Technical summary

ALMA basic parameters

 

Array

Antennas 12m Array ACA

50 (up to 64) 12(7m) + 4 (12m)
Array

Angular Resolution 0.02 (wavelength/1 mm)(10 km/distance) arcsec 5.7(wavelength/1mm) arcsec
Baseline Lengths 150 - 16,000 m
Pointing ±25 mm, 0.6" reference pointing in 9m/s wind, 2" absolute pointing all-sky

 

ALMA Frequency Bands

Bands in bold will be used for early science and those highlighted
will be installed on all available antennas. Bands in italics will be
the last to be implemented.

Band

Frequency Range

Wavelength Range

Receiver Noise

Primary beam

(GHz)

 (mm)

(K)

(arcsec)
1 31-45 6-10 17 -26 140
2 67-90 3.5-4.5 0-47 70
3 84-116 2.6-3.6 37-60 56
4 125-163 1.8-2.4 51-82 48
5 163-211 1.4-1.8 65-105 35
6 211-275 1.1-1.4 83-136 27
7 275-373 0.8-1.1 147-219 18
8 385-500 0.6-0.8 196-292 12
9 602-720  0.4-0.5 175-261 9
10 787-950 0.3-0.4 230-344 7

Spectrometer

Maximum bandwidth 8 GHz per polarization per baseline
Channel width 3.8 kHz to 31 MHz
Spectral Channels 4096
Total velocity coverage 10470(230/f(GHz)) km/s
Velocity resolution 0.1(230/f(GHz)) km/s to 41(230/f(GHz)) km/s
where f(GHz) is the observing frequency in GHz.

Typical Sensitivity

Line Sensitivity

Integration of 60 seconds, combining all 54 12m antennas and 12 7m antennas. 
Band Frequency Water vapour Low resolution High resolution



Bmax= 0.2 km Bmax= 14.7 km



Beamsize T(K) Beamsize T(K) T(K)

(GHz) (mm in atmosphere) (arcsec) in 1 km/s (arcsec) in 1 km/s in 25 km/s
3 100 2.3 2.8 0.10 0.038 532 106
4 140 2.3 2.2 0.10 0.030 543 109
6 230 2.3 1.3 0.15 0.018 780 156
 7  345 1.2 0.9 0.23 0.012 1240 248
 8  409 1.2 0.7 0.34 0.010 1722 344
 9  675 0.5 0.4 0.85 0.006 4200 840

 

Continuum Sensitivity

Integration of 60 seconds combining all 54 12m antennas and 12 7m antennas. Table and values from article by A. Wootten. A value of precipitable water vapour (pwv) of 0.5mm corresponds to the 25th percentile of the distribution of pwv over time.
Band Frequency Continuum rms flux

(GHz) (mJy per beam
3 100 9
4 140 9
 6  230  13
 7  345  21
 8  409  63
 9  675  80
A full sensitivity calculator

is available on the ESO website.

 

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