LE3 Location Table

Metadata

Data product name	DpdSirLE3LocationTable
Data product custodian	SIR
Name of the Schema file	euc-sir-LE3LocationTable.xsd
Processing function using the data product	LE3

Proposed for inclusion in EAS/SAS

This product is proposed for inclusion in the SAS: yes.

Data product elements

Header	object of type sys:genericHeader
Data	object of type sir:le3LocationTable
QualityFlags	object of type dqc:sqfPlaceHolder
Parameters	object of type ppr:genericKeyValueParameters

Detailed description of the data product

This product is not used by SIR pipeline, it was requested by LE3 to locate spectra on the raw frames. More in detail it contains information to locate the central row of the 1^st order spectrograms on the 2D background subtracted frame (see Science Frame Product).

The SIR_Extract_Spectra pipeline produces 1 dpdL3LocationTable for each observed frame and saves it as a FITS Binary table.

The primary header contains keywords useful to link this product with its background subtracted frame and the combined spectra to analyze.

HDU PRIMARY: header
	Name	Description	Value
Keywords	FITS_DEF	FITS name definition	string = sir.le3LocationTable
	FITS_VER	FITS version	string = 0.2
	TELESCOP		string = EUCLID
	INSTRUME	or NISPsim for simulations	string = NISP
	VERSION	Data Release version	string
	DATE	UT date when this file was created	string
	ORIGIN	FITS file originator	string
	SOFTVERS	Version of the processing function pipeline	string
	DITHOBS	eso:observationSequence:DitherObservation Number sequence of dithering i.e. [1-4] for WIDE survey	integer
	PTGID	eso:observationSequence:PointingID Integer number defining exposure inside observation	integer
	GWA_POS	GWA position (RGS270,RGS000,RGS180,BGS000,OPEN)	string
	GWA_TILT	Commanded Grism Tilt Angle	integer
	FIELDID		integer
	PATCH_ID	Patch ID	integer
	OBS_ID	eso:observationSequence:ObservationId Running Sequence number of the Observed block	integer
	CALBLKID	Calibration Block ID	string
	CALBLKVR		string
	EXPNUM	eso:observationSequence:Exposure Internal integer counter for single images	integer
	TOTEXP	eso:observationSequence:TotalExposure Total number of Exposures in specific pointing	integer
	DATE-OBS	img:spaceObservationDateTime:OBT Date of observation (start), e.g. ‘2014-03-15T09:30:09.313’	string
	UTC-OBS	ObservationDateTime:UTC UTC time correlated to the on-board time by the Mission Operation Centre, e.g. 2014-03-15T09:30:09.313Z	string
	MJD-OBS	img:spaceObservationDateTime:MJD MJD start time, e.g. 56731.39594113	integer

Data are stored in the LOCTAB extension:

HDU LOCTAB: header
	Name	Description	Value
Keywords	EXTNAME		string

HDU LOCTAB: 11 columns table
	Name	Description	Unit	Format
Columns	OBJ_ID	MER-specified identifier of the m-th object, int 64	Number	FITS K
	PTGID	eso:observationSequence:PointingID Integer number defining exposure inside observation	Number	FITS K
	DET_ID	Detector ID of the current spectrum, uint 8	Number	FITS B
	X0	LAMBDA0 detector coordinate X, float 32	pixel	FITS E
	Y0	LAMBDA0 detector coordinate Y, float 32	pixel	FITS E
	LAMBDA0	Wavelenght value of the pixel (X0,Y0), float 32	pixel	FITS E
	X1	LAMBDA1 detector coordinate X, float 32	pixel	FITS E
	Y1	LAMBDA1 detector coordinate Y, float 32	pixel	FITS E
	LAMBDA1	Wavelenght value of the pixel (X1,Y1), float 32	pixel	FITS E
	APER	Object aperture size, int 16	pixel	FITS I
	APER_ANG	Virtual slit orientation (CW) wrt detector Y axis, float 32	Number	FITS E

The table contains one entry for each 1^st order spectrum located on a given detector, declaring:

• OBJ_ID: the MER object ID;

• PTGID: the pointing ID;

• DET_ID: the detector ID;

• [X0,Y0,LAMBDA0]: the starting pixel (x₀,y₀) of the spectrogram: the pixel where \(\lambda_0\ [\mathring{A}]\) is located (\(\lambda_0\) is the bluest lambda available for the current object);

• [X1,Y1,LAMBDA1]: the ending pixel (x₁,y₁) of the spectrogram: the pixel where \(\lambda_1\ [\mathring{A}]\) is located (\(\lambda_1\) is the reddest lambda available for the current object);

• APER: the aperture size [pixel], computed using the SEMIMAJOR_AXIS column of the MER catalog;

• APER_ANG: the aperture orientation angle [deg]. This is the angle of the object on the detector and it is derived combining the POSITION_ANGLE column of the MER catalog with the recomputed PA exposure angle value.

Fig. 42 : An example of spectrum (RGS180) fully contained in the detector 34. (\(\lambda_0 \equiv \lambda_S = 11900\) and \(\lambda_1 \equiv \lambda_E = 19000\) in this example).

If the spectrum is fully contained within a single detector, \(\lambda_0\) and \(\lambda_1\) are the extraction limits used by the SIR_Extract_Spectra pipeline: \(\lambda_S\) and \(\lambda_E\) (see Fig. 42).

Otherwise, these \(\lambda_{0,1}\) values, define the wavelength range spanned by the current object on this detector (\(\lambda_S\ \le \lambda_0\ \le \lambda_1\ \le \lambda_E\), see Fig. 43).

Fig. 43 : An example of spectrum (RGS180) not fully contained in the detector 44: the reddest part of the spectrum ends at 12082.956 \(\mathring{A}\) on the pixel (958.373, -0.5) (due to spectra curvature a part of the trace is out of the detector).

Fig. 44 : An example of spectrum (RGS180) which covers 2 adjacent detectors: 11 and 21.

Moreover, in case the spectrogram it spanned across two detectors, two entries will exists for a single objects (see Fig. 44).

NOTE: The SIR Pipeline counts pixels starting from 0 (like Python or C++) and the pixel reference point is the center of the pixel (like DS9 does). This means, SIR assumes the NISP detectors lower left corner is (-0.5,-0.5) and the upper right corner is (2039.5,2039.5).

For this reason in the figure Fig. 43 the Y₁ value is -0.5; while in the figure Fig. 44 the first part of the spectrum ends at X₁ = -0.5 and the second part starts at X₀ = 2039.5.

DataContainer file name description

The following XML keywords:

• Data.ObservationSequence.ObservationId (OBSID)

• Data.ObservationSequence.DitherObservation (DITH)

are combined to create the DataContainer file name:

EUC_SIR_W-LOCTAB_LE3_<OBSID>-<DITH>-NO_DET_<TIMESTAMP>.fits.gz

Here below and example:

EUC_SIR_W-LOCTAB_LE3_65879-0-NO_DET_20250410T104148.557157Z.fits.gz