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Atacama Large Millimeter Array Update. Slides Unabashedly Stolen by Al Wootten NA ALMA Project Scientist From ALMA NA Cost/Management Review January 30 – February 1 2006. The ALMA Partnership. ALMA is a global partnership in astronomy to deliver a truly transformational instrument

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Atacama large millimeter array update

Atacama Large Millimeter Array Update

Slides Unabashedly Stolen by

Al Wootten

NA ALMA Project Scientist


ALMA NA Cost/Management Review

January 30 – February 1 2006

ALMA NA Cost/Management Review

The alma partnership
The ALMA Partnership

  • ALMA is a global partnership in astronomy to deliver a truly transformational instrument

    • North America (US, Canada; Taiwan in process)

    • Europe (via ESO with Spain)

    • Japan (now including Taiwan)

  • Key Science goals include

    • Image protoplanetary disks, to study their physical, chemical, and magnetic-field structures, and to detect tidal gaps created by planets undergoing formation in the disks;

    • image starburst galaxies as early as z = 10;

    • image normal galaxies like the Milky Way out to z = 3

  • Located on the Chajnantor plain of the Chilean Andes 16500’ above sea level

  • The way ALMA is being built is via a 50:50 partnership between NA & Europe and a closely coordinated but separate effort from Japan

  • ALMA will be Operated as a single Observatory with scientific access via regional centers

    • North American ALMA Science Center (NAASC) is here

ALMA NA Cost/Management Review

What is alma
What is ALMA?

  • Up to 64 12m antennas

    • Plus the Compact Array of 4 x 12m and 12 x 7m antennas from Japan

  • Baselines from 15m to 15km

  • 5000m site in Atacama desert

  • Receivers: low-noise, wide-band (8GHz), dual-polarisation, SSB

  • Digital correlator, >=8192 spectral channels, 4 Stokes

  • Sensitive, precision imaging between 30 and 950 GHz

    • 350 GHz continuum sensitivity: about 1.4mJy in one second

    • Angular resolution will reach ~40 mas at 100 GHz (5mas at 900GHz)

    • First light system has 6 bands: 100, 230, 345 and 650GHz

    • Japan will provide 140, 460 and 900GHz

  • 10-100 times more sensitive and 10-100 times better angular resolution compared to current mm/submm telescopes

ALMA NA Cost/Management Review

El llano de chajnantor

Where is ALMA?


El llano de Chajnantor

ALMA NA Cost/Management Review











43km=27 miles

ALMA NA Cost/Management Review


V. Licancabur

Cº Chajnantor

Pampa La Bola

Cº Toco

Cº Chascón


Center of Array

ALMA NA Cost/Management Review

Osf facilities alma and contractors camps
OSF Facilities ALMA and Contractors Camps

Contractors Camp


Contractors Lay-down area

ALMA NA Cost/Management Review

Osf facilities alma and contractors camps1
OSF Facilities ALMA and Contractors Camps

ALMA camp

Contractors recreation room

Water tanks

Contractors Dormitories

Contractors kitchen and dining room

Contractors offices

ALMA NA Cost/Management Review

Recent camp development
Recent Camp Development

Dormitories at ALMA Camp

ALMA NA Cost/Management Review

Recent Camp Development

Contractors Camp dining room

ALMA NA Cost/Management Review

APEX - The Atacama Pathfinder Experiment

A Vertex RSI Antenna Operating at Chajnantor

Bonn 21.10.05

ALMA NA Cost/Management Review


AOS Facilities

Access Road

AOS Technical Building

85 % complete

ALMA NA Cost/Management Review

Aos technical building
AOS Technical Building

ALMA NA Cost/Management Review

Aos tb construction 1
AOS TB Construction (1)

General view, January 2006

ALMA NA Cost/Management Review

Aos tb construction 2
AOS TB Construction (2)

ALMA NA Cost/Management Review

Vertex SEF grading

ALMA NA Cost/Management Review

Alma status
ALMA Status

  • ALMA has just undergone a major rebaselining and subsequent review

  • The review declared the technology readiness of ALMA very high and judged that most technical risk has been eliminated

  • Five years ago ALMA was a "must do" scientifically but with high technical risk pushing the state of the art

  • We now have:

    • prototype antennas that meet ALMA’s demanding requirements

    • receivers with near quantum-limited performance, unprecedented bandwidth and no mechanical tuning

    • the first quadrant of the correlator completed below cost and with enhanced performance

    • The baseline includes appropriate contingency for remaining technical risks (e.g. photonic local oscillator, highest frequency cold multipliers)

ALMA NA Cost/Management Review

Front end key specifications and preliminary results
Front End Key Specifications(and Preliminary Results)

* - between 370 – 373 GHz Trx is less then 300 K

  • Dual, linear polarization channels:

    • Increased sensitivity

    • Measurement of 4 Stokes parameters

  • 183 GHz water vapor radiometer:

    • Used for atmospheric path length correction

ALMA NA Cost/Management Review

Software Architecture

ALMA NA Cost/Management Review

Pre-production ALMA

Water Vapor Radiometer

Operating in an SMA

Antenna on Mauna Kea

(January 19, 2006)

Relay mirrors

Photo courtesy of

Magne Hagstrom &

Ross Williamson

ALMA NA Cost/Management Review

System integration activities prototype integration
System Integration Activities: Prototype Integration

Electronics are first integrated as a system and characterized in the lab at AOC, Socorro.

ALMA NA Cost/Management Review


  • Canada is part of the North American ALMA project

  • As part of this they are members of the North American Partnership in Radio Astronomy

    • This gives them the “right to compete” for time on all NRAO facilities including ALMA

  • They are delivering on of the receiver bands (Band 3) plus cash and software effort to an agreed Value of $20M FY2000

    • They are also committed to providing 7.25% of the ALMA Operations costs

  • Canada will cover all cost overruns associated with their work

    • As such they were not part of the ALMA rebaselining exercise

  • Canadian ALMA work is covered by an MOU which empowers the NA ALMA PM and the relevant NA IPT leads to direct their work

ALMA NA Cost/Management Review


  • Japanese contribution to ALMA – Enhanced ALMA

  • Atacama Compact Array (ACA) System

    • Twelve 7-m antennas + four 12-m antennas

      Higher photometric accuracy

    • ACA Correlator

      high sensitivity, simultaneous realization of wide

      frequency coverage and high spectral resolution

  • New frequency bands

    • Band 4 (125-163GHz), Band 8 (385-500GHz), and Band 10 (787-950GHz) [R&D]

    • Emphasis on submillimeter wavelengths

  • Contributions to infrastructure & operations

ALMA NA Cost/Management Review

Alma j plans
ALMA-J plans

  • Reexamine funding/Value agreements between projects

  • Complete agreement with ALMA-J – June 2006

  • Respond to RFQ – summer 2006

  • Late 2006 – 3rd Executive, E-ALMA

ALMA NA Cost/Management Review

Enhanced alma
Enhanced ALMA

12-m array


ALMA NA Cost/Management Review

Reviews reviews and more reviews

Reviews, Reviews and More Reviews

ALMA NA Cost/Management Review




































Time Now

1.09 Science Summary Schedule

(Data from IPS as of 2006Jan13)

ATF Testing

June ’06 ATF First Fringes

SE&I Reference

OSF Integration – Start dates








ATF Testing Support


Site Characterization

Science Support OSF

Commissioning Antenna Array – Finish dates




AOS 6 Ant Array Evaluation Complete




Science Verification


Mar ’09 Early Science Decision Point

Call for Proposals / Early Science Preparation

Jan ’10 Early Science

Sept ’12 Start of Full Science

ALMA NA Cost/Management Review

J1148 5251 an eor paradigm with alma
J1148+5251: an EoR paradigm with ALMA

CO J=6-5

  • Wrong declination! But…

  • High sensitivity

    • 12hr 1 0.2mJy

  • Wide bandwidth

    • 3mm, 2 x 4 GHz IF

    • Default ‘continuum’ mode

    • Top: USB, 94.8 GHz

      • CO 6-5

      • HCN 8-7

      • HCO+ 8-7

      • H2CO lines

    • Lower: LSB, 86.8 GHz

      • HNC 7-6

      • H2CO lines

  • C18O 6-5

  • H2O 658GHz maser?

  • Secure redshifts

  • Molecular astrophysics

  • ALMA could observe CO-luminous galaxies (e.g. M51) at z~6.

ALMA NA Cost/Management Review

ALMA into the EoR

Spectral simulation of J1148+5251

  • Detect dust emission in 1sec (5s) at 250 GHz

  • Detect multiple lines, molecules per band => detailed astrochemistry

  • Image dust and gas at sub-kpc resolution – gas dynamics! CO map at 0”.15 resolution in 1.5 hours





N. B. Atomic line diagnostics

[C II] emission in 60sec (10σ) at 256 GHz

[O I] 63 µm at 641 GHz

[O I] 145 µm at 277 GHz

[O III] 88 µm at 457 GHz

[N II] 122 µm at 332 GHz

[N II] 205 µm at 197 GHz

HD 112 µm at 361 GHz

ALMA NA Cost/Management Review

Bandwidth Compression

Nearly a whole band scan in one spectrum



Schilke et al. (2000)

ALMA NA Cost/Management Review

Antenna designs in alma
Antenna Designs in ALMA

  • Three antenna designs currently in hand:

    • Two will be operated in PSI interferometer in near future:

      • Vertex (APEX close copy operational at Chajnantor, destiny of this prototype uncertain).

      • AEC (Basis of AEM design, destiny uncertain).

    • MElCo prototype disassembled for retrofit to design similar to 3 MElCo production antennas

  • Four others expected

    • Production Vertex design (25-32 antennas)

    • Production AEM design (25-32 antennas)

    • Production MElCo 12m antennas (3 antennas)

    • Production MElCo 7m antennas (12 antennas)

  • For present purposes, only consider production Vertex and AEM designs

    • As these are evolving, must assume they will be identical to the prototype antennas

ALMA NA Cost/Management Review


  • Demanding ALMA antenna specifications:

    • Surface accuracy (25 µm)

    • Absolute and offset pointing accuracy (2 arcsec absolute, 0.6 arcsec offset)

    • Fast switching (1.5 deg sky in 1.5 sec)

    • Path length (15 µm non-repeatable, 20 µm repeatable)

  • To validate these specifications: two prototype antennas built & evaluated at ATF (VLA)

ALMA NA Cost/Management Review

Aec prototype antenna
AEC Prototype Antenna

ALMA NA Cost/Management Review

Vertex prototype antenna
Vertex Prototype Antenna

ALMA NA Cost/Management Review

Vertexrsi and aec prototype antennas
VertexRSI and AEC Prototype Antennas

ALMA NA Cost/Management Review

Science implications
Science Implications

  • Prototypes accepted from manufacturers

  • Final technical evaluations complete

  • Both antennas meet the specifications

  • What happens with two different antenna "designs"

    • common mode errors don’t cancel

    • But differences may help

    • cost (construction, commissioning, operation)

    • other ?

  • Consider:

    • Surface differences

    • Pointing

    • Pathlength

    • Mosaicking and polarization

ALMA NA Cost/Management Review

Science implications the antenna surfaces
Science Implications:The Antenna Surfaces

Source: AEG Results

Both telescopes easily meet specifications (<25 µm); both are excellent antennas.

ALMA NA Cost/Management Review

Prototype pointing results
Prototype Pointing Results

Source: AEG Results

Spec: 2” all-sky; 0.6” offset pointing under primary operating conditions

ALMA NA Cost/Management Review

Fast switching
Fast Switching

Specification: 1.5 degrees in 1.5 seconds, settling time under 3 seconds.

ALMA NA Cost/Management Review

Path length stability
Path Length Stability

  • Spec: 15/20 µm repeatable/nonrepeatable

*Δt = 3, 10, 30 minutes; **Wind-induced, Δt = 15 minutes

ALMA NA Cost/Management Review

Science implications1
Science Implications

  • Pointing

    • Both antennas meet specifications, but the character of pointing differs

    • in compact configuration

      • WIND: wind "shadowing“ may have some effect

      • SUN: sunrise may have some effect

      • GRAVITY: both designs are essentially rigid

    • in other configurations

      • WIND: differs over the site as will the antenna response

      • SUN & GRAVITY remain constant over the site

  • Fast Switching

    • Both antennas meet specifications

      • Awaiting redesign of AEC quadripod

    • If not, effect would be to decrease throughput/efficiency

ALMA NA Cost/Management Review

Science implications2
Science Implications

  • Phase / pathlength / focus

    • as pointing, but a more subtle effect.

    • Axis non-intersection may be the dominant effect on pathlength (baseline) prediction, and has no common mode error

    • Other mechanical deformations would benefit from identical antennas

      • Gravitational sag, thermal deformation, perhaps other environmental items

  • Phase effects due to fiber length

    • Fiber run to antenna is dominant in effective length change (but if monitored and corrected, no common mode)

  • Polarization matching and primary beam shape

    • determined by quadripod leg design (shadowing of quadripod legs, but exact shape plays a minor role too)

    • Lesser effect from the differing arrangement of panels and therefore character of scattering from the edges

ALMA NA Cost/Management Review

Fiber length
Fiber Length

  • The effective length of the fiber is dominated by the run up the antenna (see ALMA Memo 443).

  • Differences in the two designs include

    • Length of fiber run

    • Degree of thermal shielding

  • Such variations are monitored and compensated.

ALMA NA Cost/Management Review

Pathlength effects
Pathlength Effects

  • Temperature:

    • Surface RMS changes with ambient temperature from holography:

      • * VertexRSI: ~0.6-0.7 micron/K.

      • * AEC: ~0.8 micron/K.

      • Both deformations had a high degree of structure (like BUS segment print-through for VertexRSI, large-scale 45-degree plus inner-ring print-through for AEC); probably in the noise at highest frequencies, where frequent calibration will be done in any event.

    • Focal length change due to ambient temperature changes:

      • * VertexRSI:

        • 34 micron/C from holography

        • 36 micron/C from radiometry

      • * AEC:

        • 14 micron/C from holography

        • 20 micron/C from radiometry

  • All within specification and unlikely to impact science (focus tracked; surface changes small)

ALMA NA Cost/Management Review


  • The optical path from the sky off the reflector to the subreflector intercepts the quadripod. In both designs, the solid angle subtended by the quadripod is minimized and the point of attachment to the antenna is as close as possible to the edge of the reflector to minimize shadowing.

  • The shadowing profile is less than 1% of the antenna diameter.

    • Owing to careful minimization of the quadripod profile, the sidelobes will be small and distant from the primary beam.

    • Beam profiles were calculated from the shadowing profiles (next slide).

      • Quadripod shadowing is known for the Vertex design (ALMA Antenna Group Report #40), estimated for the AEC design by Lucas.

  • Reflections are minimized by profiling of the inward edge of the quadripod legs.

  • Different lateral motion of the subreflectors with elevation in a homologous antenna could effect cross-polarization; amenable to calculation.

  • Shadowing is measured using holography and is the same for both antenna designs within a few tenths of a per cent.

    • Integrated power <1% of that in the main beam, hence sidelobe power will be more than 40 dB below that of the main beam.

ALMA NA Cost/Management Review

Quadripod dependent questions
Quadripod-dependent Questions




Three sorts of interferometric baselines provide three sorts of beams:

Vertex-Vertex, AEC-AEC, and Vertex-AEC. For the most sensitive imaging,

these must all be measured and tracked. The most sensitive images include

mosaics and polarization images.

ALMA NA Cost/Management Review

Effects of quadripod differences
Effects of Quadripod Differences

  • “If one ignores the effects of the sidelobes, it is better to have antennas with different configurations; if you are going to correct for it then it is easier if they are all the same.” –James Lamb

  • Case One—no correction

    • The effect of the different sidelobes is small

    • Since the sidelobes differ, a source won’t be in both at once and the effect on an image is diminished

    • Interferometric data provide a strong discriminant for sources near the main beam owing to fringe rotation/delay offset

  • Case Two—correction applied

    • Worst case is an interfering source in a sidelobe. But with two designs it cannot be in a sidelobe of all antennas at once. One will want to correct for the different antenna patterns

ALMA NA Cost/Management Review


  • If quadrupod layout is identical, advantage of a single design exist, but is rather limited

  •  25 excellent antennas + 25 good antennas is better than 50 good antennas

  •  50 (or 64) excellent antennas is even better

  • Each prototype met specifications and qualifies as an excellent antenna

  • Conclusion: The effect of having two designs for the 12m antennas in ALMA is small. Any imaging effect can be dealt with for the most sensitive images which might need additional care.

  • Cost probably has a greater effect

    • 2 designs

    • 2 software interfaces

    • 2 Assembly, integration, verification, commissioning and science verification

    • 3 beams to track in the most sensitive applications

ALMA NA Cost/Management Review

The Atacama Large Millimeter Array (ALMA) is an international astronomy facility. ALMA is a partnership between Europe, North America and Japan, in cooperation with the Republic of Chile. ALMA is funded in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC), in Europe by the European Southern Observatory (ESO) and Spain. ALMA construction and operations are led on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI), on behalf of Europe by ESO, and on behalf of Japan by the National Astronomical Observatory of Japan.