[Vlavlbausers] News for VLA/VLBA/HSA/VLBI Proposers
Lori Appel
lappel at nrao.edu
Fri May 16 16:24:54 EDT 2008
News for proposers, May 16, 2008
This "News" posting contains the following sections
General news
* Support for PhD dissertations using NRAO facilities
* Large proposals
* Proposals for the LCROSS mission
News for VLA proposers
* General observing capabilities
* 74 MHz observing in the A configuration
* EVLA impact and availability
News for VLBA/HSA/VLBI proposers
* Regular proposal deadline is 2008 Jun 2 for trimester 2008-T3
* Preparing VLBA or HSA proposals
* Documentation
* GLAST collaborative observing
* VLBI at the VLA
* Preparing proposals involving the EVN
------------------------------------------------------------------------
1. General News
a. Support for PhD dissertations using NRAO facilities
Students planning to use an NRAO telescope for their PhD dissertation
(particularly if more than one proposal will be required) should submit
a "Plan of Dissertation Research" of no more than 1000 words with their
first proposal. This plan can be referred to in later proposals. At a
minimum it should contain a thesis time line and an estimate of the
level of NRAO telescope resources needed. The plan provides some
assurance against a dissertation being impaired by adverse referee
comments on one proposal, when the referees do not see the full scope of
the project. This requirement applies to all three of the NRAO major
instruments: VLA, VLBA and GBT. Shortly after the submission of the
first proposal, please email your research plan to Carl Bignell
(cbignell at nrao.edu) for the GBT and Joan Wrobel (jwrobel at nrao.edu) for
the VLA, VLBA and HSA.
b. Large proposals
Large proposals to use NRAO instruments will be accepted at the June 2,
2008, proposal deadline, and at all subsequent proposal deadlines. There
will no longer be separate, annual, calls for large proposals. The
definition of "large" and other policy issues relating to the submission
of large proposals is described in the Large Proposal Policy
(http://www.nrao.edu/administration/directors_office/largeprop.shtml).
c. Proposals for the LCROSS mission
NRAO will accept proposals for review related to the Lunar Crater and
Observation Sensing Satellite (LCROSS) Mission at the 2 June 2008
deadline. This opportunity was described in the October 2007 NRAO
Newsletter (http://www.nrao.edu/news/newsletters/nraonews113.pdf) p.
29-30. More details are available at http://lcross.arc.nasa.gov.
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2. News for VLA Proposers
a. General observing capabilities
The 2 June 2008 deadline is for the A configuration, scheduled between 3
October 2008 and 12 January 2009. Proposals to use the move time from
the D configuration to the A configuration (16 September to 2 October
2008) will also be reviewed. Proposers are encouraged to consider
proposals for projects that might fill gaps in the dynamic schedule,
i.e., one or more short (1-2 hour) observations covering a variety of
LSTs.
We are currently considering a plan to reverse the order of the
configuration cycles of the VLA/EVLA from the long-used D-> A-> B-> C-> D
to D-> C-> B-> A-> D, beginning with the D configuration at the end of
2009, to facilitate correlator commissioning and early science with the
EVLA. No decision has been taken, but were it to be made, it would be
some time (~September 2010) before the A configuration is again
available for users.
For the 2 June 2008 proposal deadline all VLA proposers must use the
NRAO Proposal Submission Tool (PST). Several modifications to the PST
have been made and will be in place starting 12:00 EDT Friday, 16 May
2008, and accessible from NRAO Interactive Services (http://my.nrao.edu).
The PST can now upload a Plan of Dissertation either within the Author's
page for a specific proposal or from a student's profile under user
preferences. For more details see the latest release notes
(https://wikio.nrao.edu/bin/view/Software/PSTReleaseNotesJun2008).
During this period the number of EVLA antennas will continue to
increase. We have passed the point where more than half of the antennas
in the array are EVLA antennas. This has three major consequences for
users: (1) increased observing capabilities with extended tuning ranges
available at L, C, K, and Q bands, as described below; (2) revised
observing and data reduction procedures are needed when using the
"transition" system. These are described in some detail at the EVLA
returns <http://www.vla.nrao.edu/astro/guides/evlareturn/> web page and
are outlined briefly under "EVLA impact and availability" (section
2b(i)) below; (3) aliasing of continuum emission in the bottom ~0.7 MHz
of baseband on EVLA-EVLA baselines may severely compromise projects
proposing to use high-resolution spectroscopy, as described at the EVLA
returns <http://www.vla.nrao.edu/astro/guides/evlareturn/> page. The
problem arises in the hardware used to convert signals from the EVLA
antennas into a format to be read into the VLA correlator. We have come
to the decision that a hardware solution to this problem is not
feasible, and so we are working hard to mitigate the problem in
post-processing data reduction procedures. Users need to take this
problem into account during the preparation of their proposals for the 2
June deadline.
The new EVLA antennas will not be outfitted with 15 GHz receivers until
the end of the construction project. The number of 15 GHz receivers in
the array is therefore steadily declining as new EVLA antennas are
added, and this should be taken into account in considerations of
sensitivity, time requests, and uv-coverage. For continuum observations
the use of EVLA antennas at 18 GHz (at the low frequency end of K-band)
should be considered as an alternative to using the 15 GHz receivers
(see section 2b(i) below).
b. 74 MHz observing in the A configuration
Recently we have determined that having the 74 MHz dipoles installed
causes a temporal variation, with a time scale of about 1 hour, in the
cross-polarization of order 1% at L-band (1.0 - 2.0 GHz) on EVLA
antennas, as well as a loss of up to 10% in the forward gain of the
antennas at the L-band, up to 8% at C-band (4 - 8 GHz), and up to 6% at
the X-band (8.0 - 8.8 GHz). For these reasons, we plan to install the 74
MHz dipoles near the end of the A configuration, for up to 2 weeks,
depending upon demand. This will help us to schedule L-band polarimetry
so that it does not coincide with the presence of the dipoles. No
decision has yet been made whether the dipoles will remain installed for
BnA and B configurations.
c. EVLA impact and availability
i. Short Term (October 2008 - March 2009)
At the beginning of this period there will be 17 EVLA antennas in the
array rising to 20 in the spring of 2009. The EVLA antennas therefore
comprise a substantial portion of the array, and users must be very
careful in setting up and reducing their data in order to obtain the
best science during this transition period. The issues are described in
detail at the EVLA returns
(http://www.vla.nrao.edu/astro/guides/evlareturn/)
page and are summarized here.
The new online system provides users with raw correlation coefficients
rather than estimates of the visibility as was the case with the old
Modcomp system. The 31DEC06 (or later) version of AIPS is needed in
order for these data to be properly calibrated, but users are encouraged
to obtained the latest frozen release of AIPS (31DEC07) in order to have
access to other bug fixes and tasks needed to deal with EVLA data.
Online Doppler tracking should be used only for projects using only EVLA
antennas, such as those making use of the extended EVLA tuning ranges.
Online Doppler tracking should not be used if VLA-EVLA baselines are
included in an experiment because of phase jumps on VLA-EVLA baselines
introduced by the VLA Fluke synthesizers at any change in frequency or
bandwidth. For the same reason, phase calibration must be included at
any frequency or bandwidth change for observations using both VLA and
EVLA antennas.
The use of narrow-bandwidth modes on EVLA-EVLA baselines is currently
compromised by the aliasing of emission outside the band as described in
section 2a above. This problem will go away once the EVLA correlator is
available. The latest information on attempts to compensate for the
aliasing effect during the VLA to EVLA transition will be provided on
the EVLA returns web page.
Recent observations have shown that the bandpass stability of EVLA
antennas is approximately a factor of 10 better than that for VLA
antennas. Users making observations of sources with weak
line-to-continuum ratios may want to use EVLA antennas, only.
Extended tuning ranges are available at L-band (1.0-2.0 GHz), C-band
(4.2-7.7 GHz), and K-band (18.0-26.5 GHz). The ranges outside the
nominal VLA frequencies for C and L band (especially the former) have
poor sensitivity and polarization performance, as compared with the
nominal VLA frequencies. Further details of the sensitivity as a
function of frequency for these bands can be found at the EVLA returns
(http://www.vla.nrao.edu/astro/guides/evlareturn/) page.
In addition to the increased tuning ranges on the EVLA antennas it is
now possible to tune the two IF pairs anywhere within the available
C-band simultaneously. IFs separated by up to 4 GHz at K-band (18.0-26.5
GHz) and Q-band (40-50 GHz) are also possible.
Ka-band (26.5-40 GHz) receivers will begin to be installed on the EVLA
antennas in Q2 2008, and there will be a call for shared-risk Ka band
proposals when there are at least 5 available (likely in Q4 2008).
S-band (2-4 GHz) receivers will begin to be installed on the EVLA
antennas Q4 2008, and will be available for shared-risk observing when
there are at least 5 available, in 2009.
JObserve cannot be used directly to make observe files for the new
tuning ranges. Users wishing to take advantage of the new tuning ranges
should check the EVLA returns web page for further information. A new
observation preparation tool (OPT) is currently undergoing testing,
in preparation for observers who are successful for the shared-risk Ka
-band call.
On-the-sky testing of the prototype EVLA correlator is currently planned
to begin summer 2008. This is not expected to have a major impact on
observing.
In October 2008, part of the final WIDAR correlator will begin to arrive
at the VLA site; testing and commissioning of this partial correlator
will begin soon thereafter. More components of the WIDAR correlator will
continue to arrive over this time frame. We will be putting full effort
into making the EVLA correlator operational as quickly as possible.
Correlator commissioning may have an impact on both the amount of
observing time and user support available during this period. We may
issue a special call for proposals in Q1, 2009, to carry out possible
early, resident shared-risk observing with a subset of the WIDAR
correlator in Q4 2009.
ii. Medium Term (April 2009 - December 2009)
By the end of 2009 there will be approximately 24 EVLA antennas
available and it is likely that we will stop using the remaining VLA
antennas in the array sometime during this year. Depending on how the
WIDAR commissioning is progressing, the VLA correlator may be
decommissioned late in this time frame.
The configuration schedule may be modified during 2009 to accommodate
WIDAR and other EVLA commissioning. Consideration is also being made to
reverse the current order of VLA configurations (see "General observing
capabilities", above). Users should not rely on the regular
configuration cycles being maintained throughout 2009.
iii. Long Term (2010 - 2012)
In 2010, the primary EVLA retrofit will be completed, although not all
the frequency bands will be installed on all antennas. Open shared risk
observing is expected to begin in 2011 using the full EVLA correlator,
with full science operations being implemented in 2012.
------------------------------------------------------------------------
3. News for VLBA/HSA/VLBI Proposers
a. Regular proposal deadline is 2008 Jun 2 for trimester 2008-T3
This deadline applies to regular observing proposals requesting
* the Very Long Baseline Array (VLBA), alone or with affiliate(s)
* the High Sensitivity Array (HSA)
* the European VLBI Network (EVN)
* Global cm VLBI (EVN+VLBA) in the Oct/Nov session
b. Preparing VLBA or HSA proposals
We announce the capability for proposal submission for the VLBA/HSA
using the NRAO Proposal Submission Tool (PST) accessible from NRAO
Interactive Services (http://my.nrao.edu). For the June 2, 2008 proposal
deadline, using the PST to submit VLBA/HSA proposals will be an optional
method, but we encourage users to try this method. For this deadline, we
will still accept VLBA/HSA proposals prepared using the LaTeX template
(http://www.nrao.edu/administration/directors_office/vlba-gvlbi.shtml)
and then submitted via e-mail to propsoc at nrao.edu. Global 3mm VLBI
proposals, VLBA+Effelsberg proposals, and requests for using the Bonn
correlator should continue to use the LaTeX template, and also be sent
to propvlbi at mpifr-bonn.mpg.de. Financial support for US-based students
is available via the NRAO Student Observing Support Program
(http://wiki.gb.nrao.edu/bin/view/Observing/NRAOStudentSupportProgram).
c. Documentation
A new version of the VLBA "Information for Astronomers" web page is
available at http://www.vlba.nrao.edu/astro. The primary purposes of
the revision are to
* Make the list of documents and links accessible from the top page,
reducing searching among subsections for the appropriate document;
* Produce a page that parallels, as closely as possible, the similar
VLA page at http://www.vla.nrao.edu/astro/, so that astronomers
can find information for the two telescopes in exactly the same
manner; and
* Update the documentation and links, removing or replacing obsolete
material.
c. GLAST collaborative observing
Through an agreement with the Gamma-ray Large Area Space Telescope
(GLAST) mission, up to 10% of the total observing time on NRAO
telescopes may be allocated for collaborative observing with GLAST
(http://www.nrao.edu/pr/2007/glast/). The GLAST Cycle 1 Peer Review was
held in 2007 December. Approximately 300 hours of collaborative
observing was allocated on the VLBA, with less time allocated on the VLA
and the GBT. GLAST is presently scheduled for launch no earlier than
2008 May 31. GLAST Cycle 1 is expected to begin about 2 months after
launch and to continue for 1 year. Thus GLAST collaborative observations
are expected to begin late in 2008-T2 and continue through 2008-T3.
d. VLBI at the VLA
VLBI at the VLA is working well, but proposers should be careful about
scheduling untested modes, particularly those using EVLA frequencies and
512 Mbps. We are actively working on calibration transfer for the VLA.
f. Preparing proposals involving the EVN
For all classes of proposals involving the EVN, *only* the on-line tool
NorthStar should be used to prepare and submit proposals. This includes
Global cm VLBI (EVN+VLBA) proposals. Access NorthStar at
http://proposal.jive.nl.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
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