CALBLOCK-F-001: Self Calibration¶
Observation configuration file¶
Scheduling¶
Scheduled every 25-40 days, adding flexibility for survey planning.
In case of failure, skip and continue with survey plan.
Dependencies¶
None
Objective¶
These observations provide the baseline to monitor Euclid’s spectrophotometric response to space weathering and outgassing. This is achieved by multiple dithered exposures of the Self-cal field.
Observations¶
Execute the ROS_D1 with a specific grism, at each of 60 pointings
A total of 4 self-cal visits is required to observe all grisms at all 60 dithers
BGS observations require an \({\rm AA}\) offset of at least \(\pm1.4\) to facilitate spectra-order decontamination, better \(\pm2.0\). Whether the negative or positive offset is executed first does not matter. Should the blue-grism offsets violate MOCD-A requirements, then they may be chosen asymmetrically around \({\rm AA}\). However, this could imply a large slew that impacts the thermal equilibrium. In that case EC-SURV may consider scheduling the Self-cal visit at another time.
The grism order must be preserved as outlined in the pseudo-code, as it can be executed any time without violating slew constraints.
\({\rm AA}\) may vary during a visit due to orbit progression
\({\rm AA}\) can be fine-tuned around \({\rm AA}=-5.5\) to minimise thermal transients and meet VIS straylight requirements, but the offset blue-grism observations must stray within the allowed limits.
The illumination-correction maps for the VIS and NISP imaging channels can exploit the additional, rotated blue-grism dithers, bringing the total from 60 to 76 exposures.
Note the rolling order of the red grisms in the 4 visits
The blue grism repeats 4 central dithers at the end of the 4th configuration
The ROS_D1 VIS variants are mostly NominalScience+ShortScience [NS+SS] (72 pointings), with 4 cases of [NS+Bias] distributed evenly. The 4 biases provide instrumental reference; each Self-cal visit starts and ends with the NS+BI variant of the ROS_D1. The Short Science exposures are required for VIS absolute photometric calibration, as well as BFE and NL monitoring.
ma ~ -5.5 (chosen AA for red-grism observations)
Set AA = ma-2
Dithers 42, 44, 45, 48, 2, 3, 30, 32: BGS000
Set AA = ma
Execute 60 dithers as specified, red-grism order: RGS000, RGS180_rot, RGS000_rot, RGS180, repeat
Set AA = ma+2
Dithers 41, 43, 47, 46, 1, 4, 29, 31: BGS000
Set AA = ma-2
Dithers 53, 54, 49, 50, 37, 39, 26, 25: BGS000
Set AA = ma
Execute 60 dithers as specified, red-grism order: RGS180_rot, RGS000_rot, RGS180, RGS000, repeat
Set AA = ma+2
Dithers 56, 55, 51, 52, 38, 40, 28, 27: BGS000
Set AA = ma-2
Dithers 10, 11, 5, 7, 23, 21, 18, 19: BGS000
Set AA = ma
Execute 60 dithers as specified, red-grism order: RGS000_rot, RGS180, RGS000, RGS180_rot, repeat
Set AA = ma+2
Dithers 9, 12, 6, 8, 22, 24, 17, 20: BGS000
Set AA = ma-2
Dithers 13, 14, 33, 36, 57, 58, 41, 42: BGS000
Set AA = ma
Execute 60 dithers as specified, red-grism order: RGS180, RGS000, RGS180_rot, RGS000_rot, repeat
Set AA = ma+2
Dithers 16, 15, 34, 35, 59, 60, 43, 44: BGS000
Fulfilling¶
Targets and pointing constraints¶
Pointing: Straylight suppression as per MOCDA-SYS-003. The 60 dithers for the red grism should be observed at the mean \({\rm AA}\) of the contemporary survey patch. They must be executed in the order given in CSV file. The 16 dithers for the blue grism use two different \({\rm AA}\) offset with respect to the mean \({\rm AA}\) of the survey patch.
Figure 10: The Self-cal field is located near the NEP. It includes a hot White Dwarf (blue asterisk) for CALBLOCK-PV-002: NISP-P and VIS Absolute Photometric Standards. The green and orange outlines show the boundaries for visits at two different times, where orbit progression results in boundary rotation.¶
Figure 11: Self-cal dither pattern. Observations must step through the dithers as specified in this CSV file¶
# ID |
R.A. |
Dec |
SELFCAL-CENTER |
268.812745 |
65.2855857 |
Instrument configuration¶
Instrument: Wide survey
Methodology / Uplink procedure¶
Entity: VIS & NISP
Commanding Method: NISP: Observation, VIS: Science
Dither Sequence: ROS_D1.
The ROS_D1 is executed at each of these Self-cal dither positions. The order in which they are executed does not matter, within a fixed \({\rm AA}\) setting. The grism to be used at a specific dither is given in the observations.
Inter-operability constraints¶
None
In-orbit duration¶
In-orbit Duration: 23.5 h
Data volume¶
76*ROSD1 = 99028 MB
Processing input¶
Ground Processing Input Data: All calibration products to run the standard science pipeline (BPM, darks, flat, nonlinearity etc), small scale flat fields
Data Description: Each visit provides: 225 photo-MACC images, 76 spectro-MACC images, 76 VIS nominal science, 72 VIS short science exposures, and 4 VIS bias exposures.
Processing output¶
Large scale flat field for VIS and all NISP filters and grisms
NISP-S dispersion check using secondary wavelength calibrators
Absolute photometric zeropoint for VIS and NISP.
Coarsely binned (e.g. 100x100) illumination correction map, and monitoring
VIS and NISP focal plane astrometric solutions
Monitoring of system parameters.
Required accuracy, constraints¶
Images successfully acquired
Processing tools¶
Pipeline: VIS_LargeFlatCalibration_Pipeline
PE: VIS_LargeFlatCalibration
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Contact person¶
Calibration Lead