CALBLOCK-PV-022: VIS PRNU and Brighter-fatter Effect

Observation configuration file

ocf_CALBLOCK-PV-022_BF-40000ADU.csv
ocf_CALBLOCK-PV-022_LOW1-1000ADU.csv
ocf_CALBLOCK-PV-022_LOW2-5000ADU.csv
ocf_CALBLOCK-PV-022_PRNU1-25000ADU.csv
ocf_CALBLOCK-PV-022_PRNU2-10000ADU.csv

Scheduling

Once, during PV phase. LEDs 5+6 can be split off and scheduled at a later time, at the end or shortly after PV.

In case of failure, repeat at next possible opportunity.

Time-critical

No

Dependencies

VS-CU commissioned

Objective

Obtain near-monochromatic flat fields using the 6 LEDs in VS-CU. They form the basis to correct the small-scale features and pixel response non-uniformity (PRNU) (CALPRODUCT-VS-014: VIS LED Pixel Response Non-uniformity (PRNU)), and the brighter-fatter effect (CALPRODUCT-VS-004: VIS Brighter-fatter Effect (BFE)).

LEDs 5 and 6 are not used during normal observations in routine phase. Hence they can be taken after PV, at a suitable time. The pseudo-code below is refactored accordingly.

Observations

  • PRNU: Obtain pairwise flats with dithers between pairs, at fluences 10 (16 pairs), 25 (7 pairs), and 40 (5 pairs) kADU. Like this, a S/N of about 1000 per pixel per fluence is achieved, assuming a gain of 3.48 e-/ADU, and allowing for 10% variation in gain and flatfield illumination. The total S/N should be up to 1700 before masking cosmic rays and bright sources.

  • BFE: Obtain pairwise flat fields with dithers in between, with fluence 1, 5 and 10 kADU, and LED1 to LED4. Direct observations of a stellar field (Self-cal) are also required, because the effect in flat fields is increased by space charges.

To neutralize AOCS wait times, and to accommodate antenna repointing, the following strategy provides flat field images for both PRNU and BFE calibration.

The spacecraft must not dither or slew during VIS flat field exposures.

A science exposure is required for each dither to enable object masking, and sky-background correction.

Observation instructions 35: Flat-field pairs for PRNU and BFE calibration, part #1 (LEDs 1-4). The integration time of the short science (SS) exposure is defined by the ROS (total of 95 s, including the 5.48 s for the shutter movements). Dithers are random in a 3’ box.
BIAS
Repeat 10x:
   2 flats LED_1 with fluence 1 kADU
   2 flats LED_2 with fluence 1 kADU
   SS, dither
   2 flats LED_3 with fluence 1 kADU
   2 flats LED_4 with fluence 1 kADU
   SS, dither

BIAS
Repeat 10x:
   2 flats LED_1 with fluence 5 kADU
   2 flats LED_2 with fluence 5 kADU
   SS, dither
   2 flats LED_3 with fluence 5 kADU
   2 flats LED_4 with fluence 5 kADU
   SS, dither

BIAS
Repeat 16x:
   2 flats LED_1 with fluence 10 kADU
   2 flats LED_2 with fluence 10 kADU
   SS, dither
   2 flats LED_3 with fluence 10 kADU
   2 flats LED_4 with fluence 10 kADU
   SS, dither

BIAS
Repeat 7x:
   2 flats LED_1 with fluence 25 kADU
   2 flats LED_2 with fluence 25 kADU
   SS, dither
   2 flats LED_3 with fluence 25 kADU
   2 flats LED_4 with fluence 25 kADU
   SS, dither

BIAS
Repeat 5x:
   2 flats LED_1 with fluence 40 kADU
   2 flats LED_2 with fluence 40 kADU
   SS, dither
   2 flats LED_3 with fluence 40 kADU
   2 flats LED_4 with fluence 40 kADU
   SS, dither
Observation instructions 36: Flat-field pairs for PRNU and BFE calibration, part #2 (LEDs 5+6).
BIAS
Repeat 16x:
   2 flats LED_5 with fluence 10 kADU
   2 flats LED_6 with fluence 10 kADU
   SS, dither

BIAS
Repeat 7x:
   2 flats LED_5 with fluence 25 kADU
   2 flats LED_6 with fluence 25 kADU
   SS, dither
Repeat 5x:
   2 flats LED_5 with fluence 40 kADU
   2 flats LED_6 with fluence 40 kADU
   SS, dither

Fulfilling

CALPRODUCT-VS-014: VIS LED Pixel Response Non-uniformity (PRNU)

CALPRODUCT-VS-004: VIS Brighter-fatter Effect (BFE)

CALPRODUCT-VS-011: VIS Photon Transfer Curve (PTC)

CALPRODUCT-VS-018: VIS Extended Pixel Edge Response (CTI-EPER)

CALPRODUCT-VS-007: VIS Cosmetic Map

Targets and pointing constraints

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

Table 59: SELFCAL-FAINT CSV file

# ID

R.A.

Dec

SELFCAL-FAINT

268.51

65.09

Instrument configuration

Instrument: VS-CU on

Inter-operability constraints

None.

In-orbit duration

In-orbit Duration:

  • 51.2 h + dither(x96) [LED1234]

  • 15.6 h + dither(x28) [LED56]

Note that 66s of the CDPU processing time can be accommodated into the dither/slew duration.

1k ADU, 4 LEDs: 9.8 h + dither (x20) (CDPU processing buffer time for 1k ADU Flats: 295s)

5k ADU, 4 LEDs: 10.3 h + dither (x20) (CDPU processing buffer time for 5k ADU Flats: 320s)

10k ADU, 4 LEDs: 17.2 h + dither (x32) (CDPU processing buffer time for 10k ADU Flats: 340s)

25k ADU, 4 LEDs: 8.0 h + dither (x14) (CDPU processing buffer time for 25k ADU Flats: 370s)

40k ADU, 4 LEDs: 5.9 h + dither (x10) (CDPU processing buffer time for 40k ADU Flats: 380s)

10k, 25k, 40k ADU, 2 LEDs: 15.6 h + dither (x28)

2x(10+10+16+7+5) + 1x(16+7+5) = (96 + 28) = 124 dither slews: 124*66s = 2.3 h

Data volume

Total = 418,170 MB

124*VS + 5*VB = 57,050 MB

80*VF = 45,600 MB (VF=570 MB)

80*VF = 54,400 MB (VF=680 MB)

192*VF = 142,080 MB (VF=740 MB)

84*VF = 68,040 MB (VF=810 MB)

60*VF = 51,000 MB (VF=850 MB)

Processing input

Ground Processing Input Data: BPM, nonlinearity calibration correction, ground-based QE

Data Description: Total: 496 flats, 124 SS, 5 biases

Processing output

Normalized combined flat fields for each LED, trend analysis

Required accuracy, constraints

Expected flux levels within TBD%, stable within TBD%, spatial irradiance as expected (within requirement, ground-based measurements)

Processing tools

Pipeline: VIS_MasterFlat_Pipeline

PEs: VIS_BiasCorrection, VIS_PRNUCalibration

Quality control parameters

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

Contact person

VIS instrument scientist