Almost all of the effort on the construction site currently is directed toward preparing the R1
module for lifting out of the center portion of the BUS and onto the antenna box structure. This
makes it possible to install a large guy derrick in the hole in the BUS left the R1 module. This
derrick will be used to pick the BUS modules from the left half of the structure and lift them into
the air where they will be transferred overhead to the main derrick which will then place the
modules on the box structure. The modules on the right half of the structure will be lifted directly
by the main derrick. Altogether, there are 22 modules in the BUS.
In addition, the horizontal feed arm is now complete, and the walkway to the vertical feed arm
elevator platform is in place. Wiring to the elevation drives is almost complete. Servo testing of
the upper feed arm is currently on hold awaiting the return of the subreflector actuator motors
sent out for repair.
The 140 Foot is thus once again open for new telescope proposals. However, the "final" call for
proposals earlier this year resulted in a demand which outstripped the available telescope time by
a factor of about 2.5. The Telescope is fully subscribed for the remainder of 1997. A deadline of
3 November 1997 has been established for receipt of proposals for observations in the first half of
1998. There will be another deadline in the spring of 1998 for receipt of proposals for
observations in the second half of 1998. Further information will be given in the next Newsletter
and on the WWW. As always, proposals to make time-critical observations can be submitted at
The HALCA data in which we detected fringes were recorded at the NRAO OVLBI Earth
Station in Green Bank, and received at the AOC on 5/27. A tape recorded for this observation at
the Usuda tracking station, and tapes recorded at the Green Bank and Goldstone tracking stations
in other test runs, were received subsequently.
For sixteen days, no fringes were detected in any of these tracking passes. Although extensive
tests, reported in several previous NRAO Newsletters, had verified nearly all aspects of the
correlator's Space VLBI capabilities, we disabled all of the functions except the spacecraft orbit,
to ensure they were not somehow preventing detection of fringes. We could operate in this
simplified mode in a few carefully selected cases, but still detected no fringes.
The most likely remaining cause appeared to be overall time-setting errors, at all of the tracking
stations. Timing in Space VLBI is more difficult than in even the earliest ground-based VLBI
observations, where one could and the pioneers of this technique did, sometimes at great effort
bring an atomic clock along to establish the local time to sufficient accuracy. In Space VLBI, it
is only possible to compute the time on the spacecraft, combining the propagation time to the
tracking station with an additional instrumental component, potentially quite large, which depends
on the details of all the equipment along the signal path. Some of the conceivable errors in
determining this additional offset are much larger than any practical wide delay search in the
correlator. Thus, it is essential that the tracking stations determine the offset extremely
The Green Bank tracking station became the first to do so, suggesting a new timing offset to be
searched. This led immediately to detection of fringes, first in the observation described above,
and within days in three other test runs for which Green Bank tracking passes were available.
Once having detected fringes, we proceeded immediately to correlate the entire tracking pass in
which fringes to HALCA were first discovered. This pass includes only the phased VLA on the
ground for the first two hours, which is then joined by the VLBA for a final hour. Despite this
relatively sparse coverage, the combined data set was adequate to image the source, which had
been selected for this fringe search from a set expected to be extremely compact and relatively
strong. The observations indeed yielded an unresolved image of about 2.3 by 0.7 milliarcsec, with
peak-to-sidelobe dynamic range of about 100 the first image achieved by the VSOP mission.
Such a point image is a strong verification that the entire Space VLBI system is functioning
With the new timing offset, we have also been able to correlate the entire Green Bank tracking
pass in each of seven VSOP in-orbit tests observed through the end of June. One of these, with
about 2.5 hours of Halca-VLBA baselines, has already yielded an image of 1156+295, showing a
typical VLBI core-jet structure. A VLBA-only image from the same data reveals only a slightly
extended single component. Another Halca observation of the same source four days later,
involving six telescopes of the European VLBI Network in addition to the VLBA, nicely
complements the (u,v) coverage from the original session, so that we anticipate being able to
produce a high-quality image despite the limited Halca tracking available with only one tracking
Notes added in proof: On 97/7/8, the VLBA correlator detected its first fringes to Halca via the
Goldstone tracking station. On 7/9, we detected the VSOP mission's first fringes at 5 GHz, also
via Goldstone, and on 7/10 our first fringes via the Usuda tracking station, again at 5 GHz.
|08 Sep to 01 Oct 1997||1.3 cm, 6 cm, 18 cm, 3.6/13 cm||03 Feb 1997|
|03 Nov to 27 Nov 1997||1.3 cm, 6 cm, 18 cm, 3.6/13 cm||02 Jun 1997|
|10 Feb to 06 Mar 1998||1.3 cm, 6 cm, 18 cm, other?||01 Oct 1997|
|20 May to 08 Jun 1998||1.3 cm, 6 cm, 18 cm, other?||01 Oct 1997|
|07 Sep to 02 Oct 1998||1.3 cm, 6 cm, 18 cm, other?||02 Feb 1998|
|10 Nov to 04 Dec 1998||1.3 cm, 6 cm, 18 cm, other?||01 Jun 1998|
It is expected that European VLBI observing during the next year will be dominated by
observations with the VSOP satellite.
It is recommended that proposers use a standard cover sheet for their VLBI proposals.
Fill-in-the-blanks TeX files are available by anonymous ftp from ftp.cv.nrao.edu, directory
proposal or via the VLBA home page on the WWW. Printed forms, for filling in by typewriter,
are available on request from Betty Trujillo, AOC, Socorro.
Any proposal requesting NRAO antennas and antennas from two or more institutions in the
European VLBI network constitutes a Global proposal. Global proposals must reach both
Network's Schedulers on or before the proposal deadline date; allow sufficient of time for mailing.
In general, fax submissions of global proposals will not be accepted. Proposals requesting use of
the Socorro correlator must be sent to NRAO even if they do not request the use of NRAO
antennas; proposals for the use of the Bonn correlator must be sent to the MPIfR if they do not
request the use of any EVN antennas. For Global proposals, or those to the EVN alone, send
R. Schwartz Max Planck Institut fur Radioastronomie Auf dem Hugel 69 D 53121 Bonn Germany
For proposals to the VLBA, or Global proposals, send proposals to:
Director National Radio Astronomy Observatory 520 Edgemont Road Charlottesville, VA 22903-2475 USA.
Proposals may also be submitted electronically, in Adobe Postscript format, to
firstname.lastname@example.org or email@example.com, respectively. Care should be taken to
ensure that the Postscript files request the proper paper size.
Images are sought on the basis of visual appeal and scientific significance. While striking visual
impact helps for public-education and media purposes, we also want images that illustrate
important scientific advances as well as those that show a variety of astronomical phenomena as
seen with VLBI resolution. We prefer images in the form of FITS or PostScript files. For caption
information, please give either a brief description or a reference to a published description.
For information, and to arrange a file transfer, contact Dave Finley at the AOC ((505) 835-7302
|Configuration||Starting Date||Ending Date||Proposal Deadline|
|C||27 Jun 1997||22 Sep 1997||3 Feb 1997|
|DnC||3 Oct 1997||20 Oct 1997||2 Jun 1997|
|D||24 Oct 1997||12 Jan 1998||2 Jun 1997|
|A||30 Jan 1998||18 May 1998||1 Oct 1997|
|BnA||29 May 1998||15 Jun 1998||2 Feb 1998|
|B||19 Jun 1998||14 Sep 1998||2 Feb 1998|
|CnB||25 Sep 1998||12 Oct 1998||1 Jun 1998|
The maximum antenna separations for the four VLA configurations are: A-36 km, B-11 km, C-3
km, D-1 km. The BnA, CnB, and DnC configurations are the hybrid configurations with the long
north arm, which produce a round beam for southern sources (south of about -15 degrees
Approximate Long-Term Schedule
Observers should note that some types of observations are significantly more difficult in daytime
than at nighttime. These include observations at 327 MHz (solar and other interference; disturbed
ionosphere, especially at dawn), line observations at 18 and 21 cm (solar interference),
polarization measurements at L band (uncertainty in ionospheric rotation measure), and
observations at 2 cm and shorter wavelengths in B and A configurations (tropospheric phase
variations, especially in summer). They should defer such observations for a configuration cycle
to avoid such problems. In 1997, the D configuration daytime will be about 16h RA and in 1998
the A configuration daytime will be about 0h RA.
Time will be allocated for the VLBA on intervals approximately corresponding to the VLA
configurations, from those proposals in hand at the corresponding VLA proposal deadline. The
first observations with the VLBA and the HALCA long-baseline interferometry satellite were
done in May, and increasing amounts of observing time will be devoted to this through the
summer, approaching a long term average of about 30 percent of VLBA observations devoted to
Any proposal requesting NRAO antennas and antennas from two or more institutions affiliated
with the European VLBI network is a Global proposal, and must be sent to the EVN scheduler as
well as to the NRAO. VLBA proposals requesting only one EVN antenna, or requesting
unaffiliated antennas, are handled on a bilateral basis; the proposal should be sent both to NRAO
and to the operating institution of the other antenna requested. Coordination of observations with
non-NRAO antennas, other than members of the EVN and the DSN, is the responsibility of the
Installation of a dedicated SPARCstation IPC as our WWW and anonymous ftp server is imminent. We urge users to access these sites using the generic "www.nrao.edu" and "ftp.aoc.nrao.edu" addresses, which will make the actual switch transparent.
Local computer support at the AOC received a boost when we hired two new people: Tom
Wilson will be responsible for further developing our Web site, for supporting visitors and staff in
areas related to non-NRAO software systems (IRAF, IDL, TeX, etc.), and in lending
programming support to projects such as the VLA archive project. Victor Kiff joins the systems
support staff. His arrival enables us to streamline contact between users and system staff. We
have devoted one office to user support and have introduced a generic "nmhelpdesk" account for
visitors and staff to receive prompt help.
G.A. van Moorsel
The school will entail a week of lectures on aperture synthesis theory and techniques at a level
appropriate for graduate students in astrophysics. Practical tutorials demonstrating data
collection, calibration, and imaging of both VLA and VLBA data will be given.
There will be a nominal registration fee, sufficient to cover only the cost of the meeting. Our
budget is unable to provide financial support for attendees. Lodging for participants will be at
G.B. Taylor, C. Carilli, & T. Hankins
(1) Dome inspection and repair.
(2) Automation enhancements to receiver tuning software.
(3) Installation of the central cold load calibration system.
(4) Installation of a new digital phase lock system.
(5) Improvements to the receiver and IF system to increase continuum sensitivity.
J.G. Mangum & D.T. Emerson
The second significant development of the last quarter was a meeting held in Charlottesville to
discuss the feasibility of merging the MMA and the European Large Southern Array (LSA) into a
common, joint project. Both projects have been studying potential sites in Chile. Although the
projects have somewhat different scientific emphases, it is clear that both projects have
requirements for outstanding sites and could realize cost saving were they to share a common
site. Could we envision a single array on this common site that would satisfy the scientific goals
of both communities? For two days delegations representing the LSA and the MMA discussed
The two groups agreed that if a common array were to encompass the scientific scope defined by
both the LSA and the MMA, it would of necessity be larger than either project alone. Further, it
was agreed that there is much to be gained scientifically with such an array. The delegations
resolved to form a partnership to explore the union of the two projects. Specifically, the
partnership will study the technical, logistical, and operational aspects of a joint project. Of
particular importance, the two antenna concepts currently under consideration in the U.S. and
Europe will be studied to identify the antenna size and design, or combination of sizes, best able
to address the scientific needs of the two communities. Working groups have been organized that
utilize the expertise in each community's research institutions and universities to explore the issues
associated with a merger of the LSA and MMA. The working groups are to report and a decision
taken on proceeding to the next steps toward a joint project by the end of the year. Finally, both
delegations recognized the importance of the Japanese plans to build the Large
Millimeter/Submillimeter Array (LMSA) and agreed that cooperative activities with the LMSA
should and would continue.
The Committee expressed its concern that the loss of the Brookhaven National Laboratory
operating contract not affect AUI's Cooperative Agreement with the NSF for operation of the
NRAO. The Committee strongly endorsed the continued management of the NRAO by AUI.
The Committee asked that the policy regarding user-built instrumentation be re-stated to make it
clear to all users under which conditions observing equipment custom built by individual users
would be maintained by the Observatory and made available to all users.
The Committee strongly endorsed the report of the Bridle Committee on policies regarding large
scale observing proposals.
The Observatory was encouraged to continue the tradition of open communications with its user
community and to press on with the current effort to improve the availability of documentation,
reports, technical memos, manuals, etc., on the WWW.
The Users Committee also wanted to express its strong interest in seeing that NRAO improve its
educational outreach activities, i.e., to explain why the science done with radio telescopes is
important to society.
Support for the operation of the 12 Meter Telescope is strong. NRAO was encouraged to keep
the 12 Meter running until the Millimeter Array (MMA) begins operation or there is general
access for U.S. observers to an alternative large aperture single dish millimeter telescope. The
Committee asked for a plan to be published that would make clear the future course of operations
of the 12 Meter. The Committee was pleased to see progress on receiver systems, even though
progress is slow on many projects due to lack of personnel. On-The-Fly mapping was noted as a
particularly significant advance in capability, one that should also be implemented on the Green
Bank Telescope (GBT). The construction of a new spectrometer was endorsed and the synergy
with that for the GBT was noted. Expansion of the time allocated to millimeter wavelength VLBI
was strongly encouraged.
The Committee expressed its disappointment in the delays in completing the GBT. At the same
time, the Observatory was encouraged to expand the number of scientists in Green Bank, plan for
first science by sponsoring a workshop, and continue to test GBT systems and train personnel on
the GBT instrumentation mockup to minimize the time required for telescope commissioning.
Concerns over the stability of the fiber optic IF transmission system are fading now that initial
tests of a gain control system show it to be successful. NRAO was urged to continue operation
of the 140 Foot, with more general observing in addition to the orbiting VLBI support that was
planned, until the completion of the GBT.
The Committee noted the usefulness of the Very Large Array (VLA) sky surveys, the new
capability the Q-band receiver system has enabled, the project to widen the IF bandpass from 50
to 80 MHz, the prospect of 74 MHz receivers with Naval Research Lab support, and the
near-completion of the new archive of all VLA data. They suggested the Socorro on-line
reservation system for visitors be implemented at the other sites. The Committee strongly urged
that the VLA OBSERVE program be upgraded, as a high priority. The plans to hold an Imaging
Synthesis Summer School (17-19 June 1998) were noted with hopes that use of the AIPS++
imaging processing system would be included.
NRAO was encouraged to continue the effort to improve the Very Long Baseline Array (VLBA)
operating efficiency. Strong encouragement was given to implementing dynamic scheduling. The
switch to using only thin tape for recording data to be correlated with the VLBA correlator was
endorsed. The Committee is pleased to see initial progress on the pulsar gating mode, called for
implementation of a burst mode, urged that an improved amplitude calibration process be finished
soon, and expressed hopes that fringes would be detected in orbiting VLBI (HALCA) data.
The Committee gave a high priority to developing plans for a VLA upgrade, bringing the 1970s
era electronics to the level expected in the 21st century, improving the antennas, and adding
antennas to fill in the uv-spacings intermediate to those of the VLA and VLBA. Current
proposals pending at the NSF to complete the Q-band system and to link the Pie Town VLBA
antenna in real time to the VLA were noted with the hope that matching funds and Foundation
approval would be forthcoming.
Improvements in computing hardware capability available to users during the past year were
noted as well as improvements in networking. NRAO was encouraged to continue to replace
aging computers with modern machines. The Committee expressed a willingness to endure the
inconvenience that implementation of better computer security measures would impose.
The Committee noted the importance of AIPS and the improvements that have been made in
AIPS. Much of the improvements have gone into CPU-heavy tasks such as IMAGR; the
Committee would like to see more effort in interactive tasks as well, for example, TVFLAG and
LISTR. The Committee was pleased to hear that an effort is being made to address parallelization
of AIPS routines to take advantage of RISC multiprocessor architectures. Strong encouragement
was given to developing a plan for merging AIPS and AIPS++.
The Committee applauded the progress in AIPS++: a limited beta release, implementation of
several synthesis imaging tasks, use of AIPS++ as a base for the Parkes multi-beam and telescope
control and analysis software. It was suggested that beta tester workshops be held in Socorro to
bring together the programmers and expert users. A number of specific items were noted for
improvement in the next release. The Committee was excited over the possibility of including in
AIPS++ an AIPS wrapper that would allow an AIPS++ user access to the full functionality of
classic AIPS. The Committee was disappointed to see that no published scientific paper has yet
to appear based on data analysis using AIPS++. It recommended that there be more easily
accessed management information, that development of documentation continue, and that
documentation be maintained in an easily accessed, web-browsable fully-indexed data base. It
was the Committee's stated opinion that user efforts to test AIPS++ should be matched by efforts
of the NRAO staff scientists.
The Committee was pleased to see a request for funding of a design and development phase of the
MMA in the NSF proposed budget for 1998. The Observatory was urged to follow through with
its plans to pursue this development phase with the involvement of the university millimeter
astronomy groups. The recommendation that the MMA be sited in northern Chile was strongly
endorsed. The Committee was concerned that the prospects for finding international partners
might not be all that good, given economic conditions abroad, and urged the NRAO to approach
the NASA Origins program. There is an obvious strong overlap in scientific goals between those
of the MMA and Origins. It was hoped that the next Decade Report would highlight the MMA
and NRAO was encouraged to hold a science workshop in preparation for the upcoming decade
The Committee noted the value of the technology development done in the Central Development
Laboratory, a continuing flow of mixers, amplifiers, and other devices that advance the state-
of-the-art. Involvement in the MAP project has strained the lab and delayed delivery of devices
for other projects, but it was felt the involvement was worthwhile in the return of a better
infrastructure for the lab and the development of amplifiers useful to all of radio astronomy.
NRAO was encouraged to continue its efforts in spectrum management. Of particular importance are the tests to be conducted with the Motorola Iridium project. In these matters, the Committee urged the NRAO to interact regularly with other observatories in establishing policy.
Don Backer will chair the Committee for its 1998 meeting.
R.S. Foster, Chair Users Committee
(Naval Research Laboratory)
E.R. Schulman, J.J. Wiseman, & R.A. Perley
D. G. Finley