Transcript Introduction Robert Lucas

Observing Modes
from a Software viewpoint
Robert Lucas
and Philippe Salomé
(SSR)
Observing Modes
• Observing modes are pre-defined ways to use ALMA to obtain
science and calibration data.
• Use of standard modes individually tested for accuracy and
efficiency makes operation easier for ALMA observers and for
ALMA staff.
• Choice, definition of standard modes and their order of
implementation and commissioning is an important element of
observatory development.
• A sequential implementation of Observing Modes is very
important for software deployment and testing, once the basic
computing structures are in place.
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Observing Modes of two kinds
• Observer Modes:
– Open to the general
science observer
– Aimed at obtaining
general science data
– Examples:
• Single-field mapping with
interferometry
• OTF single-dish maps
• Full mapping of sky area
with long, short, zero
spacings
• Observatory Modes:
– For the observatory staff
– Aimed at obtaining array
calibration data used by
science projects
– Examples:
• Measure antenna precise
positions
• Measure pointing models
• Check antenna surface
accuracy with holography
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How do we define Observing
Modes?
•
Basic modes defined by the hardware, e.g. :
– Correlators: ACA/Baseline, correlation and autocorrelation, or autocorrelation only,
polarizations, resolution, bandwidths…
– Continuum detectors: integration time
– Local oscillators: Frequency switching, side band separation/rejection
– Nutator: beam switching
– Antenna: OTF scanning, individual pointings …
– WVR receivers: apply mode (model, empirical)…
Note: These are not independent as e.g. some switching choices may restrict correlator
configuration
•
Definitions of simple modes are based on the science goal, with sub-modes
defined when there are hardware options, mainly dictated by the calibration
strategy
– Example: a single dish continuum map may use OTF scanning with or without beam
switching; a line map may use spatial referencing or frequency switching.
•
For many science goals a combination of simple modes are needed:
– Example: extended source mapping will need short spacing, total power, long spacing
data, that are obtained sequentially using basic simple modes.
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The structure of a Project
•
•
•
•
•
•
One ObsUnitSet is aimed at a
science result (e.g., one image)
One ObsUnitSet applies a simple
observing mode
A ObsUnitSet may need one ore
more SchedBlocks to be
observed (e.g. several
configurations
There can also be several
ObsUnitSets in a project, as
several science results may be
required, with (may be)
different modes.
A complex observing mode uses
several simple modes
Thus there can be several
ObsUnitSets in an ObsUnitSet
(hierarchy of observing modes).
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Standard Observer Mode:
Simple/Complex
Example:
1. Simple Standard Mode: single field interferometer map
• One ObsUnitSet, one or a few SB, which may be
repeated
2. Complex Standard Mode: extended object map
Uses the hierarchy of ObsUnitSets:
• One ObsUnitSet for an interferometer map
– interferometer pointed mosaic
• One ObsUnitSet for an interferometer map
– ACA single-dish and short-spacing map
• Top Level ObsUnitSet produces final combined map
• This complexity affects the OT, scheduling, pipeline, but
not Control, Quick Look, or On-line calibration
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Standard Observer Mode Contents
• Parameters (defaults when possible) to be defined in the Observing
Tool:
– Observing parameters
• Area to be mapped
• Spectral definition from science point of view
• Quality parameters (sensitivity, dynamic range…) resulting in scheduling
constraints
– Pipeline parameters and options
• Should be minimal, we leave to standard observing mode heuristics
what can be decided in an automated way
– SB definition policy, as specific rules for each mode may be needed
• Standard Mode observing script:
– One per simple mode and per kind of SB generated in that mode
– Actually controls the observations
• Standard mode data reduction script (pipeline heuristics)
• And naturally user documentation.
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Observing Tool Snapshot
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An example SchedBlock
• The contents of the
Scheduling Block are
stored in an xml file.
• This contains all the
information needed to
schedule it, and execute
it; in particular the
reference to a standard
mode script that will
perform the actual
observing on the
telescope.
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Observing Script
Commands (in Control Command Language) in order to:
– Recover user’s input parameters (SB content)
– Frequency setup, correlator setup commands, using the SB content
as input
– Real time choices (e.g. which calibrators)
– Perform calibrations as needed:
• Some calibrations are in Observing Mode SB script: pointing,
focus, amplitude, phase,…
– With script logic to decide when to calibrate
• More expensive calibrations, e.g. BandPass calibration
– Check if calibration exists already (query Calibration Data Base)
– Perform calibration if needed
– Recover calibration results from on-line calibration (TelCal)
– Observing cycles; stop when conditions met (e.g. time elapsed).
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Example of script (holography)
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Example ExecBlock (ASDM)
Holography ASDM
Two of 24 tables, mostly in xml
format:
Pointing table, TotalPower table are
stored in binary format for
efficiency.
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Tentative list of
Simple Observer Modes (1)
1. Pointed interferometer mosaic map
2. On-the-fly interferometer mosaic map
3. Pointed single-dish map
1. Position switched spectral/continuum
2. Beam switched spectral/continuum
3. Frequency switched spectral
4. On-the-fly single-dish map
1. Position switched spectral/continuum
2. Beam switched spectral/continuum
3. Frequency switched spectral
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Tentative list of
Simple Observer Modes (2)
5. Simultaneous pointed interferometer / single dish
mosaic map
1. Position switched spectral/continuum
2. Beam switched spectral/continuum
3. Frequency switched spectral
6. Simultaneous on-the-fly interferometer / single dish
mosaic map
1. Position switched spectral/continuum
2. Beam switched spectral/continuum
3. Frequency switched spectral
These are the ACA modes of course; more complexity may be
actually involved…
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Observatory Modes
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Transmitter holography
Astronomical holography
Optical pointing model
Radio pointing model
Antenna position measurements
Axes offset measurement
Focus model (using holography)
Delays
Receiver band pointing offsets
Beam shape determination
Primary feed illumination (size and offsets)
Primary amplitude calibration (standard flux calibrators)
… any other, found necessary during commissioning
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Observing Mode Development
• Start with simple observer modes
–
–
–
–
How many standard observer modes?
If too many, gets too complicated for user
If too few, they get complicated
E.g.
• single field interferometry and pointed mosaic are probably one mode.
• Position switch and frequency switch in Single-dish are two modes.
• Observatory Modes are needed first
– Optical pointing, Holography
• In CIPT the modes are developed both
– at the instrument level (control, correlator subsystems)
– at the observatory level (end-to-end approach) in function-based teams.
• They are the object of Integrated User Tests (e.g. optical pointing at
the ATF).
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Modes for Commissioning
This sets in practice an order of priorities, according to needs for
antenna acceptance and commissioning plan, e.g.:
1. Single Dish Holography
2. Optical Pointing
3. Single Dish with Total Power detectors only
–
–
–
No nutator, then nutator
Focus checking, beam maps
Radio Pointing model determination
4. Single Dish with Correlator
–
Position, Beam, Frequency switching
5. Interferometry
–
–
Baseline measurement
Interferometer holography
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Observer Modes Implementation
• We need to work on the science modes in parallel
with the commissioning
– we need ultimately to commission the science modes one
after the other
• Work first on single-field interferometry
– using hardware simulation at the array level, for an end-to
end approach (OT to Off-line data reduction) before the
whole hardware is available
• Further work will soon involve single-dish modes.
• Naturally the order of priority of implementation and
testing of observer modes is a science issue.
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Present Status: Observatory Modes
• Optical Pointing implemented, and tested March
2006.
– A report on the integrated user testing is available
– Actually bad weather did not allow a full science checking
at the time
• Transmitter Holography implemented (still to be
tested; hw expected in 2007-Sep. at ATF)
– Control software ready and tested in simulation
– Data reduction identical to that used in Antenna Evaluation
– Data format now converted to new ALMA Science Data
Model (ASDM).
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Present Status: Single Field
Interferometry
• Implemented in simulation, waiting for hardware to be ready at ATF
– While first fringes should be reached soon, the end-to-end software will not
be used (or desired) to obtain them. Real tests of end-to-end software with
hardware will start only at that point.
• Next Stage (end of October) should include, in simulation mode:
– a target source
– several phase calibrations, with on-line phase interpolation between them
– Main development areas:
• Validate the ASDM: from DataCapture to Off-Line Filler
• LO phase and delay tracking
• Shift Log prototype implementation
– Secondary development areas:
• Usage of standard mode scripts
• Feedback of on-line calibration results
• Performance validation of ASDM
• Quick-Look display of Calibration results
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Next Observer Modes
• Need to define priorities for Single-Dish
– Should have simple single dish modes to test the antennas
(2007/2008)
– Should also aim particularly towards the main science modes for
ACA single-dish (science input needed):
• Relative priorities of simple and combined switching modes.
• Pointed Mosaics
– Really a variation of the single field interferometry, but more
complex for OT and pipeline
• OTF Mosaics
– Probably not for Early Science
– When we can do this end-to-end we’re in a good shape.
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