Quality Control and
Data Processing

HC PLOTS
background rate for DBI mode
background rate for DPI mode
background rate for LSS mode
QC1 database (advanced users): browse | plot

Dark frames are taken with INS1.OPTI1.NAME=CLOSED to measure the detector dark current, while IRDIS background calibration frames are acquired with INS1.OPT1.NAME=OPEN to measure the instrumental background.

The background is dependent on the set of used filters:

CPI neutral density filter (IN4.FILT2.NAME = OPEN, or ND_2.0, or ...)
IRDIS broad band filter (INS1.FILT.NAME = B_H or B_Y or ...)
IRDIS dual beam filter (INS1.OPTI2.NAME = CLEAR or D_H12 or ...)

QC1_parameters

FITS key	QC1 database: table, name	definition	class*	HC_plot**	more docu
QC.MEDIANMASTER	sphere_irdis_background..qc_med	product background median	HC		[docuSys coming]
[QC procedure]	sphere_irdis_background..qc_backrate	rate in ADU/sec	HC		[docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter **There might be more than one.

IRDIS raw background frame with DIT=30 sec, averaged over NDIT=15 sub integrations for the D_K12 dual beam filter. Image cuts -5 and 1000 ADU.

Trending

The trending plot shows background rate values for DBI mode only:

• (1) negligible background in the H-band (no ND filter)
• (2) stable background for the K-band
• (3) no background for H-band plus neutral density filters
• (4) K-band background correlates with the temperature of the neutral density filters. Both temperature values (red and green little dots) are given in [C] and have been scaled via: T(in the plot) = 1.452 T - 1.409 to fit the background rate values given in [ADU/sec].

The background rate (in ADU/sec) is monitored for the DBI modes only (INS1.OPTI2.NAME != CLEAR).

As can be seen on the health check plot , the background in the H-band is stable with about 0.13 ADU/sec (upper left box) and shows a larger scatter for the K-band at 17 ADU/sec (upper right box).

The lower right box shows the K-band background when there is a neutral density filter in the CPI (large back and blue symbols). In this configuration the measured background follows the temperature of the neutral density filter. The black, blue and green symbols show the mesred background rate, while the red small symbols show the scaled temperature sensor value and demonstrates the correlation. The following scaling is used for the temperature sensor INS4.TEMP449.VAL located in the common path interface: i

T(in the plot) = 1.452 * T - 1.409

The background rate is monitored for the less frequently used modes DPI and LSS, but not for CI mode.

Scoring&thresholds IRDIS background rate

The background rates are scored for the DBI mode H and K bands without neutral density filter.

History

The background is stable within the known temperature fluctuations since begin of operations.

Algorithm IRDIS background rate

The pipeline returns the median level of the raw frame cube. The QC script divides this value by DIT.