Cycle 11
Observing Capabilities
Hiroshi Nagai, EA-ARC, ALMA Project, NAOJ

1. ALMA Basics

ALMA Arrays
See Cycle 11 “A Primer”

12m array

ACA(7m array + TP array)Three Important Angular Scales
TW Hydra (Tsukagoshi+ 2019)

Largest angular size < MRS

FoV

AR

Smoothly distributed emission overthe disk with some variation.

AngularResolution(AR)• Resolution element of image• Determined by the maximum
baseline length (λ/Dmax)

Maximum
Recoverable
Scale (MRS)• The largest structure that can beimaged without missing flux
• Determined by the minimumbaseline length (λ/Dmin)

Field of View(FoV)• FoV of a single telescope pointing• Equal to antenna beam sizeMosaicking / Multiple Pointing• Angular structure that is larger than single pointing FoV, or multiple sources
spread over a larger area, must be mosaicked or used multiple pointings.
Single pointing

Mosaicking

Multiple pointingFrequency Bands• 10 receiver bands (Band 2 will be available in future)• Multiple band data cannot betaken simultaneously in a singleexecution.
(except for B2B phase transfer)• Atmospheric opacity and phasestability tends to be poor at
higher frequencies and at
frequencies near water
absorption lines.
• Requires good weather
condition

Frequency vs. Weather

Instantaneous frequency coverage (B3-8)
Lower sideband

Upper sideband• ALMA receives signals in two sidebands (green-ish color).
• Up to four basebands with 2-GHz width can be placed either in a sideband or twosidebands. (Red boxes. Not possible to put 3 in one sideband and 1 in the other. )• Up to four spectral windows (spws) in each of basebands (blue-ish bars) .
• Each spw forms a final contiguous spectrum (You will not receive data outside ofspws)

Instantaneous frequency coverage (B9-10)
Lower sideband

Upper sideband• For Bands 9 and 10 (Double Sideband system), up to four basebands can be placedin a sideband. The same number of basebands is automatically placed in anopposite sideband.
• Allows to place up to four spectral windows (spws) in each of basebands (blue-ishbars) .
• You may suppress one sideband by using LO-offsetting only if TDM or FDM with1.875GHz BW is selected.

Instantaneous frequency coverage (B1)
Single sideband• Band 1 employs single-sideband system (SSB).
• Up to 4 basebands with 2-GHz width are placed in a sideband.
• Allows to place up to four spectral windows (spws) in each of thesebasebands (blue-ish bars) .

Intermediate Frequency (IF) Range

4.5 GHz10 GHz4.5 GHz10 GHz• For the case of Band 6, IF range is from νLO1+/- 4.5 GHz to νLO1+/- 10 GHz, andtherefore the width of each sideband is 5.5 GHz.

Frequency Resolution

OT⇒Polarization
Xpol, Ypol
Antenna m
Xpol, Ypol
Antenna n

ALMA correlator

𝑋𝑋𝑚𝑚 𝑋𝑋𝑛𝑛∗ = 𝐼𝐼 + 𝑄𝑄
𝑌𝑌𝑚𝑚 𝑌𝑌𝑛𝑛∗ = 𝐼𝐼 − 𝑄𝑄
𝑋𝑋𝑚𝑚 𝑌𝑌𝑛𝑛∗ = 𝑈𝑈 + 𝑖𝑖𝑖𝑖
𝑌𝑌𝑚𝑚 𝑋𝑋𝑛𝑛∗ = 𝑈𝑈 − 𝑖𝑖𝑖𝑖

XXDualFull• ALMA can provide full polarization products (XX, YY, XY, YX) so that one canproduce Stokes I, Q, U, and V images.
• At least ~3-hrs observation is required to calibrate instrumental polarization.

2. Cycle 11 Capabilities

What’s New in Cycle 11?
• Full-polarization in Band 1 on the 12m array. The polarization accuracy andcapability will be the same as in Bands 3-7.
• Band 1 on the 7m array for Stokes I only.
• High-frequency and long-baseline observations with Band 9 in C-10
configuration, and Band 10 in configurations of C-9 and C-10.
• 4x4-bit spectral mode on the 7-m Array (dual polarization).

Antennas, Receiver Bands• Number of antennas• ≧43 antennas in the 12-m Array.
• ≧10 7-m antennas (for short baselines) and 3 12-m antennas (for single dish) in theACA.
• Receiver bands• Bands 1, 3, 4, 5, 6, 7, 8, 9, and 10.

Configuration

See Technical Handbook

Config. ScheduleNotes on 4x4-bits (introduced from Cycle 10)• User can choose 2x2-bits or 4x4-bits in the Spectral Setup.
• 4x4-bits provide a better sensitivity at fixed
spectral resolution and integration time.
• This mode is only allowed for the5 FDM setups with the 12-m and 7-m array.
• 4x4-bits mode cannot be used in
the same baseband with 2x2 bitmodes, but a mixture of basebands
using 4x4 and basebands using 2x2
is allowed.

https://almascience.nao.ac.jp/documents-and-tools

Backup slides

Time MultiplierBasic Observing Modes• Spectral line, continuum, mosaic observations• Spectral line and continuum observations with the 12-m Array and the 7-m Array inall bands• Single field interferometry (Bands 3-10) and mosaics (Bands 3 to 9) with the 12-m
Array and the 7-m Array. In Band 1, single-field interferometry and mosaics are
only available with the 12-m Array.
• Single dish spectral line observations in Bands 3 to 8
• Spectral scan (useful for spectral survey and redshift search)• Up to 5 different tunings can be requested per SG.
• Single-dish spectral scan is also allowed in bands 3-8 from this Cycle.
• Target of Opportunity• Large program• >50 hours for 12m array• >150 hours for 7m array

Polarization (no change from previous cycle)• 12m• Single pointing (within 1/3 of PB) of continuum and spectral line polarimetry are offered in Bands 1,and 3-7 for linear polarization.
• Only continuum linear polarimetry for mosaicking with default continuum setup.
• Only single pointing within 1/10 of PB is offered in Bands 1, and 3-7 for circular polarization.
• Systematic error (minimum detectable degree of polarization)• Linear polarization: 0.1-0.2% of peak Stokes I flux and 1 degree in polarization position angle
within 1/3 of PB in both continuum and spectral line observations.
• Linear polarization mosaicking: Within the FWHM of a given pointing, the estimated upper
limits are 4 degrees in polarization position angle and 0.5% in polarization percentage.
• Circular polarization: 1.8% of peak Stokes I flux in both continuum and spectral resolution
observations.
• 7m• Only single pointing (<1/3 PB) or multiple pointings (each of pointing with 1<3 PB FoV), linear
polarization of continuum and spectral line is offered in Bands 3-7. No circular polarization, nomosaicking.
• The systematic error is the same as the 12m case.
• Data combination of 12m and 7m will not be supported.

High Frequencies

TargetνHF

νLF• Observations in Bands 7-10 may require Band-to-Band (B2B)
Phase calibrator
phase transfer calibration in order to find a nearby andsufficiently bright phase calibrator to ensure phasecalibration quality.
• The OT will automatically check the availability of suitable phase calibrators
during proposal validation and will automatically trigger the B2B mode
where required.
• The OT will emit an error if a source does not have a suitable calibrator evenwith B2B. PIs are advised to begin preparing their proposals early to ensurethat a suitable calibrator is available for their targets.
• No cap for B2B projects

VLBI• VLBI observations in Bands 1, 3, 6, & 7 will be conducted using a“campaign mode” (actual date will be set after the proposal review).
• Both continuum and spectral line with flexible tuning are allowed.
• The proposers are required to enter a VLBI total time requested.
• ALMA’s VLBI observing window in a given cycle will not exceed twoweeks, so if multi-epoch observations are requested, they must fit
within that time frame and the total time request must be theaggregate time of all observations.

Pulsar observations (phased-array mode)• Users can propose pulsar observations with the aid of phase-up mode thatworks as “a large single dish” in Bands 1, 3, 6, and 7.
• Only pulsar-science projects will be accepted for this mode.
• Both time domain data in PSRFITS format and standard interferometric data
will be provided.
• Time resolution of time domain data is an integer multiple of 8 μs.
• The total time available for this mode will be limited to 50 hours.

Solar Observations (as of Cycle 10)• Proposals will be accepted for ALMA interferometric and Total Powerobservations.

• Will be conducted only during the periods when the 12-m Array is in one of theallowed configurations for the requested band, namely C-1 to C-4 for Band 3, C-1 toC-3 for Band 5, C-1 to C-3 for Band 6, and C-1 to C-2 for Band 7.
• The interferometric component of Solar observations will be conducted using a
special combined array comprising both 12-m and 7-m antennas (to ensure sufficientshort baselines) except for polarization observation in Band 3.

• Full polarization (XX, YY, XY, YX) are only offered in Band 3 with the 12-m
array.

Solar Observations• The Total Power component of solar observations consists of fast-scanningmapping observations to recover the largest angular scales forinterferometric observations. Proposals requesting only Total Power singledish observations will not be accepted. The Total Power observations will betaken contemporaneously with the interferometric observation.
• Time cadence of full-sun images is about 10, 13, 15 and 25 minutes for Bands 3, 5, 6,and 7, respectively.
• Time cadence of fast regional mapping (small FoV around a region of interest)

Notes on Solar Polarization• Only in Band 3• Although the interferometric component of Solar observations will beconducted using a special combined array comprising both 12-m and 7-m
antennas, no 7-m antennas will be provided for Band 3 polarimetry.

Calibration Accuracies• Image dynamic range (Ipeak/rms)• ~100 for compact 12m arrays and ACA, ~50 for more extended than ~2km and at Bands 8,9, and 10 for
nominal phase calibration.
• Self-calibration will be required to achieve image DR of ~1000 or larger.

• Absolute flux accuracy• ~5% in Bands 1-5, ~10% in Bands 6-8, ~20% in Bands 9-10

• Spectral dynamic range (desired SNR per spectral resolution element)• Demonstrated ~1000 in Bands 3-6 (except for Ozone line at 183GHz in Band 5), ~400, 250, 170, and
150 in Bands 7, 8, 9, and 10, respectively, but spectral DR can depend on the brightness of bandpass
calibrator (see THB 10.4.6 for more details). Band 1 spectral DR has not been extensively tested, but
we will expect to achieve ~1000.

• Total power calibration accuracy• 5% in Bands 3-7, 15% in Band 8• Astrometric accuracy• At best ~5% of synthesized beam for angular resolution > 150 mas, ~10% of synthesized beam forhigher angular resolution.
• Choose “enhanced position accuracy” in the OT if you need astrometric accuracy better than thenominal one.