Minutes of the Third GALFA Consortium Meeting


			GALFA Meeting 3
			August 29, 2994
			Arecibo Observatory
	
Note: These notes were taken by Di Li, and edited by Paul Goldsmith.  
We apologize for their rough nature, but it seemed more important to get 
something out that would give the flavor of the meeting, even if it were 
not perfect. Please send corrections and/or comments to PG.
	
This meeting was held on the day before the start of the "Heiles Fest" 
Conference at Arecibo.  Consequently, a number of interested astronomers,
who were not members of GALFA Consortium were present, as well as some
people who just happened to drop by.

The GALFA Consortium thanks the members of the Arecibo Staff who put a lot
of time into organizing the logistics for this meeting, and also the 
Organizing Committee itself, which helped ensure that key topics were 
fitted properly into the agenda.

The following is brief summary of presentations and discussion.

8:30  	Paul Goldsmith 
	Review of the Agenda.  Pointed out that GALFA is still 
		open to new members. 
		
8:45 	Paul Goldsmith 
	Powerpoint presentation reviewing highlights of GALFA 
		Science.  This should be available on the web.
	
	Three "subgroups", Continuum (CON), Recombination Lines (RRL) and HI.
	Due to realities and membership size, the first two will be considered
		to be on par with subprojects contained within GALFA-HI.	
	Science:
		CON (esp. polarimetry): "disembodied" polarization features
			confusion limited 20 micro Jy /beam => rapid scan

		RRL (radio recombination lines):
		multiple lines in ALFA passband, but weak
		300s /pointing => 10mK RMS 

		HI various projects at high and low latitude
		beam spacing 125", 22deg rotation of dewar

		turbulence: need lbv cube
		HI/H2:  relationship of atomic and molecular clouds & ISM phases
		ISM cold HI: why temperature range
		Halo clouds: HVC origins
		High Velocity line wings
		High latitude clouds
		Low latitude surveys: HISA |b|<5	 

9:00 	Steve Torchinsky
	ALFA status

		Frontend installed and generally working satisfactorily
		WAPPs used as spectrometer and for pulsar work
		cold testing, Mar 2004
		delivery, April 1, on time
		lift/installation, April 21
		OH possible with front end filter off, May 2004
		New pulsar, Aug 1

		intermittent short circuit in one of the two LNAs of
		the central beam, Aug 5 (still off-line, but can
		sometimes be revived)

9:15 	A. Deshpande
	ALFA testing and performance

	Precommissioning testing well underway.  Some selected results (much
		information available on web)
	
	Frequency channel correlation with common noise input, some channels
		fall out with longer integration time, unstable.
	Dynamic range, ~40 dB and 30 dB head room for RFI
	SEFD for the central pixel vs ZA, FWHM
	Motor door shielding important
	Coma very clearly seen in beam maps; level not far from that expected
	Rotation in RA DEC; underlying ellipses does not rotate
	TO DO: beam maps at ZAs, gains at ZAs, polarization calibrations

9:33 	Ellen Howell  OH Observations

	Comet Linear: 2-4 km/s outflow, 140 mJy, ALFA gave 2.4 times
		lower line intensity 
		3-level sampling of ALFA vs 9-level for AO,
		Tsys(ALFA)?>30 K 
		Spider scans, off-center pixels have ~8db sidelobe,
		with one up to 6 db, 
		SEFD of off-center pixels is 1.33 times that of the
		center.

		Conclusion: beam 0 has 75% sensitivity of L-wide,
		      off-center pixels have 55% of L-wide sensitivity.  
		For extended sources, net improvement is factor of 2 to 3.
		More if you consider value of simultaneous observations.

9:47 	Dan Werthimer
	GALFA spectrometer

	Jeff Mock, builder (TIVO designer)
	100 MHz bandwidth + 7 MHz (highres) in  each of 14 channels
	35-45 dB image rejection
	Digital spectrometers board: Xilinx FPGA chip, compact PCI format
	Two spectrometers in the chip: 256 channels (broadband for removing
		standing wave) and 8192 channels (for real spectroscopy)

	Fixed integration time: 988ms (99% efficiency)
	File written every 15s: 2*8K+2*256K
	ADC on same board: spurs at +-25 MHz
	Dynamic range, overflow
	Unknown LO phase shift
	see: http://seti.berkeley.edu/GALFA

10:00 	Giacomo Comes
	P-ALFA backend

	Polyphase filter, 1024 FFT, demuxer
	Ready in 6 months (?)

10:13 	Carl Heiles
	GALFA HI calibration

	Try to separate G_if G_rf
	Baseline ripple at AO: reflection between structures => 1MHz~200km/s
	G_if is stable (change 0.l% day to day)
	Thinking in Fourier transform space -
	1 microsecond peak, same height during night, changes faster in daytime
	There are other peaks at 2.2 to 2.5 microseconds delay
	It is not clear what causes them
	Baseline ripple due to reflections is not polarized
	PA of ellipse of OH varies from 50-120 degrees from beam to beam of 
		ALFA
	Need to measure that for HI band too.

Questions/Comments

Tom: What integration time do you need for removal?
Carl: 10 min at beginning of the day on a random position on the sky

Mike Davis: longer time delays are likely a result of multiple reflections,
	perhaps including the ground screen

10:35	Chris Salter
	GALFA continuum transit survey

	HII, SNR 
	Galactic background
	spectral index
	Faraday tomography
	extragalactic sources
	using P-ALFA, 300 MHz, 0.3 MHz channel, full stokes
	Problems: temporal drifts, 8-db coma, spurious polarization=>
		fast scanning, basket-weaving
	Current plans include:
	LBW precursor, 400 MHz, 1msec dump
	ALFA precursor, map the same field as LBW
	Part II:  Full-Stokes mapping of point sources 
	Part III: Linear polarized pulsar

10:48  Snezana Stanimirovic GALFA testing observations: A1943

	Test mapping modes, reference position+freq switching, standing wave 
		extraction, cross/spider scans
	Science projects: L1544, CHVC218+29+145, high latitude MBM40, 
		forbidden velocity line wings
	Observing plans: 7 beam (WAPP) in 10 MHz narrow mode, 1 WAPP 100 MHz 
		wide
	Driving rate 0.95d /min ~ 3.5 sidereal rate, ALFA 75 d, beam separation~
		2.8m, one up and down sweep takes 3min, int 15s/footprint
		4x1deg covered in 25mins with 3 crossings per point, 10x1 deg 
		covered in 55 mins

Riccardo: How do you handle fast up, slow down?
Snez: answer not recorded

Mike: Fixed rotation angle?
Snez: yes

11:20 	Russ Taylor
	GALFA software group

	Image products: GALFA-HI narrow-band HI spectral cube
		galfa-rrl narrow-band multiple line cube
		galfa-con wide-band, polarization
	Phases: I data acquisition, II image formation, III scientific process, 
		archiving
	GALFA-CON: Desh has written phase 1, Calgary working on phase II
	GALFA-HI: 	phase I output to "big dish" fits; 
			phase II Josh in IDL; 
			phase III Richard Gooch, karma?
	Issues: quality oversight, code base IDL?
	
Comments/questions:
Naomi: IDL cost?
Russ:  Not much discussion. 
Riccardo: much broader user base and support than just astronomy
Martha: only expensive in Germany not in other European countries
Tom:  IDL executable is free. can run but cannot write programs

11:33 	Steve Torchinsky
	ALFA software at NAIC

	Big Dish fits (ATNF) still working with GBT
	reduction software produced by consortia
	CIMA: Control Interface Module for Arecibo
      	IF/LO, Backend, pointing (choose particular beam), observing mode
		On-line Data Display: 
      	waterfall plots, spectra, dump plots to files, header, 
      		real time monitoring
      	engineering monitor:motor, total power, etc.
	Big Dish Fits
	WapRed: reduction software for WAPP

Riccardo: thanks Miguel for the fits header software

Tom:  When is the big fits produced?
Steve: only WAPP data is written in Big dish format

Tom: Is there a script?
Steve: command file observing. Load/save state: configuration. CIMA can
be run off-line. 

Dan: What about commensal observing?
Steve: backends can be configured independently, but software is not there yet.

11:57 	Josh Goldston
	GALFA mapping

	Basket-weave vs typewriter: slow up quick down
	Least square gain fitting on cross points
	ALFA orientations depends on scanning methods
     	Discrete scanning rate for basket weaving for Nyquist sampling
	Pros: 	Typewriter: less timing, long RA regions, better for sidereal 
		rate
      		BW: long dec regions, variable scan rate, preserve beam pattern
	Gridding: non-simple beams, preserve information, Tegmark 1997=> 
		least square solutions

Q: data loss for slow scans
Josh: weight the balance between overheads

Paul: what is the story with regridding?
Josh: close to COBE's method 

12:15 	Riccardo Giovanelli
	E-ALFA Surveys

	5 projects
but will focus on the drift mode surveys
	
	DRIFT: ALFALFA VAVA
		Science: HI mass function
		Drift: no problem for point sources
		E-ALFA: HIPASS software, IDL
		minimal intrusion data taking: 900s scans
		Data in converted from fits to IDL "d" structure on the fly
		Be prepared to have less than 7 pixels
		Level I data product: 	noise calibrated IDL structure
		Level II:    		tiled structure including continuum 
					calibration, regridding
		Level III: 		source catalogue, NVO domain HI node, 
					etc.
		Current problem with calibration: CIMA cal not synchronized 
			with data records
		Tsys ~ 30 K
		
Questions/Comments

Dan: should fix a bad pixel quickly
Jay: should work without all 7 pixels


Break for lunch and discussion of separate project/observing proposal groups

15:00 Tom Bania (session chair)

Tom: Is there a preference for proposals with commensal considerations?
Bob: Preferred for practical reason, but not officially for review
Tom: Formal proposal commensal proposal?
Bob: No. Science driven, commensal later

15:11 	Yervant Terzian
	GALFA-RRL

	Galactic plane, long integration, >100MHz, dv < 1km/s
	Will propose commensal observing with pulsar survey
	Desh has proposed testing with WAPP

Tom: Need new backend?
Yervant: Pulsar people is getting their own, but the E-ALFA backend may also 
	be relevant

Dan: reconfiguring GALFA spectrometer for multiple narrow sub bands is possible, 
	but is not currently implemented

15:18 	Russ Taylor
	GALFA-CON

	Need all sky survey, night time, 1000 hours
	P-ALFA spectrometer with full stokes
	Prefer larger bandwidth (200MHz)
	Precursor observations in December
	Commensal with GALFA HI using P-ALFA spectrometer with basket-weaving

Questions/comments
Bob: Typewriter?
Russ: no. too slow. 
Mike: convenient for scheduling
Desh: Winking cal issue

15:26 	Paul Goldsmith 
	
	Molecular clouds

	Basket-weaving preferred, narrow bandwidth high velocity resolution
	A question - OH: can it be done simultaneously?
	Snez: A test proposal was not well received, but there could be
		another precursor proposal in October?

Steve: maybe use GALFA spectrometer for test observations scheduled to start 
	this coming Friday.

15:32 	Jay and Snezana
      	Halo clouds merged with disk halo connection (?)
	Snez
		Stray radiation and standing wave are big concerns
		Use GBT maps for correction
		Will propose precursor objects
	Jay
		More careful determination of galactic HI spectra
		
Questions/Comments

Paul: independent from the pipeline development?
Jay: yes.
Russ: stray radiation also a concern for CON.
Snez: seasonal switching. 
Mike: seasonal switching only works for spectral line not for continuum.
Tom: Stray radiation correction?
Jay: no. just for noise, gain characterization

15:39 	Eric Korpela	
	High latitude clouds

	Stray radiation is a major issue
	Commensal with DRIFT survey
	Might need extra observations to produce crossing points

Q: How many people?
Eric: 6.

15:42 	Tom Bania
	Low latitude survey

	Not sure the system is good enough for a clear science case
	Team with pulsar and e-alfa to further study how to do galactic plane 
		mapping
	May go commensal with several projects

Steven Gibson: I did not get advance notice, so hard to organize CNM group.

Comments and Questions

Tom Bania: re. Data Rights and Access

	Riccardo suggests that the data is made public through NVO
	rather early.  Is there a NAIC policy?
Bob:    No strict policy. But would like to only make available
        calibrated data.
Tom: 	Who controls the quality? Who releases?
     	Do not necessarily need perfect data
Bob:    Some group should vouch for the quality. NAIC should  be
	playing a role.  
        Goes into NVO as NAIC product.
Ed:  	Would NAIC have manpower?
Bob: 	NAIC would always involved (but would not do it [?]) 
Paul: 	No person in H2/HI has stepped forward

Tom:    Glimpse and Ring surveys have shown commitment to make data
	public immediately.
	We should consider that in detail.
Bob:    This view is consistent with NAIC attitude: data public as
	early as possible.
	Individual proposal will be assigned time in blocks. More time
	depends on data release.
Ed: 	Archiving takes a lot of effort.
Bob: 	NAIC is writing guidelines. No strict time table.
Paul: 	Different from surveys "fully supported" by NSF and NASA. 
Tom:  	What's the division of labor of software development?
Bob:  	Steve has a philosophy. 
Tom: 	Big surveys write their own codes.
Alex: 	1 km/s and 3' is ok
Peter: 	Data reduction could be redundant between subgroups. 
	More work will be needed 

16:20 	Paul Goldsmith
	Jigsaw Puzzle Approach 

	Has morphed into separate continuum and RRL proposals, plus
		those of the HI projects
	NAIC => Big dish fits
	HI groups needs to agree on a set of observing mode that
		can be supported by the pipeline, a single GALFA HI
		pipeline

Ed:     Why do HI and RRL require different reduction?
Paul: 	Pulsar spectrometer is not here.
Russ:   How many observing projects or science projects? How many
        proposals?
Tom: 	No clear answer yet.
Josh: 	We need a specific guidelines for pipeline. 
Carl:   Spectrometer configures differently for CON, RRL, HI. Cannot
		use same pipeline.
Phil:   Consider the "pipeline" to consist of various modules.  If they
		are done properly you can make various pipelines by
		hooking up various modules.  You don't have to think of
		the various pipelines as totally different.
Peter: More effort required for that.
Mike:  NAIC observatory should keep expertise for calibration. at least 
		adopt existing good
software.
Carl: 	There needs to be a person at AO to maintain and update software
Riccardo: Tools developed will be specifically designed
Paul: one modular GALFA HI pipeline and adaptable by NAIC

Outcome of all this:  pipeline(s) can be configured from modules for
	different needs.  We must not forget that NAIC will have
	observers who want to use ALFA, but who may not be members of
	any consortium.  There thus must be software for them to use,
	which again could be configured from pipeline modules, but for
	this reason alone, NAIC must have software person familiar with
	all the pipeline procedures.  This adds to NAIC responsibility,
	but doing this as well maintaining the software is critical.

16:47
	Trish Henning 
	Overview of E-ALFA Surveys

	ALFALFA (shallow)
		expect 7000 new galaxies
	AGES (mid)
		HI mass function, spatial distribution, 3000 galaxies
		at larger Z
     		HI mass to 6e6 solar masses. Virgo, local void, NGC2903 outer 
     			region of nearby target
     		Drift scanning, step and stare
	AUDS (ultra-deep)
     		evolution of gas Z<0.15, 5e16 / 5km/s sensitivity, low column 
     			density gas in the local universe
     		OH megamaser, HI absorption
     		0.36d^2 in 1000 hours, repeated drift
	Zone of avoidance (commensal)
     		cuts through several known regions, Taurus, etc
     		Commensal option 1 GALFA: double drift? 2 PALFA

Paul: precursor time?
P.  : 70 hours drift, 35 on source

17:10 	Paulo Freire
	ALFA Pulsar Surveys

	300 MHz 1024 channels, 65 microsecond dump
	Search for millisec pulsar, 1PByte of data!
	Mid 2005 complete PALFA spectrometer; 
	Now using WAPP: discover brightest ms pulsars, radio loud young pulsars
	       100 MHz 256 channels
	Proposed tiling leaves small holes, use sidelobes to fill in
	1 degree limit for the galactic center survey
	ongoing ALFA surveys
	results: PHP/MySQL viewing, first new pulsar: 68 ms object not 
		detectable at 430 MHz
	Commensality: RRL, SETI (no cal)


OTHER TOPICS DISCUSSED AND CLOSING POINTS

The issue of Guidelines for GALFA consortium was discussed.  Although
available on the web, many people present had not had a chance to read
them.  Thus, it was felt that adoption would have to be deferred and
handled by some electronic means.  There was general feeling that some
guidelines would be appropriate.

The guidelines as proposed were based on concept of PIs of individual
projects forming a Coordinating Committee.  There was discussion about
this, which was not unanimous.  In fact, during the lunch project group
meetings, it was evident that there had been some consolidation of
projects.  It could be that initially there would only be 2 or 3 HI
projects, but there is nothing to prevent additional ones from forming
and submitting proposals later on.

The feeling of chairperson was that to get people to make the effort of
doing observing, working on software, etc, would require a real
scientific motivation. Being part of one HUGE GALFA proposal would just
not stimulate most people.  While the idea of one giant survey that
would produce all the data for all projects has a certain appeal, who
is going to do it?  That is why the Jigsaw approach seemed originally
to be attractive, and why translating it into separate proposals for
separate areas of the Galaxy, could work.  It is obviously important
that surveys be planned in a way to function as pieces of the puzzle,
but the first order thing that needs to be done is to get people
involved in planning the proposals and getting them committed to doing
what has to be done!

So far, the HI/H2 Connection group has Di Li and Hector Arce as
co-PIs.  For the other groups, no individuals have yet been identified
(to the GALFA Chairperson), but this must be rectified in the near
future.

We hope to tackle the idea of GALFA Consortium Guidelines and Project
PIs for GALFA Projects in the near future.