CALBLOCK-F-011: NISP Reciprocity Failure

Observation configuration file

ocf_CALBLOCK-F-011_PHOTO-H.csv

Scheduling

Yearly, beginning one year into the survey.

In case of failure of the first execution 1 year into the survey, repeat at next possible opportunity because we do not know then the long-term stability. Either include in generic survey replanning, or compute a new survey specifically for this.

In case of failure of the second or later executions years into the survey: in case the effect appears stable, just include the calibration in the next survey replanning. If that replanning is getting close to the next planned execution anyway, then it can be skipped. In case the effect is unstable, it must be replanned.

Objective

Validate the reciprocity failure (flux-dependent nonlinearity, charge trapping) for each detector. Trapping and detrapping effects are poorly understood, impact photometric measurements, and exhibit strong spatial variations across detectors. This validation is a spot check to see whether anything has changed since the more extensive ground characterization, and to obtain similar measurements with real targets under in-flight conditions.

Trapping/detrapping is likely wavelength independent (verified during PV phase). In flight, only one LED will be tested, unless the test during PV phase shows differently.

Observations

To test the functional behaviour of reciprocity failure or trap filling on photometry, the same sources are observed with and without additional background light. The expectation is that additional background signal passivates the traps more quickly, and hence more source photons are detectable.

Repeat the S-dither pattern at the Self-cal field 18 times, with small (arcminute-scale) random offsets between the repeats. The 1st, 3rd, 5th, etc executions are done without any additional background light from the NI-CU LEDs. Typical total background levels (zodi, in-field and out-field straylight) in a photo-MACC exposure are on the order of about 160 e-/pixel in J-band (15-20% lower in Y and H).

For the 2nd, 4th, 6th etc repetition, LED ‘D’ is turned on with increasing fluxes of 2, 4, 8, … , 512 e-/s/pixel, providing additional background signal between 220-56,000 e-/pixel.

It is not necessary that the stars fall exactly into the same pixels for both sets of exposures, without and with LED illumination. We cannot calibrate all pixels anyway with stellar observations, and AOCS jitter would modify the pixel counts. It is sufficient to infer the general behaviour for each detector, using a sufficiently large number of stars per detector.

Observation instructions 14: Observing instructions for NISP reciprocity failure
filter = "H"
LED = "D"

for flux_i in [2, 4, 8, ... , 512] e-/s:

        Repeat 8x: (persistence decay, measurement without LED)
            "1 NISP photo-MACC exposure"
            "Random dither offset in a 3' box"

        Repeat 4x:
            "Turn on LED with flux_i"
            "1 NISP photo-MACC exposure"
            "Turn off LED"
            "Random dither offset in a 3' box"
Table 32: NISP LED flux lookup table. Numbers in parentheses were not verified on ground, but are reasonably close to be extrapolated. Missing data values indicate negative PWM values when using linear extrapolation. CSV file

# Flux [e-/s]

Flux [ADU/frame]

Int-A [mA]

PWM-A [%]

Int-B [mA]

PWM-B [%]

Int-C [mA]

PWM-C [%]

Int-D [mA]

PWM-D [%]

Int-E [mA]

PWM-E [%]

#

LED A

LED A

LED B

LED B

LED C

LED C

LED D

LED D

LED E

LED E

2

1.45

1.0

21.4

1.0

8.6

4

2.91

1.0

5.0

1.0

26.1

1.0

11.4

8

5.82

1.0

8.2

1.0

11.9

1.0

5.4

1.0

35.4

1.0

17.0

16

11.6

1.0

18.8

1.0

29.2

5.0

6.3

5.0

7.2

1.0

28.2

32

23.3

1.0

39.8

5.0

17.1

5.0

11.6

5.0

9.9

5.0

8.9

64

46.6

5.0

21.9

5.0

30.6

5.0

22.2

5.0

15.4

5.0

14.4

128

93.2

5.0

41.8

10.0

30.2

5.0

43.3

5.0

26.3

5.0

25.5

256

186.3

10.0

43.9

30.0

19.8

10.0

45.4

5.0

48.2

10.0

21.8

512

372.7

30.0

30.0

30.0

39.4

30.0

30.5

10.0

32.0

30.0

11.6

Fulfilling

CALPRODUCT-NI-013: NISP Reciprocity Failure

Targets and pointing constraints

Pointing: No angle constraints

Table 33: Self-cal center. CSV file

# ID

R.A.

Dec

SELFCAL-CENTER

268.812745

65.2855857

Instrument configuration

Instrument: NI-CU on, NI-GWA open, VS-CU off

Inter-operability constraints

None

In-orbit duration

In-orbit Duration: 5.3 h

Assuming 70 s for each dither offset, plus 20 s (estimate) for NI-CU turn-on/off. 9 sequences with and without LED, 4 dithers, 1 filter only

((111+70)s * 8 + (111+20+70)s * 4) * 9 = 5.3 h

Data volume

108*NP = 9558 MB

Processing input

Ground Processing Input Data: All calibration products to run the standard science pipeline (BPM, darks, flat, nonlinearity etc), reference measurement of standard star, RSR curves (relative spectral response of the system (mirrors, optics, instrument)

Data Description: NISP: 108 photo-MACC images

Processing output

Percentage or decade of flux reciprocity failure, if present. Comparison with a model prediction from ground characterization data. A warning must be triggered if the reciprocity failure deviates more than TBD % from the prediction.

Required accuracy, constraints

Flux level of sources can be measured, not affected by saturation, flux measurement comparison with and without extra background illumination

Processing tools

L1 science pipeline and absolute calibration pipeline, additional offline trend analysis of flux measurements

Quality control parameters

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

Contact person

NISP-P calibration scientist