In February, we were very pleased to learn that the National Science
Foundation (NSF) plans for FY1998 include funding for the Design
and Development phase of the Millimeter Array (MMA). The D&D work is
a three-year program addressed to the detailed design and
prototype of major MMA subsystems. At the conclusion of this phase we
expect to be able to demonstrate the technical performance of
the critical MMA instrumentation and to use the experience to anchor the
construction cost estimate for the array. The NSF FY98 plan
requires Congressional approval and the funds for the MMA and other NSF
programs will have to be appropriated by Congress. The
Congressional authorization and appropriation process will occur over the
next six months.
The MMA construction itself, a project that will require an additional
six years, will need separate approval both by the NSF and through
It is interesting to consider what we are trying to design: it is an
array to be complete in the three years of the D&D phase plus the six
years of actual construction; together this brings the completion date to
2006. This time scale makes the project very much like a space
project with the same potential liability, namely that if one designs an
instrument at the state-of-the-art today it might be well behind
the state-of-the-art by the time it is complete. We don't want that to
happen. The alternative is to be aggressive with the technical design
and build in some well defined fallbacks. We will adopt the latter
approach which we believe can lead us to a state-of-the-art instrument
The hallmark of an innovative design is the sound ideas of creative
people and to this end we hope to recruit to the MMA D&D project
the participation of many experienced people in the U.S. millimeter-wave
community. A vital aspect of this is a broadening of the
involvement of the MMA Development Consortium, both through the MDC
working groups and via specific design tasks done on the
existing arrays and later on the merged university array. In the next
several months the details of this collaboration will be defined in
a way that we anticipate will strengthen all of U.S. astronomy.
On March 16-19 a joint Japan-U.S. workshop was held in Tokyo to discuss
the scientific opportunities that would arise should it be
possible to combine the capabilities of the MMA with those of the similar
Japanese project called the Large Millimeter and
Submillimeter Array (LMSA). Sites being studied in Chile for both the MMA
and the LMSA are large enough in principle to
accommodate both arrays and, were the two instruments to co-locate, one
could construct for little incremental cost a combined array
configuration 10-15 km in extent that would permit observations at ~10
milli-arcsecond resolution at millimeter and submillimeter
wavelengths. The combined instrument is referred to as the Atacama Array
(named after the Atacama desert that dominates northern
Chile west of the array sites being studied in the Altiplano of the
Andes). The Atacama Array is very much a "virtual" instrument
because neither one of its constituent parts, the MMA and LMSA, yet exist.
Nevertheless, should it become a reality it is in the interest
of both the Japanese and the U.S. groups to provide a means to exploit the
capabilities inherent in the Atacama Array concept in a way
that extends the scientific program presently forecast for the MMA and
LMSA alone. This requires planning; hence the need for the
Nearly 120 scientists attended the Atacama Array Workshop. The meeting was hosted by the National Astronomy Observatory of Japan and the Nobeyama Radio Observatory. The meeting venue was the National Olympics Memorial Youth Center south of the Shinjuku area of Tokyo. Invited and contributed papers were presented by more than 50 speakers on
very high resolution millimeter and submillimeter observational
opportunities that the Atacama Array would support on objects from
those in the solar system, to those in protostellar and protoplanetary
disks, and those in forming galaxies at cosmological distance.
Poster papers provided an interesting supplement to the oral
presentations. A lively discussion of the technical compatibility issues
that need to be addressed followed the scientific sessions.
As a purely practical matter having both arrays occupy sites in
proximity to each other, and for that matter in proximity to other
observatories existing or planned in northern Chile, provides an
opportunity for substantial cost savings in items related to capital
infrastructure, staffing, and common facilities. For this reason alone
collaborative discussions are useful and indeed it is considerations
such as this that have led to a series of MMA/LMSA meetings dating back
three years. The Atacama Array science workshop is an
extension of this effort; we are grateful to all the participants and
especially to the NAOJ/NRO local organizing committee for a very
stimulating meeting. We are grateful also to the International Division
of the National Science Foundation and the Japan Society for
the Promotion of Science, agencies that co-sponsored the workshop.
The Atacama Array Workshop provided an important perspective into the
science goals that could be done with ~10 milli-arcsecond
angular resolution and the priorities for such research. The next step is
to use this perspective to examine carefully the technical
compatibility of the MMA and LMSA planning. A meeting on this topic will
be held around the first of the year.
R. L. Brown
AIPS++ has passed an important milestone with the beta release made on
February 26. This version (0.8) of AIPS++ has been installed
at all NRAO and other AIPS++ consortium sites and a few external sites,
and is now being tested. Anyone interested in acting as a beta
tester is invited to contact Tim Cornwell (email@example.com). The release
is patched for minor upgrades every few weeks, and two
more major beta releases are planned before a general open release of the
system in the fall.
AIPS++ is now being used for real-time reduction of observations from the Australia Telescope Parkes Observatory 21 cm Multibeam Receiver System. To see a display of results and for more on the multi-beam project, see:
As part of the computer procurement at the end of 1996, there are now
several powerful computers for general use in Charlottesville.
2 DEC Alpha 500 1 DEC Alpha 3000 2 IBM RS/6000 1 Sun Ultra2 (dual processor) 1 Sun SPARCStation20
The new machines (DEC Alpha 500/400 and Sun Ultra2) have more than 20
GB of user disk space available.
Visitors who would like to reserve one of these should consult Jim
Condon <firstname.lastname@example.org> or Gareth Hunt <email@example.com>.
As mentioned in the previous issue (No. 70, 1 January 1997), new public
workstations were acquired in 1996 and are now available
for use. Two of these are in Tucson, one in Green Bank, two in
Charlottesville, and six in Socorro. All except the Dec Alpha 500 in
Charlottesville are Sun Ultra computers.
The cost of these acquisitions was covered partially by removing the
old public IBM RS/6000 computers in Socorro and Charlottesville
from their maintenance contract. Most of the IBMs are still available for
use, but will not be repaired when they break. In the case
of CPU failure, data on disk can be recovered (with difficulty). They
will obviously be phased out gradually.
Faint Images of the Radio Sky at Twenty-cm are now available on-line at
the FIRST Survey's URL: http://sundog.stsci.edu. The
complete set of 9735 coadded images covering the 3000 square degrees
observed in the B-configurations of 1993, 1994, and 1995/6
are served at full resolution (and unmodified for compression) from a
machine at the Institute for Geophysics and Planetary Physics
at Livermore. Thus, a user can specify a sky position, an image size from
arcseconds to degrees, an image display scaling factor, and
whether the image is desired as a GIF image on the screen, a FITS image
loaded automatically into a pop-up SAOimage window, or
a FITS file for off-line analysis. This capability has also been
integrated into the FIRST catalog search engine. This powerful browser
now allows the user to enter a sky position and search radius to obtain a
complete listing of FIRST radio sources within a given region.
In addition to the line of catalog information on each source are three
buttons: "NED" performs an on-the-fly search of the current NED
database (in which FIRST sources are now the most common entry), "DSS"
pops up the Digitized Sky Survey optical image of the
region requested, and "FIMG" retrieves the full-resolution radio image as
described above. The catalog now contains over a quarter
of a million radio sources with subarcsecond positions down to the survey
threshold of 1.0 mJy. For those requiring large quantities
of image data, the archives of the NRAO, the STScI, the Canadian Astronomy
Data Center, and Mullard Radio Observatory at
Cambridge all have the survey database online and available for
We welcome suggestions from users for improvements we could make in the
utility of the FIRST data products.
It is a pleasure to announce the selection of Professor James Peebles of Princeton University as this year's Jansky Lecturer. Professor Peebles is well known for his seminal work in many areas of Physical Cosmology like the determination of the primeval abundance of 4He, the formation of structure in the universe, the genesis of anisotropies in the cosmic microwave background, and his proposal that searches should be made for primeval galaxies. He pioneered the use of statistical tools to describe the large-scale structure of the universe introducing the two-point correlation function as well as higher-order estimators. His influence has shaped research in cosmology over the last 30 years through his numerous articles and well-known books. The Jansky Lecture will be given in Charlottesville on October 28 and in Socorro on October 31, the topic to be announced at a later date.
P.A. Vanden Bout
This international meeting will be held in Socorro,
1997 April 21-26. Preparations for the meeting are well
advanced. About 200
visiting participants are expected from about 20 countries. Many NRAO
staff will participate as well.
This meeting marks the 30th anniversary of the first successful
experiments in Very Long Baseline Interferometry (VLBI). The
meeting's scientific program reflects the rapid maturing of VLBI as an
astronomical research tool, and covers topics as diverse as
gamma-ray blazars, molecules and atoms in active galaxies, intraday
variability, gravitational lenses, black holes in nearby galaxies,
astrometry of pulsars and stellar companions, supernova evolution, and
magnetic fields in stellar atmospheres. A special session is
also planned for users of the first space VLBI mission (VSOP/HALCA).
Lists of oral and poster papers, plus abstracts of all papers, are
available from the IAU164 web page. That page can be reached by
selecting "Meetings & Workshops" from the NRAO home page at <http://www.nrao.edu/>. The conference
proceedings are scheduled
for completion this summer. Preprints will be made available on the WWW.
If you have further questions regarding this meeting, please send email
The meeting organizers wish to acknowledge the sponsorship of IAU
commissions 28 (Galaxies) and 40 (Radio Astronomy), URSI
(commission J), NRAO/AUI, and the New Mexico Institute of Mining and
J.M. Wrobel and J.A. Zensus
A committee consisting of Alan Bridle (chair), Don Backer,
Ed Churchwell, Martha Haynes, Jackie Hewitt, Dave Hogg, and Fred Lo
was asked to consider whether or not the NRAO should have a policy for
the consideration of unusually large observing proposals.
If so, what should the policy be?
Their report can be found at the NRAO URL: http://www.cv.nrao.edu
/~abridle/lpc/lpc.html. The report recommends that there be
a policy for the treatment of large proposals and the committee's
recommendations for that policy have been adopted. The following
is a summary of the policy.
Expanded "Skeptical Review." All proposals that ask
for more observing time than a (telescope-specific) threshold, and, at the
Director's discretion, some proposals requesting less time than this, will
initially be evaluated by an expanded "skeptical review" panel
of five or more referees.
The panel will be drawn from the normal pool of proposal referees for
the telescope, augmented if necessary by others who have recently
been proposal referees. The panel will be roughly balanced between
"experts" in the astronomical sub-discipline addressed by the large
proposal, and cross-disciplinary "skeptics."
The panel will assess: the scientific priority for the proposal in
competition with all other astronomy that is being done at the telescope;
whether the telescope is well suited to the proposal; whether the total
duration proposed for the project is well-defined and
commensurate with the scientific priority; whether there should be any
proprietary holding time for the data, and if so, for how long;
whether the proposal is suitable for use as a back-up project in a dynamic
scheduling strategy for the telescope. The panel will provide
the Director with a recommended course of action and a summary of its
Thresholds. For the VLA and VLBA, the threshold for
skeptical review is around 300 hours of observing time. For the 12 Meter
Telescope it is around 1000 hours. For the GBT, the threshold will change
as new instruments and higher-frequency capabilities are
commissioned, and will need continual review. In all cases, these
thresholds are explicitly fuzzy and the Director has the option to send
some proposals below these thresholds for expanded "skeptical review."
Volunteering for Skeptical Review. Proposers of
moderate-sized (below-threshold) projects may also volunteer for expanded
review" of their proposals. This option provides a way to obtain a
stronger guarantee of observing time for moderate-sized projects
whose science could clearly be advanced by receiving such guarantees, in
return for submitting them to a more demanding initial
review. This option is expected to be used rarely, and only in
exceptional cases where the science would suffer if the project was done
piecemeal through the regular proposal process.
Ongoing "Expert Review." The skeptical review panel
for a large proposal will also advise the Director whether any further
review" of the proposal is needed in four main areas: scientific issues of
observing strategy; technical issues of observing strategy and
data acquisition; ongoing review of project progress; and public
availability of the data products.
Not all large proposals will require further review in all of these
areas, and many may not require further review at all. If a highly-rated
large proposal is of sufficient scope or technical complexity to warrant
ongoing review, the NRAO will make every effort to achieve
this without over-burdening either the proposers or the expert referees.
The arrangements for any ongoing "expert review" would be
made at the discretion of the Director on a case-by-case basis.
Upper Limits to the Total Time for Large Proposals. If
several large proposals for a given telescope are highly rated by the
review panels, the Director will seek advice from a cross-disciplinary
subset of the regular proposal referees about upper limits to the
fraction of all observing time that should be devoted to them. Such upper
limits are not to be interpreted as "quotas" to be filled with
No Announcements of Opportunity. The NRAO will not
make "announcements of opportunity" for the submission of large proposals.
Large proposals should be submitted at the normal proposal deadlines,
without special solicitation by the Observatory.
P.A. Vanden Bout
Thanks to a mild Green Bank winter (the mildest on record by some
accounts), work on the GBT has progressed well since the last
report. The site is a busy place with close to 100 workers engaged in the
construction, including ironworkers, operating engineers,
painters, electricians and management staff. The accompanying photographs
depict the structure status in mid-February. Additional
progress has been made since the photos were taken. For example, on the
antenna the horizontal feed arm is now complete with the
exception of four small (a relative term) cubes which tie the two ends
together. In addition, all counterweight boxes are now in place
and welded, and the actuator room and access walkway are in position.
Electricians are wiring the three remaining servo control
cabinets in the equipment room on Level One.
On the ground, the backup structure (BUS) is approximately
90 percent complete. All BUS parts are on site and of the 6,652
in the BUS, about 6,000 are in place in the trial erection. Truss
assembly is continuing and all the trusses should be made within two
months. In addition, some of the large weldments which make up the
permanent BUS supports are being added to the structure.
Walkways to facilitate the installation of the over 2,200 active surface
actuators also are being built. The upper feed arm with all of
its mechanisms and the feed room are nearly ready for testing.
Work through the spring will consist mainly of completing the BUS on
the ground and preparing to separate it into the 22 modules
for lifting onto the structure. The first module is scheduled to go up in
June with additional modules following weekly through the
summer, fall, and early winter. The lower vertical feed arm will begin its
upward growth on the end of the horizontal feed arm later
in the summer. That season will also see construction of a heavy lifter
crane necessary for part of the BUS erection, as well as the
smaller, but no less necessary, jobs such as installation of access
walkways, cable trays, actuators, continuance of the necessary HVAC
and electrical work, and cable pulling.
In January, the GBT Electronics and Monitor/Control groups began to
assemble and interconnect most of the GBT electronics and
monitor/control hardware in the basement of the Jansky Lab. This facility
will allow us to test the entire receiving chain (including
cryogenic front-ends, local oscillators, IF systems, and certain backends)
with the controlling computer hardware and software.
Currently, most of the initial set of hardware is in place and system
debugging has begun. Development of the computer screens for
user interfaces is underway. These will be evaluated and improved in
conjunction with the system mockup.
Construction of the new GBT spectrometer is nearing completion and
debugging is underway. Software for the spectrometer is now
under development, and our goal is to move the spectrometer to Green Bank
this fall for integration with the IF system and with the
GBT monitor/control software.
The NRAO team that is responsible for monitoring the contractor's
antenna servo development, and for the NRAO software that
interacts with these servos, are looking forward to the start of field
tests of the contractor's feedarm servo systems. These systems
control the subreflector positioner and other feedarm mechanisms. Field
tests will begin in April and will be the first opportunity to
evaluate the servo performance while attached to the actual mechanisms.
Software interfaces and portions of the NRAO control
software will also be tested with the servo systems.
This past winter concrete was poured for nine of the twelve laser
rangefinder ground monuments planned around the perimeter of the
GBT site. Underground cable conduits for seven of these are now in place,
and we are preparing to outfit these monuments this spring
and summer. Production continues on the twenty rangefinders required to
measure the surface and pointing, and is scheduled for
completion by this fall. This summer, the laser testbed facility around
the base of the 140 Foot Telescope will demonstrate tracking
of multiple targets on the moving antenna and an attempt will be made to
correlate the laser ranging data with 140 Foot pointing
measurements. This experiment is a major step toward development of the
GBT precision pointing strategy.
It is expected that this summer the contractor will begin installation
of surface actuators on the backup structure. The NRAO Open-loop
Surface group has completed virtually all the hardware development
associated with the surface actuators and the associated software
is scheduled for completion by this winter. Over 2000 surface
retroreflector assemblies have been completed.
Within a few weeks, we will go out for bids for the construction of a
control building at the GBT site. Construction drawings and plans
are now being completed, and we hope to begin construction this summer.
The Green Bank Earth Station support of the Japanese Space Agency VLBI
Space Observing Platform (VSOP) began on 1997 March
21. The VSOP satellite was acquired shortly after satellite rise and
downlink data were recorded until scheduled satellite hand off. The
station real-time logs indicate downlink from the satellite was un-broken
the entire tracking pass.
During the tracking pass, wide-band data were written to VLBA tapes.
Satellite Telemetry header data were successfully extracted, and
this data was made available in near real time. Calibration tones injected
into the spacecraft RF system were extracted at the tracking
station. The calibration tones were confirmed to be present in both C and
L bands at approximately the expected signal level.
Electronics and software systems testing will continue throughout the
Also during the week, Max Avruch and Froney Crawford, two graduate
students from MIT, came to Green Bank to make the first
interface tests of the MIT Near Real Time Correlator. The interface to
the 140 Foot Telescope was successfully checked. The interface
to the tracking station antenna was not checked, but will be checked in
early April 1997.
A number of proposals have been received in response to the final call
for 140 Foot proposals given in the last issue of the Newsletter.
These are now being refereed. All observers who have a proposal in the 140
Foot queue will be informed in May of the status of their
An S2 VLBI recording system has been received from the Canadian Space
Agency and has been installed at the telescope. It will be
used for experiments in conjunction with VSOP. The GBT C band receiver is
nearing completion and will be installed at the 140 Foot
Cassegrain focus sometime this summer. This will allow rapid switching
between C, X, and K band experiments. When these systems
are operating we will try some experiments in contingency scheduling that
should give us experience that will be relevant to the GBT.
An interference monitoring program was conducted with the NRAO 140 Foot
Telescope from May 1995 to July 1996. The sky
frequencies monitored during the program ranged from 50 MHz to 3.4
GHz. The monitoring data were analyzed by Samantha Fore,
an undergraduate at Virginia Tech, who has worked at NRAO through a
student cooperative work program. Ms. Fore's results can be
found at http://www.gb.nrao.edu/~sfore.
The results are presented as spectra of interference amplitude and
frequency of occurrence.
With these spectra, one can estimate to what degree interference may
adversely impact spectral line observations. Additionally, the
spectra can be used to identify relatively clean observing bands for
Work has begun on a new digital correlator for the 12 Meter Telescope.
This new correlator will follow closely the GBT correlator
design, will use correlator chips already owned by NRAO, and will be a
replacement for the hybrid correlator now in use at the
telescope. It will support the existing 1.3 mm and 3 mm, and any future,
multi-beam systems on the telescope. The new correlator
will have an instantaneous bandwidth of 950 MHz; the current hybrid
correlator system only supports 300 MHz in 8-beam mode. 300
MHz is inadequate for some Galactic observations at 1.3 mm, and inadequate
for most extra-galactic observations. The new system
will not rely on hybrid technology, so avoiding the platforming and
ramping problems which exist in the existing hybrid correlator.
We hope to complete the project in two years.
The 8-beam 1 mm array receiver has been in routine use on the telescope
since late January. The 4x2 beam cluster can map in both
(RA,Dec) and (II,bII) coordinates while tracking parallactic angle with an
arbitrary position angle offset. The current performance
of the receiver represents a substantial gain over the existing dual-beam
system for making narrow-bandwidth maps of extended
regions. We are currently working on solving an instability in the system
which can adversely affect baseline stability for
wide-bandwidth measurements. Several observing teams will be using this
system over the next several months.
J.G. Mangum for the Tucson Group
Some recent changes to the 12 Meter Telescope home page (http://www.tuc.nrao.edu/12mete
r.html) have improved the information
we provide to prospective observers. We have added a page which contains
information on the current status of all of the telescope
systems. We update this status page approximately every week so that
observers with impending observing sessions can better plan
their observations. We are also working to supply html-format versions of
many of the documents for prospective observers as a
supplement to the existing postscript-format versions. Comments regarding
the 12 Meter home page are encouraged and appreciated.
In order to make the best use of the telescope, prospective and
scheduled observers are strongly encouraged to contact the Friend of
the Telescope, Jeff Mangum, for advice regarding their proposed
experiments. This is of particular importance for observers conducting
8-Beam and on-the-fly experiments given the complexity of these observing
modes. Send questions via email to firstname.lastname@example.org
or by voice to 520-882-8250 x113.
J.G. Mangum and D.T. Emerson
The orbiting element of the Japanese Space VLBI mission, VSOP, was
launched successfully by the Institute for Space and
Astronautical Science (ISAS) on 1997 February 12. This spacecraft,
originally known as Muses-B and renamed HALCA after launch,
has subsequently deployed its 8-m effective diameter radio astronomy
antenna, and has begun an extensive in-orbit checkout program.
The first Space VLBI observations are scheduled for the nominal issue date
of this Newsletter; the first to be correlated at the AOC will
be observed a few days later, on 1997 April 4.
All tests of the VLBA correlator's Space VLBI capabilities that could
be performed in advance of receiving these data have been
completed successfully. Many of these tests were described in NRAO
Newsletter No. 70.
A correlator software release brought several new Space VLBI features
into the standard operational code. Increased aggregate output
data rates, to reach finally the correlator's original specification of
500 KB/s, are now available for VSOP as well as for general VLBI
observations. Deformatting of the Mark 4 data format, written by new or
upgraded equipment at EVN and DSN stations, is essential
for the 16-MHz bandwidths of the VSOP/VLBA compatible mode. (Pending
further tests, however, we are not yet accepting Mark
4 format for ground-based observations.) Enhanced fringe-rotation rate
computations perform better in the presence of high geometric
rates and LO offsets. New tables attached to the correlator's FITS output
describe more completely the orbit used in generating the
spacecraft's wavefront model.
AOC personnel involved in Space VLBI have been participating actively
in planning and scheduling the in-orbit checkout and early
scientific observations. Development of local operational procedures has
The forthcoming AIPS APAR release emphasizes various specialized Space
VLBI tasks. AIPS users analyzing VSOP observations
must use this or a later version. A first draft of an AIPS Cookbook
chapter on Space VLBI data reduction has been completed. Testing
of AIPS's Space VLBI capabilities using simulated data, primarily in the
areas of fringe-fitting and model-fitting, has continued.
As part of our user-support program, we have purchased a
high-performance Silicon Graphics computing facility, consisting of an
Origin 200 compute server and two model O2 visualization workstations.
NRAO personnel tested such a configuration at the SGI
location in Albuquerque, and measured an AIPSmark(93) of 13.7
in simultaneous dual-user mode. Selected primarily to support the
demands of Space VLBI fringe-fitting and imaging, this system will be
available on the usual sign-up basis for users coming to Socorro
to analyze VSOP observations.
An AOC Space VLBI web page has been created, reachable via the NRAO or
the NRAO/Socorro home pages. In addition to general
information on the NRAO Space VLBI project, we will post updates on our
correlation of in-orbit checkout observations on this site.
Proposals for VLBI Global Network observing are handled by the NRAO.
Global network sessions currently planned are:
|21 May to 15 Jun 1997||1.3 cm, 6 cm, 18 cm *||01 Oct 1996|
|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|
* On the EVN, also includes 5 cm line observations
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
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 proposals, send proposals to:
Director National Radio Astronomy Observatory 520 Edgemont Road Charlottesville, VA 22903-2475 USA.
NASA, the USNO, and NRAO have a joint geodetic/astrometric project on
the VLBA which uses 24 hour observations approximately
every 2 months. This project serves multiple purposes including measuring
VLBA baselines, tying the VLBA to the geodetic reference
frames, supporting the celestial radio reference frame, and advancing the
techniques of geodetic and astrometric VLBI. It is possible
to insert a small number of extra sources into these observations to
obtain positions with milliarcsecond accuracy. These positions are
determined during the normal reduction of the whole observing session.
NRAO hereby offers a service to the community to provide high accuracy positions of small numbers of sources. The sources must be sufficiently compact to be seen with VLBI at 2.3 and 8.4 GHz and should have flux densities in the compact components of more than 0.2 Jy. At least initially, the program
will be administered informally. Please send requests by email to
email@example.com and include the following information:
1. A short scientific justification.
2. Source names.
3. Source coordinates good to at least 0.5 arcseconds.
4. The expected flux densities at 2.3 and 8.4 GHz.
5. Evidence that there will be compact structure.
Requests for positions of more than 10 sources will not be considered.
The requested sources will be compared with objects in recent
and proposed VLA and VLBA proposals so that conflicts are avoided.
Accepted sources will be observed as soon as possible and
positions will be returned by email. The results will be public domain
immediately and will probably be included in the source lists
associated with the geodetic/astrometric programs.
In the VLA archive project, significant progress was made in fixing the
"antenna file" problem associated with the VLA archive data
from 1976 through 1982. Soon we expect to be able to resume the copying
and reformatting of the remaining old nine track tapes to
exabyte tapes. We expect to conclude this project in the course of 1998.
The IBM RS/6000 workstations, for many years the fastest workstations
that NRAO had to offer to its visitors, were retired from active
service as public machines. They have been replaced with six
dual-processor Sparc Ultra 2 workstations, each with 384 MB of memory
and 25 GB of fast disk for data. All of these systems, as well as our two
existing Ultra 1/170's, have been connected to Uninterruptible
Power Supplies (UPS) so they can continue running through most power
failures. The savings from the canceled IBM maintenance
contract funded much of the cost of the new workstations. The new systems
will be the core of our computing power reservable by
visiting observers and in-house staff. Prospective users of these
machines are encouraged to browse our Web site for information about
booking these workstations. All IBMs except zuni will continue to be in
use by local staff until the machines become unmaintainable.
The name zuni lives on as one of the new Ultras.
Some changes have been made to the Visitor's Registration form on our
web page. Section A has been modified so that scientists or
others traveling to the AOC for reasons other than observing or processing
data, only need to fill out this part before submitting the
form to the NM Reservationist electronically.
Since the new Ultra systems require Solaris 2.5.1, that will become the
standard revision of the operating system on Suns at the AOC.
Systems currently running 2.4 will be upgraded during the next few months,
as will all but one or two of the remaining SunOS 4
Three Silicon Graphics workstations, including a powerful four-CPU
Origin 200, have been ordered for Space VLBI processing and
are expected to be installed by early April. The Origin 200 holds the
current AIPSmark(93) record with an impressive 13.7 per
In addition, the USNO has purchased an HP 9000/C110 for handling geodesy
data, which is now in operation at the AOC.
The upgrade of networking within the AOC to switched Ethernet is in
progress, but will take some time to complete. As part of the
upgrade, most Suns in the building will be given a dedicated 10Mbps
Ethernet link. The new equipment has also allowed us to provide
100Mbps (FastEthernet) networking capability for all of our Ultras.
We have plans for improvements to some services, including dedicating a
SPARCstation IPC as our WWW and anonymous ftp server.
This should be installed during the spring. The move will be transparent
if you use the "www.nrao.edu" and "ftp.aoc.nrao.edu"
addresses. Currently both of these services are provided by systems that
have a very heavy load from their other required uses.
IDL is now available observatory-wide. The terms of our agreement with
Research Systems Inc. require us to remove PV-Wave, so it
will shortly disappear. Thanks to the Intranet, a pool of 10 "floating"
licenses is being shared among the four major NRAO sites and
G.A. van Moorsel
|Configuration||Starting Date||Ending Date||Proposal Deadline|
|B||14 Feb 1997||27 May 1997||1 Oct 1996|
|CnB||06 Jun 1997||23 Jun 1997||3 Feb 1997|
|C||27 Jun 1997||15 Sep 1997||3 Feb 1997|
|DnC||26 Sep 1997||13 Oct 1997||2 Jun 1997 5 p.m. EDT|
|D||17 Oct 1997||12 Jan 1998||2 Jun 1997 5 p.m. EDT|
|A||30 Jan 1998||18 May 1998||1 Oct 1997 5 p.m. EDT|
|BnA||29 May 1998||15 Jun 1998||2 Feb 1997 5 p.m. EST|
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).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 will be done in April, 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 proposer.
On December 5, 1996 we implemented a system to automatically measure
the flux density of any recognized calibrator as it is observed
with the VLA. These flux densities are entered each week into a database
accessible via a simple graphical interface on the WWW.
Given the highly variable nature of many of the VLA calibrators, this
utility should give a much improved estimate of a given
calibrator's current flux density compared to the outdated values given in
the VLA calibrator manual. This is especially true in the
intermediate frequency bands (L, C, X, and U bands), where the accuracy of
the automatic measuring system is typically less than ten
percent. At the more extreme P, K, and Q bands the accuracy is more like
30%. For more information see the full description on the
VLA calibrator manual web page (http://www.nrao.edu/~gtaylo
r/calib.html). To explore the database, point your Java enabled
browser at http://aips2.nrao.edu/vla/ca
lflux.html, or access it from the VLA calibrator manual web page.
Recently, a few spectral line observers have lost data because the
integration time they had chosen was too short for the particular
combination of number of IFs and number of channels. For various reasons,
it is not possible to give exact minimum integration times
for each particular observation. Among other things, this depends on the
number of subarrays, which usually is not known at the time
the observe file is received. More information on this including a table
containing conservative estimates for two cases of subarrays
is available on the WWW (http://www.nrao.edu/vl
a/html/vla_integ.shtml). The same table values are available to the
program which will issue a warning, if appropriate. We are currently
investigating methods in which we can detect the occurrence
of missing integrations while the observation is ongoing, and switch to a
longer integration time if needed.
G.A. van Moorsel
During the time March 31 - September 26, the VLA will employ temporary
extra workers to help paint antennas, level track, and
replace deteriorating waveguide access ports. The plan calls for painting
three VLA antennas plus quadropods as time allows. An
antenna being painted will be removed from use while it is being actively
worked on, which means that one antenna will be out of the
array for painting during the hours 6:30 a.m. - 4:30 p.m., Monday - Friday
for much of the seasonal work schedule. Some work in the
area of the feeds and the subreflector needs careful masking. It may be
necessary to remove an antenna from use around the clock for
up to a couple of days while painting these critical areas. Only one
antenna at a time will be removed from use for painting. For
specific information on the effect of painting on your observing schedule,
contact Gene Cole at the VLA before your run. The track
and access port work is not expected to impact the observing schedule.
Maintenance and painting work at several VLBA sites also will interrupt
observing but only on a scheduled basis.
The Array Operations Center will begin using a voicemail feature on its
telephone system over the next few months. It is currently in
use on the main number (505-835-7000) to announce holiday or o ther
unexpected closings of the offices. The Reservations Office (505-835-7357)
and Assistant Director's Office (505-835-7300) will accept voicemail
messages. Eventually, most extensions will be on the
system and have the ability to receive voicemail.
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