NACO: calibration files and recipes
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NACO Calibration files and recipes

Contents:

• NC_DCAL Darks for all modes
• NC_ICTF Imaging Calibration Twilght Flats
• NC_ICSF Imaging Calibration Sky Flats
• NC_ICLF Imaging Calibration Lamp Flat
• NC_ICZP Imaging Calibration ZeroPoints
• NC_ICSR Imaging Calibration Strehl ratio

More information can be found in the NACO User Manual

Darks for all modes , NC_DCAL

TPL ID = NACO_all_cal_Darks,
DPR CATG = CALIB,
DPR TYPE = DARK,
DPR TECH = IMAGE,
DET MODE NAME = FowlerNSample (FS), DoubleRdRstRd (DR), Uncorr (UC)
DET NCORRS NAME = HighSensitivity (HS), HighBackground (HB), HighDynamic (HD), HighWellDepth (HW) (as of June 06, 2004)
WINDOW = F (full), W (windowed)

Since November 06, 2004 there has been an operational change and in addition to matching DIT, readout mode and detector mode, the darks are taken with the same camera (INS.OPTI7.NAME) as science observations.
INS.OPTI7.NAME = S13, S27, S54, L27, L54, SDI (as of November 06, 2004)

NC_DCAL_<YYMMDDV>_0_5_S27_F_DRHS.fits	NC_DCAL_<YYMMDDV>_300_L27_F_DRHD.fits
NC_DCAL_<YYMMDDV>_1_7927084_S27_F_FSHS.fits	NC_DCAL_<YYMMDDV>_1_S13_F_UCHD.fits

Purpose. Dark frames are measured to monitor the status of the array. They come in stacks of 3 raw frames. They are routinely measured every night when NACO is operational. They are all processed into master Dark frames of different discrete intergration times and read modes and quality-checked on the mountain and by QC Garching. They are not stable, hence all master NC_DCAL frames are stored in the calibration archive and individually delivered.

Recipe. The pipeline recipe naco_img_dark takes a stack of frames observed with the NACO_all_cal_Darks template, sorts the stack by means of different DITS, averages the three raw frames and determines the RON (read-out noise) of the full array. The output are master darks of several DIT and one single PAF . No median filter or median stacking is applied, hence no cosmetic correction concering hot pixels and cosmic events is applied: The recipe produces in addition a hot pixel map (all pixels above 5 sigma), a cold pixel map (all pixel above 3 sigma), and a deviant pixel map.

esorex naco_img_dark set_of_frames(sof)

QC checks. As part of the QC1 checks the following parameters are monitored: RON (read-out noise, more precisely: the statistical noise normalized to NDIT=1) for each of the four quadrants, median and mean of the whole product image. These values are accessible via the trending page. Other internal checks include the monitoring of the fixed pattern noise and the reset anomaly behaviour.

Products.

Note

The cold, hot and deviant pixel maps are produced but not used in further steps od the reduction cascade.

twilight flat, NC_ICTF

TPL ID = NACO_img_cal_TwFlats,
DPR CATG = CALIB,
DPR TYPE = SKY,FLAT,
DPR TECH = IMAGE

NC_ICTF_<YYMMDDV>_J_S13_VIS.fits	NC_ICTF_<YYMMDDV>_Ks_S27_VIS.fits
NC_ICTF_<YYMMDDV>_H_S27_VIS.fits	NC_ICTB_<YYMMDDV>_Ks_S13_VIS.fits
NC_ICTI_<YYMMDDV>_J_S54_VIS.fits	NC_ICTE_<YYMMDDV>_H_S27_VIS.fits

Purpose. The master twilight flats show the relative sensivity (the gain) of the array pixels. Twilight flats can be observed in two diffrent ways: a) a sequence of raw files all having the same filter, b) a sequence of files with four alternating filters.

The telescope is in 'STANDBY' modus and pointng to zenith during twflat observatons. Possible bright stars which are jittered out anyway appear in the errmap file as a wide trace.

Recipe. The naco cpl pipeline recipe naco_img_twflat is used. Since the exposure level is strongly increasing or decreasing during twilight, the raw frames can be used to derive the detector linearity and the gain map in one. twflat is able to sorting out the alternating filter sequence and handles each stack separately. The recipe fits a linear regression to each pixel. Isf a master dark frame is submitted twflat substitutes the 'a' in F=a+b *flux by the dark and the 'b' is stored as the flat frame. The errors are given in the errmap and would contain star trailes. The interception file contains the 'a' in case no dark frame is submitted to the recipe. The closest in time recorded dark frame is supplied with the same DET.DIT, DET.NCORRS.NAME, and DET.MODE.NAME as the raw twilight flat frames ans is included in the sof file:

esorex naco_img_twflat set_of_frames(sof)

Products.

sky flat, NC_ICTF

TPL ID = NACO_img_cal_SkyFlats,
DPR CATG = CALIB,
DPR TYPE = SKY,FLAT,
DPR TECH = IMAGE

NC_ICTF_<YYMMDDV>_Lprime_L27_VIS.fits	NC_ICTF_<YYMMDDV>_NB374_L27_VIS.fits
NC_ICTE_<YYMMDDV>_NB405_L54_VIS.fits	NC_ICTI_<YYMMDDV>_NB405_L54_VIS.fits

Purpose. The master skyflats show the relative sensivity (the gain) of the array pixels.

The Differences between TwFlats and SkyFlats are :

• twflats are used for filters with centeral wavelength bel,ow 3 micron, while skyflats are used for filters with centeral wavelength above 3 microns
• the twilight flat observation sequence uses the sky brightness change with time during dusk or dawn, the sky flats use the sky brightness gradient over the hemisphere to gain the highest possible flux range.
• the twilight flat sequence points to the zenith; altitude and azimuth does not change but RA and DEC, the filter filters change like ABCDABCDABCDABCD. The skyflat takes ~5 jittered images with filter A at low airmass (X=1.01) and then ~5 jittered images of filter B at the same airmass. This sequence isd repeats at airmass X~2 and X~2.38.
• As a consequence twflats have usually 10-20 raw frames in a stack per filter, with continuously increasing or decreaesing flux; while skyflats have usuaully 10-15 raw frames in a stack per filter, with mostly three diffrent flux values corresponding to three different airmasses.

The telescope is in 'STANDBY' modus and pointng to zenith during twflat observatons. Possible bright stars which are jittered out anyway appear in the errmap file as a wide trace.

Recipe. The same pipeline recipe as in case of twilight flats, naco_img_twflat is used. Since the exposure level is strongly increasing or decreasing during twilight, the raw frames can be used to derive the detector linearity and the gain map in one. twflat is able to sorting out the alternating filter sequence and handles each stack separately. The recipe naco_img_twflat fits a linear regression to aech pixel. Since we subm,it a master dark frame, twflat substitutes the 'a' in F=a+b *flux by the dark and the 'b' is stored as the flat frame. The errors are given in the errmap and would contain star trailes. The interception file conatins the 'a' in case no dark frame is submitted to the recipe. The closest in time recorded dark frame is supplied with the same DET.DIT, DET.NCORRS.NAME, and DET.MODE.NAME as the raw twilight flat frames:

esorex naco_img_twflat set_of_frames(sof)

Products.

lamp flat, NC_ICLF

TPL ID = NACO_img_cal_LampFlats,
DPR CATG = CALIB,
DPR TYPE = LAMP,FLAT,
DPR TECH = IMAGE

NC_ICLF_<YYMMDDV>_Ks_S13.fits	NC_ICLF_<YYMMDDV>_NB212_S27.fits

Purpose. The master lamp flats show the relative sensivity (the gain) of the array pixels. They become important when the science imaging used a diffrent read out mode than the twilight flats (their read out modes are fixed). The lamp flat template generates three LAMP=ON and three LAMP=OFF frames in an alternating order.

Recipe. The naco pipeline recipe esorex naco_img_lampflat uses the OFF frames as darks; they are subtracted from the ON frames. The recipe detremines the gain, the fixed pattern noise and the lamp flux for quality control reasons.

esorex naco_img_lampflat set_of_frames(sof)

Products.

Photometric Zeropoints, NC_ICZP
relevant FITS keys are:

TPL ID = NACO_img_cal_StandardStar
DPR CATG = CALIB, DPR TYPE = STD, DPR TECH = IMAGE

	Combination of 5 raw frames (two of them are subtracted to get rid of the background) to demonstrate where the photometric standard star occurs in the individual frames.
	Product frame of the zpoint recipe showing 8 difference images produced with 5 raw input frames.

Purpose. Photometric standard stars are observed in four filters: J, H, Ks, and L_prime whenever possible, preferably in clear and photometric nights at low airmasses.

This kind of exposure provides a fundamental parameter: the total sensitivity of the telescope and the instrument.

Recipe. The naco_img_zpoint recipe reads a stack of jittered standard star images. The frames are subtracted from each other, which makes dark correction unnecessary, and each difference frame is evaluated individually. The subtraction pattern is: #1-#2, #2-#1, #2-#3, #3-#2, #3-#4, #4-3, #4-#5, #5-#4. In current calibration scheme no flatfield correction is applied. The recipe provides the median instrumental magnitude (not corrected for extiction and color-terms) that is also written in the PAF. In addition the Strehl ratio is measured.

esorex naco_img_zpont set_of_frames

Products.

Strehl ratio, NC_ICSR

relevant FITS keys are:

TPL ID = NACO_img_acq_MoveToPixel
DPR CATG = TEST, DPR TYPE = PSF-CALIBRATOR, DPR TECH = IMAGE or SPECTRUM

Purpose. Seeing as an observation constraint is available before launching an observation block, Strehl ratio not, hence two Strehl ratio frames are taken before the start of any science OB to check the requested Strehl ratio against the specified.

Recipe. The esorex naco_img_strehl recipe reads two raw frames with DPR.TYPE=PSF-CALIBRATOR, determines the Strehl ratio from the diffrence and writes the results in the fits and in the PAF (VLT compliant parameter ascii file).

esorex naco_img_strehl set_of_frames(sof)

Products.

Send comments to <Danuta.Dobrzycka@eso.org>  Last update: August 07, 2006