CALBLOCK-REC-002: VIS Flat Nonlinearity

Observation configuration file

ocf_REC-002.csv

Scheduling

Execute once after a full decontamination, after thermal stability of the VI-CU and VI-FPA have been reached (<0.1 K/h).

Time-critical

No.

Dependencies

VI-CU commissioned

Objective

Radiation damage may slightly alter voltages in the VIS electronics, changing the VIS nonlinearity as well as the PSF model. The VIS nonlinearity must be monitored continuously.

This CalBlock obtains the nonlinearity estimate from flat fields, complementing CALBLOCK-PV-024: VIS On-sky Nonlinearity.

Observations

Parallel schedule: CALBLOCK-PV-010: NISP LED flats as necessary; this CalBlock is driven by VIS.

Accurate Bias subtraction is essential for the low fluence settings. The intermediate flats with 2000 ms duration are for the control of any LED drifts.

With windowed flats, the 120 lines of overscan provide added value for CTI as well as a possible CTI correction to the measured signal. The first 1086 lines are flushed with a TOI=143\(\,\mu{\rm s}\), the rest of the image is read out normally. The trail (if any) can be compared with the nominal EPER trail.

For offset construction, the parallel overscan of the serial overscan should be used at higher signal levels. Therefore, increasing the parallel overscan may also be useful.

The Short Science (SS) frames are necessary to remove astronomical objects from the FLAT images. They will be scaled to match the FLAT exposure time.

Observation instructions 57: VIS flat field nonlinearity sequence, with interspersed exposures of 2000ms integration time to control LED drifts. SS refers to a short science exposure. Times are in milliseconds.
BIAS settings:
   in full frame (at the top of the sequence)
   in windowed mode,  VSTART=1086 (0x043E), VEND=2186 (0x088A) (the latter includes 120 overscan lines)

Flat setting:
   LED3 with 3 mA
   Use windowed mode, VSTART=1086 (0x043E), VEND=2186 (0x088A) (the latter includes 120 overscan lines)
   EXPTIME should be 500ms up to 200ms LED_DELAY, otherwise add 500~2500s to LED_DELAY for EXPTIME

SS setting:
   Use windowed mode, VSTART=1086 (0x043E), VEND=2186 (0x088A) (the latter includes 120 overscan lines)
   EXPTIME should match what is used in the FLAT (there should be two different EXPTIMEs per dither)

Full-frame BIAS
in windowed mode:  BIAS, SS, 2000, 1, 2, 3, 4, SS, dither
in windowed mode:  BIAS, SS, 2000, 5, 6, 7, 10, SS, dither
in windowed mode:  BIAS, SS, 2000, 20, 32, 40, 50, SS, dither
in windowed mode:  BIAS, SS, 2000, 100, 200, 300, 400, SS, dither
in windowed mode:  BIAS, SS, 2000, 500, 750, 1000, 1500, SS, dither
in windowed mode:  BIAS, SS, 2000, 3000, 3750, 5000, SS, dither
in windowed mode:  BIAS, SS, 2000, 6000, 6500, 7000, SS, dither
in windowed mode:  BIAS, SS, 2000, 8000, 2000, SS, BIAS, dither

Full-frame BIAS
in windowed mode:  BIAS, SS, 2000, 1, 2, 3, 4, SS, dither
in windowed mode:  BIAS, SS, 2000, 5, 8, 9, 12, SS, dither
in windowed mode:  BIAS, SS, 2000, 16, 24, 28, 32, SS, dither
in windowed mode:  BIAS, SS, 2000, 64, 86, 128, 150, SS, dither
in windowed mode:  BIAS, SS, 2000, 400, 600, 750, 1000, SS, dither
in windowed mode:  BIAS, SS, 2000, 1250, 2500, 3500, SS, dither
in windowed mode:  BIAS, SS, 2000, 4000, 4500, 5500, SS, dither
in windowed mode:  BIAS, SS, 2000, 7500, 8500, 2000, SS, BIAS, dither

Note: The NL calibration at low fluence can be refined if the same sequences can be run at a different LED current (via better understanding of the exact LED actuation duration). Such a variant sequence is defined in a separate CALBLOCK (TBW) to be run after PV, if necessary.

Fulfilling

CALPRODUCT-VS-016: VIS Nonlinearity

Targets and pointing constraints

Pointing: Straylight suppression as per MOCDA-SYS-003.

Table 71: SELFCAL-FAINT CSV file

# ID

R.A.

Dec

SELFCAL-FAINT

268.51

65.09

Instrument configuration

Instrument: VI-CU LED3 on

Inter-operability constraints

NISP mechanisms must not move while VIS observes on sky.

In-orbit duration

In-orbit Duration: 6.4 h + dither (x16)

Note that 66s of CDPU processing time has been absorbed into each dither/slew.

Data volume

Total = 31786 MB

VB = 2*250 MB = 500MB for the full-frame Bias
18*VB(117MB) + 32*VS(240MB) = 9786 MB for the Bias and SS (windowed)
27*VF (200 MB) = 5400 MB for 27 flats below 0.6 kADU
14*VF (300 MB) = 4200 MB for 14 flats below 6 kADU
18*VF (350 MB) = 6300 MB for 18 flats with 13 kADU (2000 ms interspersed images)
14*VF (400 MB) = 5600 MB for 14 flats higher than 30 kADU

Processing input

Ground Processing Input Data: None

Data Description: 2 full-frame Biases (LE1), 18 windowed Biases (LE1), 32 windowed SS (LE1+CR removal), 73 windowed flats (LE1)

Processing tools

Cosmic ray removal of the SS images.

Quality control parameters

DataModel: https://gitlab.euclid-sgs.uk/

Contact person

VIS instrument scientist