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
January 30 2006
ALMA NA Cost/Management Review
1
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
January 30 2006
ALMA NA Cost/Management Review
2
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
January 30 2006
ALMA NA Cost/Management Review
3
Where is ALMA?
El llano de Chajnantor
ALMA
January 30 2006
ALMA NA Cost/Management Review
4
Chajnantor
AOS
TB
Toco
Chajnantor
Road
Negro
Chascón
Macón
OSF
Honar
43km=27 miles
January 30 2006
ALMA NA Cost/Management Review
5
Chajnantor
V. Licancabur
Cº Chajnantor
Pampa La Bola
Cº Toco
AOS TB
January 30 2006
Cº Chascón
Center of Array
ALMA NA Cost/Management Review
6
OSF Facilities ALMA and
Contractors Camps
Contractors Camp
ALMA Camp
Contractors Lay-down area
January 30 2006
ALMA NA Cost/Management Review
7
OSF Facilities ALMA and
Contractors Camps
ALMA camp
Contractors
Dormitories
January 30 2006
Contractors
recreation
room
Contractors
offices
ALMA NA Cost/Management Review
Water tanks
Contractors
kitchen and
dining room
8
Recent Camp Development
Dormitories at ALMA Camp
January 30 2006
ALMA NA Cost/Management Review
9
Recent Camp Development
Contractors Camp dining room
January 30 2006
ALMA NA Cost/Management Review
10
APEX - The Atacama Pathfinder Experiment
A Vertex RSI Antenna Operating at Chajnantor
30 2006
Bonn January
21.10.05
ALMA NA Cost/Management Review
11
R.Güsten
AOS Facilities
Access Road
AOS Technical Building
85 %
complete
January 30 2006
ALMA NA Cost/Management Review
12
AOS Technical Building
January 30 2006
ALMA NA Cost/Management Review
13
AOS TB Construction (1)
General view, January 2006
January 30 2006
ALMA NA Cost/Management Review
14
AOS TB Construction (2)
January 30 2006
ALMA NA Cost/Management Review
15
Vertex SEF grading
January 30 2006
ALMA NA Cost/Management Review
16
January 30 2006
ALMA NA Cost/Management Review
17
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)
January 30 2006
ALMA NA Cost/Management Review
18
Front End Key Specifications
(and Preliminary Results)
Receiver noise temperature
ALMA
Band
Frequency Range
1
Mixing
scheme
Receiver
technology
Responsible
TRx over 80% of
the RF band
TRx at any RF
frequency
31.3 – 45 GHz
17 K
28 K
USB
HEMT
Not assigned
2
67 – 90 GHz
30 K
50 K
LSB
HEMT
Not assigned
3
84 – 116 GHz
37 K (35K)
62 K (50K)
2SB
SIS
HIA
4
125 – 169 GHz
51 K
85 K
2SB
SIS
NAOJ
5
163 - 211 GHz
65 K
108 K
2SB
SIS
6 units EU ?
6
211 – 275 GHz
83 K (40K)
138 K (60K)
2SB
SIS
NRAO
7
275 – 373 GHz*
147 K (80K)
221 K (90K)
2SB
SIS
IRAM
8
385 – 500 GHz
98 K
147 K
DSB
SIS
NAOJ
9
602 – 720 GHz
175 K (120K)
263 K (150K)
DSB
SIS
SRON
10
787 – 950 GHz
230 K
345 K
DSB
SIS
NAOJ ?
* - between 370 – 373 GHz Trx is less then 300 K
•Dual, linear polarization channels:
•183 GHz water vapor radiometer:
•Increased sensitivity
•Measurement of 4 Stokes parameters
January 30 2006
•Used for atmospheric path length correction
ALMA NA Cost/Management Review
19
Executive
h. Store admin data
d. Notify
of
Special
Condition
f. Get science data
2. Store observing
project
Archive
Researcher
Observation
Preparation
e. Start
Stop
Configure
1. Create observing project
9. Get project
data
Principal
Investigator
g. breakpoint
response
Telescope
Operator
8. Notify PI
c. Alter Schedule / Override action
Software
Architecture
A
r
c
h
i
v
e
3. Get project
definition
Scheduling
6. Start data reduction
7.1. Get raw data & meta-data
Data Reduction
Pipeline
7.2. Store science results
4. Dispatch scheduling block id
5.6. Store calibration results
5. Execute scheduling block
Real-time
5.1. Get SB
5.4. Store
meta-data
a. Monitor
points
Control System
Calibration Pipeline
5.2 Setup correlator
5.5a. Access raw data & meta-data
5.5b. Access raw data & meta-data
b. Monitor
points
5.3. Store
raw data
Correlator
Quick Look Pipeline
5.7. Store quick-look results
ALMA Common Software
January 30 2006
Primary functional paths
Additional functions
ALMA software subsystem
ALMA NA Cost/Management Review
external agent
20
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
January 30 2006
ALMA NA Cost/Management Review
21
System Integration Activities:
Prototype Integration
Electronics are first integrated as a system and
characterized in the lab at AOC, Socorro.
January 30 2006
ALMA NA Cost/Management Review
22
Canada
• 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
January 30 2006
ALMA NA Cost/Management Review
23
Japan
• 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
January 30 2006
ALMA NA Cost/Management Review
24
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
January 30 2006
ALMA NA Cost/Management Review
25
Enhanced ALMA
12-m array
ACA
January 30 2006
ALMA NA Cost/Management Review
26
Reviews, Reviews and More Reviews
January 30 2006
ALMA NA Cost/Management Review
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1.09 Science Summary Schedule
2006
1
2
3
2008
2007
4
1
2
3
4
1
2
3
2009
4
1
2
3
(Data from IPS as of 2006Jan13)
2010
4
1
2
3
2011
4
1
2
3
2012
4
1
2
3
4
Time Now
June ’06 ATF First Fringes
OSF Integration – Start dates
1st
2nd 3rd
8th
50th
32nd
16th
ATF Testing Support
Site Characterization
Science Support OSF
OSF/AOS
SCIENCE SUMMARY
ATF
SE&I
Reference
ATF Testing
AOS 6 Ant
Array
Evaluation
Complete
Commissioning Antenna Array – Finish dates
`
8th
16th
32nd
50th
Science Verification
Mar ’09 Early Science Decision Point
Call for Proposals / Early Science Preparation
Jan ’10 Early Science
Sept ’12 Start of Full Science
January 30 2006
ALMA NA Cost/Management Review
28
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.
January 30 2006
ALMA NA Cost/Management Review
29
ALMA into the EoR
Spectral simulation of J1148+5251
CO
Detect dust emission in 1sec (5) at
250 GHz
 Detect multiple lines, molecules per
band => detailed astrochemistry
HCO+
HCN
CCH
 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
January 30 2006
ALMA NA Cost/Management Review
30
Bandwidth Compression
Nearly a whole band scan in one spectrum
January 30 2006
LSB
ALMA NA Cost/Management Review
USB
Schilke et al. (2000)
31
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
January 30 2006
ALMA NA Cost/Management Review
32
Antennas
• 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)
January 30 2006
ALMA NA Cost/Management Review
33
AEC Prototype Antenna
January 30 2006
ALMA NA Cost/Management Review
34
Vertex Prototype Antenna
January 30 2006
ALMA NA Cost/Management Review
35
VertexRSI and AEC Prototype Antennas
Property
VertexRSI
AEC
Base/Yoke/Cabin
Insulated Steel
Steel/Steel/CFRP
BUS
Al honeycomb with CFRP
plating, 24 sectors, open
back, covered with
removable GFRP
sunshades
Solid CFRP plates, 16
sectors, closed-back
sectors glued and bolted
together
Receiver Cabin
Cynlindrical Invar;
thermally stabilized steel
CFRP; direct-connection
cabin to BUS
Base
3-point support; bolt
connection with
foundation
6-point support; flanged
attachments
Drive
Gear and pinion
Direct-drive with linear
motors
Brakes
Integrated on servo motor
Hydraulic disk
Encoders
Absolute (BEI)
Incremental (Heidenhain)
Panels
264 panels, 8 rings,
machined Al, open-back,
8 adjusters (3 lateral/5
axial) per panel
120 panels, 5 rings, Al
honeycomb with
replicated Ni skins. Rh
coated, 5 adjusters per
panel
Apex/Quadripod
CFRP structure, “+”
CFRP structure, “x”
configuration
configuration
ALMA NA Cost/Management Review
January 30 2006
36
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
January 30 2006
ALMA NA Cost/Management Review
37
Science Implications:
The Antenna Surfaces
Source: AEG Results
Both telescopes easily meet specifications (<25 µm); both are excellent antennas.
January 30 2006
ALMA NA Cost/Management Review
38
Prototype Pointing Results
Source: AEG Results
Spec: 2” all-sky; 0.6” offset pointing under primary operating conditions
January 30 2006
ALMA NA Cost/Management Review
39
Fast Switching
Specification: 1.5 degrees in 1.5 seconds, settling time under 3 seconds.
January 30 2006
ALMA NA Cost/Management Review
40
Path Length Stability
*Δt = 3, 10, 30 minutes; **Wind-induced, Δt = 15 minutes
• Spec: 15/20 µm repeatable/nonrepeatable
January 30 2006
ALMA NA Cost/Management Review
41
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
January 30 2006
ALMA NA Cost/Management Review
42
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
January 30 2006
ALMA NA Cost/Management Review
43
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.
January 30 2006
ALMA NA Cost/Management Review
44
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 printthrough 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)
January 30 2006
ALMA NA Cost/Management Review
45
Quadripods
• 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
January 30 2006
46
antenna designs within a ALMA
fewNA Cost/Management
tenths ofReview
a per cent.
Quadripod-dependent Questions
Vertex
AEC
Cross
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.
January 30 2006
ALMA NA Cost/Management Review
47
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
January 30 2006
ALMA NA Cost/Management Review
48
Summary
• 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
January 30 2006 verification
ALMA NA Cost/Management Review
49
www.alma.info
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.