Transcript ALMA Presentation

CSV Plan status
Robert Laing
ESO
Science IPT
Recent changes
• Complete rewrite to take account of rebaselining
and revised delivery schedule
• Proposal for delay to Early Science
• Relation to AIV and Operations
• Change of scope: additional ALMA-J antennas
and receiver bands; initial consideration of 7m
array
• Schedule
• Staffing plan
• Verification matrix
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Definitions
• ASAC report Oct 2005. No conceptual changes, but terminology is
different from that of Jan 2005 AIVC meeting and earlier ASAC
meetings.
• Assembly, Integration and Verification (AIV) is a construction
activity led by the JAO Project Engineer to integrate the ALMA subsystems into a single working system.
• Commissioning covers initial testing, interaction with SI and other
construction IPTs to identify and resolve faults, optimization, training
of Operations staff and documentation
• Science Verification (SV) is the end-to-end testing of an ALMA
science mode done using a science project proposed by an external
user (ASAC).
• An ALMA public image (API) is a large-scale project whose primary
purpose is to convince the wider community/public of the value of
ALMA (ASAC).
• CSV = Commissioning and Science Verification
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Equipment available
• CSV starts with the delivery of a verified 3-element
interferometer at the AOS, although there are precommissioning activities in support of AIV.
• Bands 3, 4, 6, 7, 8, 9 available (maybe not 4 and 8 on the
first few antennas)
• All types of 12m antenna used for inteferometric
commissioning.
• Test single-dish and interferometric observing in parallel;
2 subarrays.
• Initial configurations compact; thereafter First Science
Configurations as already defined
• Baseline correlator + Tunable Filter Bank
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Early Science
• Current schedule and definition of Early Science assumes
an antenna delivery profile which is no longer valid.
• Decision on what modes to offer for early Science would
have to be made very soon (~3 months) after the start of
CSV.
• Therefore (in accordance with ASAC recommendations)
consider a delay to Early Science, but enhanced capability.
• Current proposal is a straw man, for discussion, but is
consistent with the most recent Operations budget and
staffing plan.
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Early Science – proposed definition
• At least 16 antennas fully commissioned (more in process
of integration)
• Receiver bands 3, 4, 6, 7, 8, 9
• Interferometry in single field or pointed mosaic mode
• Significant (TBD) range of spectral modes, including TFB
• Circular and linear polarization (not mosaic)
• Single-dish mosaic (position and beam-switch) and OTF.
• 2 subarrays operational
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Timescales
• CSV milestone on handover of verified 3-element
interferometer at AOS (currently 2008Q4)
• Early Science decision point (which modes to be
offered) CSV + 12 months
• Early Science CSV + 20 months
• (For reference, 16 antennas available for
commissioning CSV + 15 months)
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AIV Activities
• AIV is responsible for:
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Antenna acceptance
Antenna integration
Single-antenna tests at OSF
Single-baseline interferometry at OSF
Single-antenna and single-baseline interferometry at
AOS
• CSV team needs to be closely involved in these
tests, both to contribute experience and to train
new staff. Details are TBD.
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Main CSV activities (1)
• Close-packed array
– antennas 1-4 on closely-spaced pads
– Band 3 only
• Early Science array
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Additional bands
Baselines to 4(?)km – depends on pad availability
Correlator configurations
Mosaics
Polarization
Addition of total power data
Verification against Science Requirements
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Main CSV activities (2)
• Observation calibrations
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Phase calibration, fast switching and WVR development
Calibrator surveys
Temperature and flux scale
Bandpass
Instrumental polarization
• Antenna and array calibrations
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Pointing, focus
Primary beam and surface
Antenna location
Delay
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Main CSV activities (3)
• Single-dish modes
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Mosaic with beam and position switching
On-the-fly mapping
Autocorrelation and continuum total power
[Frequency switching]
Total power calibration
• ACA 7m array (from CSV + 12 months, roughly)
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Task durations (1)
• Split into broad categories:
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Commission observing modes
Observation calibration
Array and antenna calibration
Single-dish
ACA 7m array
• Estimate durations and approximate phasing
within CSV phase up to early Science
– Many activities in parallel (flexibility; weather)
– Assumptions about SV fraction, array downtime
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Task durations (2)
• Current numbers:
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Modes 230 days
Observation calibration 150 days
Array/antenna calibration 95 days
Single dish 60 days (in parallel)
ACA 7m array TBD (in parallel)
• Assume 20% downtime on average (more
initially) and 10% SV fraction
• Consistent with a ~20-month programme
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Staffing
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Project Scientist + 2 commissioning scientists
Science IPT staff on rotation
Division of Science Operations
Ad hoc specialists
ARC staff on rotation
Concept is that Operations staff form an integral part
of the commissioning team: there is no
“handover”
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Staffing profile
Required/available
2008 20/31.5
2009 27/33
2010 34/35.5
Numbers 2011-2012 TBD, but essentially no
Science IPT manpower available to supplement
Operations.
Marginal, given the additional duties of Operations
staff: more tuning required.
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Science Verification
• Discussed by ASAC in October 2005
• Main goals
– Test ALMA modes end-to-end using projects from user
community
– Feedback to CSV team
– Early access to ALMA data for the community
• Modes fully commissioned before SV; PS responsible for
decision to issue call
• Open call for proposals, not using formal machinery;
review for scientific value (external) and feasibility (CSV
team)
• Data public immediately
• Projects executed by CSV team/Operations; include QA
• ALMA Public Images are a subset of SV
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Verification
• Draft verification matrix available
• Need to demonstrate that ALMA meets its science
requirements, but with an incomplete array.
• Verification matrix is more complex,
parameterized by number of antennas, range of
baselines, …..
• Scaling for sensitivity is straightforward, image
fidelity and dynamic range somewhat less so.
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Commissioning after Early Science
• Much still to do, including completion of ACA
7m array, Band 10
• Primarily carried out by Operations staff
• Planning just starting …
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