CHAR-SURV-004: Zodiacal Model¶
Parent requirement¶
Cadence¶
First initialization during PV phase; if necessary, updated with background estimates from wide survey exposures.
Objective¶
Validate and update (if necessary) the zodi model for NISP and VIS based on PV phase and routine wide survey fields. This will not sample the full ecliptic longitude and latitude space, but at least the range that we routinely observe.
We do not expect large deviations. The zodiacal background is fairly well-known from different space missions. Changes of the true background value measured in Euclid bands compared to model predictions are expected on the level of 5-10%, limited by
the accuracy of our absolute flux calibration,
the intrinsic variability of the zodi background,
uncertainties in the straylight model,
uncertainties in the transformations from the known zodi-model SED to the Euclid passbands.
The background would need to be substantially higher than expected to make Euclid not achieve its survey goals, since the throughput estimates were fairly conservative, and the as-built hardware is considerably better. For example, the expected \(5\sigma\) depth for point sources in the NISP imaging channels is 24.4 AB mag at the beginning of the survey operations, compared to a goal of 24.0 AB mag. Even with a reduction of 5% (0.05 mag) at the end-of-life this leaves a substantial margin of about 30% for the zodi background. Only then would we need to consider changing the survey operations (from a NISP perspective).
Observations¶
Methodology / Uplink procedure¶
Targets and pointing constraints¶
Instrument configuration¶
Inter-operability constraints¶
Dependencies¶
Fulfilling¶
Fulfilled by¶
Time-critical¶
No
Validation¶
Compare the prediction of the zodi model with the currently observed values at a given ELON and ELAT position. We expect to be within \(5-10\%\) of the model predictions.
When compared to the model, if the measured background is:
<10% higher (likely): Update zodi model, survey continues as planned.
10-20% higher (less likely): As above. Are additional absolute flux-calibration crosschecks needed (if not done already)? Is the PLM contaminated, increasing out-of-band fluxes? Is the straylight model correct?
20-30% higher (unlikely): As above, but there is a possibility that the planned survey depths over the target area cannot be reached anymore with a 5% throughput loss at end-of-life. We can probably start the survey, but the priority of different survey areas should be reconsidered depending on their background level.
30-40% higher (very unlikely): The ROS and RSD in their launch configurations are probably insufficient to achieve the Euclid core science goals.
Recovery¶
In-orbit duration¶
Processing time¶
Standard wide-survey SGS processing.
Processing input¶
Ground Processing Input Data:
Data Description:
Data volume¶
38*ROSD1 = 49514 MB
Processing tools¶
Processing element¶
DataModel: https://gitlab.euclid-sgs.uk/
Quality control parameters¶
DataModel: https://gitlab.euclid-sgs.uk/
Required accuracy, constraints¶
Processing method¶
Processing output¶
Median background value per detector.
Contact person¶
Calibration Lead
Status¶
2026/09/18 - In progress.
Comments¶