Glossary#

airmass#: Atmospheric path length relative to zenith: \(\text{airmass} = 1 / \sin(\text{elevation})\).
ATM table#: Precomputed atmospheric model providing opacity coefficients \(b(\nu)\) and \(c(\nu)\) as a function of frequency and pressure. Produced by atmospheric radiative transfer codes.
COLD load#: Cryogenic calibration source, typically liquid nitrogen (~77 K).
DSB#: Double-sideband — both signal and image sidebands contribute to the detected power.
dump#: A single time integration sample within a subscan.
f_amb#: Ambient coupling fraction: \(f_{amb} = 1 - f_{eff}\).
foeff#: Forward efficiency — fraction of the beam that terminates on the sky (as opposed to ambient spillover). Typically 0.95–0.99.
g_i x_i#: Image sideband gain × suppression product. For an ideal DSB receiver: 0.5.
g_s x_s#: Signal sideband gain × suppression product. For an ideal DSB receiver: 0.5.
gamma#: Gain calibration factor converting count differences to temperature differences (K/count).
HOT load#: Ambient-temperature blackbody calibration source (~300 K).
L0#: Raw data level — uncalibrated counts and metadata in Zarr format. Produced by zarr-fits-core from FITS files.
L1#: Calibrated data level — antenna temperature \(T_A^*\) spectra, system temperature, flags, and quality metrics.
L1b#: Reduced data level — baseline-subtracted, flagged, and quality- checked spectra. Produced by the reduction pipeline.
L2#: Science-ready data level — gridded spectral maps. Produced by the reduction pipeline.
OTF#: On-the-fly mapping — the telescope scans continuously across the source, recording multiple dumps per subscan.
PWV#: Precipitable water vapour — column-integrated water vapour along the zenith line of sight (mm).
scan#: A complete observation unit containing source subscans and associated calibration data.
sobsmode#: Subscan observing mode string (ON, OFF, OTF-ON, OTF-OFF, HOT, COLD, COL, SKY, ZERO).
SSB#: Single-sideband — calibration convention where the atmospheric correction is applied to the signal sideband only.
subscan#: One continuous observing phase (e.g., one ON pointing or one OTF scan leg) within a scan.
T_A*#: Antenna temperature corrected for atmospheric absorption (K). The primary output of the calibration engine.
T_rec#: Receiver noise temperature. T_rec_prime is the double-sideband value; T_rec_SSB is the single-sideband value.
T_sys#: System temperature — total noise contribution including receiver, atmosphere, and load coupling (K).
TP#: Total power — position-switched observation with discrete ON/OFF pointings.
Zarr v3#: Chunked array storage format used for all data levels. Supports zstd compression and vlen-utf8 strings.
zenith opacity#: Optical depth along the zenith direction: \(\tau_0 = b(\nu) \cdot \text{PWV} + c(\nu)\).