EWG Update

gtrichards
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Joined: Tue Feb 25, 2014 3:16 pm

EWG Update

Postby gtrichards » Mon Apr 07, 2014 10:02 am

Here is the update that we just sent the SSG in advance of the
VLASS phone-con this afternoon. Let us know if you have
corrections or other thoughts that we should address at the
meeting.

Gordon & Jackie

############

The EWG hasn't specifically identified trip points for the proposed 3
tier plan, however between online discussions and those among the
people attending the Exascale conference this week, we
can identify them and highlight where things are.


ALL-SKY would be pointless shallower than 100uJy as that is already
only as deep as FIRST. Moreover, that would push it below the realm
that we agreed was the minimum for VLASS (i.e., it could be done as PI
science).

Not all points on the sky are created equal and ALL-SKY could probably
drop to ~25k sq. deg and still cover most regions of interest (~18k
sq. deg if considering just extra-galactic science). In particular:
* dec > SDSS max dec isn't as valuable
* dec <-30 not necessary if could do with ATCA (and Pan-STARRS stops there)
* dec <-10 adds complications for array choice
* dec >+75 similarly adds complications

WIDE would be pointless shallower than 50uJy (currently spec'd at
30uJy) as it wouldn't be enough deeper than FIRST to be generically
interesting.

WIDE statistically could drop to ~2500k sq deg., but then wouldn't
have full coverage of DES+HSC (if we still want those regions).


We have pretty much settled on S-band for WIDE and ALL-SKY, with
polarization tipping the balance (see Mao white paper).

We are still leaning towards the B-array, though there have been some
arguments for A. Those could be characterized as "we wouldn't be able
to do X unless we did A", but not "it would be irresponsible not to do
A". Choosing A would require significant discussion about surveying
dec<-10 and dec>75. Jackie can elaborate on discussion about this
from Exascale. Moreover there are some technical concerns about using
A array (regarding data rates) that Rick White can elaborate on.


As spec'd WIDE and ALL-SKY are not nearly as valuable without each
other as one probes more area than FIRST and the other greater depth.
It *is* possible to combine them if we are willing to make some
sacrifices to depth of WIDE and area in ALL-SKY. Indeed, if the data
rate concerns are valid, it might push us to this for technical
reasons.


A lot of data has been gathered on the various potential DEEP fields,
including the uv coverage, visibility, multi-wavelenth data, bright
sources, and RFI. No firm decisions have been made though there is
still a strong argument that 10 sq. deg is the minimum area. ECDFS,
which would otherwise be a top choice, may be sufficiently less than
ideal that its gets bumped off the list (for an L-band survey).

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