AUI Maintains Its Commitment to
On May 1 of this year Secretary of Energy Pena terminated the contract
under which AUI has
operated the Brookhaven National Laboratory (BNL) since its founding, 50
years ago. In doing
so, he commended AUI's scientific management, but criticized our
management of environment,
safety and health issues, and claimed that there had been an unacceptable
loss of public trust.
While the Trustees of AUI strongly object to the Secretary's decision and
disagree with the stated
basis for termination, we have been relatively silent over the last
several months, hoping that we
might yet have an opportunity to continue that relationship with
Brookhaven by successfully
competing for the contract in collaboration with others.
On August 1 the AUI Board of Trustees made the extremely difficult decision of deciding not to submit a bid for a contract to run BNL. Despite its own evaluations over the last ten years, which regularly gave AUI grades of "Good" to "Excellent" in all categories, the Department of Energy made public statements regarding AUI's chances of success in regaining the BNL contract that effectively made it impossible for AUI to win. Specifically, it proved impossible to find partners willing to join AUI in a bid.
This means that commencing with the 1998 calendar year, AUI will be
operating the NRAO and
only the NRAO. To do so will require some restructuring of the
corporation. That process is
being planned now and it is already clear that a restructured AUI will be
able to conduct all its
management and oversight functions of the NRAO as it has for the past 40
Over the last several months, as the situation at BNL continued to unfold, we have met with officials at the NSF, including the Director and all leadership in the Astronomy Division, to keep them up to date and to make them aware of contemplated adjustments in AUI structure, and to assure them of AUI's continuing commitment to NRAO. Although some changes in AUI policy and procedure may be required as the corporation adjusts to new circumstances, we want to assure all members of the Astronomy community that the AUI Board of Trustees has placed stewardship of the National Radio Astronomy Observatory as its top priority and that all actions considered by AUI will be examined in that context.
P. Martin (Chairman, AUI Board of Trustees) and L.
Schwartz, President of AUI
Planning for an expected start to the Millimeter Array Design and
Development phase in FY98
has accelerated recently. In collaboration with the MDC universities,
technical working groups
have been formed that are in the process of laying out the detailed plan
for development of the
instrumentation that will satisfy the technical specifications of the MMA.
In many cases the
baseline plan includes development of competitive approaches with a
decision point scheduled
some time in the future for a choice to be made based on consideration of
cost and performance.
In other cases the approach has been to refine the instrumentation used on
existing facilities. In
all cases the developments will be carried through to the point that
reliable cost and performance
figures can be established.
An important part of the MMA development phase is the assembly of a
test interferometer at the
VLA site that will be used to conduct real-world performance evaluations
of all the MMA
instrumentation. Here the emphasis will be on validation of such things
as the antenna's ability to
fast switch and point accurately. Development of the software to control
the test interferometer is
a goal equal in importance to development of the hardware. The test
interferometer will allow us
to debug much of the MMA instrumentation such that the hardware sent to
the array site will be,
ideally, operational and easily integrated on-site.
Discussions addressed to establishing foreign partnership in the MMA
continue to progress in
promising ways. Development of the Atacama Array concept, a collaboration
between the MMA
and the Large Millimeter and Submillimeter Array, a project of the
Observatory in Japan, will take the next steps with a technical meeting
planned in December. At
the same time, a partnership has been formed between the European
(ESO) and the NRAO to study a merger of the MMA and the European Large
U.S. and European joint study groups are looking into questions having to
do with science,
technical issures, and management considerations. Talks are scheduled to
continue in the fall.
In the next (December) NRAO Newsletter we hope to be able to report the
results not only of the
fate of the FY98 funding but also of progress in establishing partnerships
for the MMA.
The Millimeter Array (cont.)
Note added: At the end of September the House-Senate Conference Committee agreed to begin the MMA Design and Development with FY98 funding of $9M. The Conference report still needs to be approved by both the Senate and the House and it must be signed by the President before it can take effect. While still preliminary, this is very positive news indeed for the MMA.
AIPS++ Second Beta
AIPS++ issued the second beta release on September 11. This release has
improvements in a wide
range of different areas. The most important for the user is that spectral
line imaging is now
supported, and the speed and memory use of continuum imaging have been
substantially. AIPSView has a number of new capabilities, mostly
concerning control over the
appearance of plots. The robustness of Glish has been improved
considerably. The image-handling
tool has a number of new methods, such as Hanning smoothing, and a wide
range of algorithms
for producing moment images. In addition, functions of applications such
as the image tool can
now be run asynchronously.
Current work on the third beta release, expected 2-3 months from now,
is proceeding, focusing
on providing graphical user interfaces for a number of AIPS++
applications, including the
image-handling tool, and the synthesis imager object. In addition, we
expect that the single dish
analysis environment, which is itself gui-based, will be part of the third
beta release, as will a
visibility visualization tool, and a significantly improved
We are still looking for beta-testers. If you are interested in
helping, and have access to a machine
with memory 64Mbytes or more running Solaris or Linux, please contact Tim
The first limited public release of AIPS++ is planned to occur early next year.
The NRAO VLA Sky Survey
Observations for the 1.4 GHz NRAO VLA Sky Survey (NVSS) began in 1993
nearly covered sky north of -40 declination (82% of the celestial sphere)
by the end of 1996.
Observations to fill the few remaining gaps are scheduled for the fourth
quarter of 1997. All of
the data taken through 1996 have been processed. The principal data
A set of 2326 continuum map "cubes," each covering 4 deg x 4 deg with
containing the Stokes I, Q, and U images. They were made with a
relatively large restoring beam
(45 arcsec FWHM) to yield the high surface-brightness sensitivity needed
for completeness and
photometric accuracy. Their rms brightness fluctuations are about 0.45
mJy/beam = 0.14 K
(Stokes I) and 0.29 mJy/beam = 0.09 K (Stokes Q and U). The rms
uncertainties in right
ascension and declination vary from < 1 arcsec for relatively strong (S
> 15 mJy) point sources to
7 arcsec for the faintest (S = 2.3 mJy) detectable sources.
A catalog of discrete sources on these images (currently containing 1.7 million sources).
Processed (u,v) data sets. Every large image was constructed from
more than 100 smaller
"snapshot" images. All of the edited and calibrated single-source (u,v)
data sets used to make the
snapshot images contributing to each large image have been combined into a
(u,v) file for users who want to investigate the data underlying the
The NVSS is being made as a service to the astronomical community, and the principal data products are being released as soon as they have been produced and verified. To access the NVSS data on the web, go to the NRAO home page (http://www.nrao.edu) and click on NVSS. The web pages contain a paper describing the survey, a postage-stamp image server, a catalog browser, and other software for extracting subsets of the source catalog.
J.J. Condon, W.D. Cotton, E.W. Greisen, Q.F. Yin, R.A. Perley, G.B.
Taylor, and J.J. Broderick
Year 2000 Issues and the
When the Year 2000 (Y2K) arrives in just over 800 days, the potential
exists for many computer
systems, software, and "smart" hardware containing embedded
microprocessors to malfunction.
The convention of using 2 digits for the year instead of 4 has created a
time bomb inside date-aware software and hardware. Its effects may be
disastrous for organizations which are unprepared.
The NRAO has begun assessing the potential for Y2K problems in its own
software. We believe that our Y2K problems will be manageable, as long as
aggressively to address them soon. We have formed a working group with
each of the NRAO's major sites, and from the Business and Personnel
divisions, to identify and
help mitigate potential Y2K problems. The members of this group are: R.
Simon and G. Hunt
(Computer Division), A. Beasley (AOC), C. Bignell (Personnel), A. Bridle
Desmond (Fiscal), J. Hagen (Tucson), and B. Vance (Green Bank).
As part of our efforts to raise awareness and foster internal
communications about Y2K matters, a
web page has been created at http://www.cv.nrao.edu/y2k/. NRAO
users may find this web site a
useful source of links to information available on the Internet about Y2K
A detailed inventory of the NRAO's possible points of exposure to Y2K
problems is now
underway. The observatory does not use massive amounts of customized
software, so we should not face the severe problems which confront many
businesses and financial
institutions. We recognize, however, that we are not immune to such
problems. The broad areas
where potential risks exist are as follows:
Fiscal, Payroll, and Personnel: These functions at the NRAO are of
high priority for the smooth
operation of the Observatory. Many have been outsourced to vendors with
compliance efforts, and their progress will be monitored closely. Those
internally-written software are actively being reviewed.
Telescope Operations: Most of NRAO's online systems should be Y2K
compliant by design,
because they rely on Julian dates unaffected by the century change.
Because of the uniqueness
and complexity of these systems we plan to evaluate their Y2K compliance
by actual testing as
soon as possible after an overall code review. Detailed tests will
require considerable planning to
ensure a straightforward return to normal operations once the tests are
Embedded Chips: Many of our most complex electronics systems use
embedded PC's and chips.
Detailed testing will be needed to reveal if any mission-critical systems
are not Y2K compliant,
and thus require update or replacement. There are numerous old
computers in use, many of which are not expected to be fully Y2K
compliant. The essential
question is "how important is their non-compliance?." We will focus our
attention initially only
on mission-critical systems, as identified by the site managers; others
will be renovated or replaced
as part of normal refurbishment.
Communications: Our phone systems and PBX's, the NRAO Intranet
linking our sites, the
Internet, and long distance telephone services are all potentially
vulnerable. We are reviewing the
weaknesses or potential problems in the hardware that we own.
Utilities and Other Key Outside Services: We are aware that, even if
we have our own house in
good order by the Year 2000, preparedness in the commercial and
governmental world around us
is a matter for great concern. Our Y2K contingency planning will
therefore consider possible
disruptions in outside services and utilities essential for our
Computing Facilities and Software: The century change problem can
affect the operating
systems, utility scripts, and application software run on Observatory
computers, including UNIX
workstations, PC's, and Fiscal systems. An initial review of NRAO's
vulnerabilities in these areas
is in progress. Of particular interest to users of FITS data is the fact
that the original FITS
specification was not Y2K compliant; a new FITS specification is now
available and will be
incorporated into NRAO software which reads or write FITS data (for
further details see
The full size of the Y2K problem at NRAO can not be accurately estimated until inventory, assessment, and initial testing of critical and high priority systems has been completed. We hope to complete this phase of Y2K work at the NRAO by the end of 1997.
R.S. Simon and A.H. Bridle
Graduate Summer Research Program
at the NRAO
In 1998 several summer positions at the NRAO will be available to
graduate students who have
completed one or two years of graduate study in radio astronomy at a U.S.
The purpose of this program is to provide students in radio astronomy with
an intense research
experience done in collaboration with a NRAO scientist. The graduate
summer appointment is
accompanied by a summer salary, transportation reimbursement to the NRAO,
and use of the
research facilities at the NRAO. Graduate summer appointments are
available at all of the NRAO
Students interested in the graduate summer program should provide the
A letter expressing interest together with a CV that describes the academic background of the candidate;
A concise statement of the research area that the candidate is interested in pursuing in his/her Ph.D. research;
The names of three academic references whom the candidate has asked to
send letters of
reference to the NRAO.
Applications should be sent to:
Director's Office Graduate Summer Research Program National Radio Astronomy Observatory 520 Edgemont Road Charlottesville, VA 22903
Application deadline is January 20, 1998.
We appreciate the help of graduate advisors bringing this opportunity to the attention of students in their departments who have expressed an interest in radio astronomy research.
The National Radio Astronomy Observatory awards Jansky Postdoctoral
provide outstanding opportunities for research in radio astronomy. Jansky
formulate and carry out investigations either independently or in
collaboration with others within
the wide framework of interests of the Observatory. Current areas of
cosmology; theoretical and observational studies of radio sources; the
interstellar and intergalactic
medium; structure and dynamics of galactic and extragalactic sources;
physics of HII regions,
stars, solar system objects; and astrometry. The research staff is also
involved in instrumentation
development and image processing; applicants in these areas are
Appointments, which are available at any of the major NRAO sites, are made for a term of two years and may be renewed for a third year. Successful applicants must have received their Ph.D. prior to beginning the appointment and normally within the past four years. Application may be made to:
Director National Radio Astronomy Observatory 520 Edgemont Road Charlottesville, VA 22903-2475
The application should include a curriculum vitae and a brief statement
of the type of research
activity to be undertaken at the NRAO. (Do not staple or duplex
application documents.) The
applicant should have three letters of recommendation sent directly to the
The application deadline is December 15, 1997. All letters of reference must be received by December 31, 1997. The announcement of the Jansky Postdoctoral appointments will be made in compliance with the AAS resolution on uniform notification dates for postdoctoral appointments.
1997 and 1998 Summer
The 1997 Research Experiences for Undergraduates at NRAO has ended with
the 17 students
heading for their colleges from the four NRAO sites. As examples of the
sorts of research
students and their advisers undertake at the four NRAO sites, we give a
short summary of the
research accomplished by two students--further description is available at
Student Frances Ockels (U. of Arkansas, Little Rock) worked with Eric
(Charlottesville) on a project to determine if high velocity clouds of HI
accompany the spiral
galaxy NGC 1300. They found hints of some high-velocity gas.
Naveen Reddy (University of Texas) worked with Min Yun in Socorro. They
luminosity function of 1.4 GHz radio sources from the NVSS with the
Strauss IRAS redshift
survey. The starburst sample luminosity function agreed well with
Condon's spiral galaxy
luminosity function; a second radio population dominated by AGN may also
Information and application forms will soon be mailed soliciting
applications for research
assistantships next summer. The majority of the assistantships will be
offered to undergraduate
students who are currently enrolled in U.S. undergraduate institutions and
who will not receive
their degrees before or during the summer of 1998. A limited number of
assistantships may be
available for graduate students or students from non-U.S. institutions.
Owing to the large number of applicants, and the difficulty of
distributing materials among sites
across the continent, the deadline for receipt of application materials
will be January 20, 1998;
notice of decisions will be sent by March 1, 1998. Forms are available
from Department Heads,
on the WWW (URL http:
//www.cv.nrao.edu/html/headquarters/summer-students.html), or by
Summer Student Program Director National Radio Astronomy Observatory 520 Edgemont Road Charlottesville, VA 22903-2475 Telephone: (804) 296-0225
The Green Bank
The accompanying photographs of the Green Bank Telescope (GBT),
taken in late September
1997, shows that major portions of the tipping structure are in place atop
the alidade. These
include the elevation shaft, box structure, horizontal section of the Feed
Arm, and the elevation
wheel. Primary elements of the servo and electrical systems have been
installed on the alidade and
the antenna is rotated frequently to aid in the erection process.
The reflector backup structure (BUS) has been completed on the 175-foot
square concrete slab at
the telescope site and lifting of its 22 modules onto the box girder has
begun. The entire BUS
was constructed on the ground and consists of 7,652 different members and
approximately 2.1 million pounds. During construction, all joints in the
BUS were aligned with a
positional accuracy of ± 0.25 inches. When finished, the jacks
at the top of the 110 scaffolding
towers were backed-off, leaving the BUS supported only by the 17
reinforced concrete piers on
which it was built. The deflected shape of the BUS under gravity load was
measured to verify the
predicted values of the finite element analysis.
The Contractor has brought in additional heavy lifting equipment to
reposition the 11 modules on
the left side of the BUS because they are out of range of the main tower
modules will be sequentially placed at the base of the main derrick; the
surface panel support
actuators will be installed; and the module will then be lifted and placed
on the box structure.
Modules vary in weight between 25 tons and 74 tons, the rigging used
for lifting weighs an
additional 40 tons, making the heaviest lift 114 tons. As the
modules are placed on the structure,
the 1,072 interconnecting beams between the modules will be reinstalled
for both stability and
accurate positioning of neighboring units. Completion of the reflector
BUS is scheduled for mid
The upper 60-foot portion of the Feed Arm was trial erected at the site
including the deployable
prime focus boom, the prime focus rotation mount, the subreflector, and
adjustment mechanism. The feed/receiver room has been located nearby with
the secondary focus
feed turret in its roof. The Feed Arm servo, which controls all of the
above equipment, has been
installed and tested along with some of the NRAO monitor and control
Photogrammetric setting of the subreflector surface and calibration of the
"Stewart platform" actuators remains to be done. These calibrations will
be made by the fall of
The 200-foot dual tower section of the vertical Feed Arm was trial
erected at the Contractor's
fabrication plant in Mexia, Texas. It has been disassembled and shipped
to the Green Bank site
where final assembly will begin mid October 1997. It is scheduled for
erection after the BUS is in
place. At that time it will be installed on the structure along with the
upper 60-foot tip of the
The 2,004 main reflector panels are now in production at the Contractor's plant. Installation and alignment of the surface is scheduled for late summer of 1998.
Phoenix Receiver and Signal
Processor Available at Green Bank
Since October of 1996, SETI observations have been conducted using the
NRAO 140 Foot
Telescope in Green Bank. An innovative wideband, prime focus receiver,
OMT, and a pair of
corrugated feed horns cover the 1 - 3 GHz frequency range, providing a
/Tsys > 0.2 K-1
and dual circular polarization accessible at 590 MHz as a 300 MHz wide IF.
The Phoenix signal
processing backend routinely provides 20 MHz, dual polarization power
spectra with resolution
of 0.67 Hz every 1.4 seconds and a 643 Hz resolution time-averaged
spectra every 14 seconds.
While the full bandwidth can be written to storage at 643 Hz resolution,
only 2 subbands of width
643 Hz can be stored at the full resolution.
Observing proposals making use of the Phoenix receiver are welcomed as part of the normal 140 Foot proposal process. Observers wishing to use the Phoenix backend should arrange collaboration with one of the Phoenix scientific staff prior to proposing to Green Bank to insure that this non-standard processor is capable of producing the desired scientific results.
Jill Tarter, Director, Project Phoenix
Receivers at the 140 Foot Telescope
In August the 4-6 GHz receiver newly-built for the GBT was installed at
the Cassegrain focus of the 140 Foot replacing the 12-15.4 GHz GBT system.
This receiver is equipped with a local
oscillator for VLBI, and will
allow much more flexible scheduling of VLBI observations, particularly
those involving HALCA.
The following table summarizes the receivers that will be available on
the 140 Foot Telescope
|Prime Focus||Cassegrain Focus|
|3.95-5.85 GHz (only for VLBI)
More details can be found on the Green Bank web page. Please note that the 12-15.4 GHz and 26-36 GHz receivers will not be in use during 1998.
140 Foot Telescope Data
The data archive for the 140 Foot Telescope currently goes back to
early 1992. Over the last few
months, the approximately 250 nine-track and 170 Exabyte tapes that make
up the archive have
been copied to 25 compact disks. This was done in order to better preserve
the data as well as to
reduce the necessary storage requirements. The archive was also copied to
a second set of CDs in
the off chance a CD was ever to be damaged. Even though some of the
original tapes had already
deteriorated, we were able to copy to CD more than 95 percent of the
data. Hanna Smith, a 1997
graduate of Pocahontas County High School, and Don Nelson, a 140 Foot
deserve our thanks for their dedication in completing an often frustrating
Since the format of the data on the CD is equivalent to the original Modcomp telescope tape format (see the 140 Foot manual or the UniPops cookbook for a description of the format), one simply uses the UniPops cvt.disk-disk routine to read the data off the CD. Each CD contains additional files that either summarize the contents of the CD or log every observation on the CD. The CD also contains data base files that can be read by most commercial spreadsheet and data base programs. Anyone who uses the data base files can query the contents of the archive for observations that meet a very wide range of selection criteria (see the July 1995 Newsletter for an article describing archive data base).
R.J. Maddalena and B. Vance
140 Foot Telescope Proposal
As announced in the previous Newsletter, the 140 Foot Telescope will continue normal operations throughout 1998. There will be two deadlines for receipt of proposals to use the telescope during this period: 3 November 1997, and 30 March 1998. Successful proposals received by the November deadline will generally be scheduled during the first half of 1998. Proposal cover sheets as well as information on the telescope and its capabilities can be retrieved from the NRAO WWW site: http://info.gb.nrao.edu.
Space VLBI: VSOP In-Orbit
Checkout at the AOC
After detecting the VSOP mission's first VLBA-format fringes to the
HALCA spacecraft and
producing the first Space VLBI images in mid-June, NRAO Space VLBI Project
been immersed in the in-orbit checkout (IOC) phase of the mission. A
total of 16 observations
has been processed at the VLBA correlator, comprising 30 partially or
tracking passes and 112 hours of Space VLBI observing. (Two complete
observations, and a
total of 19 tracking passes either known to have failed, or searched
unsuccessfully, were not
correlated.) In the process, the first fringes recorded in VLBA format
were detected via the
tracking stations at Green Bank (6/12), Goldstone (7/8), Usuda (7/10),
Tidbinbilla (9/15), and
A major emphasis at the correlator has been completion of the
operational procedures for fetching
and managing the many externally-generated files necessary for correlation
observations. A few functions already have been turned over to VLBA
minor bugs also were discovered, and corrected, in the correlator's Space
principally in the computation of the projected baseline coordinates
included in every output data
record. The correlator's ground-based performance was not affected by
these bugs in any way,
nor was the wavefront model used in Space VLBI correlation.
The VLBA correlator has also provided extensive feedback to other
mission elements, principally
the tracking stations, to facilitate their development of high-quality
recording, and complete,
accurate logs and time corrections. All these will be essential for
efficient correlation, and to limit
output datasets to reasonable volumes. All five tracking stations are
recordings on thin tape, although a few miscalibrated capstans remain. On
the other hand, time
corrections the Space VLBI equivalent of a ground telescope's
slowly and linearly varying clock
offset, but allowing for large and potentially rapid variations
have turned out to be particularly
difficult to implement properly, with corrections for many effects being
addressed only recently.
The objective is for the time corrections to leave residual delays not
much larger than the 50 - 100
nanoseconds typical of ground-based VLBA observations. At present, a
variety of constant
offsets, glitches, oscillations, and incomplete files persist. Usable
time corrections have been
produced for only three of the five tracking stations, and for only two of
these in multiple
With early, albeit partial datasets available, it has become possible
to begin exercising the new
AIPS tasks developed principally for Space VLBI applications with real
data for the first time.
The Space VLBI material in the AIPS Cookbook chapter on VLBI has been
and expanded. A "VSOP Data Reduction" email exploder, firstname.lastname@example.org,
The VSOP International Scientific Council (VISC) decided at its meeting
in August to bring the
IOC phase to a close and begin General Observing Time (GOT). Three
observations already have
been released to the Principal Investigators, and several more are
pending. A large increase in
observing rate has begun with the September European VLBI Network session,
and is scheduled
to continue and expand subsequently.
Users receiving VSOP datasets, and based at U.S. institutions, may wish
to take advantage of the
NASA-funded Space VLBI User Support facility at the AOC. The Silicon
facility purchased for this purpose was described in NRAO Newsletter No.
71. At least one of
the two front-end workstations will be available for users coming to
Socorro to analyze VSOP
observations, and may be requested just by indicating data type "VSOP" on
Visitor Registration form. For a limited period, the NRAO Space VLBI
Project also will pay the
$150 deductible of the NSF-sponsored transportation reimbursement.
Current information on VSOP observations scheduled to be processed at the VLBA correlator is available on the NRAO Space VLBI Project web pages, accessible under "Major Initiatives" on the NRAO home page.
Space VLBI observations are becoming routine in Green Bank. We have now successfully found fringes between VSOP/HALCA and the 140 Foot Telescope, via the Green Bank Tracking Station at both L and C bands. The fringes have been detected at both the VLBA correlator in Socorro New Mexico and at the Canadian S2 Correlator in Penticton, Canada.
VLBI Network Call For
Proposals for VLBI Global network observing are handled by the NRAO.
sessions currently planned are:
|03 Nov to 27 Nov 1997||1.3 cm, 6 cm, 18 cm, 3.6/13 cm||02 Jun 1997|
|11 Feb to 04 Mar 1998||1.3 cm, 6 cm, 18 cm, other?||01 Oct 1997|
|27 May to 10 Jun 1998||1.3 cm?, 6 cm, 18 cm, 3.6 cm?||01 Oct 1997|
|09 Sep to 30 Sep 1998||1.3 cm?, 6 cm, 18 cm, other?||02 Feb 1998|
|11 Nov to 02 Dec 1998||1.3 cm?, 6 cm, 18 cm, 3.6 cm?||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
Fill-in-the-blanks TeX files are available by anonymous ftp from
proposal or via the VLBA home page on the web. 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 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 even if they do not request the use of any EVN antennas. For Global proposals, or those to the EVN alone, send proposals to:
R. Schwartz Max Planck Institut fur Radioastronomie Auf dem Hugel 69 D 53121 Bonn, Germany
For proposals to the VLBA, or Global network proposals, send proposals to:
Director National Radio Astronomy Observatory 520 Edgemont Road Charlottesville, VA 22903-2475 USA.
Proposals also may be submitted electronically, in Adobe Postscript format, to email@example.com or firstname.lastname@example.org, respectively. Care should be taken to ensure that the Postscript files request the proper paper size.
Changes to the 90 cm (P band)
Due to strong and ever-present RFI at 332.7 MHz from an instrument landing system (ILS) at the Albuquerque airport, on September 10, 1997, we changed the default frequency setups for P-Band in Observe and in the on-line system. The BD IF is now set to a center frequency of 321.5625 MHz, chosen to eliminate aliasing from a birdie at 320 MHz. The AC IF has been left at 327.5 MHz which seems to be in a relatively clean part of the spectrum. As before, the default bandwidths are 3.125 MHz. New and improved plots of the spectrum from 300-350 MHz are available on the web at http://info.aoc.nra o.edu/doc/vla/html/rfi.shtml. All P band users are encouraged to consult these plots, especially if they desire to use non-standard frequencies. In Observe, the P band defaults now invoke spectral line mode 4. Spectral line mode allows for RFI to be more easily removed with less loss of data. Note, however, that in the few instances where linear polarization information is desired, correlator mode 4 cannot be used and the spectrapolarimetry mode PA is recommended. For those who don't use Observe, a band designation of PP given to the on-line system invokes the new defaults, but in continuum mode unless otherwise specified. The defaults for simultaneous 20 and 90 cm observing (designated LP), and simultaneous 90 cm and 4 m observing (designated 4P), have been modified to employ the 327.5 MHz window instead of the old 333 MHz window.
The NRAO site testing interferometer (STIfR) is now operational at the
VLA, and software has
been installed for real-time monitoring of the phase stability (special
thanks to Tom Folkers,
NRAO, Tucson). The STIfR is a device that measures the tropospheric
contribution to the
interferometric phase using an interferometer composed of two 1.5 m dishes
separated by 300 m,
observing an 11 GHz beacon from a geostationary satellite (Radford,
Reiland, and Shillue 1996,
PASP, 108, 441).
The STIfR measures a time series of phases with an averaging time of 1
s. The real-time analysis
software accesses a 600 s time series of phases and generates a temporal
root phase structure
function from the data, corresponding to the root mean square (rms) of the
phase differences as a
function of lag-time for lags from 1 s to 300 s (Holdaway, Radford, Owen,
and Foster 1995,
MMA Memo Series). The software then fits for: (i) the power-law index,
for short lags, (ii)
the constant "saturation rms," , for long lags, and
the "corner time," tcorn, corresponding
to the intersection of the powerlaw and the constant (saturation)
functions. The corner time
corresponds roughly to the time required for a parcel of troposphere to
cross the length of the
interferometer baseline. These standard data products can be used to
estimate the calibration
cycle time necessary to achieve the desired residual rms phase noise at a
given VLA observing
frequency in the case of fast-switching phase calibration (Carilli,
Holdaway, and Sowinski 1996,
VLA Scientific Memo Series), or the coherence in a given averaging time in
the case of
As an example, typical values for the standard data products from the
STIfR at the VLA under
good weather conditions are: tcorn = 20 s, = 0.7, and
= 3°. These
conditions are the norm on
fall and winter nights. Under these conditions, a Fast Switching phase
calibration cycle time of 50
s should result in residual rms phase variations of 10° at 43 GHz,
thereby limiting the image
dynamic range to about 100. Under poor weather conditions (summer days),
the value of can
increase to 10° or more.
The data from the STIfR are meant to be used for semi-real-time
decision making by the user
when observing with the VLA at high frequency. The data can be accessed
via the NRAO web
page at URL: http://www.nrao.edu/
The web software produces a series of X-windows plots on the user's
workstation showing the
current root phase structure function plus fit, a 24 hour running history
of the standard data
products from the STIfR, and a histogram of the rms phase stability over
the last 24-hours, with
current conditions high-lighted. There also is a window showing a 24 hour
running history of
data from the VLA weather station, including barometric pressure,
temperature, dew point, and
surface wind speed. The web page also has a series of help files
explaining the various windows,
and providing equations for converting the STIfR standard data products
into VLA observing
The STIfR system for real-time monitoring of VLA observing conditions is currently experimental. Suggestions on how to improve the implementation are welcome.
C.L. Carilli, A.L. Roy, and G.B. Petencin
After filling several vacancies, the Computer Operations Department is
fully staffed again. As a
result, there is excellent progress on the VLA archive project. Earlier
this summer, the correction
of missing antenna files for the years 1976 to 1982 was completed, and
work has started on the
remainder of the VLA archive project for the years 1985 to 1987. We
intend to finish this project
in the course of 1998, by which time the complete VLA archive will be
available on 8 mm
Exabyte tape, and the complete catalog of observations will be accessible
on the web. Sometime
before then, we will examine various possibilities (e.g., optical storage,
DVD) as a possible future
medium for the VLA (and possibly VLBA) archive.
During July and August, 23 new SPARC Ultra 1/170 workstations were
installed on staff
desktops at the AOC. The systems which were replaced, mostly SPARCstation
IPXs, were in
turn trickled down to staff with slower systems. In total, 60 upgrades
were done, and the 23
trade-ins were all SPARCstation 1's and old IPCs. The Sun at the VLA site
near-real-time observing and data reduction was upgraded from a SPARC 2 to
a SPARC 20, with
vastly improved performance. All the Suns at the VLA site now are running
Solaris 2.5.1, as are
the majority of systems at the AOC. All of the AOC systems reservable by
visitors now are either
dual-processor SPARC 20s or Ultras.
Wiring of the AOC for switched Ethernet is complete. Testing during the summer revealed that we will have to migrate all the systems on a given subnet at once, rather than individually, as we had hoped. As a result, the move was delayed until after all workstation upgrades were completed. We expect to begin this move in September; since it requires considerable coordination with staff, it probably will take a couple of months before all AOC workstation subnets are connected to switched Ethernet.
G. A. van Moorsel
|Configuration||Starting Date||Ending Date||Proposal Deadline|
|DnC||03 Oct 1997||27 Oct 1997||2 Jun 1997|
|D||31 Oct 1997||01 Feb 1998||2 Jun 1997|
|A||19 Feb 1998||01 Jun 1998||1 Oct 1997|
|BnA||12 Jun 1998||29 Jun 1998||2 Feb 1998|
|B||03 Jul 1998||21 Sep 1998||2 Feb 1998|
|CnB||02 Oct 1998||19 Oct 1998||1 Jun 1998|
|C||23 Oct 1998||11 Jan 1999||1 Jun 1999|
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 declination) and extreme northern sources (north of about 80 degrees declination).
Observers should note that some types of observations are significantly
more difficult in daytime
than at nightime. These include observations at 327 MHz (solar and other
ionosphere, especially at dawn), line observations at 18 and 21 cm (solar
polarization measurements at L band (uncertainty in ionospheric rotation
observations at 2 cm and shorter wavelengths in B and A configurations
variations, especially in summer). They should defer such observations
for a configuration cycle
to avoid such problems. In 1998, the A configuration daytime will be
about 0h RA and the B
configuration daytime will be about 8h 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
Increasing amounts of VLBA observing time will be devoted to observations
with the HALCA
long-baseline interferometry satellite, approaching a long term average of
about 30 percent of
VLBA observations devoted to space VLBI.
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 proposer.
NRAO to Develop a Fiber Optic
Link between the VLA and Pie Town
The National Science Foundation (NSF) announced September 9, 1997,
that it has awarded funds
to the National Radio Astronomy Observatory (NRAO) sufficient to permit
the VLBA antenna at
Pie Town, New Mexico, to be connected to the VLA. The NSF award
is for $466,000, and the
project will take three years to complete.
In February of this year, the NRAO submitted a proposal to the NSF
under the Major Research
Instrumentation (MRI) program to develop a fiber optic link between the
VLA and the VLBA's
Pie Town (PT) antenna, with a goal of doubling the VLA's resolution.
The funding of this proposal will enable the Observatory to take
advantage of two very fortuitous,
but non-accidental, situations: The VLBA's Pie Town antenna is located 35
km from the closest
VLA antenna--exactly the diameter of the VLA's 'A' configuration, and a
fiber optic line
belonging to the Western New Mexico Telephone Company already joins the
room to the PT antenna. Thus, the most expensive components of such a
are already in place.
When completed, this link will enable operation of the PT antenna as if
it were a VLA antenna,
doubling the resolution of the array, while maintaining its total
sensitivity. For northern objects,
(declinations north of 50 degrees), the u-v coverage, and synthesized beam
characteristics will be
excellent. For objects south of this, the beam becomes increasingly
elliptical (with the high
resolution axis lying in a SENW line) with decreasing declination.
The goal will be to provide
the full current bandwidth, and possibly up to the proposed increase to
70 MHz per IF channel.
The success of this proposal is due to the hard work of many individuals. I'd like to thank Alan Bridle for his efforts on behalf of the science justification section, the technical group at the AOC, led by Dick Sramek, for their efforts on behalf of the technical sections, and Billie Rodriguez and The Director's Office for their considerable efforts in putting everything together in time for submission.
NRAO 1998 Synthesis Imaging
The Sixth Summer School in Synthesis Imaging will take place from June
through June 23 (Tuesday) of 1998. The summer school will be hosted by
NRAO and New
Mexico Tech and held in the new Workman center on the Tech campus in
Socorro, New Mexico.
Data reduction tutorials on June 20 at the Array Operations Center (AOC)
will allow attendees to
get "hands-on" experience with data calibration and imaging for both VLA
and VLBA data.
NRAO scientific staff will be available at the AOC to aid and advise
participants. A tour of the
VLA site will be given on June 21.
The Summer School will cover all basic aspects of radio interferometry,
including both connected
element (e.g., the VLA) and Very Long Baseline interferometers (e.g., the
VLBA). Lectures will
be given by the NRAO staff, faculty from New Mexico Tech, Harvard, Univ.
of Chicago, and
Caltech, and by staff members of other observatories around the world.
The range of subjects will
be similar to past Summer Schools, and can be reviewed by consulting
"Synthesis Imaging in
Radio Astronomy," the published collection of lectures from the 3rd NRAO
Summer School (ASP Conference Series, Volume 6, 1989). The lectures will
be given at a level
appropriate for graduate students in astrophysics. There will be ample
time for questions and
discussion following each lecture. Copies of the lectures from the 1998
Summer School will be
distributed to attendees in Socorro and collected and published by the
Astronomical Society of
the Pacific following the school.
There will be no limit on attendance. A fee of $45 will be assessed,
sufficient only to cover our
local expenses. No financial assistance will be possible. The
registration fee will include
transportation between Socorro and Albuquerque airport on June 16, and on
June 24 or 25, daily
transportation to/from hotels, and a tour of the VLA on June 21. A summer
school dinner, held
outdoors on the New Mexico Tech Campus on Friday evening also is included
in the registration
Rooms will be blocked out at Socorro motels for the school, and
information on these motels will
be sent to participants in a general mailing in February of 1998. The
daily cost of a single room
currently ranges from $22-$55 and sharing a double room from $16-$30 per
registration will be the responsibility of the attendees.
To indicate your interest in attending the summer school, please register electronically by directing your web browser to http://www.nrao.edu/~gtay lor/synth98.html, and following the directions for electronic registration. More information about the meeting, hotel accommodations, and the town of Socorro is available from the web page. You also may register by filling out the accompanying registration form, and mailing it by April 1, 1998 to: Terry Romero, NRAO, P.O. Box 0, Socorro, NM 87801.
G.B. Taylor and C.L. Carilli
Sixth Synthesis Imaging Summer School
Socorro, New Mexico
June 17-23, 1998
Please return by April 1, 1998 to:
Mail: Terry Romero National Radio Astronomy Observatory P. O. Box 0 Socorro, NM 87801 - or - Fax: 505-835-7027 E-Mail: email@example.com
Do not send money with this form; invoices will be included in
a future mailing to
participants. If there are any subjects you wish to have discussed,
please list them or E-Mail to: <firstname.lastname@example.org>
If your address during April/May, 1998 is different than above, please
indicate that address
along with applicable dates.
( ) I definitely plan to attend
( ) I hope to attend and will confirm later
Please indicate your professional level:
( ) Undergraduate
( ) Graduate Student
( ) Postdoctoral
( ) Faculty
( ) Scientific or Engineering Staff
( ) Other
Have you observed with:
VLA ( ) Yes ( ) No
VLBA ( ) Yes ( ) No
Completed 74 MHz System on VLA
Available for Trial Observing
Last month, an announcement was sent via email to announce the
availability of a trial 74 MHz
system on all twenty-seven VLA antennas for the upcoming A configuration.
At least twenty
proposals have been submitted in response to that announcement. The
purpose of this note is to
update the information provided in the email announcement in the light of
Funding for this initiative has been provided by the Naval Research
Lab. Namir Kassim was
instrumental in obtaining this grant. Bill Erickson designed the new
receivers, and both Namir
and Bill have spent much time at the NRL and at the VLA in building,
checking, installing, and
testing these new systems. We are very grateful for the time and effort
contributed by Bill and
Namir to this project.
By early October, fifteen antennas were outfitted, enabling detailing
imaging with the CnD array.
Long observations were scheduled for three objects--Perseus A, W51, and
the Sun. The data
quality is extremely good--calibration is very straightforward with such
short baselines--but the
internally generated RFI is a severe problem which we now are addressing.
We will require new
software to better identify and remove these unwanted correlations. Only
a few percent of the
spectral channels are affected--but efficiently identifying and removing
these is very laborious
when done by hand. Fortunately, this RFI is not expected to be a severe
problem in the A and B
The full installation plan remains the same as announced earlier--the
full complement of 27
receivers and dipoles will be installed by late January for the A
configuration. The dipoles will be
removed when all scheduled observations are completed.
Observers interested in using this system in other configurations are
encouraged to apply for time.
If there is sufficient demand, the dipoles may be re-mounted near the end
of the scheduled B
configuration time, in order to permit B and C configuration observing.
Our new data have not yet been reduced sufficiently to give further
information on system
sensitivity. We are sure that a 12 hour observation will result in an rms
noise less than 100 mJy.
It probably is optimistic to believe that a sensitivity better than 20 mJy
can be achieved.
The resolution of the array at this frequency in the B and C
configurations is about 75 and 250
arcseconds, respectively. The useable bandwidth is limited to 1.6 MHz by
the front-end filters,
and it is strongly recommended that observations be taken in spectral line
mode to permit
calibration of instrumental delays and removal of any RFI. Calibration of
data from the B and C
configurations is not expected to be very difficult, especially the
If you have any questions, please contact me by telephone (505-835-7312) or by email (rperley@ nrao.edu).
12 Meter Participation in the
Mars Global Surveyor Mission
Mars Global Surveyor (MGS), which entered Mars orbit on September 12,
1997, is an orbiter
mission which will conduct, among other things, the first global mapping
of the surface
mineralogy and elevations, magnetic field measurements, and high/medium
During the next three months, Todd Clancy of the Space Science Institute
and Brad Sandor of
JPL will conduct observations of the martian CO absorption using the 12
Meter Telescope which
are being used to provide atmospheric sounding measurements of the martian
support of the aerobraking maneuvers of the MGS orbiter. During these
MGS will dip into the upper atmosphere of Mars in order to circularize
it's orbit for mapping
operations. Because the three month aerobraking phase of MGS coincides
with the global dust
storm season on Mars, it is important to obtain real-time
characterizations of the Mars
atmosphere during this period.
12 Meter observations of the martian atmospheric CO absorption provide measurements of the dust heating of the lower martian atmosphere (0-50 km). These measurements will provide early warning to associated changes in the atmospheric densities to be encountered by the MGS orbiter. For example, the 12 Meter observations from September 12-21 showed cold, dust free atmospheric conditions for the Mars atmosphere as MGS entered orbit. However, they also indicated a significant trend of increasing atmospheric temperatures up to September 21, which points to increasing dust loading of the lower atmosphere. This inferred increase in the martian atmospheric dust loading was consistent with the increased atmospheric density experienced by the MGS orbiter as it made its first aerobraking maneuver. Since observations of the martian atmosphere are being taken every three days at the 12 Meter, it will soon be possible to determine whether the current dust behavior is a short-term phenomenon such as observed during the March-July period, or is the beginning of truly global dust storm activity on Mars.
Improvements to the 12 Meter
During the 1997 summer shutdown period, the following improvements were
made to the 12
(1) New UPS system. Two Franlin UPS systems were installed this
summer replacing the Atlas
UPS system. These new UPS systems have larger capacity than the old
system and have been
installed in parallel for greater reliability. A modern lightning
arresting system was installed to
protect the new UPS system. These additions will help minimize observing
downtime from power
(2) New low-noise mixers for the 68-90 GHz system. These new mixers
yield approximately ten
percent better system temperatures. At 90 GHz, the performance of these
new 68-90 GHz mixers
is the same as that of the mixers for the 90-116 GHz band.
(3) New analysis computer and operating system. A Sparc Ultra II
(called modelo) is now the observer's main computer. We have also
"upgraded" all workstations
(4) New central selection mirror and vane servos. The central
selection mirror and hot load vane
have new servo systems. These new servos should be faster and more
reliable. The speed and
accuracy of the central selection mirror servo system has shortened the
time to switch from one
receiver to another to less than 5 seconds, which will allow easier
pointing with the various 12 Meter receivers. For example, we are
investigating the possibility of
using pointing measurements at 3 mm to predict the pointing offsets
for the 1 mm systems.
(5) New central cold load system. The central selection mirror has
been equipped with a
cold-load system which we will use to conduct more accurate receiver
tuning and monitoring of
the receiver temperatures. Since we will no longer need to use the sky as
a cold load for tuning,
the biggest immediate advantage of this new central cold load system will
be in the tuning of the 1
mm receivers. We are also investigating the possibility of using this
central cold load system for
an improved antenna temperature calibration scheme.
(6) New digital phase lock for 2/3 mm receiver. Two new digital
phase lock boxes (dplb) have
been installed in the 2/3 mm receiver. These new lock boxes will
allow for easier phase locking of
these receivers and frequency switch throws as large as ±35 MHz. All
of the 12 Meter receivers
will eventually be outfitted with new dplb systems.
(7) New filter bank switcher. An electronic filter bank switcher
system has been installed. It is
now no longer necessary to move the multi-pin connectors which feed the
filter banks, improving
the reliability of these backends and minimizing the number of bad
channels in these
(8) On-line CLASS data converter. The uni2class UniPOPS-to-CLASS data
format converter is
now integrated into the control system. All scans except continuum and
OTF measurements are
automatically converted to CLASS format and put in a file called class.12m
in the observer's
directory. The usual SDD-format data files which we have used for several
years continue to be
written, with no change. Although writing data simultaneously in both data
formats does take
more disk space, this is not a significant overhead.
(9) NRAO Tucson home page. We have revised the NRAO Tucson home page.
updated information has been added to this site, including the ability to
access our historical tipper
(10) User's manual update. The 12 Meter User's Manual has been revised. In addition to some minor rearranging, the continuum and spectral line observing sections have been rewritten and several new appendices have been added. Comments on this document are appreciated.
J.G. Mangum and D.T. Emerson for the Tucson Staff