Cycle 8 2021
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• Sources larger than single pointing FoV, or multiple sources spread over alarger area, must be mosaiced together using multiple pointings.
Single pointing

Mosaicking

Multiple pointingFrequency Bands• 10 receiver bands (Band 1&2 will be available future)• Atmospheric opacity and phasestability tends to be poor at
higher frequencies and at
frequencies near water
absorption lines.
• Requires good weatherconditionInstantaneous frequency coverage• ALMA receives signals in two sidebands (green-ish color)• Up to four basebands can be placed either in a sideband or two sidebands• Possible to place up to four spectral windows (spws) within each of thesebasebands (blue-ish bars)• Each spw forms a final contiguous spectrum (You will not receive data outside ofspws)

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 calibration instrumentalpolarization.

2. Cycle 8 2021 Capabilities

New in Cycle 8• Solar observations in Band 5 in Configurations C-1, 2, 3
• Bands 9 and 10 with the stand-alone 7-m Array• Spectral scans with the 7-m Array• Mosaicking of continuum linear polarization observations (Bands 3 to 7) with the 12-mArray• Stand-along 7m polarization (single field/multiple pointing, linear, Bands 3-7, only inmain call)• VLBI observations of faint science targets (A passive-phasing mode that allows
observations of fainter VLBI targets with a correlated flux density < 500 mJy)
• Observations of pulsars using the 12-m Array as a single dish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 3, 4, 5, 6, 7, 8, 9, and 10.

ACA 7m arrayConfiguration• Maximum baselines for the antennaconfigurations will vary from 0.16 km to
8.5 km. Configurations C-9 and C-10 will
not be offered in Cycle 8 2021.
• Maximum baselines of 3.6 km for Bands 8,
9 and 10• Maximum baselines of 8.5 km for Bands 3
to 7

Not offered in Cycle 8

Configuration

Longest baseline

LST for best observing
conditions

2021 October 1

C-8

8.5 km

~ 22—10 h

2021 October 20

C-7

3.6 km~ 23—11 h2021 November 20

C-6

2.5 km

~ 1—13 h2021 December 1

C-5

1.4 km

~ 2—14 h2021 December 20

C-4

0.78 km~ 4—15 h2022 January 10

C-3

0.50 km

~ 5—17 htart date

2022 February 1

No observations due to maintenance2022 March 1

C-1

0.16 km

~ 8—21 h

2022 March 20

C-2

0.31 km

~ 9—23 h2022 April 20

C-3

0.50 km~ 11—0 h

2022 May 20

C-4

0.78 km~ 12—2 h2022 June 20

C-5

1.4 km

~ 13—4 h2022 July 11

C-6

2.5 km

~15—6 h2022 July 30

C-51.4 km~17—7 h2022 August 20C-4

0.78 km~19—8 h2022 September 10C-3

0.50 km~20—9 hBasic Observing Modes• Regular• Spectral line and continuum observations with the 12-m Array and the 7-m Array inall bands• Single field interferometry (all bands) and mosaics (Bands 3 to 9) with the 12-m
Array and the 7-m Array• Single dish spectral line observations in Bands 3 to 8
• VLBI/pulsar in phase-up mode
• Target of Opportunity• Large program• >50 hours for 12m array• >150 hours for 7m array

Polarization

I said spectral line polarimetry is also allowed for 12m mosaicking atthe meeting, but it is not true. Only continuum linear polarimetry isallowed for 12m mosaicking. Sorry for confusion.

• 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.
• 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 within 1/3 of PB in both continuum andspectral line observations. The error will be slightly worse at the outside of 1/3 PB formosaicking case (TBA).
• 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.

VLBI• VLBI observations in Bands 3 & 6 will be conducted using a “campaignmode” (acutual date will be set after the proposal review).
• New to Cycle 8 2021, VLBI observations will be permitted for science targets
with correlated flux densities < 0.5 Jy through use of apassive phasingmode.
The user must select a bright (>0.5 Jy) phase calibrator (phasor), ideallywithin 6 or 3 degrees of the science target.
• 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• Users can propose pulsar observations with the aid of phase-up mode that works as “alarge single dish”.
• Only pulsar-science projects will be accepted for this mode.
• Both time domain data in PSRFITS format and standard interferometric data will beprovided.
• Time resolution of time domain data is an integer multiple of 8 μs.

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.

• Only proposals for continuum observations in Bands 3, 5, 6 and 7 will
be accepted.
• Observations may be performed using dual linear polarization (XX,YY) or single polarization (XX) correlations; full polarization
measurements are not currently offeredQ&A at the meeting• Q: Is the passive phasing (target source flux < 500mJy) also applicable forspectral line VLBI?
A: Spectral line VLBI is not offered in Cycle 8 2021.
• Q: Is it possible to put 3 spws in one baseband and 1 spw in anotherbaseband in the same sideband?
A: Yes, it is possible.