Calibration of millimeter-wavelength spectral lines - Effect of harmonic mixer response
Abstract
The cooled Schottky-diode receivers used to observe millimeter-wavelength spectral lines exhibit harmonic response, that is, response in sidebands associated with harmonics of the local oscillator frequency. Ignoring this response leads to a systematic error if the line intensities are calibrated by observing braod-band noise sources. The inferred line intensities are all lower than the true values. Experimental data confirm the relevance of the effect for astronomical observations. Although the error is not large, careful observers should be aware of it for projects that require exceptionally well-calibrated data.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1985
- DOI:
- 10.1086/163358
- Bibcode:
- 1985ApJ...295..139V
- Keywords:
-
- Calibrating;
- Line Spectra;
- Millimeter Waves;
- Radio Sources (Astronomy);
- Radio Spectra;
- Frequency Response;
- Harmonic Oscillators;
- Radio Astronomy;
- Schottky Diodes;
- Sidebands;
- Astronomy