CALBLOCK-F-002: Noise Bias Fields (Euclid deep fields)

Observation configuration file

Not applicable

Scheduling

Planning and replanning by EC-SURV.

Grism ratio and completion: The final blue:red grism ratio is 25:15. A single pass shall always use the same grism. As a goal, a strong imbalance between blue and red data should be avoided toward the data releases. However, technical constraints and space weather may interfere with this goal.

Zodi corrections: The total number of passes, and the exposure-time ratio of 25:15, may require smaller corrections because of the actual zodiacal background at these fields. Corrections are at the discretion of EC-SURV.

Data sharing between EDFs and CPCs: The EDF-N, EDF-S, CPC-N, and CPC-S share the same sky areas, and the same blue:red exposure-time ratio. A deep observation therefore contributes toward completing the CPC, and vice versa.

Time-critical

No.

Objective

A sample of 200000 galaxies shall be obtained with a S/N 6 times that of the wide survey area, obtained from a 40 square degree area constituted by the Euclid Deep Fields (EDF-North, EDF-South, and EDF-Fornax).

The primary drivers of this calibration are VIS and the WL experiment to quantify the noise bias in the wide survey.

Observations

Observe the deep field areas using the ROS, until at least 40 square degrees are covered to 6 times the average S/N of the wide survey area.

Blue grism: The exposure time ratio is blue:red = 25:15, to account for different zodi background, and the reduced number of photons per flux per wavelength interval in the blue grism compared to the red grism.

Dithering: Each pass of a Deep Field consists of a regular grid. The regular grid is offset at every visit. The offsets lie along a spiral, producing a non-regular, yet fairly uniform distribution. In polar coordinates \((\rho, \theta)\), and for a total of \(n\) points, the position of point \(k\) is given by:

\((\rho, \theta) = (scale * \sqrt{k} / 60, k* GoldenAngle)\), with

\(scale = width / (2 \sqrt{n})\)

\(GoldenAngle = (3 - \sqrt{5}) * 180\;{\rm deg}\)

\(3' < width < 6'\) (chosen by EC-SURV according to their constraints)

This produces \(n\) points inside a circle of diameter \(width\) (in arcmin). The division by 60 converts arcmin to degree. The circle size increases with the number of points.

VIS Cycling: The VIS ROS-inline calibrations follow the nominal wide-survey cycling, as described in ROS: inline VIS calibrations and cadences.

Fulfilling

CALPRODUCT-VS-015: VIS Noise Bias Calibration Fields (REPLACED)

CALPRODUCT-NS-010: Completeness and Purity Calibration (CPC) (REPLACED) (partially)

Targets and pointing constraints

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

Table 19: Noise bias fields. CSV file

# ID

R.A.

Dec

EDF-N

269.733

+66.018

EDF-S

61.241

-48.423

Fornax

52.932

-28.089

Instrument configuration

Instrument: Wide survey; including blue-grism observations

Inter-operability constraints

None

In-orbit duration

In-orbit Duration:

Processing input

Ground Processing Input Data:

Data Description:

Quality control parameters

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

Contact person

Calibration Lead