surveyinit¶

Summary:: Design hour angles calculated during survey initialization.
Naming Convention:: surveyinit.fits
Regex:: surveyinit.fits
File Type:: FITS, 36 KB

Contents¶

Number	EXTNAME	Type	Contents
HDU0	WEATHER	IMAGE	Nightly dome-open fractions assumed to calculate available LST.
HDU1	DARK	BINTABLE	Summary of hour angle optimization for the DARK program.
HDU2	GRAY	BINTABLE	Summary of hour angle optimization for the GRAY program.
HDU3	BRIGHT	BINTABLE	Summary of hour angle optimization for the BRIGHT program.
HDU4	DESIGN	BINTABLE	Design hours angles for all programs.

FITS Header Units¶

HDU0¶

EXTNAME = WEATHER

Nightly dome-open fractions due to weather that are are assumed when calculating the available LST per program, as an input to the design hour-angle optimization.

Required Header Keywords¶

KEY	Example Value	Type	Comment
NAXIS1	2556	int	Length of dimension 1.
FIRST	2019-01-01	str	Date of the first tabulated night.
YEARS	2007,2008,2009,2010,2011,2012,2013,2014,2015,2016,2017	str	List of years averaged to calculate predicted dome-open fractions.
START	2019-12-01	str	Nominal survey start date used for hour-angle optimization.
STOP	2024-11-30	str	Nominal survey stop date used for hour-angle optimization.
TWILIGHT	F	bool	Was twilight included in the BRIGHT program schedule for optimzation?

Data: FITS image [float64, 2556]

The HDU data consists of a 1D array of dome-open fractions estimated by averaging historical weather data. The value at index K corresponds to the night of FIRST plus K days. Note that dome-open fractions are tabulated for an extended date range that covers the nominal survey dates but also commissioning and survey validation.

Use load_weather to read the dome-open fractions as a 1D array, optionally sliced to a specified range of dates.

HDU1¶

EXTNAME = DARK

Summary of hour angle optimization for the DARK program.

Required Header Keywords¶

KEY	Example Value	Type	Comment
NAXIS1	24	int	length of dimension 1
NAXIS2	192	int	length of dimension 2
ORIGIN	-60.0	float	Low edge of first LST histogram bin in degrees.

Required Data Table Columns¶

Name	Type	Description
AVAIL	float64	Histogram of available LST in the DARK program.
INIT	float64	Histogram of initial LST usage, before optimization.
PLAN	float64	Histogram of planned LST usage, after optimization.

Histograms are normalized to the (dimensionless) units of sidereal hours per LST bin integrated over the survey.

HDU2¶

EXTNAME = GRAY

Summary of hour angle optimization for the GRAY program.

Required Header Keywords¶

KEY	Example Value	Type	Comment
NAXIS1	24	int	length of dimension 1
NAXIS2	192	int	length of dimension 2
ORIGIN	-60.0	float	Low edge of first LST histogram bin in degrees.

Required Data Table Columns¶

Name	Type	Description
AVAIL	float64	Histogram of available LST in the GRAY program.
INIT	float64	Histogram of initial LST usage, before optimization.
PLAN	float64	Histogram of planned LST usage, after optimization.

Histograms are normalized to the (dimensionless) units of sidereal hours per LST bin integrated over the survey.

HDU3¶

EXTNAME = BRIGHT

Summary of hour angle optimization for the BRIGHT program.

Required Header Keywords¶

KEY	Example Value	Type	Comment
NAXIS1	24	int	length of dimension 1
NAXIS2	192	int	length of dimension 2
ORIGIN	-60.0	float	Low edge of first LST histogram bin in degrees.

Required Data Table Columns¶

Name	Type	Description
AVAIL	float64	Histogram of available LST in the BRIGHT program.
INIT	float64	Histogram of initial LST usage, before optimization.
PLAN	float64	Histogram of planned LST usage, after optimization.

Histograms are normalized to the (dimensionless) units of sidereal hours per LST bin integrated over the survey.

HDU4¶

EXTNAME = DESIGN

Optimized design hour angles for each tile in all programs.

Required Header Keywords¶

KEY	Example Value	Type	Comment
NAXIS1	16071	int	length of dimension 1
NAXIS2	10	int	length of dimension 2

Required Data Table Columns¶

Name	Type	Units	Description
INIT	float64	deg	Initial hour angles before optimization.
HA	float64	deg	Final hour angles after optimization.
TEXP	float64	s	Irreducible exposure time due to dust extinction and airmass at the design hour angle.

Each row of the table corresponds to one tile with indexing that matches desisurvey.tiles.Tiles.

Use load_design_hourangle to read the HA column as a 1D array.

Notes and Examples¶

The histograms of available LST in each program are calculated by get_available_lst.

Hour angle optimization is performed by desisurvey.optimize.Optimizer and documented in DESI-3060.