specifications and design memos are being generated, and a
lot of thought and testing is going into the specifications for a computer
capable of handling the most ambitious observing technique, "on-the-fly"
mapping, where correlation coefficients flowing from as many as 32 beams on
the sky must be transformed into a spectral-line data cube. Parallel
computing concepts will be necessary to cope with data rates as high as 10
Mbytes per second.

There is a high level of activity in the group working on the Future of
Radio Astronomy. This edition of Cassiopeia includes a report from a
meeting held in Sydney (Australia) in December, 1997, where it was agreed
that the Square Kilometre Array must work at short centimetre wavelengths
(an important requirement of Canada's astronomers). At home, a grant has
been received from NRC which will kick-start detailed engineering studies
of the Large Adaptive Reflector (LAR). At a meeting in Calgary in February,
plans were laid to tackle the engineering work needed to establish the
feasibility of the LAR. Researchers from the Universities of B.C, Alberta,
Calgary, Manitoba and Toronto were there. With co-ordination from DRAO, the
work will begin at once, with this phase set to end in March 1999. With a
further grant from NRC, DRAO has been able to buy a set of powerful
antenna-design software. Specifying and selecting this software was a
complex task, which occupied Bruce Veidt for several months. It will soon
be in place, and will allow research into alternative feed designs for the
LAR. Incidentally, it will be made available to small companies working on
antenna design. This use of the software will be in co-operation with NRC's
IRAP division (Industrial Research and Assistance Progam).

Two graduate students, Leonid Belostotski and Anne Thorsley, both M.Sc.
candidates in Electrical Engineering, are working at DRAO. Leonid is
developing a local oscillator system for the Large Adaptive Reflector, and
Anne is measuring the figure of the antennas of the DRAO Synthesis
Telescope using holographic techniques.

Later this year, DRAO will be host for an international workshop entitled
"New Perspectives on the Interstellar Medium", to be held at Naramata, near
Penticton. This conference will be a focus for our Canadian Galactic Plane
Survey research, and it will help us put the research of our Consortium
into a wider perspective. The Scientific Organizing Committee is in place
and the Local Organizing Committee at DRAO (chaired by Lloyd Higgs) is at
work.

David Lacey retired from DRAO in October 1997 after more than 35 years at
the Observatory. David was responsible for engineering for the 22 MHz
telescope at DRAO, and then for the Synthesis Telescope. His expertise on
power systems and on telescope drives and controls has been a real
strength, and he gained a reputation for building things that worked. He is
also an expert on the shielded rooms and enclosures that keep the
electromagnetic radiation from our computers out of the sensitive receivers
of our telescopes.

Chris Purton will be retiring at the end of March 1998. He first came to
DRAO in the middle 60s, when he was a graduate student at the University of
Cambridge, to work on and with the 10 MHz telescope. His work helped
establish the low-frequency flux-densities of radio galaxies and quasars,
an important astrophysical question at the time. He later worked for NRC in
Ottawa, and was on the faculty of York University where his research
interests turned to radio stars and planetary nebulae. He came back to DRAO
in 1981. His recent three-year stint at the JCMT won him many accolades. He
has been the Operations Manager at DRAO since 1995, and has been
instrumental in developing the observing strategies and the team approach
that make the operation of our telescopes so successful. He plans to
continue his research at DRAO as a member of the CGPS consortium.


(Tom Landecker -- see Cassiopeia March 1998)


News from the JCMT

These are exciting times at the James Clerk Maxwell Telescope! The past
year has seen the commissioning of two major new instruments, and two more
are expected to arrive shortly. This happy conjunction of instrumental
progress is challenging the local staff in their support roles but, at
the same time, offers unprecedented opportunities for Canadian astronomers
to explore the submillimetre universe.
The JCMT, situated at an excellent location, is among
the finest submillimetre-wavelength telescopes in the world. Its preeminent
position is being strengthened by recent and imminent instrumentation advances.

With the arrival of SCUBA at the telescope
things have really changed. As the largest, fastest submillimetre camera
available today, its impact on both observatory operations and, more 
significantly,
on astronomical activities has been major. The camera consists of a 37-pixel
array optimized for use at a wavelength of 850um and a 91-pixel
array optimized at 450um. These arrays are simultaneously imaged
on the sky over a 2.3 arc-minute field at resolutions of 13 and 7 arc-seconds.
In addition, there are 3 photometric pixels operating at 1100um,
1350um and 2000um.

The heart of SCUBA, which houses the bolometer arrays, consists of
6.6 kgm of metal cooled by a He-3 dilution refrigerator to 75mK. 
SCUBA is designed to be photon-noise limited. Each of its pixels is
about ten times more sensitive than the single detector of its predecessor,
UKT14. This improvement, coupled with the size of its arrays, translates into
an increase of more than 5000 in mapping speed at 450um for extended
sources! Such large single improvements in observing capability occur
seldom in a lifetime, and this offers a great opportunity for Canadian 
astronomers to help push back the frontiers of submillimetre astronomy.
SCUBA can be used in a number of modes, depending upon the source 
characteristics.

Mapping with SCUBA

For relatively compact sources, so-called "jiggle mapping" provides
simultaneous two-colour images of a 2.3 arc-minute field. If you're a
submillimetre continuum buff, you'll be impressed by sensitivities of
about 6mJy (1-sigma) at 850um after about 1 hour, and the current best
value of about 0.5 mJy, achieved after binning adjacent pixels
following 4 shifts of integration.

Recently, scan-mapping has been used successfully to provide spectacular
images of extended sources. Under good sky conditions
a region 10 arc-minutes on a side can be mapped to a 1-sigma level of about
70 mJy in 1 hour. Such fields can be combined to form considerably larger
mosaics. Similar mapping modes are available to provide simultaneous images
at 350um and 750um.

Photometry

In addition to the arrays at 350, 450, 750 and 850um, SCUBA provides
single-pixel photometry at 1100, 1350 and 2000um. The spectral 
information so obtained is useful for modeling source temperatures and
the frequency-dependence of dust emissivity.

Polarimetry

The interstellar magnetic field is one of the key physical parameters
affecting a host of astrophysical processes, including the fundamental
one of pre-protostellar cloud contraction. At submillimetre
wavelengths the dust emission is polarized with the E-vector
perpendicular to the field.  An advantage of measuring the
polarization at submillimetre wavelengths is that the emission is
optically thin regardless of the visual extinction.  Consequently,
it's possible to study the magnetic field direction deep within
molecular clouds, where all of the star formation occurs. SCUBA
presently offers single-pixel polarization capability using either or
both central pixels of the two arrays or any of the photometric
bolometers. Within the year it is expected that full-array
polarization will be possible.

Spectral Line Receivers

SCUBA, for all its exciting capabilities as a submillimetre camera,
does not provide any dynamical information. This vital third dimension
of the "data cube," plus direct access to the physical state of the
dominant gas component, must be acquired through spectral line
observations.

The arcane JCMT terminology for designation of the heterodyne
instruments has its origin in the chronological order in which receivers
were delivered to the telescope. This meant that the lowest-frequency (easiest
technology) band received the first, trend-setting letter. Thereafter, the
pattern was set.  The lowest frequency atmospheric window is
A-band (215-270 GHz, 1200um), then comes
B-band (315-370 GHz, 870um),
C-band (450-500 GHz, 630um),
D-band (630-700 GHz, 450um) and
E-band (800-900 GHz, 350um). Thus, Receiver B3 is the third receiver at
the telescope for the 315-370 GHz window. 

Receiver B3

The newest of the heterodyne receivers is RxB3, built by HIA's JCMT
Group in collaboration with RAL (UK) and SRON (Netherlands).  It was
commissioned early in 1997. This dual-beam receiver offers quick,
remote tuning, wide instantaneous bandwidth and flat baselines.  It
has a single sideband filter and state-of-the-art sensitivity. This
instrument provides an increase in speed of about a factor of 5 over
its predecessor, RxB3i. It can be used in the standard JCMT observing
modes, including frequency switching and raster mapping.

Receiver A3i

The oldest of the active receivers at the JCMT is RxA2. Very shortly
this venerable old workhorse will be retired, to be replaced by A3i.
Those of you who have passed your immersion course in JCMT-speak will
understand that this designation means the receiver is designed to
cover the 210-275 GHz window, with plans for upgrades in the future.
RxA3i will have a tunerless mixer, which will permit lightning-fast
tuning (figuratively speaking), and provide enhanced sensitivity and a
broader tuning range than A2.

Receiver W

Given that E-band is the shortest-wavelength submillimetre window, you
might reasonably infer that this receiver's designation indicates that
the JCMT aspires to branch out into x-ray astronomy. Such is not
actually the case, although there are ongoing efforts to optimize the
JCMT's surface accuracy.  "W" in this case stands for "Wide-band"
because the receiver will cover both the C- and D-band windows, with
two orthogonally polarized beams in each window.

With its dual-beams and improved mixer performance, RxW will greatly
enhance the JCMT's capabilities in the two atmospheric windows where
the Mauna Kea site is truly advantageous in terms of accessibility and
sky transmission. RxW is expected to arrive this spring. It will
replace the existing C2 receiver and will provide, for the first time,
a resident capability in the important D-band window.

What else ?

Together these new instruments represent a suite of powerful tools for
exploring the submillimetre universe. In addition, there are plans and
efforts on many fronts to improve capabilities - the Antenna Surface
and Telescope Control System Upgrades, an interferometry link with the
SMA, a receiver for E-band, an 8-beam spectral-line camera for B-band,
and a new autocorrelator spectrometer, ACSIS.  ACSIS will serve as the
back end of the future for all the JCMT line receivers including the
B-band camera. Details on these and other activities can be found on
the JCMT home page.  So the future looks bright and the coming decade
promises to be an exciting one at the JCMT.


(Lorne Avery -- see Cassiopeia March 1998)

Claude Carignan,
for the CASCA radio astronomy committee