NIRPS-ETC

Exposure Time Calculator (ETC) and radial velocity precision estimator for the Near InfraRed Planet Searcher (NIRPS) spectrograph

February 2022 - Before NIRPS on sky

Original NIRPS ETC code by Bruno L. Canto Martins 2018-2019

Additional edits by Nolan Grieves (University of Geneva) 2020-2022

Overview

• The NIRPS ETC uses spectra from the NASA Infrared Telescope Facility (IRTF) as SEDs to get estimated flux values for different spectral types: http://irtfweb.ifa.hawaii.edu/~spex/IRTF_Spectral_Library/
• The ETC calculates efficiency at different wavelengths using seeing, atmospheric efficiency from TAPAS (http://cds-espri.ipsl.fr/tapas/), and the measured global efficiency of the instrument
• The signal to noise ratio (SNR) at each pixel or bin is calculated from the fiber diameter, sampling, readout noise, resolution, efficiency, and flux in the pixel or bin from the IRTF template (flux=(10.**(0.4*(Ho-H)))*flux_st)
• RV precisions are calculated using, dRV=c/(Q*sqrt(Ne-)), equation 12 of Bouchy et al. (2001: https://ui.adsabs.harvard.edu/abs/2001A%26A...374..733B/abstract). The quality factors Q for spectra are calculated with ENIRIC from Phoenix simulated spectra or from spectral templates from the Spirou spectrograph
  • -> see: NIRPS-ETC/intermediate_preparation/update_RV_estimates/README_update_RV_estimates

Use

$ python NIRPS_ETC.py

• change observing options within the code at the top
  • Observation Mode (HA/HE)
  • Seeing, in arcsec (range 0.7-1.2)
  • Airmass (range 1.0-2.0)
  • Object magnitude (H band)
  • Exposure time (in sec)
  • Spectral type (F0V/F5V/G0V/G5V/G8V/K0V/K3V/K7V/M0V/M1V/M2V/M3V/M4V/M5V/M6V/M7V/M8V/M9V/L1V/L2V/L3V/L4V/L5V/L6V/L8V/T2V)
  • bandpass ('CFHT' or 'Eniric') #YJH bandpasses that will affect the range of the spectra used to calculate RV precision
• outputs mean SNR, in YJH, and each order, and RV precisisons for certain spectral types

OR use script version:

$ python NIRPS_ETC_script.py

• change inputs for each target in a space separated text file with columns:
  • target st obs_mode seeing airmass H t_exp bandpass
• change input and output text files within code to desired option
• outputs to file the mean SNR, YJH SNRs, and RV precisions

Contents

• inputs/
  • NIRPS_STAR_templates.txt
    • SEDs from IRTF (update with intermediate_preparation/update_effs/update_effs.py)
  • NIRPS_effs.txt
    • global efficiency of instrument (update with intermediate_preparation/update_effs/update_effs.py)
  • NIRPS_tapas.txt
    • atmospheric efficiency from TAPAS (update with intermediate_preparation/update_effs/update_effs.py)
  • NIRPS_wave_range.txt
    • wavelength range of echelle orders (update with intermediate_preparation/update_effs/update_effs.py)
  • phoenix_Q_conversions_CFHT-bandpass.txt
    • Q factor conversions for different resolutions in CFHT defined YJH bandpasses (update with intermediate_preparation/update_RV_estimates/phoenix_qfactor_resolution_conversion.py)
  • phoenix_Q_conversions_eniric-bandpass.txt
    • Q factor conversions for different resolutions in Eniric defined YJH bandpasses (update with intermediate_preparation/update_RV_estimates/phoenix_qfactor_resolution_conversion.py)
  • phoenix_eniric_Qfactors_CFHT-bandpass.csv
    • Q factors from Eniric in CFHT defined YJH bandpasses (update with eniric using command in intermediate_preparation/update_RV_estimates/README_update_RV_estimates)
  • phoenix_eniric_Qfactors_eniric-bandpass.csv
    • Q factors from Eniric in Eniric defined YJH bandpasses (update with eniric using command in intermediate_preparation/update_RV_estimates/README_update_RV_estimates)
  • spirou_fit_Qvalues_CFHT-bandpass.txt
    • Q factors from Spirou templates in CFHT defined YJH bandpasses (update with intermediate_preparation/update_RV_estimates/fit_spirou_qfactors.py)
  • spirou_fit_Qvalues_eniric-bandpass.txt.
    • Q factors from Spirou templates in Eniric defined YJH bandpasses (update with intermediate_preparation/update_RV_estimates/fit_spirou_qfactors.py)
• intermediate_preparation/
  • ETC_v3.0_CantoMartins/
    • original ETC by Bruno Canto Martins
  • add_stellar_templates/
    • add and update stellar templates
  • update_RV_estimates/
    • update RV estimates and Q values
  • update_effs/
    • update efficiency files and resample wavelength grid for tapas, effs, and star_templates
• outputs/
  • outputs SNR for each order and wavelength vs SNR plot from NIRPS_ETC.py
• NIRPS_ETC.py
  • main ETC code for a single star
• NIRPS_ETC_script.py
  • script that runs ETC for stars in etc_targets_input.txt and outputs to etc_targets_output.txt
• etc_targets_input.txt
  • example input file for NIRPS_ETC_script.py
• etc_targets_output.txt
  • example ouput file for NIRPS_ETC_script.py
• nirps_etc_lib.py
  • definitions for fucntions in ETC code