Sir Raw Frame Product¶
Data product name¶
SirRawFrame
Data product custodian¶
LE1
Data model tag¶
R-1.6.7
Name of the Schema file¶
euc-test-le1-SirRawFrame.xsd
Schema documentation tag¶
A NISP-S raw exposure, both for calibration and scientific exposures
Data product elements¶
Header of type: sys:genericHeader
Data of type: le1nisp:sirRawFrame
Parameters of type: ppr:genericKeyValueParameters
Processing Element(s) creating/using the data product¶
LE1 NISP Processor
Processing function using the data product¶
SIR Processing Function (pre-processing is in common with the NIR processing function)
Detailed description of the data product¶
Analogously to the Nir Raw Frame Product, each calibration and scientific exposure is provided as one multi-extension FITS (MEF) file. In particular, a NISP-S exposure file contains two extensions per detector: one extension for the detector scientific data, and one extension for the detector Chi2 data. The total number of the extensions in the files is hence 32.
For the detectors numbering and location on the NISP Detector System Assembly see Nir Raw Frame Product.
Data encoding¶
For each detector:
pixels in the scientific extension are in units of ADU, 16-bit unsigned integer.
- pixels in the Chi2 extension provide the linear Weighted Least Square Fit computed, on-board, on the signal derivatives, and stored as an 8-bit value. The Chi2 is computed using the following formula, valid for equi-sparsed readouts (ref. NISP Data Processing Definition and Justification File, EUCL-OPD-RP-7-003):\chi^2 = \frac{1}{1+\alpha}\lfloor2\times(M-1)\times a - 2\times(S_M - S_1)-2\times(M-1)\times\beta)\rfloorWhere:M = number of MACC groupsN = number of samples per groupD = number of discarded readouts between groupsS_i = signal value at point i\sigma^2_r = read noise in e^-\gamma = \frac{2\times\sigma_r^2}{N}\alpha = \frac{1 - N^2}{3\times N\times(N+D)}\beta = \frac{\gamma}{\alpha+1}a = \sqrt{\frac{\sum_{i=2}^{M}(S_i - S_{i-1} + \beta)^2}{M-1}}
Header content¶
The required keywords are specified below (with an example of value when possible):
Primary header
TELESCOP |
= EUCLID |
/ |
Also ground telescopes from EXT |
INSTRUME |
= NISP |
/ |
Other values: VIS |
SURVMOD |
= WIDE |
/ |
Survey mode: Wide, Deep |
OBSTYPE |
= SPECTROSCOPIC |
/ |
Observation type - IMAGING or SPECTROSCOPIC |
OBSMODE |
= MULTIACCUM |
/ |
Observation mode: e.g. MULTIACCUM |
DATE-OBS |
= 2025-06-22 18:56:13.000Z |
/ |
Date of observation (start) |
MJD-OBS |
= 9304.78981695 |
/ |
MJD start EXPTIME |
EXPTIME |
= 552.7199999999999 |
/ |
Total integration time in seconds |
RA |
= 8.819091727789999 |
/ |
Center of field of view right ascension (deg) |
DEC |
= -19.474857937 |
/ |
Center of field of view right declination (deg) |
PA |
= -24.9556027707 |
/ |
Position angle (deg) |
EQUINOX |
= 2000.0 |
/ |
Standard FK5 (years) |
RADECSYS |
= FK5 |
/ |
Coordinate reference frame |
OBSID |
= 52926 |
/ |
Observation ID |
DITHSEQ |
= 1 |
/ |
Number sequence of dithering |
EXPNO |
= 1 |
/ |
Exposure sequence ID |
FILTER |
= OPEN |
/ |
Filter wheel position |
GRISM |
= RED0 |
/ |
Grism wheel Position |
Extension headers
For each NISP detector, two extensions will be provided: a science “layer”, containing the pixel data, and a data quality layer that, for the photometric data, will just contain 1 bit of information per pixel, reporting the cosmic-ray hits detected on-board.
The science layer will include the following header keywords
EXTNAME |
= DET11.SCI |
/ |
Detector ID and SCI data |
DET_ID |
= 11 |
/ |
Detector ID |
CRVAL1 |
/ |
Right ascension at ref pixel |
|
CRVAL2 |
/ |
Declination at ref pixel |
|
CRPIX1 |
/ |
Reference pixel x coordinate |
|
CRPIX2 |
/ |
Reference pixel y coordinate |
|
CDELT1 |
/ |
Incremnt of x coordinate |
|
CDELT2 |
/ |
Incremnt of y coordinate |
|
CTYPE1 |
/ |
Coordinamte 1 type |
|
CTYPE2 |
/ |
Coordinamte 2 type |
|
CD1_1 |
/ |
Translation matrix element |
|
CD1_2 |
/ |
Translation matrix element |
|
CD2_1 |
/ |
Translation matrix element |
|
CD2_2 |
/ |
Translation matrix element |
|
DATAUNIT |
= ADU |
/ |
Pixel data unit |
GAIN |
= 1.5 |
/ |
e- to ADU conversion factor |
BIASLEV |
/ |
Bias level in ADU |
|
SATURATE |
= 64000 |
/ |
Pixels are saturated if counts >= 64000 ADU |
The WCS keywords information is just a baseline set of coefficients estimated during ground tests. They are needed by the SIR Spectra Location astrometric modeling in order to refine and compute the correct astrometric solution.
No specific keywords are espected in the data quality layer.
EXTNAME |
= DET11.DQ |
/ |
Detector ID and quality layer (Chi2) |
DET_ID |
= 11 |
/ |
Detector ID |