StarDICE news

LSST-France APC

Slides from Thierry Souverin PhD defence

28/11/2024

T. Souverin, J. Neveu, M. Betoule, S. Bongard, J. Cohen Tanugi, S. Dagoret Campagne, F. Feinstein, M. Ferrari, C. Juramy,

L. Le Guillou, A. Le Van Suu, P. E. Blanc, E. Nuss, B. Plez, E. Sepulveda, K. Sommer, N. Regnault

Photometric calibration transfer

2

???

POWR facility

Houston et al. 2006

CALSPEC primary standard stars

Photometric calibration transfer

3

More sensitive detectors

Pros: In situ conditions, full pupil illumination

Cons: Broadband fluxes

Pros: High wavelength resolution

Cons: Laboratory conditions, partial mirror illumination

Measurement of the spectra of CALSPEC standard stars

Atmosphere

Two paths for atmosphere analysis:

• Photometry at different elevations
• Spectrophotometric measurements

Observatory of Haute-Provence

4

StarDICE telescope

5

StarDICE telescope on its mount

Newton telescope:

• D=40cm
• f=1.6m
• 1.68’’ resolution
• 28.6’ x 28.6’ field of view

​

Filterwheel:

• “ugrizy” photometric filters
• Diffraction grating

​

Monitoring instruments:

• Hygrometer
• Thermometers
• Barometer
• Rain detector

​

Fully robotic

Artificial star

6

Artificial stars LEDs off

Artificial stars LEDs on

Helmet enclosing the artificial star

• 16 LEDs covering visible and near-IR range
• Flux calibrated in laboratory
• Mounted in July 2024

What is a CBP ?

7

CBP, for Collimated Beam Projector, is a calibration device emitting a monochromatic light of known flux, in a parallel beam

​

⇒ calibrate the response of a photometric instrument and its filters.

Two purposes:

• Calibrate the StarDICE telescope response
• Proof of concept for the CBP at Rubin Observatory for the LSST

CBP

8

CBP optics

1. CBP response measurement

(2) StarDICE response measurement

Tunable laser

Integrating sphere w/ monitoring instruments

Full illumination synthesis

9

Uncertainty propagation for on-sky flux measurements, after simulating the recalibration with the artificial star:

Airmass regression

10

X_i

X =

X

Zero points vs airmass

11

Scintillation, PSF variation…

Results

12

StarDICE performances projection

13

• 9 photometric nights
• StarDICE 2-year survey estimation ⇒ 84 nights
• ~0.2 to 0.4% uncertainty

​

⇒ 2 to 4 times the suitable value to fully exploit the future LSST SNe Ia dataset

How to fight the extra RMS?

• Observation of the artificial star to check instrument stability (ongoing)
• Development of infrared camera to monitor clouds (Kélian Sommer thesis)
• Development of slitless spectrophotometry to monitor atmosphere (new PhD!)

14

How to fight the extra RMS?

• Observation of the artificial star to check instrument stability (ongoing)
• Development of infrared camera to monitor clouds (Kélian Sommer thesis)
• Development of slitless spectrophotometry to monitor atmosphere (new PhD!)

15

How to fight the extra RMS?

• Observation of the artificial star to check instrument stability (ongoing)
• Development of infrared camera to monitor clouds (Kélian Sommer thesis)
• Development of slitless spectrophotometry to monitor atmosphere (new PhD!)

16

437 spectra of a bright isolated star

H₂O

H₂O

O₂

Summary

• Despite bad weather ⛆, we got a few nights with LEDs: analysis is ongoing
• Maintenance mission by Marc and Seb right now! 🌳

​

​

​

​

​

• 2023 - 2024: 1 artificial star, 2 PhD defenses, 3 papers, 4 proceedings 😅
• 2025 plan:
• a second artificial star (nearly ready)
• visit of the traveling CBP
• joint observations with CALSPEC and LEDs
• publication of at least a systematic on CALSPEC calibration, or recalibration of CALSPEC if we are lucky

17