QC PLOTS
	CURRENT	HISTORY
dark level
readout noise
hot pixel
QC1 database (advanced users): browse | plot
Click on CURRENT to see the current trending (Health Check).    Click on HISTORY to see the historical evolution of the trending.

The IRDIS NIR detector is operated in cube mode and in nondestructive readmode (DET.READ.CURNAME=Nondest). All NDIT sub integrations are resolved and are stored in a cube frame with NDIT (~10), NAXIS=3 and NAXIS3=NDIT, meaning a cube frame with NDIT planes of with 2048x1024 pixel. Detector characteristics are monitored via three raw types: DARK, BACKGROUND and GAIN calibrations. DARK frames and GAIN calibrations are used to monitor the health of the detector, while BACKGROUND calibrations are used in the cascade to calibrate science data

IRDIS raw dark frame with DIT=30 sec, averaged over NDIT=15 sub integrations.

IRDIS dark frames are taken in regular intervals for the following setups

• DIT=2sec, NDIT=40
• DIT=8sec, NDIT=25
• DIT=30sec, NDIT=15

In addition dark frames are also acquired with the DIT and NDIT of the science observations.

The darks come as a single frame with one cube (NAXIS=3).

QC1 parameters

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.

Trending

Dark level and number of hot pixel is monitored for the three mentioned acquired health check setups.

History

From 2017-12-01 on the RON is based on the v0.28 version pipeline recipe. Values are about 1% lower with respect to the pre 2017-12 values obtained froma QC script.

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 frames come as a single frame with one cube (NAXIS=3).

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

 

IRDIS background calibration frames are acquired with the same DIT and and NDIT as the dark frames, but with INS1.OPT1.NAME=OPEN. 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

Trending

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:

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