[Vlavlbausers] News for VLA/VLBA/HSA Proposers
Lori Appel
lappel at nrao.edu
Thu Jan 15 13:04:08 EST 2009
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approximately two weeks ahead of all proposal deadlines.
News for VLA/VLBA/HSA Proposers, January 15, 2009
This "News" posting contains the following sections:
General news
* Support for PhD dissertations using NRAO facilities
* Large proposals
News for VLA proposers
* General observing capabilities
* Shared risk Ka-band and C-band observing
* EVLA impact and availability
* VLA Observational Status Summary
News for VLBA/HSA/VLBI proposers
* Regular proposal deadline is 2009 Feb 2 for trimester 2009-T2
* VLBA default continuum data rate increased
* SCHED release
* VLBA at the VLA
* VLBA or HSA proposals
* Proposals involving the EVN
* Global 3mm VLBI proposals
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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) must 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. The plan can be
submitted via the NRAO Interactive Services, at http://my.nrao.edu.
Proposers are reminded to prepare the plan comfortably in advance of
the proposal deadline. This requirement applies to all three of the
NRAO major instruments: VLA, VLBA and GBT.
b. Large proposals
Large proposals to use NRAO instruments will be considered at the
February 2, 2009, proposal deadline, and at all subsequent proposal
deadlines. There is no longer a separate call 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, at http://www.nrao.edu/admin/do/largeprop.shtml.
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2. News for VLA proposers
a. General observing capabilities
The 2 February 2009 deadline is for the CnB (scheduled between 29
May 2009 and 15 June 2009) and C configurations (scheduled between
19 June 2009 and 14 September 2009). Proposals to use the
reconfiguration time from the B configuration to the CnB
configuration (18 May to 29 May 2009) and the reconfiguration from
the CnB to the C configuration (15 June to 19 June 2009) 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.
Proposers are warned that the availability of day time observing
will be limited due to EVLA tests and commissioning.
The number of EVLA antennas continues to increase at a rate of one
every two months. At the beginning of the C-configuration we will
have 21 EVLA antennas in the array. This has at least two major
consequences for users: (1) increased observing capabilities with
extended tuning ranges available at L, C, K, and Ka 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 web page, at
http://www.vla.nrao.edu/astro/guides/evlareturn/, and are outlined
briefly under EVLA impact and availability (section 2c(i)) below.
New EVLA antennas will not be outfitted with 12-18 GHz (U-band)
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 2c(i) below).
In late October 2008 it became clear that the VLA's 327 MHz (P-band)
receivers are incompatible with the wideband EVLA electronics due to
strong, internally-generated interference. No proposals for 327 MHz
will be considered until we find a way to solve this problem, which
is not expected in the immediate future.
For the 2 February 2009 proposal deadline all VLA proposers must use
the NRAO Proposal Submission Tool (PST). A few minor modifications
to the PST have been made, including the addition of Ka-band for the
VLA, and will be in place starting 12:00 EDT Friday, 16 January
2009, and accessible from NRAO Interactive Services at
http://my.nrao.edu. For more details see the latest release notes,
at https://wikio.nrao.edu/bin/view/Software/PSTReleaseNotesFeb2009.
We plan to reverse the order of the configuration cycles of the
VLA/EVLA from the traditional D->A->B->C->D to D->C->B->A->D,
beginning at the end of the D configuration in January 2010, to
facilitate correlator commissioning and early science with the
EVLA. Please see the VLA Configurations and Proposal Deadlines web
page, http://www.vla.nrao.edu/genpub/configs/, and section 2c(ii)
below for further details.
b. Shared risk Ka-band and C-band observing
i. Ka-band
At the beginning of the CnB configuration we predict there will 14
EVLA antennas with 26.5-40 GHz (Ka-band) receivers installed. These
will be made available for science in the CnB and C configurations,
using standard VLA correlator set-ups. IFs B and D are able to tune
over the full 26.5 to 40 GHz, while IFs A and C cover 32-40 GHz. IFs
A/C and B/D can be separated by up to 10 GHz.
The default continuum frequency has been set to 33.5 GHz, close to
the center of the band. This is where the system is most sensitive
for continuum observations, since both IFs can tune to this
frequency. The "K" factor to be used in calculating expected
sensitivities at the default continuum frequency is 20 (see the
Observational Status Summary,
http://www.vla.nrao.edu/astro/guides/vlas/current/node11.html). The
relative sensitivity as a function of frequency across the entire
band can be found at the relevant EVLA returns page, at
http://www.vla.nrao.edu/astro/guides/evlareturn/extendedbands/Kaband/.
The new Ka-band system is being made available on a "shared-risk"
basis, and beyond granting observing time NRAO makes no guarantee of
data or of data quality. Potential observers should be aware that
unlike the standard VLA bands there are no atmospheric opacity
measurements yet, and the usual means of applying an opacity
correction based on weather data to the initial CL table may not be
available in AIPS. Furthermore, there are no models for the primary
flux calibrators at Ka-band, and users will have to experiment with
extrapolating from the existing 22 and 43 GHz models of extended
sources for absolute flux determination, or use limits on the
uv-range. Observers will use the new EVLA Observation Preparation
Tool (OPT) for setting up Ka-band observations, and are requested to
contact NRAO staff at vlahelp at nrao.edu for help at least a week
prior to their observations. The use of subarrays will be supported
only for fixed-date (not dynamic) observations using the OPT.
Beginning March 2, 2009, we will also consider "exploratory
proposals" (see "Rapid Response Science", at
http://www.vla.nrao.edu/astro/prop/rapid/) to use the Ka-band system
in the current B configuration. Such proposals should request a
maximum of 8 hours, and will also be considered to be "shared
risk". Users allocated time will be testing the new OPT and will be
expected to provide feedback on its fuctionality. We expect 8
antennas to have Ka-band systems at the beginning of the
B-configuration, rising to 14 by the end of May.
ii. C-band
At the beginning of CnB configuration we predict there will be 9
EVLA antennas equipped with 4-8 GHz (C-band) receivers containing
EVLA-style ortho-mode transducers (OMTs). This means that the
polarization purity and sensitivity is good across the whole of the
band, and polarimetry away from the traditional VLA bands can now be
undertaken. Plots of the sensitivity and cross-polarization
(D-terms) are available at the relevant EVLA returns page, at
http://www.vla.nrao.edu/astro/guides/evlareturn/extendedbands/Cband/.
The EVLA C-band receivers cover the full 4.0-8.0 GHz range with the
sensitivities shown in these plots.
c. EVLA impact and availability
i. Short term (May 2009 - December 2009)
At the beginning of this period there will be 21 EVLA antennas in
the array. As long as we continue to use the VLA correlator,
hardware limitations prevent the signals from more than 22 EVLA
antennas (plus any remaining VLA antennas) from being correlated.
Therefore the maximum number of antennas that can be used for
science will be 26 (21 EVLA, 5 VLA) at the beginning of this period,
decreasing to 24 (22 EVLA, 2 VLA) by December 2009. A subset of the
final WIDAR correlator will be undergoing tests at the VLA site
throughout this period, and will impact the amount of observing time
available. WIDAR and other commissioning activities may also have an
impact on user support available during this period.
As more EVLA antennas come on line, we continue to caution that
users must be very careful in setting up and reducing their data in
order to obtain the best science during the transition period.
Issues that are important are described in detail at the EVLA
returns web page, http://www.vla.nrao.edu/astro/guides/evlareturn/.
A few of the most important are summarized here:
* Online Doppler tracking should be used only for projects
employing 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 on the EVLA returns web page. Please consult
this web page for latest information on post-processing
compensation for the aliasing effect. This problem will go away
once the WIDAR correlator is used for all antennas.
* Some on-line flagging issues remain. In particular, there are
some cases in which the first few records of a scan are
actually data from the previous scan, but are not flagged by
the online system. In addition, the first 10-20 seconds after
a change of band is often bad and not flagged. Users should
make sure to observe a calibration source after a band change.
The origins of the problems are known, and software changes
are underway to eliminate them. Until those software changes
occur - and are tested - users should critically examine their
data to find and flag such problems.
In addition to the new Ka-band and C-band capabilities announced
above, extended tuning ranges are available at L-band (1.0-2.0 GHz),
and K-band (18.0-26.5 GHz). At C-band the EVLA antennas with
receivers lacking the new OMTs are able to tune from 4.2 to 7.7
GHz. The ranges outside the nominal VLA frequencies for C and L
bands 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 page,
http://www.vla.nrao.edu/astro/guides/evlareturn/.
It is now possible to tune the two IF pairs anywhere within the
available C, K, and Q-bands simultaneously on EVLA antennas.
We also expect that in this time frame the installation of S-band
(2-4 GHz) receivers will have begun on the EVLA and testing of this
new observing capability will be underway. S-band receivers will be
available for shared-risk observing when there are at least 5 have
been commissioned, currently expected in late 2009.
ii. Medium term (January 2010 - December 2010)
The transition from the VLA correlator to the EVLA correlator is
currently planned to take place in January 2010, at the end of the D
configuration. At that time the VLA will remain in the D
configuration for a further trimester and the order of the
configuration cycle will change to D->C->B->A, as announced above.
Shared-risk observing with the new WIDAR correlator will begin with
the EVLA in the D configuration. Capabilities of the new correlator
will be announced in NRAO eNews and via the "News for Proposers"
prior to the 2009 Oct 1 deadline.
Any remaining VLA antennas will be decommissioned at the same time
that the VLA correlator is turned off, and will no longer be used
for astronomy until they have been retrofitted to the EVLA design.
The primary antenna retrofits will be completed in mid-2010,
although not all the frequency bands will be installed on all
antennas. The wide-band Q, Ka, K, and C band receiver systems are
expected to be completed by the end of 2010.
iii. Long term (2011 - 2012)
The fast samplers needed to access the full 8 GHz of bandwidth at
high frequencies will be installed in all antennas by mid-2011, and
the remaining receiver bands will be completed by Q4, 2012.
d. VLA Observational Status Summary
The VLA Observational Status Summary has been updated, including
information on the VLA to EVLA transition, EVLA receiver
availability, and Ka-band sensitivity. It is available in html, pdf,
and ps formats, at http://www.vla.nrao.edu/astro/.
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3. News for VLBA/HSA/VLBI proposers
a. Regular proposal deadline is 2009 Feb 2 for trimester 2009-T2
This deadline applies to regular observing proposals requesting
* the Very Long Baseline Array (VLBA), alone or with
affiliate(s)
http://www.vlba.nrao.edu/astro/
* the High Sensitivity Array(HSA)
http://www.nrao.edu/HSA/
* the European VLBI Network(EVN) [deadline Feb 1]
http://www.evlbi.org/
* Global cm VLBI (EVN+VLBA) in the May/Jun session
[deadline Feb 1]
* Global 3mm VLBI in the Oct session [deadline Feb 1]
http://www.mpifr-bonn.mpg.de/div/vlbi/globalmm/
This deadline also applies to large observing proposals requesting
the VLBA, alone or with other NRAO resources.
http://www.nrao.edu/administration/directors_office/largeprop.shtml
b. VLBA default continuum data rate increased
Beginning with VLBA proposals submitted for the Feb 2 deadline, the
default data rate for continuum observations will be increased from
128 Mbps to 256 Mbps. Recording at 512 Mbps is possible when
required for scientific reasons and justified carefully in the
proposal.
c. SCHED release
Version 8.0 of SCHED was released on 2008 Dec 14; please see
http://www.vlba.nrao.edu/astro/#D5
Users are encouraged to use the latest version when scheduling
projects. During 2009 there are expected to be very significant
changes in the hardware at the stations as the digital backends are
implemented. During this period, it will be especially important to
keep the scheduling software up-to-date. Also, during 2009 the VLBA
will transition to DiFX, the new software correlator. DiFX, in turn,
will change from correlation jobs derived from VLBA monitor data, as
has been necessary for testing, to control directly from project VEX
files (.skd files). The new version of SCHED produces VEX files by
default for all projects, not just projects that have Field System
controlled stations.
d. VLBA 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. Problems with the transfer of amplitude
calibration for the phased VLA have been solved and the attached
calibration information for the VLA can be used without alteration.
e. VLBA or HSA proposals
Proposal preparation and submission are via the NRAO Interactive
Services, http://my.nrao.edu/.
f. Proposals involving the EVN
For all classes of proposals involving the EVN, only the on-line
tool NorthStar http://proposal.jive.nl should be used to prepare and
submit proposals. This includes Global cm VLBI (EVN+VLBA) proposals.
g. Global 3mm VLBI proposals
Proposal preparation is via the LaTeX template,
http://www.nrao.edu/administration/directors_office/vlba-gvlbi.shtml.
Proposal submission is via e-mail to propsoc at nrao.edu and
propvlbi at mpifr-bonn.mpg.de.
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