Cycle 10
Observing Capabilities
Hiroshi Nagai, EA-ARC, ALMA Project, NAOJ

1. ALMA Basics

ALMA Arrays
12m array

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

Largest angular size < MRS

FoVAR

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 minimum
baseline 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 mosaiced together using multiplepointings.
Multiple pointing
Mosaicking
Single pointingFrequency Bands• 10 receiver bands (Band 2 will be available in future)• Multiple band data cannot betaken simultaneously in a single
execution.
(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. )• Allows to place up to four spectral windows (spws) in each of these basebands (blue-ishbars) .
• Each spw forms a final contiguous spectrum (You will not receive data outside of spws)

Instantaneous frequency coverage (B9-10)
Lower sideband

Upper sideband• For Bands 9 and 10 (Double Sideband system), up to four basebands can be placed in asideband. The same number of basebands is automatically placed in an opposite
sideband.
• Allows to place up to four spectral windows (spws) in each of these basebands (blue-ishbars) .
• You may suppress one sideband by using LO-offsetting only if TDM or FDM with 1.875GHz
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 GHzFor 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⇒

PolarizationXpol, 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 10 Capabilities

What’s New in Cycle 10?
• Band 1 on the 12-m array• Observations will be available for Stokes I only (no Stokes Q/U/V) andare anticipated to be available from March 2024. Band 1 will not beavailable in configurations C-7 and C-8.
• Spectral scan that includes the Total Power observations• 4 x 4-bits spectral line observations on the 12-m array.
• This will provide an increase in sensitivity by 12%.
• Solar observations in full polarization in Band 3 using only the 12-m Array.
• Phased array mode in Bands 1, 3, 6 and 7.
• The total time available for this mode will be limited to 50 hours.
• Continuum and spectral line VLBI in Bands 1, 3, 6 and 7, including flexible
tuning.

Additional New Items• TP data will be correlated using the ACA spectrometer, which is a new GPU
spectrometer developed by EA, instead of traditional ACA correlator.
• No action is needed on the user side.

• B2B phase transfer method is also applicable for all array configurations.
• In case that no phase calibrator can be found within a nominal
separation angle at the target frequency, the OT automaticallytriggers the B2B mode.
• For the B2B mode, phase calibrator is observed at lower
frequency and transfer the phase calibration to the target(high) frequency. This will increase a chance to find phasecalibrator.
• A maximum of 65 hours for 12-m and 85 hours for 7-m array.

TargetνHF

νLF
Phase calibrator

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

Config. ScheduleBand 1 startNotes on Band 1• Will start to offer in March 2024.

• Users must choose the requested angular resolution and MRS that can be achieved
with C1-C6 in their proposals. The OT does not give warning/error even if you set
angular resolutions that cannot be achieved C1-C6 configurations.
• Both continuum and spectral line including spectral scan are allowed.
• No polarization (only Stokes I).
• No 7m nor TP.

Notes on 4x4-bits• User can choose 2x2-bits or 4x4-bits in the Spectral Setup.
• 4x4-bits provide a better sensitivity at fix
spectral resolution and integration time.
• This mode is only allowed for the5 FDM setups with the 12-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.
• Don’t worry to use 4x4-bits, though the OT returns a warning message.

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-mantennas, no 7-m antennas will be provided for Band 3 polarimetry.

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 primary beam) of continuum and spectral line polarimetry are offeredin Bands 3-7 for linear polarization.
• Only continuum linear polarimetry for mosaicking with default continuum setup.
• Only single pointing within 1/10 of primary beam is offered in Bands 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.
• A maximum of 75 hrs will be offered.

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.
• A maximum of 65 hours for 12-m and 85 hours for 7-m array will beavailable for the observations requiring B2B calibrations.

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• 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 sufficient
short baselines) except for polarization observation in Band 3.

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

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)

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.