Detalles de publicación
PP 026088
GroundBIRD: First On-Sky Responsivity Calibration at the Teide Observatory
(1) IAC, (2) Korea University
GroundBIRD is a cosmic microwave background (CMB) experiment located at the Teide Observatory (altitude ∼2400 m, Spain) that is designed to measure large-angular-scale intensity and polarization anisotropies (ℓ≳6 up to ℓ∼300) with the goal to constrain the optical depth to reionization, τ . The instrument employs a rapidly rotating telescope with the elevation fixed at 70 deg and is equipped with 161 lenslet-coupled kinetic inductance detectors (KIDs): 138 KIDs at 145 GHz dedicated to CMB observations and 23 KIDs at 220 GHz for thermal dust characterization. All detectors are operated at a temperature of ∼ 280 mK. This scan strategy provides daily coverage of approximately 40% of the Northern Hemisphere sky.
We present the first on-sky responsivity calibration model for GroundBIRD, derived from repeated observations of Jupiter using the most stable subset of twelve KIDs from GroundBIRD array 6 (GB06). The analysis focuses on developing and validating a calibration methodology on this restricted subset of detectors and yields the first empirical characterization of detector responsivity as a function of precipitable water vapor (PWV). We find that the detector responsivity decreases by approximately 30% across the sampled PWV range and is well described by a linear PWV-dependent model under typical observing conditions. A comparison with observations of the Moon reveals the existence of distinct detector operating regimes associated with different optical loading conditions. This analysis demonstrates that the detector responsivity is governed by the total optical load, rather than exclusively by the atmospheric contribution to the optical load.
The Jupiter-based calibration achieves a precision better than 20% under typical observing conditions and exhibits a relative stability better than 20% over a one-month timescale. These results underscore the critical importance of accounting for atmospheric effects in responsivity calibration and provide the foundation for extending the calibration methodology to the full GroundBIRD focal plane.
We present the first on-sky responsivity calibration model for GroundBIRD, derived from repeated observations of Jupiter using the most stable subset of twelve KIDs from GroundBIRD array 6 (GB06). The analysis focuses on developing and validating a calibration methodology on this restricted subset of detectors and yields the first empirical characterization of detector responsivity as a function of precipitable water vapor (PWV). We find that the detector responsivity decreases by approximately 30% across the sampled PWV range and is well described by a linear PWV-dependent model under typical observing conditions. A comparison with observations of the Moon reveals the existence of distinct detector operating regimes associated with different optical loading conditions. This analysis demonstrates that the detector responsivity is governed by the total optical load, rather than exclusively by the atmospheric contribution to the optical load.
The Jupiter-based calibration achieves a precision better than 20% under typical observing conditions and exhibits a relative stability better than 20% over a one-month timescale. These results underscore the critical importance of accounting for atmospheric effects in responsivity calibration and provide the foundation for extending the calibration methodology to the full GroundBIRD focal plane.