[Vlavlbausers] NEWS FOR VLA/VLBA/HSA/VLBI PROPOSERS

Fri May 15 12:11:25 EDT 2009

NEWS FOR VLA/VLBA/HSA/VLBI PROPOSERS, May 15, 2009

This "News" posting is also available on the web, at
http://www.vla.nrao.edu/astro/guides/news/.  It contains the
following sections

General news

     * Support for PhD dissertations using NRAO facilities
     * Large proposals

News for VLA proposers

     * General observing capabilities for the 2009 June 1 proposal
       deadline
     * EVLA Early Science
           o VLA to shut down for 2 months, will return as the EVLA
     * EVLA impact and availability

News for VLBA/HSA/VLBI proposers

     * Regular proposal deadline is 2009 June 1 for trimester 2009-T3
     * DiFX software correlator
     * SCHED release
     * VLBI at the VLA
     * VLBI at the EVLA
     * VLBA or HSA proposals
     * Proposals involving the EVN

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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
2009 June 1 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. We
particularly encourage large proposals to use the last VLA
D-configuration (see News for VLA proposers and EVLA Early Science
below for more details about the VLA/EVLA transition).

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2. News for VLA proposers

a. General observing capabilities for the 2009 June 1 proposal
deadline

The 2009 June 1 deadline is for the last trimester to use the VLA
correlator before it is turned off and the VLA becomes the EVLA,
using the WIDAR correlator. Further details of this transition are
described below, under EVLA Early Science. Proposals for the DnC
(scheduled between 2009 September 26 and 2009 October 11) and D
configurations (scheduled between 2009 October 17 and 2010 January
11) will be considered at the June 1 deadline, along with proposals
to use the reconfiguration time from the C configuration to the DnC
configuration (14-25 September 2009) and the reconfiguration from
the DnC to the D configuration (12-16 October 2009). 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, but especially 0-6 hrs.
Proposers are warned that the availability of day time observing
will be limited due to EVLA tests and commissioning, in preparation
for EVLA Early Science.

The number of EVLA antennas continues to increase at a rate of one
every two months. At the beginning of the D-configuration we will
have 23 EVLA antennas in the array, increasing to 25 by the end of
the trimester. However, the VLA correlator can handle a maximum of
22 EVLA antennas (plus all remaining VLA antennas) so the VLA will
have a maximum of 25 antennas through the end of the VLA
D-configuration.

For the trimester under consideration we will be offering extended
EVLA tuning ranges at L, C, K, Ka, and Q bands. Some of these
systems are "interim", which means they use old VLA polarizers. At
C-band the EVLA antennas with receivers containing the old
polarizers 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, at
http://www.vla.nrao.edu/astro/guides/evlareturn/.

The numbers of receiver systems available at the beginning of the D
configuration are approximately as follows:

    Band: L
    Tuning range: 1-2 GHz
    Number: 5(EVLA)+17(interim)

    Band: C
    Tuning range: 4-8 GHz
    Number: 14(EVLA)+8(interim)

    Band: K
    Tuning range: 18-26.5 GHz
    Number: 22

    Band: Ka
    Tuning range: 26.5-40 GHz
    Number: 19

    Band: Q
    Tuning range: 40-50 GHz
    Number: 25

Along with the extended tuning range systems above, all antennas
will have the VLA X-band (8.0-8.8 GHz) receivers available as well.
For those EVLA antennas whose receivers support the wide bandwidths
it is now possible to separate the two IF pairs by 10 GHz.

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. By the end of
the upcoming D-configuration there will be only three antennas
remaining with this capability, so we will not accept any 15 GHz
proposals at the 2009 June 1 proposal deadline. 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.

Similarly, users are reminded that no proposals for 327 MHz will be
considered until we find a way to solve the problem of the
incompatibility of the 327 MHz receivers with the wideband EVLA
electronics, announced in the January 15 edition of the News for
Proposers.

The VLA D-configuration will be followed by an EVLA D-configuration
using the WIDAR correlator. There will be a separate call for
proposals for the EVLA D-configuration for the 2009 October 1
deadline. Proposals received in response to the 2009 June 1 proposal
call will not be held over for the EVLA D-configuration.

Proposal preparation and submission are via the Proposal Submission
Tool at http://my.nrao.edu. Several modifications to the PST have
been made and will be in place starting 12:00 EDT (noon) Friday, 15
May 2009. (See the PST Release Notes (01 June 2009) at
https://safe.nrao.edu/wiki/bin/view/Software/PSTReleaseNotesJun2009
for details of recent changes.)

b. EVLA Early Science

We will be reversing the order of the configuration cycles from the
traditional D->A->B->C->D to D->C->B->A->D, beginning at the end of
the VLA D-configuration in January 2010, to facilitate correlator
commissioning and early science with the EVLA. Also at the end of
the VLA D-configuration we will be turning off the VLA correlator.
This begins a shut-down of the array of approximately 2 months,
during which we will be transferring hardware from the VLA
correlator to the EVLA correlator, and commissioning the first
observing modes to be offered for general use using the EVLA. At the
end of this period we will begin the EVLA D-configuration. At
present the usual trimester system is expected to apply, so the EVLA
D-configuration is likely to be shorter than a normal
D-configuration due to the shut-down. However, if demand for the
preceding VLA D-configuration is light, we will make every effort to
move the shut-down earlier, thus enabling an earlier start to the
EVLA D-configuration. There is some flexibility in the start date of
the EVLA D-configuration, although it will be no earlier than
mid-January 2010.

The EVLA Early Science programs were advertised in the February 2009
NRAO eNews
(http://www.nrao.edu/news/newsletters/enews/enews_2_2/enews_2_2.shtml#widar).
This announcement, along with descriptions of the capabilities to be
offered for EVLA Early Science, are available at the EVLA
Information for Astronomers web page,
http://www.aoc.nrao.edu/evla/astro/. In summary, the Open Shared
Risk Observing program will continue to provide access to new EVLA
capabilities for the whole user community as soon as the
capabilities can be supported for general use. Those expert users
who are able to reside in Socorro to help with EVLA commissioning
for a period of time will have access to enhanced EVLA capabilities
through the Resident Shared Risk Observing program. The first call
for EVLA Early Science proposals will be at the 2009 October 1
proposal deadline.

c. EVLA impact and availability

i. Short term (September 2009 - December 2009)

At the beginning of this period there will be 23 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 by the end of this period will be 25 (22 EVLA, 3 VLA). 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. 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
       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.

The installation and testing of S-band (2-4 GHz) receivers has begun
on the EVLA. S-band receivers will be available for shared-risk
observing when 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
VLA D-configuration, as described under EVLA Early Science above. 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. 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 the end of
2010, and access to the wide bandwidths for general use is expected
in 2012. The remaining receiver bands will be completed by Q4, 2012.

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3. News for VLBA/HSA/VLBI proposers

a. Proposal deadline is 2009 June 1 for trimester 2009-T3

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)
         http://www.evlbi.org/
     * Global cm VLBI (EVN+VLBA) in the Oct/Nov session

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

The observing period is 2009 mid-September through 2010 mid-January.

b. DiFX software correlator

By the end of this year we expect to replace the original,
hardware-based VLBA correlator with the new, software-based
VLBA-DiFX system that has been under development for several years.
This transition should have no impact on observations already
approved, and will not occur until we are reasonably certain this
statement will be true.

After the transition, we will issue a call for immediate Exploratory
Proposals for observations that can scientifically exploit these two
extended capabilities supported by DiFX:

     * High spectral resolution, up to 32768 spectral points.
     * Extremely short integration intervals, in principle as short
       as a single FFT interval (equal to the number of spectral
       points divided by the baseband bandwidth, for Nyquist
       sampling).

c. SCHED release

Version 8.1 of SCHED was released on 2009 Feb 24; please
http://www.vlba.nrao.edu/astro/#D5 for further information.

Users are encouraged to employ the latest version when scheduling
projects. During 2010 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, the new software
correlator, DiFX, will be controlled 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. VLBI at the VLA

VLBI at the VLA is expected to continue working well through 2009.
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. VLBI at the EVLA

There will be an interval of two months, beginning in 2010 Jan,
during which the array will be unavailable due to the replacement of
the VLA correlator with the WIDAR correlator. The array will resume
operation as the EVLA with the WIDAR correlator without VLBI
capabilities. Although it is expected that WIDAR commissioning will
eventually include VLBI capabilities, no definite timescale for
implementing this has yet been set.

f. VLBA or HSA proposals

Proposal preparation and submission are via the NRAO Interactive
Services, http://my.nrao.edu/.

g. 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.