Miscellaneous¶

Base class¶

class darc.base.DARCBase(source_queue, target_queue=None, second_target_queue=None, control_queue=None, config_file='/opt/hostedtoolcache/Python/3.8.6/x64/lib/python3.8/site-packages/darc/config.yaml')¶

Bases: multiprocessing.context.Process

DARC Base class

Provides common methods to services

Parameters

source_queue (Queue) – Input queue
target_queue (Queue) – Output queue
second_target_queue (Queue) – second output queue
control_queue (Queue) – Control queue
config_file (str) – Path to config file

cleanup(abort=False)¶

Stub for commands to run upon service stop, defaults to self.stop_observation

Parameters: abort (bool) – Whether to abort running observation

get_attribute(command)¶

Get attribute as given in input command

Parameters: command (dict) – Command received over queue

load_config()¶: Load config file

process_command(command, *args, **kwargs)¶

Process command from queue, other than start_observation and stop_observation. By default only provides get_attribute command

Parameters

command (dict) – Input command
args (list) – process command arguments
kwargs (dict) – process command keyword arguments

run()¶

Main loop

Receive commands on input queue, calls self.start_observation, self.stop_observation, else self.process_command

start_observation(*args, reload=True, **kwargs)¶

Start observation. By default only (re)loads config file.

Parameters

args (list) – start_observation arguments
reload (bool) – reload service settings (default: True)
kwargs (dict) – start_observation keyword arguments

stop(abort=False)¶

Stop this service

Parameters: abort (bool) – Whether to abort running observation

stop_observation(*args, **kwargs)¶

Stop observation stub, should be overridden by subclass if commands need to be executed at observation stop

Parameters

args (list) – stop_observation arguments
kwargs (dict) – stop_observation keyword arguments

Control¶

darc.control.main()¶

DARC command line interface

This function is called by the darc executable

Run darc –help for usage

darc.control.send_command(timeout, service, command, payload=None, host='localhost', port=None)¶

Send a command to the DARC master service

Parameters

timeout (float) – Timeout for reply in seconds
service (str) – Service to send command to
command (str) – Which command to send
payload (str) – Payload for command (optional)
host (str) – Hostname to connect to (default: localhost)
port (int) – Port to connect to (default: get from DARC config file)

Returns

reply from DARC master

Definitions¶

darc.definitions.AP_EFF = 0.6¶: Apertif/ARTS aperture efficiency

darc.definitions.ARRAY_ITRF = <Quantity [3828630.63486201, 443593.39226634, 5064922.99755 ] m>¶: ITRF WSRT reference position

darc.definitions.BANDWIDTH = <Quantity 300. MHz>¶: Apertif/ARTS bandwidth

darc.definitions.CONFIG_FILE = '/opt/hostedtoolcache/Python/3.8.6/x64/lib/python3.8/site-packages/darc/config.yaml'¶: Full path to config file: $HOME/darc/config.yaml if present, else default shipped with package

darc.definitions.DISH_DIAM = <Quantity 25. m>¶: WSRT dish diameter

darc.definitions.MASTER = 'arts041'¶: ARTS master name

darc.definitions.NCHAN = 1536¶: Apertif/ARTS number of channels

darc.definitions.NDISH = 8¶: Apertif/ARTS number of dishes in use

darc.definitions.NTAB = 12¶: Number of tied-array beams

darc.definitions.NUMCB = 40¶: Apertif/ARTS number of compound beams

darc.definitions.TIME_UNIT = 781250¶: Beamformer time constant: number of samples per second

darc.definitions.TSAMP = <Quantity 8.192e-05 s>¶: Apertif/ARTS sampling time

darc.definitions.TSYS = <Quantity 85. K>¶: Apertif/ARTS system temperature

darc.definitions.WORKERS = ['arts001', 'arts002', 'arts003', 'arts004', 'arts005', 'arts006', 'arts007', 'arts008', 'arts009', 'arts010', 'arts011', 'arts012', 'arts013', 'arts014', 'arts015', 'arts016', 'arts017', 'arts018', 'arts019', 'arts020', 'arts021', 'arts022', 'arts023', 'arts024', 'arts025', 'arts026', 'arts027', 'arts028', 'arts029', 'arts030', 'arts031', 'arts032', 'arts033', 'arts034', 'arts035', 'arts036', 'arts037', 'arts038', 'arts039', 'arts040']¶: ARTS worker names

Logger¶

darc.logger.get_logger(name, log_file, level=20)¶

Create logger

Parameters

name (str) – name to use in log prints
log_file (str) – Path to log file
level (int) – log level (default: logging.INFO)

Returns

logger

Synthesized Beam Generator¶

class darc.sb_generator.SBGenerator(fname=None, science_case=None, config_file='/opt/hostedtoolcache/Python/3.8.6/x64/lib/python3.8/site-packages/darc/config.yaml')¶

Bases: object

Synthesized beam generator

__init__ should be called by cls.from_science_case or cls.from_table

Parameters

fname – path to synthesized beam table
science_case – ARTS science case (3 or 4)
config_file (str) – Path to config file

_load_table()¶: Load SB table

classmethod from_science_case(science_case, config_file='/opt/hostedtoolcache/Python/3.8.6/x64/lib/python3.8/site-packages/darc/config.yaml')¶

Initalize default table for given science case

Parameters

science_case (int) – science case (3 or 4)
config_file (str) – Path to config file

Returns

SBGenerator object

classmethod from_table(fname, config_file='/opt/hostedtoolcache/Python/3.8.6/x64/lib/python3.8/site-packages/darc/config.yaml')¶

Initalize with provided SB table

Parameters

fname (str) – Path to SB table
config_file (str) – Path to config file

Returns

SBGenerator object

get_map(sb)¶

Return mapping of requested SB

Parameters: sb (int) – beam to return mapping for
Returns: SB mapping for requested beam

property reversed¶

Whether or not the SB table is reversed for use on filterbank data

Returns: reversed (bool)

synthesize_beam(data, sb)¶

Synthesize beam

Parameters

data (np.ndarray) – TAB data with shape [TAB, freq, time]
sb (int) – SB index

Returns

SB data with shape [freq, time]

exception darc.sb_generator.SBGeneratorException¶: Bases: Exception

Utilities¶

darc.util.calc_snr_amber(data, thresh=3)¶

Calculate peak S/N using the same method as AMBER: Outliers are removed four times before calculating the S/N as peak - median / sigma The result is scaled by 1.048 to account for the removed values

Parameters

data (array) – timeseries data
thresh (float) – sigma threshold for outliers (Default: 3)

Returns

peak S/N

darc.util.calc_snr_matched_filter(data, widths=None)¶

Calculate S/N using several matched filter widths, then pick the highest S/N

Parameters

data (np.ndarray) – timeseries data
widths (np.ndarray) – matched filters widths to try (Default: [1, 5, 10, 25, 50, 100, 250, 500, 1000, 2500])

Returns

highest S/N, corresponding matched filter width

darc.util.clear_queue(queue)¶

Read all remaining items in a queue and discard them

Parameters: queue (queue.Queue) – queue to clear

darc.util.decode_parset(parset_bytes)¶

Decode parset into string

Parameters: parset_bytes (bytes) – raw parset bytes
Returns: parset as string

darc.util.dm_to_delay(dm, flo, fhi)¶

Convert DM to time delay

Parameters

dm (astropy.units.quantity.Quantity) – dispersion measure
flo (astropy.units.quantity.Quantity) – lowest frequency
fhi (astropy.units.quantity.Quantity) – highest frequency

Returns

time delay (astropy quantity)

darc.util.dm_to_smearing(dm, f, df)¶

Calculate intra-channel smearing time

Parameters

dm (astropy.units.quantity.Quantity) – dispersion measure
f (astropy.units.quantity.Quantity) – frequency
df (astropy.units.quantity.Quantity) – channel width

darc.util.encode_parset(parset_str)¶

Encode parset string into bytes

Parameters: parset_str (str) – parset as one string
Returns: encoded parset as bytes

darc.util.get_flux(snr, width, ndish=8, npol=2, coherent=True)¶

Compute single pulse flux density using radiometer equation

Parameters

snr (float) – S/N
width (astropy.units.quantity.Quantity) – Width
ndish (int) – Number of dishes used (default: 8)
npol (int) – Number of polarizations (default: 2)
coherent (bool) – Using coherent beamforming (default: True)

Returns

Peak flux density (astropy.units.quantity.Quantity)

darc.util.get_ymw16(parset, beam=0, logger=None)¶

Get YMW16 DM

Parameters

parset (dict) – Observation parset
beam (int) – CB for which to get YMW16 DM
logger (Logger) – Logger object (optional)

Returns

YMW16 DM (float)

darc.util.hadec_to_radec(ha, dec, t)¶

Convert apparent HA, Dec to J2000 RA, Dec

Parameters

ha – hour angle with unit
dec – declination with unit
t (Time/str) – Observing time

Returns

SkyCoord object of J2000 coordinates

darc.util.hadec_to_rot(ha, dec)¶

Convert WSRT HA, Dec to TAB rotation angle

Parameters

ha (astropy.units.quantity.Quantity) – hour angle with unit
dec (astropy.units.quantity.Quantity) – declination with unit

darc.util.makedirs(path)¶

Mimic os.makedirs, but do not error when directory already exists

Parameters: path (str) – path to recursively create

darc.util.parse_parset(parset_str)¶

Parse parset into dict with proper types

Parameters: parset_str (str) – raw parset as string
Returns: parset as dict

darc.util.radec_to_hadec(ra, dec, t)¶

Convert RA, Dec to apparent WSRT HA, Dec

Parameters

ra (Quantity) – Right ascension
dec (Quantity) – Declination
t (Time/str) – Observing time

Returns

HA (Quantity), Dec (Quantity)

darc.util.send_email(frm, to, subject, body, attachments=None)¶

Send email, only possible to ASTRON addresses

Parameters

frm (str) – From address
to (str/list) – To addresses, either single or list of addresses
subject (str) – Subject of email
body (dict) – Dict with e-mail content (str) and type (str)
attachments (dict/list) – optional dict or list of dicts with attachment path (str), type (str), and name (str)

darc.util.sleepuntil_utc(end_time, event=None)¶

Sleep until specified time

Parameters

end_time (datetime.datetime/astropy.time.Time/str) – sleep until this time
event (threading.Event) – if specified, uses event.wait instead of time.sleep

darc.util.tail(f, event, interval=0.1)¶

Read all lines of a file, then tail until stop event is set

Parameters

f (filehandle) – handle to file to tail
event (threading.Event) – stop event
interval (float) – sleep time between checks for new lines (default: .1)