Science Operations with ALMA

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Science Operations with ALMA
E.F. van Dishoeck
ESO ALMA day Nov. 8, 2002
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Guidelines for Operations

• ALMA is a service observing facility
• ALMA operations in Chile limited to activities
  needed to acquire, certify and archive scientific
  data
• For safety reasons, number of ALMA staff at 5000
  m to be kept at minimum
• Main interface between users and ALMA is through
  Regional Support Centers
• Development/upgrades on hardware and software
  contracted to Executives

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Science Operations Astronomers Perspective

• Non-experts should be able to use ALMA
• Dynamic scheduler to match observing conditions
• Reliable and consistent calibration
• 1 at mm, few at submm
• Data public in timely fashion

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ALMA Operations

• Array Operations Site Chajnantor
• Operations Support Facility San Pedro
• Central Office
  Santiago
• Regional Support Centers NA/EU
• Development / Upgrades NA/EU

Subject to approval by ALMA Board!
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ALMA Location
ALMA
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Array Operations Site

• Facilities
• Antenna Array
• Interconnections
• Antenna Maintenance
• Hangar
• Tech / Lab Building
• Refuge
• Utility Buildings

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Llano de Chajnantor
ASAC at center of ALMA array
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ASAC/ESAC

• Current members (8)
• R. Bachiller, A. Benz, R. Booth
• P. Cox, J. Richer, P. Schilke
• E. van Dishoeck, M. Walmsley
• Project scientists are ex-officio members
• New ASAC will have 5 European members, TBD by
  ALMA Board
• New ESAC will have more members, TBD by European
  ALMA Board
• Nominations for ESAC welcome!
• ASAC/ESAC reports and minutes on Web

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Main Functions AOS

• Antenna re-configuration
• Instrument module exchange
• Security of site

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Location OSF
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Main Square San Pedro
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Church San Pedro
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Public Highway
San Pedro
Pampa La Bola
Direct Link Road
AOS
OSF
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Access Road to O.S.F.
San Pedro De Atacama
Toconao
km 20.1 / Ch 23
Existing mine road up to OSF
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Views from O.S.F. Area at 2800 m
Cerro Negro
West
East
San Pedro De Atacama
North
South
Toconao
Volcan Licancabur
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Main functions OSF

• Array scheduling and operations
• Quick-look data reduction
• Maintenance and repair antennas
• Maintenance and repair instrumentation
• Administration, safety

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Dynamic Scheduler

• Dynamic scheduler selects programs according to
• Science rating
• Weather conditions transparency and phase rms
  (stringency)
• Array configuration
• Partner parity

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Transparency Variations
Annual variation
Diurnal variation
day
night
0.2
75
0.1
25
t0.05 corresponds to 1 mm precipitable water
vapor
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Phase Stability Variations
Annual variation
Diurnal variation
36 el.
day
night
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Transparency and Phase Stability
Median
Note tail in statistics of periods with good
transparency but large phase rms
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secondary, 2? max.?
primary, 0.6?
75 10.1 m s-1 50 6.3 m s-1 25 3.0 m s-1
Median
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Main functions Central Office

• Pipeline data reduction
• Quality assessment
• Production of archive
• Business functions
• Science offices

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Science operations in practice

• Phase I II proposals through RSCs
• Powerful time estimator and end-to-end data
  simulator gt scheduling blocks to OSF
• Scheduler selects programs homogeneous
  consistent calibration
• Pipeline data reduction, quality control,
  production of archive
• Complete data management system
• Advanced data reduction at RSCs

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Regional Support Centers Core Functions

• Proposal handling
• User support for proposals and (advanced) data
  reduction
• Host of copy of archive

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Regional Support Centers Additional Functions

• Advanced software and techniques (e.g. large OTF
  maps)
• Training, summer schools
• Public outreach

Only core functions to be (partly) financed by
ALMA Operations gt need national funding!
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Development / Upgrades

• New / upgrade instrumentation over lifetime of
  array, e.g.
• Additional receiver bands
• Second generation correlator
• Improved software
• To be done mostly at institutes in partner
  countries
• Development funding included in operations budget
  (10 M/year total)

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Site Test Interferometer

11.198 GHz (Intelsat) 300 m baseline 36 el.
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Seeing (Masson 1994)

• Reference measured fluctuations to zenith, frms
  A-1/2
• Scale to observing frequency, n /11.2 GHz
• Maximum usable baseline, bmax, 1 radian rms
• Median power law exponent, 0.6
• Limiting resolution, 0.7 l/bmax
• At 345 GHz,
• qsee arcsec 0.096 (frms A-1/2 degrees) 1.67

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Phase Stability
Maximum Frequency (Holdaway)
345 GHz Seeing (Masson)
nmax GHZ nmax GHZ nmax GHZ bmax
frms 70 30 57 m
148 63 2.40 52
313 134 0.69 181
655 281 0.20 625
1189 510 0.07 1691
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Intermediate array, illustrating zoom property.
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Upside down view of compact array at transit for
a 15 dec source (Orion or Monoceros molecular
clouds).
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First NS compact array, optimized for a round
beam and no shadowing at dec 30.
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Array Operations Site

• Area
• 16,275 Hectares
• Elevation
• 5000 m

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Fully Optimized Full Resolution Array
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View of terrain illuminated from the west (shows
nature of terrain well) with superimposed array
with 167 pads within 4km.
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Zoom in of pads. Note the compact array.
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Zoom in of pads. Note the compact array.
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Zoom in of pads. Note the compact array.
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