SPIRou Current Performances

System
Throughput in JHK (1)	7, 9, 9%
Peak SNR in 1h on H=11, 3100K star	100 per pix at 1.65micron
Magnitude for S/N=10 in 1h (2)	mH=14
Magnitude for 2m/s precision in 900s (3)	mH~7.0
Thermal background at 2.35 microns	100 ph/s/A between at 5C
On-sky aperture diameter	1.296"
Sensitivity of the guiding (4)	mH=11
Guiding loop	up to 50Hz for H<9, down to 1Hz for the faintest objects
Guiding CCD sampling	0.128arcsec/pix
Spectrograph
Wavelength Domain (5)	0.967-2.493 microns
Wavelength calibration	Uranium lamp, vacuum wavelength lines catalogue
Spectral Resolution from calibration lines (6)	65,000
Spectral Resolution from the broadening of stellar spectra (6)	70,000
Pixel size	2.28 km/s
Velocimeter
Radial-velocity accuracy (7)	12 cm/s (internal) ~2 m/s (on quiet M RV standards)
Method	spectral calibration: use of simultaneous FP
Polarimeter
Polarimetric sensitivity in stellar lines (8)	< 0.01%
Polarimetric crosstalk (9)	<3% (to be updated)
Detector
Type	H4RG
Dimensions	4k x 4k
Pixel size	15 microns
Red cut-off (50% QE)	2.45
Quantum Efficiency over JHK	> 80%
Cosmetics (clusters)	< 0.1% bad pixels
Readout mode	Ramp fitting
Dark current	0.018 e-/s
Readout Noise (CDS)	12 e-
Readout Noise (ramps) (10)	6.5 e-
Operations
Twilight	SPIRou observes between evening and morning -8 deg twilights
Overheads	Slew and start guiding (not charged): <90 s charged time per exposure: 28s (spectroscopy) or 35s (polarimetry)
Number of available hours per night (11)	7 h (estimate)
Precipitable water vapour 50% of time (observing airmass) (12)	2.85 mm
Precipitable water vapour 80% of time (observing airmass) (12)	5.40 mm
Calibrations	RV and telluric standards: ~20 min per night
Pipeline processing	APERO DRS version 0.7.293 for reduced data sent to CADC

Footnotes:

1. Telescope+SPIRou throughput with the new rhombs installed in Aug. 2020 and used on sky starting Aug. 25. Update Feb. 2024: SNR monitored on standard star Gl699 suggests the transmission didn't change significantly over the last semesters.

2. Limiting magnitude in 1h shows the H magnitude of a 3100K star where a SNR per pixel of 10 is achieved in median conditions (0.6 arcsec seeing in H) in a total exposure time of 1 hour.

3. Limiting magnitude for a 2m/s accuracy in 900s is the typical H magnitude of a 3100K non-rotating star where simulations predict an RV uncertainty not limited by photon noise under median conditions (0.6 arcsec seeing in H). RV uncertainty is expected on the same star and same exposure time to be up to 20 m/s if the rotation profile is 10km/s and telluric lines are just masked out.

4. Offset guiding is also possible.

5. Limit wavelength extracted by the DRS. The wavelength domain has a short gap in the K band between 2437 and 2439nm. The gap is between the last reddest orders.

6. The spectral resolution relevant for radial velocity work, Rrv, relates to the gaussian broadening that the spectrograph induces onto the spectrum of a typical M dwarf. Rcal, the resolution estimated from calibration lines, has been measured on lamp exposures. Both resolutions are not equal when the spectrograph point-spread function (PSF) is not Gaussian. For SPIRou, Zemax predicts Rcal = 63.8K and Rrv =73.4K.

7. Internal RV accuracy has been measured in the lab on continuous series of Fabry-Perot exposures. They have shown internal relative stability at a level of 12 cm/s RMS over 24h, measured on the science fibers and corrected for the absolute drift as measured on the reference fiber. Measuring the stellar RV after correcting for telluric absorption shows a precision of about 2 m/s on a quiet, non-rotating, M star (Donati et al. 2020, Monthly Notices of the Royal Astronomical Society, Volume 498, Issue 4, November 2020, Pages 5684–5703, https://doi.org/10.1093/mnras/staa2569).

8. The sensitivity of polarization in stellar lines is within specifications.

9. A residual polarization crosstalk is observed, especially at low external temperatures, of the order of 1-4%.

10. The readout noise in the ramp sampling decreases with the number of reads, until it reaches a minimum, around 6.5 electrons per pixel.

11. The observing efficiency is based on the SPIRou commissioning and takes into account specific known overheads.

12. The amount of precipitable water vapour is expected to have an impact on the spectra and radial velocity measurement. The fraction of time which minimizes the precipitable water vapour may be better adapted for extreme PRV requirements.