CALBLOCK-F-009: NISP spectro nonlinearity¶
Observation configuration file¶
Scheduling¶
There are two variants realising different LED fluences. They must be alternated. Both variants must be observed once per year, followed by the validation block. The variants can be scheduled back-to-back or independent of each other. In case of back-to-back scheduling, for example during a low-stress period, a single validation block is sufficient.
The validation block must be taken before the nonlinearity ramps to make sure there are no effects from persistence decay.
In case of failure, repeat as soon as possible (requiring survey replanning due to the very low cadence).
Time-critical¶
The validation observations should be taken before the nonlinearity ramps, to avoid any small residual effects from charge persistence.
Dependencies¶
NI-CU commissioned.
Objective¶
Determine the nonlinearity correction for the spectro MACC(15,16,11) mode. On ground we have tested five different flux levels of 16, 30, 70, 110, 150 e-/s, obtaining spectro-MACC ramps and saving each of the 15 group images. In flight we found that more fluences are required to better sample the dynamic range. The nonlinearity for the photo-MACC(4,16,4) mode is obtained through CALBLOCK-F-008: VIS PSF Calibration and NISP photo nonlinearity.
The nonlinearity model is validated by a separate visit to the self-cal field, obtaining images with two different exposure times.
Observations¶
1. Nonlinearity validation:
To validate the nonlinearity model (and CALPRODUCT-NI-003: NISP Brighter-fatter Effect), we obtain images in all filters of the Self-cal field, with the photo-MACC(4,16,4) and non-standard photo-MACC(15,16,11) ramps. We use different filters to probe for any residual sampling effects.
Slew to Self-cal field
for filter in [Y,J,H]:
Repeat 4x:
Random dither offset in a 3' box
Take 1 photo-MACC(4,16,4) image
Random dither offset in a 3' box
Take 1 photo-MACC(15,16,11) image
2. Nonlinearity measurement for MACC(15,16,11):
Observations must be done in engineering RAW mode, taking two detectors at a time (one per DPU). This gives us access to the individual group images. All detectors must finish a given fluence setting before moving on to the next higher fluence. We use LED “C”, which is the most stable and was also used on ground. A LED flux stabilization period is not required, as the LED stabilization time is much shorter than the detector burn-in time, and the first ramp is not used for the analysis. Two varinats are defined to obtain all required fluxes.
Put NISP in "engineering RAW" mode
Turn on LED "C"
for detector in [1,...,16] (two at a time):
if (fluence == 8 e-/s): 30 MACC(15,16,11) ramps
if (fluence == 16 e-/s): 30 MACC(15,16,11) ramps
if (fluence == 30 e-/s): 25 MACC(15,16,11) ramps
if (fluence == 70 e-/s): 25 MACC(15,16,11) ramps
if (fluence == 150 e-/s): 15 MACC(15,16,11) ramps
Turn off LED "C"
Put NISP in observation mode
Take 30 MACC(15,16,11) darks for persistence decay
Put NISP in "engineering RAW" mode
Turn on LED "C"
for detector in [1,...,16] (two at a time):
if (fluence == 12 e-/s): 30 MACC(15,16,11) ramps
if (fluence == 20 e-/s): 30 MACC(15,16,11) ramps
if (fluence == 50 e-/s): 25 MACC(15,16,11) ramps
if (fluence == 110 e-/s): 25 MACC(15,16,11) ramps
if (fluence == 175 e-/s): 15 MACC(15,16,11) ramps
Turn off LED "C"
Put NISP in observation mode
Take 30 MACC(15,16,11) darks for persistence decay
Fulfilling¶
Targets and pointing constraints¶
Pointing: No angle constraints
The nonlinearity validation requires on-sky observations.
# ID |
R.A. |
Dec |
SELFCAL-CENTER |
268.812745 |
65.2855857 |
Instrument configuration¶
Engineering Raw, for the nonlinearity measurement
Science for the validation
Instrument:
NI-CU on (see table below), NI-FWA closed, NI-GWA RSG000 for the nonlinearity measurement.
Uses non-standard photo-MACC(15,16,11) setting for the validation part.
# LED ‘C’ Flux [e-/s] |
I (mA) |
PWM [%] |
8 |
1.0 |
5.4 |
12 |
1.0 |
11.5 |
16 |
5.0 |
6.3 |
20 |
5.0 |
7.7 |
30 |
5.0 |
11.0 |
40 |
5.0 |
14.3 |
50 |
5.0 |
17.6 |
70 |
5.0 |
24.2 |
80 |
5.0 |
27.5 |
110 |
5.0 |
37.4 |
150 |
10.0 |
27.9 |
175 |
10.0 |
32.0 |
200 |
10.0 |
36.1 |
350 |
30.0 |
20.7 |
450 |
30.0 |
26.8 |
550 |
30.0 |
32.8 |
750 |
30.0 |
44.8 |
950 |
60.0 |
29.4 |
Methodology / Uplink procedure¶
Entity: NISP
Commanding Method: NISP: Observation; must command LED “C”. Uses both standard photo-MACC(4,16,4) as well as non-standard photo-MACC(15,16,11) setting.
Dither Sequence: None for the nonlinearity measurements. Random dithers in a 3’ box for the validation observations.
Inter-operability constraints¶
VS-CU off
In-orbit duration¶
In-orbit Duration: 340.1 h (14.2 days for scheduling both variants including two validation blocks)
8*125*573 s + 170*70s + 30*573s = 167.3 h for spectro-MACC, allowing for 170 dither slews and persistence decay
3*4*(70s+111s+70s+573s) = 2.8 h for the nonlinearity validation.
A total of 125 ramps per variant, repeated 8 times since only two detectors can be done at the same time.
The acquisition time for the Engineering Raw ramps is perhaps 20s shorter than the nominal acquisition times adopted here, since all group images simply have to be passed on to the MMU without processing. This could potentially save up to 10 h, but is ignored in the above estimate.
Data volume¶
Total: 259179 MB per variant including validation. 515694 if variants are scheduled back-to-back.
NL ramps: 125*NSR = 251625 MB
Darks: 30*NS = 4890 MB
Validation: 3*4*(NP + NS) = 2664 MB
Processing input¶
Ground Processing Input Data: BPM
Data Description: 880 ramps per variant, with additional dark frames (can be ignored). Single detectors.
Processing output¶
Linearity correction for each pixel. Comparison to ground characterization.
Required accuracy, constraints¶
Must be able to compare the in-flight high flux nonlinearity correction to the ground characterization.
Processing tools¶
L1 nonlinearity pipeline, offline analysis likely
Validation¶
Fluxes measured in the Self-cal field with both MACC*(4,16,4) and MACC(11,16,15) should be indistuinguishable within the noise in case of perfect nonlinearity calibration.
Recovery¶
The ramps that did not work must be repeated.
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Contact person¶
NISP-P calibration scientist