APEX - The Atacama Pathfinder Experiment APEX - The Atacama ...

APEX - The Atacama Pathfinder Experiment
Presentation of the Project
Rolf Güsten
for the
APEX Project Team
Bonn 21.10.05
R.Güsten

The APEX Consortium
APEX is a collaboration between the
Max-Planck-Institut für Radioastronomie (MPIfR),
Onsala Space Observatory (OSO), and
OSO
21%
Chile
10%
ESO
24%
MPG
45%
the European Organisation for Astron. Research in the Southern Hemisphere
The telescope was designed and constructed by VERTEX Antennentechnik,
under contract by MPIfR.
The Operation of APEX is entrusted to ESO.
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Project History: some basic facts
Short Project History:
• Memorandum of Understanding between the Partners June 01
• contract with Vertex Antennentechnik 02.07.01
• start construction on high site spring 03
• start commissioning, operation of first submm receiver spring 04
• successfull commissioning of the antenna 28.06.05
• facility science verificaton July 05
• begin of regular science operation of facility August 05
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The APEX base in Sequitor
The base in Sequitor is situated inside the oasis of San Pedro (2400m)
The buildings consist of a control room/office/laboratory building,
16 dormitories, a cafeteria, a meeting room and a storage area.
Electrical power is generated by two generators
Water is provided through the local water supply from San Pedro.
The base has a gasoline station, solar power heaters for hot water
and a sewage treatment plant.
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L-Å Nyman

the dormitories
footpath to office building
offices/laboratories
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meeting rooms

The Telescope Site at Chajnantor
the Atacama Pathfinder Experiment telescope
Containers, incl. control room, laboratories, kitchen, (dorm) & storage
Power is provided by two generators (450 kVA each)
Weather station & microwave link to the base in Sequitor
Location Llano de Chajnantor, 50 km East of San Pedro de Atacama
Coordinate latitude 23º00′20.8″ South
longitude 67º45′33.0″ West
elevation 5107m
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The APEX Telescope: key facts
Diameter
Total mass
Surface accuracy
Pointing accuracy
Manufacturer
12m
125 t
17 µm rms
2” rms over sky
Vertex Antennentechnik
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Telescope Commissioning: surface adjustment
Goal: adjust the surface of the main dish to better than 20µm rms
Steps towards the “perfect” telescope
requirement: deviation from perfect parabola (12m) less than ¼ the
thickness of the average human hair!
Commissioning Objectives:
• verify that the surface of the main dish can be adjusted to specifications
spec: „better than 20 µm rms“
• confirm that this surface precision can be maintained
under „normal“ operating conditions (in particular vs. elevation)
• verify that telescope can be tracked and pointed to required accuracy
spec: 2“ rms blind on sky
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Telescope Surface Adjustment I
after a series of iterations of adjustment main dish adjusted to 14-15 µm
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Telescope Surface Adjustment II
transmitte
r
preloaded
Summary of the April 2005 holography:
• the surface has been set to 14-15 µm rms accuracy (night time conditions)
with an extremely stable measurement set-up (repeatability: 5.5 µm)
• environmental conditions (thermal gradients at daytime and during
sunrise/set) will degrade the surface by a few µm
• gravitational deformation will degrade the surface at elevations ≠13.8 deg
pre-load the surface settings to El 50 deg (FE Model)
By pre-loading the surface, antenna is now optimized for astronomical observations
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Telescope: Performance on Sky I
Goal: verify telescope performance by astronomical measurements
FLASH receiver
Jupiter at 812 GHz
Beam quality: exceptionally clean beam, low sidelobes, diffraction limited optics
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Telescope: Performance on Sky II
Goal: verify coupling efficiency by astronomical measurements
drift scan at ν=462 GHz across Venus
Jupiter & Mars at 812 GHz
Gain curve: after pre-loading the dish „flat“ vs. elevation (gravity)
Coupling efficiencies: consistent with surface rms

Telescope: Pointing
Goal: blind pointing over the sky better than 2 arcsec
Remind: the beam at 1 THz observing frequency is 6 arcsec only
Optical Pointing: spec has been achieved and verified (ca. 2“)
Radio Pointing: optimization ongoing (2-3“), with room for improvements
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APEX - The Atacama Pathfinder Experiment
has been successfully commissioned and
has commenced regular scientific operation in August 2005
the world’s largest submm telescope is operational

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APEX instrumentation: today & tomorrow

The APEX Instrumentation
Bolometers
MOU commitments / PI status
• LABOCA-1: 295-channel at 870 µm (MPIfR, Bochum U., IPHT Jena) 03/06
• 37-channel at 350 µm (MPIfR) Summer 06
• 324-channel at 1.4/2 mm for Sunyaev-Zel'dovich survey (UCB, MPIfR) ongoing
Heterodyne
• 183 GHz water vapour radiometer (MPIfR) Operational
• 210-270 GHz (OSO)
• 270-375 GHz (OSO) Prel. del: 07/05, full suite 12/06
• 375-500 GHz (OSO)
Full suite of facility mixers: only 12/06
• 460/810 GHz dual channel First High-frequ. Light Apex workhorse Submm Heterdyne 05/04, upgrade Rx (MPIfR,PI) 02/06
• CHAMP + 600-720/790-920 GHz, 2×7-elements with MACS (MPIfR, 05/06 PI)
• FIR receivers: up to 1.5 THz = 200 micron (OSO, KOSMA, CfA)
11/05
Spectrometer / Backend
∙ IF Board: & autocorrelator be replaced (upgraded by MPIfR old SEST buildcorrelator) new IF and (ESO/OSO) FFTS
Software
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Commiss. 03/06 failed
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APEX Instrumentation: FLASH
• a dual channel heterodyne instrument (PI)
• operating in the 460 & 810 GHz atm. window
– simultaneous measurements in both bands
– tuning range: 420-500; 790-830 GHz
(not easy to tune)
– noise performance: 150-250 K
350-450 K
– Intermediate frequeny: 2-4 & 4-8 GHz, rsp.
FLASH is a collaboration with SRON/Groningen
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APEX Instrumentation: CHAMP+ overview
• 2 x 7 pixel heterodyne instrument
• operating in the 660 & 850GHz atm. window
– simultaneous measurements in both bands
– large tuning band for both frequency bands
– very low losses cold optics
• Champ+ will be the ultimate high-frequency
mapping machine for APEX
• Operated with MACS (32x 1024 /1 GHz max)
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CHAMP+ is a collaboration with SRON/Groningen
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APEX Instrumentation: CHAMP+ key facts
Frequency range
Noise performance
IF-bandwidth
Beam (FWHM)
Low Frequency Array
620-720GHz
< 100 K
4-8 GHz
9‘‘ arcsec
High Frequency Array
780-950GHz
< 300 K
4-8 GHz
7‘‘ arcsec
Low loss cold optics
Single Sideband Filter
Fast Frequency switch
implemented
implemented
implemented
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APEX FFT Spectrometer
• Bandwidth: 2 x 1 GHz
1 x 2 GHz (still experimental)
• Channels: 16384 frequency channels
• Resolution: 61 kHz per channel
• Sampler: 8-bit (max. dynamic range: 48 dB)
• Stability: ~5000 sec Allan Time
• Safe to use at high altitude (e.g. APEX at 5100 meter)

APEX: outlock into 2006 operation
Major Milestones for 2006:
• wobbler installation and commissioning:
• „final“ holography with new subreflector
February
March
• receiver installations and commissioinings:
• Laboca 1
• SZ experiment
• CHAMP+ /MACS
• new facility IF and FFT spectrometers
• re-start science operation(after winter)
April
(ongoing)
June
March
April+
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